Structure-function specialisation of the interfascicular matrix in the human achilles tendon.
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ABSTRACT:
SUBMITTER: Patel D
PROVIDER: S-EPMC8388240 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Tendon is a highly aligned connective tissue, in which the macro-structure consists of collagen-rich fascicles surrounded by interfascicular matrix (IFM). In a series of recent studies in equine tissue, we have demonstrated specialisation of tendon composition, structure and mechanics to achieve the tendon’s functional requirements, specifically reporting extensive specialisation of the IFM region in the energy storing superficial digital flexor tendon. We have also demonstrated loss of functional specialisms with ageing, leading to a hypothesised new paradigm for tendinopathy, focused on the importance of the IFM. However, to date, there have been no studies focused on structure-function specialisation or the IFM in functionally distinct human tendons. Here, we compare the positional anterior tibialis tendon and energy storing Achilles tendon, performing a detailed analysis of the composition and mechanical properties of both fascicle and IFM regions, to test the hypothesis that the IFM in the energy storing Achilles tendon has specialised composition and mechanical properties, and that these specialisations are lost with ageing. We demonstrate that the IFM is specialised in the energy storing Achilles tendon, with greater elasticity and fatigue resistance than in the positional anterior tibialis tendon. While there were few age-related alterations in mechanics, we did identify age-related alterations in the IFM proteome of the Achilles tendon specifically, which is predicted to be regulated by TGF-beta signalling and may be responsible for the trend towards decreased fatigue resistance observed in the Achilles IFM with ageing.
2020-11-11 | PXD018212 | Pride
Project description:The tendon interfascicular matrix (IFM) binds tendon fascicles together. As a result of its low stiffness behaviour under small loads, it enables non-uniform loading and increased overall extensibility of tendon by facilitating fascicle sliding. This function is particularly important in energy storing tendons, with previous studies demonstrating enhanced extensibility, recovery and fatigue resistance in the IFM of energy storing compared to positional tendons. However, the compositional specialisations within the IFM that confer this behaviour remain to be elucidated. It is well established that the IFM is rich in elastin, therefore we sought to test the hypothesis that elastin depletion (following elastase treatment) will significantly impact IFM, but not fascicle, mechanical properties, reducing IFM resilience in all samples, but to a greater extent in younger tendons, which have a higher elastin content. Using a combination of quasi-static and fatigue testing, and optical imaging, we confirmed our hypothesis, demonstrating that elastin depletion resulted in significant decreases in IFM viscoelasticity, fatigue resistance and recoverability compared to untreated samples, with no significant changes to fascicle mechanics. Ageing had little effect on fascicle or IFM response to elastase treatment. This study offers a first insight into the functional importance of elastin in regional specific tendon mechanics. It highlights the important contribution of elastin to IFM mechanical properties, demonstrating that maintenance of a functional elastin network within the IFM is essential to maintain IFM and thus tendon integrity. STATEMENT OF SIGNIFICANCE: Developing effective treatments or preventative measures for musculoskeletal tissue injuries necessitates the understanding of healthy tissue function and mechanics. By establishing the contribution of specific proteins to tissue mechanical behaviour, key targets for therapeutics can be identified. Tendon injury is increasingly prevalent and chronically debilitating, with no effective treatments available. Here, we investigate how elastin modulates tendon mechanical behaviour, using enzymatic digestion combined with local mechanical characterisation, and demonstrate for the first time that removing elastin from tendon affects the mechanical properties of the interfascicular matrix specifically, resulting in decreased recoverability and fatigue resistance. These findings provide a new level of insight into tendon hierarchical mechanics, important for directing development of novel therapeutics for tendon injury.
| S-EPMC7935645 | biostudies-literature
Project description:The Achilles tendon exhibits anatomical variations in subtendon twist among individuals, and its compliance can change due to conditions like Achilles tendinopathy. However, current musculoskeletal models overlook these material and morphological variations. This study aimed to investigate the impact of altering Achilles subtendon insertion points and compliance on the triceps surae muscle forces, and therefore tendon loading, during dynamic exercises in one Achilles tendinopathy patient. First, subtendon insertion points were altered in the musculoskeletal model based on a subject-specific 3D freehand ultrasound model and for three types of subtendon twists: low, medium, and high. Second, tendon compliance was modeled based on experimental values, creating three musculoskeletal models: compliant, mean, and stiff. Results indicated that tendon compliance had a larger effect than tendon twist on triceps surae muscle forces. Altering subtendon insertion points to the three types of twist showed a maximal change of 2.3% in muscle force contribution compared to the no-twist model. During the eccentric rehabilitation exercise-a common exercise choice during rehabilitation-the compliant tendon model showed substantial differences compared to the generic (control) musculoskeletal model, resulting in decreased gastrocnemius medialis (-3.5%) and gastrocnemius lateralis (-3.2%) contributions and increased soleus contribution (+ 6.6%). Our study results highlight the necessity of incorporating tendon compliance in musculoskeletal models to accurately predict triceps surae muscle forces, especially in individuals with increased tendon compliance, such as patients with Achilles tendinopathy. Such findings contribute to more accurate predictions of muscle forces and hence, personalized rehabilitation strategies.
| S-EPMC11291231 | biostudies-literature
Project description:Tendon is a simple aligned fibre composite, consisting of collagen-rich fascicles surrounded by a softer interfascicular matrix (IFM). The composition and interactions between these material phases are fundamental in ensuring tissue mechanics meet functional requirements. However the IFM is poorly defined, therefore tendon structure-function relationships are incompletely understood. We hypothesised that the IFM has a more complex proteome, with faster turnover than the fascicular matrix (FM). Using laser-capture microdissection and mass spectrometry, we demonstrate that the IFM contains more proteins, and that many proteins show differential abundance between matrix phases. The IFM contained more protein fragments (neopeptides), indicating greater matrix degradation in this compartment, which may act to maintain healthy tendon structure. Protein abundance did not alter with ageing, but neopeptide numbers decreased in the aged IFM, indicating decreased turnover which may contribute to age-related tendon injury. These data provide important insights into how differences in tendon composition and turnover contribute to tendon structure-function relationships and the effects of ageing.
| S-EPMC4740843 | biostudies-literature
Project description:Cultivation of autologous human tenocytes in a cell-free xenogenic extracellular tendon matrix (xECM) could present an approach for tendon reconstruction. The aim of this study was to achieve tendon-like tissue formation by implanting decellularized porcine Achilles tendons recellularized with human hamstring tendon-derived tenocytes into nude mice. The structure of decellularized xECM was histologically monitored before being dynamically reseeded with human tenocytes. After 6?12 weeks in vivo, construct quality was monitored using macroscopical and histological scoring systems, vitality assay and quantitative DNA and glycosaminoglycan (GAG) assays. For comparison to tendon xECM, a synthetic polyglycolic acid (PGA) polymer was implanted in a similar manner. Despite decellularized xECM lost some GAGs and structure, it could be recellularized in vitro with human tenocytes, but the cell distribution remained inhomogeneous, with accumulations at the margins of the constructs. In vivo, the xECM constructs revealed in contrast to the PGA no altered size, no inflammation and encapsulation and a more homogeneous cell distribution. xECM reseeded with tenocytes showed superior histological quality than cell-free implanted constructs and contained surviving human cells. Their DNA content after six and 12 weeks in vivo resembled that of native tendon and xECM recellularized in vitro. Results suggest that reseeded decellularized xECM formed a tendon-like tissue in vivo.
| S-EPMC6073795 | biostudies-literature
Project description:Tendons play a critical role in the transmission of forces between muscles and bones, and chronic tendon injuries and diseases are among the leading causes of musculoskeletal disability. For many types of tendinopathies, women have worse clinical outcomes than men. It is possible that sex-based differences in tendon morphology, composition and mechanical properties may explain the greater susceptibility of women to develop tendinopathies. Our objective was to evaluate the mechanical properties, biochemical composition, transcriptome, and cellular activity of plantarflexor tendons from four month old male and female C57Bl/6 mice using in vitro biomechanics, mass spectrometry-based proteomics, genome-wide expression profiling, and cell culture techniques. Differences between groups were tested using t-tests (α=0.05). While the Achilles tendons of male mice were approximately 6% larger than female mice (P<0.05), the cell density of female mice was around 19% larger than males (P<0.05). No significant differences in the length (P=0.34), peak force (P=0.86), peak stress (P=0.52) or energy loss during stretch (P=0.94) of plantaris tendons were observed. Mass spectrometry proteomics analysis revealed no significant difference between sexes in the abundance of major extracellular matrix (ECM) proteins like collagen types I (P=0.30) and III (P=0.68), but female mice had approximately two-fold elevations (P<0.05) in different minor ECM proteins such as fibronectin, periostin, and tenascin. Using microarray analysis, there was no significant differences (P>0.05) in the expression of most major and minor ECM genes, and in the expression of genes involved in tendon fibroblast specification or proliferation. Whole tendon qPCR analysis showed significant expression differences in elastin, scleraxis, and tenomodulin. Cell culture techniques to test the effects of sex-specific extracellular environment on cellular activity show significant differences in gene expression of type I and III collagen, Ki67, scleraxis, and tenomodulin. Histologic analysis demonstrated that males have larger tendon cross-sectional area and lower cell density when compared to females. However, there were no differences between the sexes in the mechanical properties of tendons or in the majority of primary structural extracellular matrix proteins, although elevations were observed in some minor ECM proteins. Microarray analysis also showed no significant sex-based differences in the expression of major genes associated with collagen composition, extracellular components and turnover, and fibroblast proliferation. Cell culture tests of non-autonomous cellular activity show no major signals for ECM synthesis nor fibroblast proliferation. Our results indicate that while male mice expectedly had larger tendons, male and female mice have very similar mechanical properties and biochemical composition, with small increases in minor ECM proteins and proteoglycans in female tendons. The role that these minor ECM proteins and proteoglycans play in tendon repair should be evaluated in future studies. No treatment administered, study done to evaluate normal expression profiles of male and female tenocytes. This analysis is based on a Mouse Gene ST 2.1 strip that was processed in the microarray facility in May 2015 using the wt-pico kit.
2016-08-11 | E-GEOD-85415 | biostudies-arrayexpress
Project description:INTRODUCTION:The risk of tendon injury and disease increases significantly with increasing age. The aim of the study was to characterise transcriptional changes in human Achilles tendon during the ageing process in order to identify molecular signatures that might contribute to age-related degeneration. METHODS:RNA for gene expression analysis using RNA-Seq and quantitative real-time polymerase chain reaction analysis was isolated from young and old macroscopically normal human Achilles tendon. RNA sequence libraries were prepared following ribosomal RNA depletion, and sequencing was undertaken by using the Illumina HiSeq 2000 platform. Expression levels among genes were compared by using fragments per kilobase of exon per million fragments mapped. Differentially expressed genes were defined by using Benjamini-Hochberg false discovery rate approach (P<0.05, expression ratios 1.4 log2 fold change). Alternative splicing of exon variants were also examined by using Cufflinks. The functional significance of genes that showed differential expression between young and old tendon was determined by using ingenuity pathway analysis. RESULTS:In total, the expression of 325 transcribed elements, including protein-coding transcripts and non-coding transcripts (small non-coding RNAs, pseudogenes, long non-coding RNAs and a single microRNA), was significantly different in old compared with young tendon (±1.4 log2 fold change, P<0.05). Of these, 191 were at higher levels in older tendon and 134 were at lower levels in older tendon. The top networks for genes differentially expressed with tendon age were from cellular function, cellular growth, and cellular cycling pathways. Notable differential transcriptome changes were also observed in alternative splicing patterns. Several of the top gene ontology terms identified in downregulated isoforms in old tendon related to collagen and post-translational modification of collagen. CONCLUSIONS:This study demonstrates dynamic alterations in RNA with age at numerous genomic levels, indicating changes in the regulation of transcriptional networks. The results suggest that ageing is not primarily associated with loss of ability to synthesise matrix proteins and matrix-degrading enzymes. In addition, we have identified non-coding RNA genes and differentially expressed transcript isoforms of known matrix components with ageing which require further investigation.
| S-EPMC4355574 | biostudies-literature
Project description:In the treatment of acute Achilles tendon rupture, recent studies demonstrate that conservative treatment with functional rehabilitation provides good results, with nearly identical postoperative rerupture rates when compared with surgical treatment. Surgical treatment is indicated in patients with particular conditions, such as patients who are young active athletes who require early return to play or those who wish to avoid the muscle atrophy associated with conservative methods. If surgery is the selected option for treatment, the postoperative complications of each type of surgery must be considered. In conventional open repair, the most common complication is soft-tissue infection due to the high tension of soft tissue affected from the bowstring of the repaired tendon being kept in the equinus position of the ankle. For percutaneous methods, sural nerve entrapment and injury are the most commonly reported complications. Other methods, including endoscopy, require technical expertise as well as special equipment. Several types of combination approaches have been explored in the literature. We describe a combined open and percutaneous technique to repair the Achilles tendon, called the hybrid Achilles tendon repair. This technique has been developed to provide a simplified and reproducible method of hybrid repair in which the complications of previous methods are avoided and which can be done without special equipment.
| S-EPMC6019910 | biostudies-literature
Project description:A balance between matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) is required to maintain tendon homeostasis. Variation in this balance over time might impact on the success of tendon healing. This study aimed to analyze structural changes and the expression profile of MMPs and TIMPs in human Achilles tendons at different time-points after rupture. Biopsies from 37 patients with acute Achilles tendon rupture were taken at surgery and grouped according to time after rupture: early (2-4 days), middle (5-6 days), and late (?7 days), and intact Achilles tendons served as control. The histological score increased from the early to the late time-point after rupture, indicating the progression towards a more degenerative status. In comparison to intact tendons, qRT-PCR analysis revealed a significantly increased expression of MMP-1, -2, -13, TIMP-1, COL1A1, and COL3A1 in ruptured tendons, whereas TIMP-3 decreased. Comparing the changes over time post rupture, the expression of MMP-9, -13, and COL1A1 significantly increased, whereas MMP-3 and -10 expression decreased. TIMP expression was not significantly altered over time. MMP staining by immunohistochemistry was positive in the ruptured tendons exemplarily analyzed from early and late time-points. The study demonstrates a pivotal contribution of all investigated MMPs and TIMP-1, but a minor role of TIMP-2, -3, and -4, in the early human tendon healing process.
| S-EPMC5666880 | biostudies-literature
Project description:PurposeTo evaluate differences of Achilles tendon (AT) hardness and morphology between asymptomatic tendons in patients with acute AT ruptures on the contralateral side and asymptomatic tendons in healthy people by using computer-assisted quantification on axial-strain sonoelastography (ASE).MethodsThe study consisted of 33 asymptomatic tendons in 33 patients (study group) and 34 tendons in 19 healthy volunteers (control group). All the tendons were examined by both ASE and conventional ultrasound. Computer-assisted quantification on ASE was applied to extract hardness variables, including the mean (Hmean), 20th percentile (H20), median (H50) and skewness (Hsk) of the hardness within tendon, and the ratio of the mean hardness within tendon to that outside tendon (Hratio) and three morphological variables: the thickness (THK), cross-sectional area, and eccentricity (ECC) of tendons.ResultsThe Hmean, Hsk, H20, H50, and Hratio in the proximal third of the tendon body in study group were significantly smaller than those in control group (Hmean: 0.43±0.09 vs 0.50±0.07, p=0.001; Hsk: -0.53±0.51 vs -1.09±0.51, p<0.001; H20: 0.31±0.10 vs 0.40±0.10, p=0.001; H50: 0.45±0.10 vs 0.53±0.08, p<0.001; Hratio: 1.01±0.25 vs 1.20±0.23, p=0.003). The THK and cross-sectional area of tendons in the study group were larger than those in the control group (p<0.05).ConclusionsAs a quantitative objective method, the computer-assisted ASE reveals that the asymptomatic ATs contralateral to acute rupture are softer than those of healthy control group at the proximal third and the asymptomatic tendons in people with rupture history are thicker, larger, and rounder than those of normal volunteers especially at the middle and distal thirds of AT body.
| S-EPMC6304598 | biostudies-literature