Morphological and molecular characterization of human hamstrings shows that tendon features are not influenced by donor age

PURPOSE

Age-related modifications of tendons, such as reduced tenocyte proliferation and modified extracellular matrix (ECM) turnover, have been previously described, but results are often incomplete and discordant. The aim of this study was to investigate, using morphological and molecular methods, the effect of ageing on human tendons and tenocytes, especially focusing on the collagen turnover pathways, in order to understand how the ageing process could influence tendon biology and structure.

METHODS

Morphological analysis was performed on fragments from human semitendinosus and gracilis tendons harvested from 10 adult (mean age 41.8 ± 13.3 years) and 6 aged healthy patients (mean age 72.7 ± 7.0 years) by haematoxylin and eosin, Sirius red and Alcian blue staining. The expression of genes and proteins involved in collagen turnover and focal adhesions was assessed by real-time PCR, slot blot and zymography in cultured tenocytes. Cytoskeleton arrangement was studied by immunofluorescence and cell migration by wound healing assay.

RESULTS

The structure and composition of ECM in ageing tendons are preserved as well as the expression of genes and proteins involved in collagen turnover pathways. Although morphological analysis revealed that ageing tenocytes tended to an impaired migration potential and that actin filaments are occasionally shorter and randomly distributed, the expression of proteins involved in focal adhesion formation is preserved.

CONCLUSION

Results of this study suggest that the structure of ageing tendons is preserved and that ageing tenocytes maintain their ability for ECM remodelling, supporting the hypothesis that ageing tendons maintain their biomechanical properties. The biological reliability of aged tendons has a clinical relevance, supporting the use of tendon autografts also in the elderly patients. Since the common and successful orthopaedic procedure of anterior cruciate ligament reconstruction using either autografts or allografts is becoming more common in older age groups, these findings suggest that the donor age would not significantly influence the clinical outcome.

Correlation Between Femoroacetabular Impingement and Hamstring Tendon Pathology on Magnetic Resonance Imaging and Arthrography

Femoroacetabular impingement (FAI) is an abnormality of the femoral head or acetabulum that leads to an increased incidence of cartilaginous injury in the hip. Femoroacetabular impingement has been associated with several structural abnormalities, including osteitis pubis and hip flexor dysfunction. The authors propose that, additionally, FAI may lead to increased damage of the hamstring tendon due to the additional stress placed on the tendon from the limited range of motion of the hip. The authors conducted a retrospective matched-pair study with the magnetic resonance imaging and magnetic resonance arthrography images of 40 patients' hamstrings with FAI and 45 age-matched controls. Images were identified and reviewed by 2 musculoskeletal radiologists for various signs of hamstring tendon pathology. Fisher's exact test and an odds ratio were used to assess for a difference in the occurrence of hamstring tendon pathology in the FAI patient cohort compared with the age-matched controls. The results showed a statistically significant increase in the occurrence of hamstring tendon pathology in the FAI patient cohort compared with the age-matched controls (P<.001). The odds ratio for hamstring tendon pathology in a subject with confirmed FAI vs control subjects was 8.30 (95% confidence interval, 3.20-21.5), indicating a significant increase in the risk of developing hamstring tendon pathology among patients with FAI (P<.001). This study suggests that there may be an increased occurrence of hamstring tendon pathology in patients with FAI. The kinetic chain of motion, where restricted rotation at the hip joint increases the stress on the hamstring tendons, leading to damage, may explain this increase. [Orthopedics. 2017; 40(6):e1086-e1091.].