Tendon lesions are among the most frequent musculoskeletal pathologies. Vascular endothelial growth factor (VEGF) is known to regulate angiogenesis. VEGF-111, a biologically active and proteolysis-resistant splice variant of this family, was recently identified. This study aimed at evaluating whether VEGF-111 could have a therapeutic interest in tendon pathologies. Surgical section of one Achilles tendon of rats was performed before a local injection of either saline or VEGF-111. After 5, 15 and 30 days, the Achilles tendons of 10 rats of both groups were sampled and submitted to a biomechanical tensile test. The force necessary to induce tendon rupture was greater for tendons of the VEGF-111 group (p<0.05) while the section areas of the tendons were similar. The mechanical stress was similar at 5 and 15 days in the both groups but was improved for the VEGF-111 group at day 30 (p <0.001). No difference was observed in the mRNA expression of collagen III, tenomodulin and MMP-9. In conclusion, we observed that a local injection of VEGF-111 improves the early phases of the healing process of rat tendons after a surgical section. Further confirmatory experimentations are needed to consolidate our results.

Platelet-rich plasma (PRP) contains growth factors involved in the tissular healing process. The aim of the study was to determine if an injection of PRP could improve the healing of sectioned Achilles tendons of rats. After surgery, rats received an injection of PRP (n = 60) or a physiological solution (n = 60) in situ. After 5, 15, and 30 days, 20 rats of both groups were euthanized and 15 collected tendons were submitted to a biomechanical test using cryo-jaws before performing transcriptomic analyses. Histological and biochemical analyses were performed on the five remaining tendons in each group. Tendons in the PRP group were more resistant to rupture at 15 and 30 days. The mechanical stress was significantly increased in tendons of the PRP group at day 30. Histological analysis showed a precocious deposition of fibrillar collagen at day 5 confirmed by a biochemical measurement. The expression of tenomodulin was significantly higher at day 5. The messenger RNA levels of type III collagen, matrix metalloproteinases 2, 3, and 9, were similar in the two groups at all time points, whereas type I collagen was significantly increased at day 30 in the PRP group. In conclusion, an injection of PRP in sectioned rat Achilles tendon influences the early phase of tendon healing and results in an ultimately stronger mechanical resistance.

Introduction The tendon is a tissue which does not heal easily. Recently, several studies have demonstrated the positive effects of platelets on the healing process of tendons. A local injection of platelet-rich plasma (PRP), which releases in situ many growth factors, has the potentiality to enhance the tendon healing process. The aim of our experiment was to ascertain by an original mechanical measure whether the use of PRP was of interest for accelerating the healing process of rats' Achilles tendons after surgical induced lesion. Methods A 5 mm defect was surgically induced in 90 rats' Achilles tendon. Rats were divided into two groups of 45: (A) control (no treatment) and (B) PRP treatment. Rats of group B received a PRP injection in situ after the surgery. Afterwards, rats of both groups were placed in their cages without immobilisation. After 5, 15 and 30 days, 10 traumatised Achilles tendons of each group were dissected and removed. Immediately after sampling, tendons were submitted to a biomechanical tensile test up to rupture, using a ‘Cryo-jaw’. After that, transcriptomic analyses were made on the tendon samples, to study the expression of type III collagen, matrix metalloproteases and tenomodulin. A hydroxyproline dosage was done to quantify the collagen in the tendon during its healing process. Tendons of the 15 remaining rats of each group were subjected to a histological study, respectively at day 5, 15 and 30 (five rats for each time). Results We demonstrated that the force necessary to induce tendon rupture during biomechanical tensile test study was greater for tendons which had been submitted to an injection of PRP compared to the control group: +19% (day 5), +30% (day 15) and +43% (day 30). Histological study showed that PRP could enhance cells proliferation, angiogenesis and collagen organisation. Our biochemical analyses did not explain beneficial effects of PRP. Indeed, there was no significant difference neither between the expression of different studied genes, nor in the quantity of hydroxyproline between both groups. Conclusion This experimentation has shown that a PRP injection could accelerate the tendons healing process and improve its quality.

Excessive biomechanical stresses are commonly believed to be important in the pathogenesis of various osteoarticular disorders. In order to explain better the relation between equine digital morphometric parameters and biomechanical stresses, a sensitivity analysis has been performed to compare individual effect of each equine digital morphometric parameter on kinetics.

For decades, incompressibility has been a major assumption in the mechanical study of brain tissue. This assumption is based on the hydrated nature of the biological tissues and the incompressibility of fluids. In this paper, an experimental validation of this assumption using digital image correlation is presented. Unconfined compression tests, relaxation tests and cyclic tests were performed on cylindrical samples of swine brains at loading rates suitable for neurosurgical applications. Digital image correlation was used to evaluate the evolution of the volume ratio throughout the tests. The preparation of the samples is described and it is demonstrated that it causes no statistically significant change of their mechanical properties. The results indicate that the brain tissue incompressibility assumption is verified.

nal areas are composed of cells that present fibroblast-like morphology and phenotype. Interestingly, there is no expression of type II collagen throughout the whole young meniscus. In the adult meniscus, however, the three analyzed areas did not show the differences in cell morphology noted for the young tissue: all cell populations showed an intermediate morphology between chondrocytes and fibroblasts. Moreover, all cell populations were positive for type II and type I collagen presenting a gradient of type II versus type I: from the inner to the outer area, type II collagen decreases while type I increases. Conclusions: These results lead to the conclusion that meniscus maturation, from young to adult, is accompanied by changes in cell phenotype; in the early stages of life the cells from the intermediate and outer part are still immature and far from a chondocyte-like phenotype; in adult life all meniscus cells assume a mature and specialized phenotype: cells of the external area maintain a fibroblasts-like phenotype, while cells of the intermediate and inner meniscus develop a chondrocyte-like phenotype.