Abstract
Symptomatic tendinopathy tends to be age‐related. However, the molecular mechanisms of ageing and its effects on tenocyte proliferation and cell cycle progression are unknown. We examined tenocytes from Achilles tendons in rats from three age groups (young, 2 months; middle‐aged, 12 months, and near senescence, 24 months). Tenocyte proliferation was assessed by 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide (MTT) assay and flow cytometry. Senescence‐associated β‐galactosidase (SA β‐gal) staining was performed in all groups of tenocytes. mRNA and protein expression of cellular senescence‐inhibited gene (CSIG) and p27 was measured by reverse transcription‐polymerase chain reaction (RT‐PCR) and Western blot, respectively. The results of MTT assay revealed that tenocyte proliferation decreased with age (p < 0.05). Cell cycle progression was arrested at G0/G1 phase in senescent tenocytes. More senescent tenocytes expressed SA β‐gal than young tenocytes did. By RT‐PCR and Western blot analysis, the gene and protein expression of CSIG was found to be down‐regulated, whereas that of p27 was up‐regulated with age. In conclusion, the proliferation of tenocytes declines with age and is associated with the down‐regulation of CSIG and up‐regulation of p27. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29: 1598–1603, 2011