Introduction: Rotator cuff tears are a common injury which affects both the young athlete and the sedentary elderly alike. This condition is commonly treated with glucocorticoid injections as part of initial management. The effects, however, of these injections on the histology of collagen and the metabolism of tendon fibroblasts are still controversial.

Materials and methods: In this study, samples from 19 patients with rotator cuff tears were taken during definitive surgery to manage these tears. There was a history of glucocorticoid injections in all of the patients. The samples were examined in terms of histopathology using light microscopy, in situ hybridization to detect the presence of glucocorticoid receptor mRNA and TUNEL assay to determine the incidence of apoptosis.

Results: Light microscopy of hematoxylin-eosin stained samples from the study group showed marked cellularity although there were no signs of inflammation. The nuclei were noted to be rounded and a significant number showed pyknosis. Angiogenesis was also noted in the sections, consistent with previous finding of angio-fibroblastic hyperplasia as a characteristic of tendinosis. Collagen structure was noted to be abnormal, with longitudinal clefts and focal areas of marked disorganization of fibers. In situ hybridization showed a strong signal for glucocorticoid receptor mRNA in all of the samples. TUNEL assay also showed a strong signal for apoptosis of the tendon fibroblasts in the study group as compared to the control group which showed almost no signal.

Conclusion: Our results suggest that although an overall picture of hypercellularity is seen in cases of tendinosis and tendon tears, a high percentage of these cells are undergoing apoptosis. This may reflect a natural high rate of turnover of cells during the process of repair or may be due to exogenous factors. Glucocorticoids almost certainly affect metabolism of tendon fibroblasts and subsequently collagen structure as seen by the abundant expression of the receptor mRNA. However, a causal relationship between glucocorticoids and apoptosis of tenocytes is yet to be established.