Dissertations / Theses on the topic 'Tendons'

Um dos maiores desafios da ortopedia moderna é recuperar o tecido ósseo que tenha sido perdido por motivo de doença ou acidente. Na busca de substitutos para os enxertos, tem-se utilizado comumente biomateriais para recuperação desse tecido. Um dos vários tipos de biomateriais usados são os preparados à base de colágeno. Além de desempenhar papel importante na estrutura dos tecidos, o colágeno é capaz de orientar a formação de tecidos em desenvolvimento fato altamente favorável na sua utilização como biomaterial. Uma nova vertente de pesquisa do processo de mineralização de matrizes colagênicas que vem sendo desenvolvida é a analise de como a organização do tecido interfere no modo como ocorre esse processo de deposição. O uso do tendão vem sido pesquisado devido ao fato de ser um tecido extremamente organizado, com as fibras colagênicas alinhadas por toda a sua extensão. Este trabalho teve como objetivo a preparação e caracterização de matrizes de colágeno tipo I, oriundas de tendão bovino (TB) e avestruz (TA) após a hidrólise alcalina e mineralização. Os tendões foram colocados em solução alcalina contendo sais de K+, Na+ e Ca2+ por 72, 96 e 120 h a 25°C e depois equilibrados em solução de sais, lavados em H3BO3, EDTA e água. As matrizes resultantes foram então mineralizadas em soluções de CaCl2 0,2 mol L-1, pH = 7,4 e de Na2HPO4 0,12 mol L-1 pH = 9,0 durante 6 h, ocorrendo a troca de soluções a cada 30 min. As matrizes antes e após mineralização foram congeladas, liofilizadas e submetidas à análise termogravimétrica (TG), calorimetria exploratória diferencial (DSC), microscopia eletrônica de varredura (MEV), espectroscopia no infra-vermelho (FT-IR) e dispersão de energia por raios-X (EDX). DSC mostrou que não houve desnaturação do colágeno durante o processo de tratamento alcalino e mineralização. A análise termogravimétrica mostrou que houve deposição de fosfato de cálcio, com o valor dependendo do número de ciclos de mineralização. MEV mostrou que essa mineralização não é uniforme, ocorrendo a formação de aglomerados. FT-IR e EDX mostrou que o fosfato de cálcio depositado provavelmente seja hidroxiapatita, mas não em sua estrutura estequiométrica.
One of greatest challenges of modern orthopedics is to restore bone tissue that has been lost due to sickness or accident. Searching for substitutes for grafts, biomaterials have been commonly used for recovery of bone tissue. Between different types of biomaterials, several are based on collagen. In addition to have important role in tissue structure, collagen is able to guide the formation of tissues, a highly favorable fact in its use as biomaterial. A possible research in collagen scaffolds mineralization is the analysis of how tissue organization interferes in deposition process. The tendon has been used because it is a highly organized tissue, with collagen fibers lined on its structure. This research aims the preparation and characterization of type I collagen scaffolds, prepared from bovine tendon (TB) and ostrich tendon (TA) after alkaline hydrolysis and mineralization. Tendons were maintained in alkaline solution containing K+, Na+ and Ca2+ ions for 72, 96 and 120 hours at 25°C and then equilibrated in salt solution, washed with H3BO3, EDTA and water. The resulting matrices were then mineralized in 0.2 mol L-1, pH = 7.4 CaCl2 solution and 0.12 mol L-1 Na2HPO4 pH = 9.0 for 6 h, changing solutions after 30 minutes. The matrices before and after mineralization were frozen, lyophilized and subjected to thermogravimetric analysis (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) and energy dispersive X-ray spectroscopy (EDS). DSC showed that the collagen was not denaturated by alkaline treatment process and mineralization. TG analysis showed deposition of calcium phosphate on the scaffolds, with values depending on the number of mineralization cycles. SEM showed that the mineralization is not uniform, forming clusters of phosphate crystals. FT-IR and EDS showed that the deposited calcium phosphate is probably hydroxyapatite, but not in its stoichiometric structure.

Fibrotic diseases account for an estimated 45% of the total number of deaths in the developed world (Wynn 2007). Tendons are an excellent model for studying the dysregulated response which leads to fibrosis, as tendons have an organized, parallel matrix, in which tissue defects could easily be distinguished. Wong et al. (2006b) demonstrated the presence of a bell-shaped region around sutures in tendons that was devoid of cells in histological sections. The mechanisms of the formation of this acellular zone, that was also noted in cornea and cartilage (Matsuda et al. 1999; Hunziker and Stähli 2008), were unknown. It was hypothesized that the acellular zone was formed by cell death and that suturing caused alterations to the extracellular matrix of sutured regions of tendon, which made the acellular zone refractory to cellular re-population. The acellular zone was tracked in sutured tendons for up to a year to determine the temporal properties of the acellular zone. Electron microscopic and time lapse studies were carried out to determine if the acellular zone formed by cell migration or cell death. Microarray analysis was conduced to confirm this and to reveal potential molecular targets for future studies. The extracellular matrix of sutured tendons was studied by electron, atomic, scanning and polarized light microscopy and mechanical measurements were obtained using nanoindentation. It was concluded that the acellular zone formed within 24 hours and persisted for up to a year. Tension and size of the suture's grasp were also shown to be important for acellular zone formation. Cell death was the main effector of acellular zone formation. Microarray analysis showed evidence of upregulation of inflammatory mediators and programmed necrosis pathways. The sutured extracellular matrix was denser, more disorganized and had a lower Young's modulus than unsutured regions of the same tendon. These differences in the properties of the extracellular matrix of sutured tendons may be the cause of the persistence of the acellular zone.

Collagenous tissues such as ligaments and tendons are viscoelastic materials. They exhibit a slow continuous increase in strain over time, or creep, when subjected to a constant stress and a slow continuous decrease in stress over time, or stress relaxation, when subjected to a constant strain. Moreover, the loading and unloading stress-strain curves are different when the tissues are subjected to cyclic loading, showing hysteresis and softening phenomena. The micro-structural origin of the viscoelasticity of these tissues is still unknown and the subject of debate among experts in biomechanics. Therefore, formulating viscoelastic models by accounting for the mechanical contributions of the structural components of these tissues can help in understanding the genesis of viscoelasticity. A nonlinear viscoelastic modeling framework has been developed to describe the elastic and viscoelastic properties of ligaments and tendons by considering their main structural components, the collagen fibers and proteoglycan-rich matrix. The mathematical models derived within this framework can illustrate the tensile behavior, stress relaxation and creep by as suming that the collagen fibers are elastic and the surrounding proteoglycan-rich matrix is viscoelastic. The collagen fibers are represented by linear elastic springs that are engaged to support load at different values of the tissue's strain according to a Weibull distribution function. The mechanical contribution of the matrix is introduced via a Maxwell-type viscoelastic element arranged in parallel with the collagen fibers. According to the proposed mathematical framework, both the collagen fibers and the proteoglycan-rich matrix are responsible for resisting tensile loads. However, the collagen fibers play a significant role in creep while the proteoglycan-rich matrix has a dominant role in stress relaxation. The model parameters that define the stress relaxation and strain stiffening phenomena are estimated by using published experimental on rabbit medial collateral ligaments and are then used to predict creep. The above modeling framework has been also extended to capture the in uence of preconditioning on the mechanical properties of ligaments and tendons. The stress softening and decrease in hysteresis that are observed during successive loading cycles in preconditioning are assumed to be determined by a decrease in the elastic properties of the collagen fibers and proteoglycan-rich matrix. Preliminary data collected on stress relaxation and preconditioning on rat medial collateral ligaments by collaborators are used to evaluate the model parameters and analyze its predictions. The elastic and viscoelastic properties of single collagen fibers are studied by formulating a nonlinear viscoelastic framework by accounting for their main components: microfibrils, cross-links and proteoglycan-rich matrix. The model illustrates tensile behavior and stress relaxation of a single collagen fiber by assuming that the microfibrils and the cross-links are elastic and the surrounding proteoglycan-rich matrix is viscoelastic. The mechanical contribution of the microfibrils is included via a linear elastic spring while the cross-links are represented by linear elastic springs that progressively fail at different values of the tissue's strain according to an exponential distribution function. The matrix is defined by linear dashpots arranged in parallel with each single spring that represents an individual cross-link. The viscous properties of the matrix associated with the unbroken and broken cross-links are assumed to have different values. In the model formulation, the microfibrils and the cross-links are assumed to determine the elastic response of the fibers while the proteoglycan-rich matrix determines the stress relaxation. Microfibrils, cross-links and the proteoglycan-rich matrix are responsible for resisting the loading force during tensile behavior. Experimental data collected by performing incremental stress relaxation tests by other investigators on reconstituted rat tail tendons are used to estimate the parameters in the model and evaluate its performance.
Ph. D.

The human Achilles tendon is the strongest tendon in the body, but it is also the tendon most prone to developing tendinopathy. Tendinopathy is a clinical term used to describe tendon pathology that presents clinically as a painful, thickened tendon with altered mechanical behaviour. The main conservative treatment for tendinopathy is exercise, typically in the form of calf muscle contractions. However calf exercises are likely to impose very different stresses and strains on the tendons of different individuals as a result of inter-subject variability in tendon geometry, tendon material properties, muscle mechanical properties and muscle activation patterns. Although there are reports of global stress and strain experienced by the Achilles tendon during voluntary contractions in the literature, little is known about the local stress and strain within the tendon. It is important to understand the local mechanical behaviour in tendon tissue because mechanical loading is a critical stimulus to tendon adaptation via localised mechano-biological pathways. Musculoskeletal tissues including tendons, are reported to have an optimal range in which mechanical loading produces positive tissue adaptation (an anabolic effect), with either too much or too little mechanical loading having a detrimental (catabolic) effect. Clinical efficacy of exercise-based training and rehabilitation for the Achilles tendon could be enhanced if an “optimal” loading stimulus is provided to the tendon. The general aim of this thesis was to investigate the influence of subject-specific tendon geometry and material properties on mechanical stress and damage in living free Achilles tendons with and without tendinopathy during submaximal, isometric loading. A methodological pipeline was developed to generate individualised finite element models of the living free Achilles tendon (n = 8 healthy, n = 8 tendinopathic). Subject-specific polynomial finite element meshes were rendered based on freehand three-dimensional ultrasound scans of the free tendon. Subject-specific material properties were obtained from numerical optimisation by minimising the difference between experimental measures of longitudinal strain under load and modelled strains. The tendon was defined as an incompressible, homogeneous and hyper-elastic material and implemented in CMISS. CMISS is a finite element software based on polynomial basis functions which can accommodate large deformation based of coarse polynomial meshes. Finite element analyses were subsequently conducted to determine the strain, stress and damage criteria within the tendon based on force boundary conditions obtained from the subject-specific experimentally measured ankle plantarflexor torque. The first study used three-dimensional ultrasound based measures of in-vivo free Achilles tendon geometry in conjunction with finite element analysis to determine the effects of subject-specific versus generic geometries and material properties on the stress distribution within the living tendon during a submaximal isometric contraction. The mean (SD) lengths, volumes and cross-sectional areas of the tendons at rest were 62 ± 13 mm, 3617 ± 984 mm³ and 58 ± 11 mm², respectively. The measured tendon strain at 70% maximum voluntary contraction was 5.9 ± 1.3%. Generic geometry was represented by the average mesh and generic material properties were taken from the literature. Local stresses were subsequently computed for all combinations of subject-specific and generic geometry and material properties. For a given geometry, changing from generic to subject-specific material properties had little effect on the stress distribution in the tendon. In contrast, changing from generic to subject-specific geometry had a 26-fold greater effect on tendon stress distribution. Overall, these findings highlight a strong variability between individual tendons and indicate that the tendon geometry has a greater influence on the stress distribution than the tendon material properties. Achilles tendon mechanical properties and geometry are altered in Achilles tendinopathy. The purpose of the second study was to determine the relative contributions of altered mechanical properties and geometry to free Achilles tendon stress distribution during a sub-maximal contraction in tendinopathic relative to healthy tendons. The average resting CSA of the free tendon was on average 35% greater for the tendinopathic tendons. At the same tensile force, the tendinopathic tendons experienced a strain of 7.1 ± 2.9% compared to 5.9 ± 1.3% for controls. The mean Young’s modulus for tendinopathic tendons was 40% of the corresponding control value. Finite element analyses revealed that tendinopathic tendons experience 24% less stress at submaximal loading compared to healthy tendons. The lower tendon stress in tendinopathy was due to a greater influence of tendon CSA, which alone reduced tendon stress by 30%, compared to Young’s modulus, which alone increased tendon stress by 8%. These findings suggest that the greater tendon CSA observed in tendinopathy compensates for the substantially lower Young’s modulus, and thereby protects pathological tendon against excessive stress. The purpose of the final study was to determine how tendinopathic alterations in Achilles tendon geometry and material properties affect damage load and location. Tendon damage load was assessed at a theoretical damage strain of 12%. The subject-specific damage load was found significantly higher for the healthy tendon (12.5 ± 5.0 kN) compared to the tendinopathic tendon (5.7 ± 1.5 kN). A 59% decrease in the damage load was observed when the average material properties of the healthy tendon were replaced with average tendinopathic material properties while retaining the average healthy tendon geometry. Damage load increased by 23% when the average healthy geometry was replaced by average tendinopathic geometry while retaining average healthy material properties. A substantial variation in damage location was observed across all tendons. Overall findings of this study suggest that tendinopathic alterations in material properties are more influential than corresponding alterations in tendon geometry in determining the load required to cause tendon damage. This thesis has demonstrated the feasibility of using a finite element modelling approach to investigate stress distributions in the Achilles tendons based on in-vivo, subject-specific measures of three-dimensional tendon geometry and tendon mechanical properties. Stress patterns in the Achilles tendon were found to differ substantially between individuals. Generic training and rehabilitation programs for the Achilles tendon are therefore likely to result in very different tendon stresses and strains between individuals. The general findings of this thesis point to the need for personalised training and rehabilitation for the Achilles tendon that takes account of the substantial variation in tendon geometry and material properties between individuals to ensure an optimal loading stimulus is provided that maximises positive tissue adaptation for healthy and tendinopathic tendons.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School Allied Health Sciences
Griffith Health
Full Text

Tendons function to transmit the forces generated by muscle to bone, resulting in movement of a joint. However some tendons have more specialized functions. Functionally distinct tendons have differences in tissue composition that relate to differences in function. However, it is unclear whether functionally distinct tendons also behave differently following injury. This study aims to investigate the normal characteristics of ovine forelimb extensor tendons and the changes that occur following injury using a combination of histological and gene expression analysis. The lateral digital extensor tendon (LDET) and two branches of the common digital extensor tendons (CDET) in the forelimb of 6 sheep were collected to study normal extensor tendon characteristics. In another 6 sheep, the LDET and two branches of the CDET were transected and harvested 8 weeks later to evaluate the characteristics of injured extensor tendons. In the third group of 6 sheep, the LDET and two branches of the CDET were harvested 8 weeks after partial transection of the superficial digital flexor tendon (SDFT) in the same limb to evaluate the effects of tendinopathy of the SDFT on the normal extensor tendon characteristics. Samples were assessed using histology and gene expression. The results demonstrate that there are gene expression differences between the extensor tendons in the ovine forelimb and the changes in the ovine extensor tendons following surgery are similar to that of other tendons studied including the “energy storing” tendons. Partial transection of the SDFT had no effect on the extensor tendons.

Ruptured tendons heal faster if they are exposed to mechanical loading. Loading creates deformation of the extracellular matrix and cells, which give rise to intracellular signalling, increased gene expression and protein synthesis. The effects of loading have been extensively studied in vitro, and in intact tendons in vivo. However, the response to loading in healing tendons is less known. The general aim of this thesis was to understand more about the response to mechanical loading during tendon healing. The specific aims were to find out how short daily loading episodes could influence tendon healing, and to understand more about genes involved in tendon healing. The studies were performed using rat models. Unloading of healing tendons resulted in a weaker callus tissue. This could be reversed to some extent by short daily loading episodes. Loading induced more matrix production, making the tendons thicker and stronger, but there was no improvement in the material properties of the matrix. Lengthening is one potential adversity with early loading, during tendon healing in patients. This was also seen with continuous loading in the rat models. However, short loading episodes did not result in any lengthening, not even when loading was applied during the inflammatory phase of healing. It also appeared as loading once daily was enough to make healing tendons stronger, while loading twice daily with 8 hours interval did not give any additional effect. The strongest gene expression response to one loading episode was seen after 3 hours. The gene expression changes persisted 12 hours after the loading episode but had disappeared by 24 hours. Loading appeared to regulate genes involved in inflammation, wound healing and coagulation, angiogenesis, and production of reactive oxygen species. Inflammation-associated genes were regulated both by continuous loading and by one short loading episode. Inflammation is an important part of the healing response, but too much can be harmful. Loading might therefore have a role in fine-tuning the inflammatory response during healing. In conclusion, these studies show that short daily loading episodes during early tendon healing could potentially be beneficial for rehabilitation. Loading might have a role in regulating the inflammatory response during healing.

Key words: End zone, prestress transfer, wire tendon, transmission length, pull-in, plain wire, indented wire, concrete strength, size of wire, gradual release, sudden release, shock release, time dependent effects.An empirical investigation into the transfer of prestress force from wire tendons to concrete in the end zones of pretensioned prestressed concrete beams was accomplished in this project. The experimental tests featured 56 small scale prestressed concrete beams.Some of the factors influencing prestress transfer which were considered in the current tests are as follows:(a) type of release - gradual, sudden or shock(b) surface condition of the wire - plain or indented(c) size of the wire(d) concrete compressive strength at the time of transfer(e) time dependent effectsMost of the tests involved gradual release of steel tendons with the prestressing force transferred in approximately ten equal increments. Sudden release in a single step was achieved by allowing the supporting abutments to retract rapidly. Shock release was implemented in some beams by angle grinding the wires. The type of release which gave the best quality of prestress transfer was gradual release. This was followed by sudden and shock releases respectively.There were four types of wires used in the laboratory tests: namely the 5 mm dia. Plain, 5 mm dia. Chevron indented, 7 mm dia. Plain and 7 mm dia. Belgian indented wires. Transmission lengths were determined from strain distributions for these wires. Pull-ins of the wire tendons at the ends of the beams were also measured.There was significant scatter in the experimental data. Different ranges of transmission lengths and pull-ins were obtained for the various types of wires used.Three equations were derived for the 5 mm dia. Plain, 5 mm dia. Chevron and 7 mm dia. Plain wires, which linearly correlated pull-ins to the transmission lengths. These relationships provide a qualitative and quantitative method of indirectly monitoring for the transmission lengths through the measurements of pull-in.Statistical inference tests proved that indented wires were superior in performance compared to plain wires, but the differences were more apparent for the pull-ins than for the transmission lengths.Comparisons on the influence of tendon size substantiated that greater pull-ins occurred for larger wires but the differences were not significant for the transmission lengths.For concrete strength at the time of transfer of less than 32 MPa, the transmission lengths and pull-ins were significantly larger than those for higher strengths. It is recommended that concrete strength at transfer be at least 32 MPa for pretensioned prestressed concrete.Apart from the maturity and strength of concrete, the quality of a mix also influenced the transmission length and there was limited data to suggest that a better grade mix despite having lower strength at a more tender age could outperform a lower grade mix with greater strength released after a longer curing period.Formulae for plain and indented wires were found by dimensional analysis which correlated the transmission length to the diameter of wire tendon and the stress/strength ratio of the prestressed beams.Pull-ins increased significantly over 6 months but the changes in the transmission lengths were small. Normalised longitudinal strain distributions did not indicate that transmission lengths would remain unchanged over time.

Key words: End zone, prestress transfer, wire tendon, transmission length, pull-in, plain wire, indented wire, concrete strength, size of wire, gradual release, sudden release, shock release, time dependent effects.An empirical investigation into the transfer of prestress force from wire tendons to concrete in the end zones of pretensioned prestressed concrete beams was accomplished in this project. The experimental tests featured 56 small scale prestressed concrete beams.Some of the factors influencing prestress transfer which were considered in the current tests are as follows:(a) type of release - gradual, sudden or shock(b) surface condition of the wire - plain or indented(c) size of the wire(d) concrete compressive strength at the time of transfer(e) time dependent effectsMost of the tests involved gradual release of steel tendons with the prestressing force transferred in approximately ten equal increments. Sudden release in a single step was achieved by allowing the supporting abutments to retract rapidly. Shock release was implemented in some beams by angle grinding the wires. The type of release which gave the best quality of prestress transfer was gradual release. This was followed by sudden and shock releases respectively.There were four types of wires used in the laboratory tests: namely the 5 mm dia. Plain, 5 mm dia. Chevron indented, 7 mm dia. Plain and 7 mm dia. Belgian indented wires. Transmission lengths were determined from strain distributions for these wires. Pull-ins of the wire tendons at the ends of the beams were also measured.There was significant scatter in the experimental data. Different ranges of transmission lengths and pull-ins were obtained for the various types of wires used.Three equations were derived for the 5 mm dia. Plain, 5 mm dia. Chevron and 7 mm dia. Plain wires, which linearly correlated pull-ins to the transmission lengths. ++
These relationships provide a qualitative and quantitative method of indirectly monitoring for the transmission lengths through the measurements of pull-in.Statistical inference tests proved that indented wires were superior in performance compared to plain wires, but the differences were more apparent for the pull-ins than for the transmission lengths.Comparisons on the influence of tendon size substantiated that greater pull-ins occurred for larger wires but the differences were not significant for the transmission lengths.For concrete strength at the time of transfer of less than 32 MPa, the transmission lengths and pull-ins were significantly larger than those for higher strengths. It is recommended that concrete strength at transfer be at least 32 MPa for pretensioned prestressed concrete.Apart from the maturity and strength of concrete, the quality of a mix also influenced the transmission length and there was limited data to suggest that a better grade mix despite having lower strength at a more tender age could outperform a lower grade mix with greater strength released after a longer curing period.Formulae for plain and indented wires were found by dimensional analysis which correlated the transmission length to the diameter of wire tendon and the stress/strength ratio of the prestressed beams.Pull-ins increased significantly over 6 months but the changes in the transmission lengths were small. Normalised longitudinal strain distributions did not indicate that transmission lengths would remain unchanged over time.

Degenerative disorders of the rotator cuff tendons account for nearly 75% of all shoulder pain, causing considerable pain and morbidity. Given the strong correlation between age and tendinopathy, and unprecedented population aging, these disorders will become increasingly prevalent. Improved understanding of tendon degeneration will guide the development of future diagnostic and treatments, and is therefore urgently needed. However, the aetiology and pathology of rotator cuff tendinopathy remain unclear. The complicated mechanical environment of the rotator cuff is hypothesised to influence the susceptibility of the tendons to degeneration and tearing. Studies have reported biological adaptations in torn cuff tendons indicative of increased compressive loading within the tendon. The material adaptations of healthy and degenerative cuff tendons are largely unreported but will provide further insight into the role of the mechanical environment in rotator cuff aetiology and pathology. This thesis examined the material adaptations of healthy and diseased tendons to explore the role of mechanical loading in rotator cuff pathology. The material adaptations of healthy animal tendons, and healthy and delaminated human cadaveric rotator cuff tendons, in response to different loading environments were characterised. The effects of age, tears, steroid injection and subacromial decompression surgery on the structural adaptations of human cuff tendons were also studied, as was the effect of tendon cell proliferation on the mechanical properties and degradation behaviour of collagen scaffolds. Loading environment significantly affected the structural adaptations of healthy tendons. Regions exposed to compressive and shear strains exhibited thinner fibres, shorter crimp lengths and thinner, less aligned fibrils compared with regions exposed to tensile strains alone. In healthy rotator cuff tendons, the inhomogeneous loading environment produced topographically inhomogeneous structural adaptations. The tendons of a delaminated rotator cuff exhibited less topographical variation in properties and thinner, less aligned fibrils compared with healthy cuff tendons. Torn cuff tendons exhibited thinner fibrils and shorter crimp lengths compared with control samples. These adaptations were identifiable early in the disease progression, and neither steroid injection nor subacromial decompression surgery significantly influenced these adaptations at seven weeks post‐treatment. Significant correlations between decreasing dimensions and increasing tear size were found when age was included as a confounding factor, reflecting the importance of age and tear size in determining the material properties of tendons. Tendon cell proliferation influenced the mechanical properties and degradation behaviour of the collagen scaffolds, emphasising the integral role of cells in the functional adaptation of biological materials. These results demonstrate the effect of mechanical environment on the material adaptations of tendons. They also indicate the importance of the complicated mechanical environment experienced by the rotator cuff tendons in predisposing the tendons to degeneration and tearing. The observed material adaptations of degenerative and torn tendons suggest that rotator cuff pathology is associated with increased levels of compressive and/or shear strains within the tendon. These changes begin early in the disease progression and neither steroid injection nor sub‐acromial decompression surgery are capable of reversing the changes in the timeframe investigated. These findings highlight the urgent clinical need for pre‐rupture diagnostic techniques for the detection of early pathological changes in the rotator cuff. They also emphasize the requirement for new intervention strategies that restore the healthy mechanical environment and reverse early pathological adaptations in order to prevent catastrophic failure of the tendons.

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OS tendões, estruturas importantes para a realização de movimentos, são constituidos por fibroblastos e fibrócitos alongados separados por uma abundante matriz extracelular (MEC) constituida por feixes de colágeno do tipo I, que são paralelos, espessos e perfeitamente arranjados, oferecendo grande resistência a força de tração. Os tendões são acometidos por lesões, principalmente por esforços excessivos, além de serem importantes fontes de enxerto para a reconstruc;ao do Ligamento Cruzado Anterior (LCA). a enxerto mais utilizado por ter caracteristicas histologicas semelhantes com 0 LCA e 0 tendao Patelar (TP). Atualmente, existem vários tipos de tratamento para reparação de tendões. Entre eles pode-se destacar a imobilização do membro afetado por vários dias. Durante o período de reabilitação da reconstrução do LCA, pouco se da importância para a reparação da fonte doadora de enxerto, podendo assim ocorrer diversas complicações com o tendão. Neste estudo, foram investigados os efeitos da imobilização e comparados com a mobilização precoce do membro afetado no processo de reparação do TP. O estudo foi realizado com 48 ratos machos da linhagem Wistar, os quais foram divididos em 3 grupos de 16 animais. Os animais sofreram uma lesão cirúrgica no TP esquerdo. Após a lesão, um grupo de animais foi solto na gaiola; o segundo grupo foi realizado mobilização precoce e solto na gaiola sendo continuado a mobilização todos os dias ate o dia do seu sacrificio; e o terceiro grupo foi submetido a uma imobilização do segmento lesado com uma tala de gesso e resina acrílica. Os animais foram sacrificados após 24, 48 horas e 7 dias de lesão. Após o sacrifício, foi coletado o TP e emblocado em parafina. Cortes foram corados pela hematoxilina-eosina e picrossírius. Além disso, nas lâminas de picrossírius foram mensurados o tamanho de ondulações...
Tendons are important structures for the movement, being constituted of layes of alonged fibroblasts and fibrocytes separated by large and aligned type I collagen fibers, providing a great tensile strenght. Tendons lesions are frequent, mainly by excessive loading or induced by surgical proceeding for anterior cruciate ligament (ACL) reconstruction. The main source of graft for ACL reconstruction is the patellar tendon. Currently, there are several treatment to improve the tendon repair after an injury, among than we can destak the immobilization and early mobilization of the joint. During the reabilitation of ACL after reconstruction little attention has been given to the repair of tendon donor of the graft. In this study, were investigated the effects of the immobilization in comparison to the early mobilization of the joint on the process of pattelar tendon repair. Forthy eight adult male Wistar Rat were divided into 3 groups of 16 animals. All the animals were submitted to a surgical lesion, under anestesia, in the central part of the left patte1ar tendon. After the lesion, a group of animals were left free in the cavage; a second group had the lesioned joint immobilized; and a third group were submitted to early mobilization of the lesioned joint and left free in the cavage. The mobilized group animals were submitted to dayly series of mobilization. The animals were euthanased 24, 48, and 168 hours after the surgery. The patellar tendon was excised and processed for Paraplast embedding. Histological sections were stained by hematoxylin and eosyn and sirius red. Furtermore, the crimp pattern was evaluated by morphometry in the sirius red stained sections observed under polarized light. Immunohistochemistry for PCNA were used to determine... (Complete abstract click electronic access below)

Post-tensioned segmental concrete bridges have been used in the United States since the mid 80's. Post-tensioning is very economical and efficient for bridges with very long spans. A segmental concrete bridge uses post-tensioning to connect concrete bridge segments and make a long span bridge. A problem that has occurred in some segmental concrete bridges is the corrosion of the post-tensioned strands. A tendon failure can be detrimental to service level bridge performance and reduce the flexural strength. The Varina-Enon Bridge has a history of corrosion related issues and the objective of this project was to investigate the consequences of transverse tendons rupture. In addition, to determine the behavior of tendons with grouted duct and smoot duct when a stand broke. Also, the results of this project identify if the bridge can perform adequately with no repair or if these failures would develop problems in the long term. A full scale specimen of a post-tensioned slab with two tendons was built at the laboratory. The full scale specimen was built to contain tendons similar to top flange near the delta frames in the Varina-Enon Bridge, where a transverse tendon was broken. An artificial corrosion process was conducted to corrode the tendons and investigate the effect of break on the slab. The specimen was instrumented with BDI strain gauges to monitor the behavior of the specimen, when the strand rupture occurred due to the accelerated corrosion. In addition, a finite element model was designed similar to the full scale specimen to compare the collected data with the data obtained from the analysis.
Master of Science
Bridges play a very important role in the Transportation Systems all over the world. According to American Society of Civil Engineering (ASCE), United States bridges get a C+ grade. The ASCE rating indicates that the US bridges need to be built more efficiently and be monitored more frequently. Regular inspection of bridges is very essential and will be beneficial in many ways. For instance, engineers can detect the possible flaws and problems that are in the bridge such as corrosion in structural elements. It is important to address these issues since these bridges are in service and being used by the public. Based on how serious the issues are, engineers will decide if the bridge can perform adequately with repair or it is is structurally inefficient and needs to be replaced. Moreover, rehabilitations method to keep the structure in service will save a lot of money compare to replacing the bridge. The Varian Enon Bridge, which carries Interstate 295 across the James River in Richmond, is a critical link in Richmond transportation a In the recent inspections of this bridge, Virginia Department of Transportations (VDOT) detected abnormal behavior of few structural elements. In this research, a full scale mock-up of a section of the Varina Enon Bridge was built at the lab. The purpose of this project was to conduct testing on the mock-up to investigate the cause of abnormal behavior of these few structural elements similar to the ones in Varina Enon Bridge. Furthermore, a final report was prepared for VDOT to decide if the bridge will perform adequately with no strengthening or providing forewarning of trouble that could develop with time.

Shoulder disease is the third most common musculoskeletal problem, and rotator cuff tendon tears account for the greatest proportion of shoulder complaints. Rotator cuff tears are estimated to affect between 5-30% of adults, with higher incidences of tearing and fa ilure to heal in elderly patients, placing a huge socioeconomic burden on an ageing British population. Serious concern arises as a large proportion of technically correct surgical repairs re-rupture. The intra-articular environment of the tendon often precludes nonnal healing and surgical repair is often necessary to improve pain and restore some function. It is feasible that there may be an inherent phys iological or biomechanical defect in the tissue that prevents complete heal ing without some further augmentation to the surgical repair. Improved understanding of the biochemical and biomechanical changes in tom rotator cuff tendons may help to reduce the high rerupture rates. This study aimed to characterise nonnal, and different sized rotator cuff tendon tears from small samples obtained intraoperatively to try to use tests that may potentially be clinica lly usefu l in the future. Tendon samples were mechanically tested using dynamic shear analysis, a fonn of rheology, to overcome gripping and slippage problems of very small specimens. It was found that tom tendons had a significandy reduced storage modulus compared to normal tendons, particularly for massive tears. Chemical analysis of tendons using Fourier transform infrared spectroscopy revealed that partial and different sized rotator cuff tendon tears are chemically distinguishable. The onset of rotator cuff tear pathology is mainly due to an alteration of the collagen structural arrangements, with associated changes in lipids and carbohydrates. Collagen structural changes in small and massive tendons were quantified us ing differential scanning calorimetry, which allows measurement of coHagen thermal properties as a reflection of their structural integrity. Small and massive tendon tears had reduced thermal properties and hence reduced collagen integrity when compared to normal tendons, although there was no difference between the two tear groups. Gene expression differences between the small, massive tears and normal tendons were studied using microarray analysis, and revealed that the different groups were biologically distinguishable.

The healing process of ruptured tendons is problematic due to scar tissue formation and deteriorated material properties. In some cases, it may take nearly a year to complete. Mechanical loading has been shown to positively influence tendon healing; however, the mechanisms remain unclear. Computational mechanobiology methods employed extensively to model bone healing have achieved high fidelity, but not yet been explored to understand tendon regeneration. The general objective of this thesis is to develop computational approaches to enhance the knowledge of the role that mechanical factors play in fibre re-organisation in healing tendons, by proposing an appropriate constitutive formulation, followed by analysing the mechano-adaptation of the models created when regulated by different biophysical stimuli. Curve fitting of an established hyperelastic fibre-reinforced continuum model introduced by Gasser, Ogden and Holzapfel (GOH) against experimental tensile testing data of rat Achilles tendons at four timepoints during the tendon repair was used and achieved excellent fits (0.9903 < R² < 0.9986). A parametric sensitivity study using a three-level central composite design, which is a fractional factorial design method, showed that the collagen-fibre-related parameters in the GOH model had almost equal influence on the fitting. The mechano-adaptation of the healing tendons when regulated by axial and principal strain predicted fibre re-organisation comparable to experimental findings, in contrast to models regulated by deviatoric strain. Also, mechano-adaptive models regulated by deviatoric strain were more spatially and temporally sensitive to different boundary conditions - length and loading magnitudes - than those regulated by axial and principal strain. This thesis describes that a hyperelastic fibre-reinforced mechano-adaptive model regulated by axial or principal strain is generally capable of describing the mechanobiological behaviours of healing tendons, and that further experiments should focus on establishing the localised structural and material parameters of collagen fibres and their mechano-adaptive behaviours in the healing tissue.

Although mechanical loading correlate to multi-hierarchical changes, the multiscale response during tendon damage remains not yet fully understood. Therefore, this thesis assessed the multiscale structure-function mechanisms in response to different levels and durations of strains in GAG and un/depleted Achilles tendons. At the nano/macroscales, increased levels and durations of strains resulted in increased changes in form and function. This thesis identifies a variety of multiscale properties that may contribute to the understanding of the mechanism of tendon pathology.

Les étirements sont aujourd'hui une pratique courante dans les milieux sportifs et de réadaptation. Ils sont habituellement recommandés dans le but de contribuer à la prévention des blessures (Willson et al. 1991 ;Pope et al. 2000), à l’amélioration de la performance sportive lorsque celle-ci nécessite une amplitude articulaire importante (Heyters, 1985 ;Hortobagyi et al. 1985) et à la récupération de la mobilité articulaire dans le cadre d’un programme de réadaptation (Magnusson et al. 1996b). Ces méthodes, qui se sont développées ces dernières années, font classiquement appel à l’étirement passif et aux étirements neurofacilités (PNF), présentés initialement par Kabat (1958). Plus récemment, un intérêt particulier a été porté au travail musculaire excentrique. Des études ont montré que celui-ci permettait également d’augmenter l’amplitude articulaire (Willson et al. 1991 ;Nelson et Bandy, 2004).

Dans une première partie de ce travail, il nous a semblé intéressant de comparer les effets de l’étirement passif à ceux des étirements PNF par "contracté-relâché" et "contracté de l’antagoniste". Si les modalités d'application de chaque étirement sont différentes, elles présentent un intérêt majeur. De fait, elles permettent de faire varier les conditions d'allongement des différentes structures du système myotendineux, en modulant l'activité volontaire des musculatures agoniste ou antagoniste. En effet, si l’étirement passif s'effectue sans activation volontaire, l’étirement par "contracté-relâché" consiste à faire précéder l'étirement passif, d'une contraction volontaire maximale isométrique de la musculature agoniste. L’étirement par "contracté de l’antagoniste" associe à l'allongement de la musculature agoniste, une contraction volontaire maximale de la musculature antagoniste. Si de nombreuses études s'intéressent encore actuellement à caractériser leurs effets respectifs, elles ont déjà permis de montrer que ceux-ci avaient au moins deux origines distinctes, l'une neurophysiologique et l'autre mécanique (Taylor et al. 1990 ;Hutton, 1993). Au plan neurophysiologique, il est bien accepté que ces méthodes induisent une modulation de l'activité réflexe tonique facilitant le relâchement musculaire et par conséquent l’amplitude articulaire (Guissard et al. 1988 ;2001). Il est également bien admis que l’importance de ces effets sur la musculature est variable selon la méthode employée (Guissard et Duchateau, 2006). Au plan mécanique, des études menées chez l’animal ont montré que l’étirement passif modifie les caractéristiques viscoélastiques des tissus (Taylor et al. 1990), et de fait favorise l’allongement des tissus myotendineux (McHugh et al. 1992). Chez le sujet humain, plusieurs expérimentations ont montré que l’étirement par "contracté-relâché" permet d’obtenir un allongement myotendineux et un gain d’amplitude articulaire plus important que par étirement passif (Moore et Hutton, 1980). D’autres études ont montré que l’étirement par "contracté de l’antagoniste" permet de majorer encore les gains obtenus par l’étirement "contracté-relâché" (Osternig et al. 1990). Une première question posée dans ce travail est de savoir si la contribution des processus neurophysiologiques et mécaniques se traduit d’une manière spécifique sur le rapport de compliance des tissus de l’unité myotendineuse. Le développement de techniques d’investigation, telles que l’échographie, permet désormais d’observer le comportement de l’unité myotendineuse, d’une manière non invasive (Fukunaga et al. 1992 ;Herbert et Gandevia, 1995 ;Kuno et Fukunaga, 1995 ;Maganaris et al. 1998). Elle permet ainsi d’étudier les effets d’un étirement ou d’une contraction (Fukunaga et al. 1996) sur le rapport de compliance des structures musculaires et des tissus tendineux.

S’il était intéressant d’étudier la spécificité de ces trois méthodes d’étirement classiques par rapport à leurs effets sur les tissus myotendineux, il nous paraissait pertinent d’observer celle d’un travail musculaire excentrique. En effet, la particularité de celui-ci est de soumettre l’unité myotendineuse préalablement activée, à un allongement. En réadaptation, le travail excentrique est généralement proposé dans le but d’améliorer plus rapidement la symptomatologie d’une tendinopathie (Stanish et al. 1986 ;Alfredson et al. 1998). Des études récentes ont indiqué qu’il peut également être proposé pour augmenter l'amplitude articulaire (Nelson et Bandy, 2004). Toutefois, ses effets sur les tissus myotendineux ne sont pas clairement définis dans la littérature. Chez l’animal, Heinemeier et al. (2007) ont comparé les effets d’un entraînement en contractions concentriques et excentriques sur les tissus de l’unité myotendineuse. Leurs résultats indiquent que si les tissus tendineux sont sensibles aux deux modes de contraction pour leurs effets favorisant la synthèse de collagène, les structures musculaires sont spécifiquement sensibles au mode excentrique. Chez le sujet humain, Crameri et al. (2004) ont observé une série de contractions excentriques d’intensité maximale augmente la synthèse de collagène au sein de l’ensemble des tissus de l’unité myotendineuse. Ces résultats montrent que les effets de ce travail ne se limitent pas aux tissus tendineux, tels que certains protocoles thérapeutiques le suggéraient, et que le tissu musculaire doit désormais être associé à la discussion des effets de ce travail musculaire. Dans ce contexte, la deuxième question que nous avons posée est de savoir si l’étirement de l’unité myotendineuse préalablement activée, telle que se caractérise une contraction excentrique, modifie le rapport de compliance des tissus myotendineux par rapport aux méthodes classiques. Autrement dit, si l’étirement de l’unité myotendineuse activée favorise spécifiquement l’allongement de l’un des tissus de l’unité myotendineuse.

Dans une troisième partie, il nous a paru intéressant d'étudier le comportement à l’étirement de l’unité myotendineuse, dont la compliance était modifiée suite à une désadaptation à long terme. L’hypertonie spastique, qui caractérise une majorité de sujets parétiques spastiques, est généralement caractérisée par une augmentation anormale des résistances opposées à l'étirement passif (Carey et Burghart, 1993). L’origine de ces résistances peut être attribuée à des adaptations tant neurophysiologiques (Pierrot-Deseilligny et Mazières, 1985) que mécaniques et structurelles des tissus de l'unité myotendineuse (Berger et al. 1984 ;Tardieu et al. 1989). Il n’existe pourtant pas encore dans la littérature de consensus les définissant clairement (Fridén et Lieber, 2003). En outre, l’étude récente de Lieber et Fridén (2002) a mis en évidence des modifications de l’architecture des muscles fléchisseurs du carpe. Contrairement à ce qui est généralement proposé au sujet de la longueur des fascicules spastiques (Tardieu et al. 1982), Lieber et Fridén (2002) n’ont pas mis en évidence de raccourcissement de ces derniers. Ainsi, l’hypothèse de Tardieu et al. (1982), selon laquelle le raccourcissement des fascicules est à l’origine de l’augmentation des résistances à l’allongement, ne peut plus être soutenue. Il nous paraissait ainsi intéressant d’associer, à l’observation du comportement des fascicules, celui des tissus tendineux, dans le but de déterminer si l’une de ces deux structures présente des caractéristiques particulières, susceptibles d’expliquer le développement plus important de ces résistances à l’allongement. La troisième question que nous avons posée dans ce travail est de savoir comment se caractérise, à l’étirement, le rapport de compliance des tissus musculaire et tendineux dans un contexte de spasticité.

Outre le fait que la réponse à ces différentes questions soit fondamentale pour mieux comprendre et spécifier la pratique des méthodes d’étirement, l’objectif de notre travail est non seulement de mettre en évidence le tissu dont l’allongement est spécifiquement favorisé par l’une ou l’autre méthode, mais également de contribuer à différencier celui qui limite l’étirement global du système myotendineux. Dans ce contexte, il sera intéressant de pouvoir recommander la pratique d’une méthode particulière, en fonction des besoins spécifiques de chacun.

Doctorat en Sciences de la motricité
info:eu-repo/semantics/nonPublished

Orientador: Laurecir Gomes
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-07T01:19:46Z (GMT). No. of bitstreams: 1 Nakagaki_WilsonRomero_M.pdf: 13678735 bytes, checksum: 4e8920e8d9da4cbdacc1d02f8a7c0e6c (MD5) Previous issue date: 2006
Resumo: Os tendões transmitem forças de tração entre músculo e osso. Os .efeitos dos estímulos mecânicos dependem da localização anatômica e níveis de atividade no tendão e da contração muscular. Além disto, em um mesmo tendão é possível observar a presença de regiões sob tensão e compressão. Diversos estudos têm relacionado alterações bioquímicas na matriz extracelular de tendões em função do exercício fisico e da idade, porém há poucos trabalhos com tendões de fTangos submetidos ou não ao exercício ativo não forçado. Neste trabalho foram analisados aspectos bioquímicos e biomecânicos do tendão calcâneo e do tendão flexor digital superficial de frangos com 1, 5 e 8 meses de idade, criados em gaiolas e em ambiente amplo. Os resultados de biomecânica mostraram que no tendão calcâneo o exercício aumentou a resistência à força de tração a partir do quinto mês, maior absorção de energia no oitavo mês, maior tensão no primeiro mês e maior rigidez no quinto mês. O exercício e a idade estimularam o aumento no conteúdo de colágeno no quinto mês. O exercício aumentou o conteúdo de glicosaminoglicanos no primeiro e oitavo mês e com o avanço da idade aumentou no oitavo mês na região de compressão e diminuiu progressivamente na região de tensão. Para o tendão flexor digital superficial, sinal de mineralização foi observado no quinto mês. Com a maturação, no grupo criado em ambiente amplo, a força (até o quinto mês) e a absorção de energia aumentaram, mas não houve alteração da rigidez, da tensão e da deformação. O exercício demonstrou que resistência à força, tensão e rigidez foram maiores no quinto mês. O conteúdo de colágeno aumentou com a idade do grupo amplo e aumentou com o exercício no quinto e oitavo meses. O conteúdo de glicosaminoglicanos diminuiu na região de tensão no oitavo mês no grupo amplo enquanto na região de compressão se manteve constante a partir do quinto mês. Com o exercício a quantidade de glicosaminoglicanos .. é substancialmente maior em SDFT jovens do que em maturos. Nossos resultados mostraram que o aumento da resistência do tendão, a maior capacidade em absorver energia e o maior conteúdo de colágeno são dependentes do próprio crescimento e maturação, mas também são influenciados pelo exercício ativo não forçado, indicando que a matriz extracelular é capaz de detectar alterações fisicas, como andar e correr, e de transmitir esta informação para as células
Abstract: The tendons transmit tensile strength between muscle and bone. The effects of the mechanical stimuli depend on the anatomicallocation and activity levels in the tendon and of the muscular contraction. Also, in a same tendon it is possible to observe the presence of regions under tension and compression. Several studies have related biochemical differences in the extracellular matrix of tendons in function of physical exercise and age, however there are few works with tendons of chickens submitted or not to the nonforced active exercise. In this work the biochemical and biomechanical aspects of the calcaneus tendon and the superficial digital flexor tendon fTom1, 5 and 8 months old chickens, caged and penned raised were analyzed.. For the calcaneus tendon the exercise increased the resistance to the load starting fTom the fifth month, larger absorption energy in the eighth month, larger stress in the first month and larger stiffness in the fifth month. The exercise and the age stimulated the increase in the collagen content in the fifth month. The exercise increased the glycosaminoglycans content in the first and eighth months and with the age it increased in the eighth month in the compression region and it decreased progressively in the tension region. For the superficial digital flexor tendon, mineralization was observed in the fifth month. With the maturation, in the penned group, the load (until the fifth month) and the absorption of energy increased, but there was not change in the stiffness, stress and strain. The exercise demonstrated that load, stress and stiffness were greater in the fifth month. The collagen content increased with the age on the penned group and with the exercise in the fifth and eighth months. The glycosaminoglycans content decreased in the tension region in the eighth month in the penned group while in the compression region it remained constant starting from the fifth month. With the exercise the glycosaminoglycans expression is substantially larger in young SDFT than in mature ones. Our results demonstrated .. that the raise in the tendon resistance, the larger capacity in energy absorption and the largest collagen content depend on the own growth and maturation, and they' re also influenced by the nonforced active exercise, indicating that the extracellular matrix is able to detect physical alterations, like walk and run, and transmit this information to the cells
Mestrado
Biologia Celular
Mestre em Biologia Celular e Estrutural

A espécie asinina (E. asinus) teve sua origem há milhares de anos, se desenvolvendo a partir de um tronco comum ao do eqüino doméstico que conhecemos. Vem passando por um processo adaptativo, apresentando características distintas, quando os observamos em diversas partes do planeta. Na região nordeste do Brasil, desenvolve um papel fundamental, influenciando diretamente na renda das famílias locais. Tendo em vista o grande número de afecções locomotoras e a falta de cuidados a que estão submetidos, realizou-se um estudo anatômico e radiográfico da região distal de seus membros torácicos, buscando-se subsídios a prática clínica e cirúrgica dedicada a esses animais, bem como a compreensão de sua maior resistência a lesões locomotoras, quando comparado ao eqüino. A avaliação anatômica revelou características musculares semelhantes as já descritas para eqüinos. O exame radiográfico evidenciou lesões severas, caracterizadas por osteíte podal e áreas de reabsorção óssea e remodelamento na margem solear, associadas à rotação da falange distal. Ainda na avaliação radiográfica, caracterizaram-se os principais vasos arteriais dessa região através de técnica angiográfica. Não se observou correlação entre o ângulo de inclinação da muralha do casco e falange distal, com a área de secção transversal dos tendões dos músculos flexores. As maiores secções transversais para o tendão flexor digital superficial, profundo e interósseo, mostraram coincidência com os pontos de maior estresse articular, caracterizando, assim, a resistência dos asininos à lesões nestas estruturas em seu aparelho locomotor.
The asinine species was originated thousands of years ago from the same branch of the domestic equine. The asinine have been undergoing to a great adaptation resulting in different characteristics of each population of asinine around the world. In the northeast region of Brazil, they play an essential role in the income of the local families. Due to a large number of locomotor disorders and a lack of professional care, an anatomic and radiographic study of the distal forelimb region of the asinine was carried out in order to gather information to improve the clinical and surgical practice in this species, and to explain the less susceptibility to locomotor disorders compared to equines. The anatomical study showed that asinine have similar muscular characteristics already described for equines. The radiographic exam showed severe lesions, characterized by pedal osteitis, bone reabsorption areas and remodelling of sole margin associated to the distal phalanx rotation. The radiographic study also showed the characterization of the main arterial vessels. No significant correlation was observed between the angle of the hoof wall and the angle of the distal phalanx with the cross section area of the flexor tendons. The larger cross section areas of the superficial digital flexor tendon, deep digital flexor tendon and interosseus tendon were coincidental with the great articular stress, explaining the greater resistance of the asinines to lesions in those structures of their locomotor apparatus.

Orientador: Sérgio Luis Felisbino
Banca: Raquel Domeniconi
Banca: Luiz Fernando Barbesian
Resumo: OS tendões, estruturas importantes para a realização de movimentos, são constituidos por fibroblastos e fibrócitos alongados separados por uma abundante matriz extracelular (MEC) constituida por feixes de colágeno do tipo I, que são paralelos, espessos e perfeitamente arranjados, oferecendo grande resistência a força de tração. Os tendões são acometidos por lesões, principalmente por esforços excessivos, além de serem importantes fontes de enxerto para a reconstruc;ao do Ligamento Cruzado Anterior (LCA). a enxerto mais utilizado por ter caracteristicas histologicas semelhantes com 0 LCA e 0 tendao Patelar (TP). Atualmente, existem vários tipos de tratamento para reparação de tendões. Entre eles pode-se destacar a imobilização do membro afetado por vários dias. Durante o período de reabilitação da reconstrução do LCA, pouco se da importância para a reparação da fonte doadora de enxerto, podendo assim ocorrer diversas complicações com o tendão. Neste estudo, foram investigados os efeitos da imobilização e comparados com a mobilização precoce do membro afetado no processo de reparação do TP. O estudo foi realizado com 48 ratos machos da linhagem Wistar, os quais foram divididos em 3 grupos de 16 animais. Os animais sofreram uma lesão cirúrgica no TP esquerdo. Após a lesão, um grupo de animais foi solto na gaiola; o segundo grupo foi realizado mobilização precoce e solto na gaiola sendo continuado a mobilização todos os dias ate o dia do seu sacrificio; e o terceiro grupo foi submetido a uma imobilização do segmento lesado com uma tala de gesso e resina acrílica. Os animais foram sacrificados após 24, 48 horas e 7 dias de lesão. Após o sacrifício, foi coletado o TP e emblocado em parafina. Cortes foram corados pela hematoxilina-eosina e picrossírius. Além disso, nas lâminas de picrossírius foram mensurados o tamanho de ondulações... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Tendons are important structures for the movement, being constituted of layes of alonged fibroblasts and fibrocytes separated by large and aligned type I collagen fibers, providing a great tensile strenght. Tendons lesions are frequent, mainly by excessive loading or induced by surgical proceeding for anterior cruciate ligament (ACL) reconstruction. The main source of graft for ACL reconstruction is the patellar tendon. Currently, there are several treatment to improve the tendon repair after an injury, among than we can destak the immobilization and early mobilization of the joint. During the reabilitation of ACL after reconstruction little attention has been given to the repair of tendon donor of the graft. In this study, were investigated the effects of the immobilization in comparison to the early mobilization of the joint on the process of pattelar tendon repair. Forthy eight adult male Wistar Rat were divided into 3 groups of 16 animals. All the animals were submitted to a surgical lesion, under anestesia, in the central part of the left patte1ar tendon. After the lesion, a group of animals were left free in the cavage; a second group had the lesioned joint immobilized; and a third group were submitted to early mobilization of the lesioned joint and left free in the cavage. The mobilized group animals were submitted to dayly series of mobilization. The animals were euthanased 24, 48, and 168 hours after the surgery. The patellar tendon was excised and processed for Paraplast embedding. Histological sections were stained by hematoxylin and eosyn and sirius red. Furtermore, the crimp pattern was evaluated by morphometry in the sirius red stained sections observed under polarized light. Immunohistochemistry for PCNA were used to determine... (Complete abstract click electronic access below)
Mestre

The introduction of Fibre Reinforced Polymers (FRP) to the civil engineering market in the late 1980s resulted in the emergence of a range of new tools for rehabilitating and strengthening concrete structures. Strengthening using FRPs is typically accomplished using non-prestressed externally bonded FRPs. The technical and economic benefits of such strengthening could be further increased by prestressing the FRPs, especially when dealing with concrete structures. Prestressing concrete structures suppresses the appearance and growth of cracks in the serviceability limit state. This in turn increases the structure’s stiffness and resistance to degradation. Prestressing also increases the structure’s yield load but does not change its failure load relative to that of an analogous non-prestressed structure, provided that all other parameters are kept constant. In 2004, a pilot study was carried out at the Luleå University of Technology (LTU) to investigate the scope for using unbonded Carbon Fibre Reinforced Polymer (CFRP) strengthening systems, particularly those involving prestressing. In the early stages of this project, a number of difficulties were encountered in anchoring the CFRP rods to concrete structures: the conical wedge anchorages that were used tended to either cause premature failure of the rods or allowed the rod to slip out of the anchorage. It was therefore decided to study the mechanisms at work within these anchorages in more detail. The goal of the project was to develop a small, practical, reliable, and userfriendly anchorage for use in unbonded external CFRP strengthening systems. On the basis of a thorough literature review, which is described in Paper 1, it was concluded that despite the difficulties encountered, the conical wedge anchorages used with steel reinforcing rods were the most promising starting point for the design of a new anchorage for use with CFRPs. Importantly, the conical wedge anchorage can be made small in size and easy to mount while retaining a high degree of versatility; this is not true of bonded, sleeve, and clamping anchorages. Analytical and numerical models were used to investigate the distribution of radial stress within these highly pressurized anchorages. Paper 2 describes an evaluation of the capability of three types of models - an analytical axisymmetric model based on the thick-walled-cylinder-theory and two Finite Element (FE) models, one axisymmetric and one three-dimensional - to predict the behaviour of a conical wedge anchorage. It was concluded that the axisymmetric models were incapable of modelling the stress distribution within the anchorage with sufficient accuracy, and so 3D FE models were used exclusively in subsequent studies. Paper 3 describes the development of a new anchorage for CFRP rods. The design process involved conducting pull-out studies on a series of prototypes, in conjunction with computational studies using a basic FE model, to identify and understand the prototypes’ failure modes. Between the computational data and experimental results, a good understanding of the factors affecting the interaction between the CFRP rod and the anchorage was obtained. The new anchorage design employs a one-piece wedge which effectively incorporates the three wedges and the inner sleeve from more conventional wedge anchorages into a single unit. This increases the reliability and user-friendliness of the anchorage because it eliminates the need to check the alignment of individual wedges. The new design has been patented; the published Swedish patent is included in the thesis as Paper 6. The newly-developed anchorage was then incorporated into a prestressing system and its performance was evaluated using a series of test beams. In parallel with the planning of these tests, a series of pull-out tests was conducted using the new anchorage. The strain measurements obtained in these experiments were compared to predictions made using a new, more advanced FE model, and used to refine the design of the new anchorage. Paper 4 describes this new FE model, the most important parameters affecting anchorage behaviour, and the final anchorage design. Paper 5 focuses on the possibilities provided by the new anchorage. Tests were performed using seven three meter long concrete beams prestressed with external unbonded CFRP tendons. One beam was unstrengthened; the other six were strengthened in different ways, with different prestressing forces, initial tendon depths, and with or without the use of a midspan deviator for the tendons. The results of these tests were compared to those obtained using otherwise identical beams prestressed with steel tendons and to the predictions of an analytical beam model developed for use with steel tendons. These tests showed that the prestressing works as intended and that the behaviour of beams prestressed with external unbonded CFRP tendons is fully comparable to that of beams prestressed with steel tendons. It was also found that the predictions of the analytical model were in good agreement with experimental observations, although there were some differences between the measured and predicted tendon stresses. The development of a functional anchorage represents a fulfilment of the objectives laid out at the start of this project, and represents an important step towards the practical use of prestressed unbonded external CFRP tendons in strengthening concrete structures. However, a number of outstanding questions remain to be addressed. Little is known about the safety of this kind of system, and the benefits of using CFRP tendons should be quantified. Furthermore, there are a number of potential technical issues that must be addressed. These include the risk of creep-rupture in the CFRP, the effects of thermal contraction and expansion on the anchorage, and the scalability of the anchorage as the tendon diameter is increased. Finally, the long-term behaviour of the anchorage and prestressing system should be investigated.
I och med introduktionen av fiberkompositer i byggbranschen under slutet av 80-talet har en rad nya verktyg för förstärkning och underhåll av betongkonstruktioner utvecklats. Förstärkning har oftast utförts med pålimmade kompositer utan förspänning. För att ytterligare öka verkningsgraden, både den tekniska och ekonomiska, kan förspänning vara en möjlighet. Särskilt för betongkonstruktioner. Förspänning av en betongkonstruktion medför att man i bruksgränstillståndet begränsar uppkomsten av sprickor och deras storlek. Det ger i sin tur en ökad styvhet hos konstruktionen. Därutöver höjs lasten för när det slakarmerade stålet flyter. I jämförelse med ospända konstruktioner är dock brottlasten densamma, så länge övriga parametrar behålls. Under 2004 genomfördes en pilotstudie vid Luleå tekniska universitet (LTU) för att undersöka framtida möjligheter och utmaningar med förspända, icke vidhäftande kolfiberkompositkablar. I det läget upptäcktes svårigheter att förankra kompositkabeln mot betongen. De koniska killås som användes orsakade antingen brott på kabeln redan vid låga belastningar eller glidning hos kabeln, som omöjliggjorde fullgod kraftöverföring. Ett beslut togs då att tills vidare fokusera på förankringen och genomföra en mer ingående studie kring denna. Som mål sattes upp att arbetet skulle resultera i en liten, tillförlitlig och användarvänlig förankring. Den skulle sen i en förlängning kunna användas för att slutföra pilotstudien och därefter i större tillämpningar. Trots de förhållandevis nedslående resultaten från pilotförsöken visade den grundliga litteraturstudien som presenteras i Artikel 1 att koniska killås trots allt verkar vara den mest lovande typen av förankring för kolfiberkablar. Den bör därför användas som utgångspunkt för fortsatt utveckling. I motsats till vidhäftande, hyls och klämmande förankringar kan killåset göras litet, lätt att montera och också användas i många praktiska tillämpningar. För att undersöka hur de höga radiella tryckspänningarna i ett sådant killås fördelas är olika former av beräkningsmodeller nödvändiga verktyg. I Artikel 2 jämförs tre olika modeller med avseende på hur väl de kan beskriva komplexiteten hos ett koniskt killås. Det är dels en analytisk axisymmetrisk modell, som också härleds i artikeln, dels en axisymmetrisk Finita Element (FE) modell och dels en 3D FE modell. Undersökningen visade att ingen av de axisymmetriska modellerna har kapacitet nog att tillförlitligt modellera killåset. I fortsatta undersökningar har därför endast 3D FE använts. Resultaten från en enkel FE modell ligger också, tillsammans med tidiga laboratorieförsök, som grund för Artikel 3. Däri beskrivs hur ett nytt killås via prototyper och nya lösningar utvecklats, och hur arbetet för att få fram det nya låset också gett en bättre förståelse för interaktionen mellan kolfiberkompositkabel och lås. Som avslutning presenteras en innovativ design där de tre kilarna och den inre hylsan sammanfogats till en enhet. Med den nyutvecklade designen blir förankringen såväl mer tillförlitlig som användarvänlig. Alla kilar har då redan från början rätt position i förhållande till varandra. Den utvecklade förankringslösningen har också lett fram till ett beviljat svenskt patent, bifogat i avhandlingen som Artikel 6. Efter utvecklingen av den nya förankringen var nästa steg i de uppsatta målen implementering av densamma i ett förspänningssystem och nya balkförsök i konstruktionslabbet. Parallellt med planeringen för balkförsöken pågick ett arbete med att ytterligare förbättra låsdesignen. Bland annat användes en mer detaljerad FE modell som sedan jämfördes med mätningar från en ny serie med dragprov. Den nya FE modellen tillsammans med en utvärdering av viktiga parametrar och den slutliga förankringsdesignen presenteras i Artikel 4. Artikel 5 sammanfattar och avslutar forskningsstudien med en testserie om sju stycken, tre meter långa, betongbalkar förspända med utanpåliggande kolfiberkompositstavar. En av balkarna provades utan förstärkning. Förstärkningen hos de övriga varierades med avseende på förspänningsgrad, förspänningens effektiva höjd och användandet av deviator vid balkmitt. Resultaten har jämförts mellan de provade balkarna, med identiska balkar förspända med stålkablar samt med en analytisk modell utvecklad för förspänning med stålkablar. Från resultaten kan utläsas att förspänningen fungerar bra och att beteendet hos balkarna förspända med utanpåliggande kolfiberkablar är fullt jämförbart med det hos balkarna förspända med stålkablar. Likaså visar jämförelsen med de modellerade beteendena på god överensstämmelse, även om vissa skillnader finns mellan uppmätta och modellerade spänningar i kolfiberkabeln. Med målen för forskningen uppfyllda och en ny fungerande förankring framtagen så har vägen till praktiska tillämpningar kortats betydligt, ändå finns några frågetecken kvar att räta ut. Ett är säkerheten hos den här typen av system och nyttan av att använda kolfiberkomposit istället för stål. Innan systemet används i praktiken bör därför följande frågeställningar belysas: Risk för krypbrott i kolfiberarmeringen, inverkan av temperaturförändringar (och temperaturrörelser) i förankringen samt eventuella storlekseffekter vid förankring av kablar med större diametrar. De här frågorna tillsammans med långtidsförsök på förankringen och förspänningssystemet bör ses som viktiga framtida forskningsfrågor.
Godkänd; 2011; 20110128 (ysko); DISPUTATION Ämnesområde: Konstruktionsteknik/Structural Engineering Opponent: PhD Chris Burgoyne, Dep of Engineering, University of Cambridge, UK Ordförande: Professor Björn Täljsten, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Fredag den 18 februari 2011, kl 10.00 Plats: F1031, Luleå tekniska universitet

Prestressed concrete was introduced in the early part of the last century and has been used in a wide range of bridge structures. It is classified into two types; pre-tensioned and post-tensioned concrete (i .e. bonded and un-bonded post tensioned concrete). Both types have proved to be a durable and economical form of construction. However, many bonded post-tensioned concrete bridges have exhibited rupture of their tendons due to corrosion. In a few extreme cases this has led to structural collapse. While much of the effort has been focused on developing corrosion detection techniques, little attention has been paid to assessing the structural behaviour of bonded post-tensioned concrete bridges with ruptured tendons. A ruptured tendon is able to re-anchor into the surrounding materials and to contribute to the structural behaviour of the corroded structure. The tendon re-anchorage has been approximated in a number of structural assessment studies using pre-tensioned concrete models or empirical bond-slip relations. In some studies, reanchoring of the ruptured tendon is completely neglected. This is attributed to the lack of models regarding the tendon re-anchorage in post-tensioned concrete. The wrong estimation of the re-anchoring phenomenon of the ruptured tendon leads to an inaccurate prediction of the structural capacity of post-tensioned concrete structures after the rupture. The aim of this research is to predict the residual structural capacity of post-tensioned concrete beams with a ruptured tendon developing a re-anchorage model of the ruptured tendon.

Tendon injury is common in humans and horses, and incidence increases with age. The high-strain energy storing equine superficial digital flexor (SDFT) is injured more frequently than the low-strain positional common digital extensor (CDET). However, previous work indicated that matrix turnover is greater in the CDET than in the SDFT. It was hypothesised that matrix turnover is programmed by the cells’ strain environment; therefore high-strain energy storing tendons would have a lower rate of matrix turnover than low-strain positional tendons and the rate of matrix turnover would decrease with increasing age. The rate of matrix turnover was investigated by measuring the potential of the cells to synthesise and degrade matrix proteins, measuring the half-life of the collagenous and non-collagenous matrix proteins and assessing collagen turnover at the protein level. In vitro cell phenotype was also assessed in 2D and 3D culture and the effect of load on cells within native tissue was determined. The results show that turnover of collagenous and non-collagenous matrix proteins is differentially regulated in the functionally distinct SDFT and CDET. CDET tenocytes show greater potential for collagen turnover, whereas SDFT tenocytes have a greater potential for proteoglycan turnover; differences that are also present at the protein level. The differences in cell phenotype identified in vivo were lost in 2D and 3D culture, but tendon organ culture resulted in the maintenance of tenocyte phenotype. The cells’ ability to turnover the matrix does not decrease with increasing age, but collagen within the SDFT appears to become more resistant to degradation with ageing. This results in the accumulation of partially degraded collagen within the SDFT which may have a detrimental effect on tendon mechanical properties. These findings will help to elucidate the mechanisms behind the development of age-related tendinopathy and will be of use when developing treatment regimes.

A failure associated with steel corrosion was identified in early 2011 in a bridge external post-tensioned tendon, approximately eight years after construction. Large voids in the grout and pockets of non-homogeneous material were identified. The non-homogeneous grout was characterized by high moisture content, and in most cases, the chloride content was lower than conservative threshold values. The non-homogeneous grout also had high pH and high content of sulfates (approximately in the range of 10,000-ppm). As a result, there was an interest in the study of possible corrosion development in repaired systems in which the affected tendons have been re-grouted with dissimilar grouts. The presence of two distinct grouting materials, manifested by the existing/simulated base grout and a newly introduced repair grout, provided the dissimilar grout condition studied. Corrosion activity was monitored in un-stressed mock up assemblies, in sections retrieved from the failed tendon, and in samples immersed in simulated pore solution. Corrosion activity was monitored through macrocell current, linear polarization resistance, open circuit potential, potentiodynamic scans, and electrochemical impedance spectroscopy. Samples in simulated pore solutions were studied at various pH levels and constituent concentrations. All samples were repaired or built with commercially available grouts. After analysis, no evidence of corrosion development was found when both existing and repair grout were free of material deficiencies. Corrosion activity was noted in the presence of nonhomogeneous grout and an increase in rate was observed due to macrocell coupling with sections containing normal grout. Results suggest that early exposure to sulfate to hydroxyl ion ratio as low 0.35 may prevent steel passivation and result in early high corrosion rates. Otherwise, sulfate to hydroxyl ratios as high as three may not be sufficient to initiate corrosion after formation of passive layer.

Tendons and ligaments play key roles in the musculoskeletal system in both man and animals. Both tissues can often be injured as result of contact based accidents or ageing and disease, causing discomfort, pain and increased susceptibility to degenerative joint disease. To date, tendon and ligament biology is relatively under-studied in healthy, non-diseased tissues. This information is essential to understand the pathology of these tissues and vital for future development of tendon and ligament tissue-engineered structures. This thesis aims to investigate the molecular and cellular differences between tendons and ligaments around the canine stifle joint. The biochemical composition, structural, and morphological characteristics were identified between the different regions of the intra- articular cranial cruciate ligament (CCL) and extra-articular medial collateral ligament (MCL), and the positional long digital extensor tendon (LDET) and energy storing superficial digital flexor tendons (SDFT). Differences in proteome composition were also assessed between CCL and LDET. Cells isolated from canine CCL and LDET were cultured in a 3D in vitro fibrin culture model and measured for differences in structural, biochemical and proteome composition. Statistical significant differences in extracellular matrix (ECM) composition in terms of glycosaminoglycan (GAG) and elastin content were primarily detected in CCL in comparison to the other three tissues. The CCL was also found to have morphological differences including less compact collagen architecture, differences in cell nuclei phenotype, and increased (GAG) and elastin content. Proteomic comparison between CCL and LDET resulted in significantly abundant fibrocartilage proteins such as collagen type II, aggrecan, versican and chondroadherin in CCL, while the LDET was more abundant in asporin and thrombospondin-4. 3D tendon and ligament constructs were able to recapitulate tendon and ligamentous tissue characteristics particularly with regards to ECM proteins present, however both construct were less abundant in ECM protein and contained a greater proportion of cellular proteins, corresponding with low collagen and high level of DNA content measured in both constructs. 3D tendon and ligament constructs derived from tendon and ligament cells had similar ECM, proteomic and structural composition, indicating that cell source may not be an important factor for tendon or ligament tissue engineering.

Many bridges in the world are classified as deficient and in need of rehabilitation or replacement. Some of them are deficient because their load-carrying capacity is inadequate for today's increased traffic load. To improve their efficiency and increase their load capacity, several methods can be used, one of them is the external prestressing. Also, to avoid corrosion problem that faced this type of strengthening, Fibre Reinforced Plastics (FRP) can be used instead of steel tendons. Within the different types of FRP, Parafil rope was established to be well suited for prestressing system, combining the benefits of light-weight, high strength, easy handling and efficient anchorage system. Thirteen prestressed beams,one with internal prestressing steel only, and the rest strengthened externally using Parafil Ropes Type G were tested up to failure under two third point loading. Six factors were studied to investigate their effect on the behaviour of strengthened beams. These factors are the value of the external prestressing force and its eccentricity, deviator position, previous loading stage before strengthening, concrete strength and (span/depth) ratio. Also, analytical investigations were conducted to propose simple equations could be used in the analysis of this beam type, regarding its deflection and flexural strength with an acceptable accuracy. The study indicated that, external prestressing using Parafil rope is a very powerful system for strengthening or rehabilitation of prestressed concrete structures. Also, providing external prestressing force by a moderate amount improves the stiffness, and both cracking and ultimate flexural strength of prestressed concrete beams without significant reduction in ductility even for cracked beams. The modifications made to the methods used to calculate deflection and ultimate moment of bonded prestressed concrete, generalised these methods so, they can be used with beams have different types of prestressing tendons (bonded, internal unbonded, external unbonded or mixture of them). These methods, after modification, were found to give fairly accurate results. Also, the novel equation described the relation between the increase in the external prestressing force and the deflection makes the analysis of the externally strengthened beams under service loads,less complicated with a reasonable accuracy.

Due to their unique properties, fiber reinforced plastics (FRPs) can provide a possible alternative to steel because of their high strength-to-weight ratio and excellent resistance to electrochemical corrosion. Accelerated exposure tests to simulated field conditions were conducted on eleven different commercially available FRP rebars and tendons. In addition, long-term relaxation losses and fatigue characteristics of two carbon and one aramid FRP tendons were also examined. Test results showed durability problems associated with E-glass and AR-glass FRP rebars, and excellent durability exhibited by the carbon and aramid based tendons. Relaxation losses were higher in solutions than in air and they were limited to 12% for carbon and 18% for aramid tendons. Excellent fatigue characteristics were exhibited by carbon and aramid tendons up to stresses corresponding to 60% of their ultimate strength and stress range up to 10% of ultimate strength.

La caractérisation des propriétés intrinsèques du muscle a largement été développée sur fibre ou muscle isolé. L’avènement de l’échographie en temps réel a permis d’apprécier le comportement des faisceaux musculaires in vivo et de façon non-invasive. Les méthodes jusqu’à présent utilisées afin de caractériser les propriétés intrinsèques du muscle in vivo sont actuellement remises en question par la présence d’interactions muscle-tendon au cours de la contraction. De manière plus générale, la capacité du muscle à produire une vitesse maximale de mouvement reste peu étudiée et mal comprise dans la littérature. L’objectif de ce travail de thèse était d’évaluer les déterminants de la performance dans la production de mouvements explosifs à partir de l’échographie ultrarapide. Ce travail a été le premier à avoir rapporté une vitesse maximale de raccourcissement des faisceaux musculaires in vivo. La capacité d’un individu à produire une vitesse maximale articulaire élevée est principalement déterminée par la vitesse maximale de ses faisceaux musculaires. Malgré son influence probable, l’organisation musculo-articulaire ne semble pas nous aider à mieux appréhender la capacité à produire des vitesses de mouvement élevées. La contribution des tissus tendineux souligne l’importance des interactions muscle-tendon même lors de contractions concentriques maximales. De nouvelles connaissances sur les limites de la performance humaine ont été apportées par les différentes études menées au cours de cette thèse
The characterisation of muscular properties has been largely developed on both fiber and isolated muscle. The development of ultrasound devices has allowed to study the behaviour of the muscle fascicles in vivo and non-invasively. Nowadays the classical methods used to in vivo characterize the muscular properties are actually doubtful due to the observed muscle-tendon interactions during contractions. Globally, the muscle capacity to produce maximal shortening velocity remains unexplored and unclear. The present thesis aims to evaluate the determinants of performance in the production of explosive movements using ultrafast ultrasound. This thesis is the first work reporting the in vivo maximal shortening velocity of the fascicles. The human capacity to produce high articular velocities is mainly determined by the fascicles’ maximal shortening velocity. Despite its probable influence, the organization of musculararticular does not seem to help for a better understanding of the capacity to produce high movement velocities. The contribution of tendinous tissues highlights the importance of muscle-tendon interaction even during maximal concentric contractions. New insights about the limits of human performance were here introduced by the studies conducted during this thesis

Les travaux exposés dans cette thèse explorent les processus biologiques sous-tendant la formation des tendons et des tissus conjonctifs du système musculosquelettique. Comprendre les mécanismes de développement des tendons revêt une importance essentielle pour la santé publique, car les blessures tendineuses sont courantes et peuvent entraîner une invalidité significative, limitant la mobilité et la qualité de vie des individus. Les progrès dans ce domaine pourraient conduire à des avancées thérapeutiques permettant de traiter efficacement les lésions tendineuses et de favoriser leur guérison. Dans le cadre de cette recherche, une étude in vitro 3D a été menée pour évaluer les propriétés mécaniques et la signature moléculaire des constructions tendineuses humaines générées à partir de cellules souches adipeuses humaines enrobées dans une matrice de collagène de type I. L'analyse a révélé des changements dans les propriétés viscoélastiques des tissus, associés à une réorganisation de la matrice extracellulaire et à l'émergence de populations cellulaires distinctes, mettant en lumière l'importance de l'environnement tridimensionnel dans le développement tendineux. Une autre partie de cette étude a porté sur une approche in vivo utilisant des agents pharmacologiques pour moduler la contraction musculaire des embryons de poulet à E7 afin d'analyser les conséquences d'un traitement de 24 ou 48h sur le développement du système musculo-squelettique et des tissus conjonctifs associés. L'analyse transcriptomique de membres entiers des embryons traités ou non a révélé des modifications dans l'expression de gènes marqueurs des tendons, du cartilage et du tissu conjonctif associé au muscle, soulignant le rôle crucial de la contraction musculaire dans le développement des tissus conjonctifs au sens large. Cette analyse nous a également permis d'identifier de nouveaux gènes impliqués dans le développement des tendons. Enfin, une étude in vitro 2D a été réalisée pour tester la viabilité des cellules souches adipeuses humaines sur différents types de supports (scaffolds) et d'analyser la différenciation des cellules souches adipeuses humaines en ténocytes. Ces résultats offrent de nouvelles perspectives pour la recherche sur le développement du tendon. En combinant ces approches complémentaires, cette thèse vise à approfondir notre compréhension des processus biologiques régissant la formation des tendons et à développer des stratégies thérapeutiques innovantes pour traiter les lésions tendineuses
The work presented in this thesis explores the biological processes underlying the formation of tendons and connective tissues of the musculoskeletal system. Understanding the developmental mechanisms of tendons is of paramount importance for public health, as tendon injuries are common and can lead to significant disability, limiting individuals mobility and quality of life. Progress in this field could lead to therapeutic advances enabling the effective treatment of tendon injuries and promoting their healing. As part of this research, a 3D in vitro study was conducted to evaluate the mechanical properties and molecular signature of human tendon constructs generated from human adipose stem cells encapsulated in a type I collagen matrix. The analysis revealed changes in the viscoelastic properties of the tissues, associated with a reorganization of the extracellular matrix and the emergence of distinct cellular populations, highlighting the importance of the three-dimensional environment in tendon development. Another aspect of this study focused on an in vivo approach using pharmacological agents to modulate muscle contraction in chicken embryos at E7 to analyze the consequences of 24 or 48-hour treatment on the development of the musculoskeletal system and associated connective tissues. Transcriptomic analysis of treated or untreated embryonic limbs revealed modifications in the expression of genes marking tendons, cartilage, and connective tissue associated with muscle, underscoring the crucial role of muscle contraction in the development of connective tissues at large. This analysis also enabled the identification of new genes involved in tendon development. Finally, a 2D in vitro study was conducted to test the viability of human adipose stem cells on different types of scaffolds and to analyze the differentiation of human adipose stem cells into tenocytes. These results offer new perspectives for tendon development research. By combining these complementary approaches, this thesis aims to deepen our understanding of the biological processes governing tendon formation and to develop innovative therapeutic strategies for treating tendon injuries