Matrix metalloproteinase-1 and matrix metalloproteinase-9 are highly expressed in the joint capsule of diabetic frozen shoulder.

The pathophysiology of frozen shoulder (FS) involves abnormal expressions of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) that lead to capsular fibrosis. However, there has been little concern for why diabetic FS has more protracted fibrotic condition. The objective of this study was to compare the expression levels of MMPs and TIMPs in the joint capsule of patients with diabetic and nondiabetic FS. Samples of capsular tissue were collected from 20 patients with FS (10 diabetic patients; diabetic group and 10 nondiabetic patients; nondiabetic group) and 10 patients (control group) with chronic anterior shoulder instability. Quantitative real-time reverse transcriptase-polymerase chain reaction and Western blot analysis were performed to determine the expression levels of mRNA and protein for MMP-1, 3, 9, 13, 14, and TIMP-1, 2. The results of quantitative real-time reverse transcriptase-polymerase chain reaction showed significantly higher expression levels of all MMPs and TIMP-1 and significantly lower expression levels of TIMP-2 in the joint capsule of patients in the diabetic or nondiabetic groups compared with the control group. Significantly higher expression levels of MMP-1, 9, 14, and TIMP-1 were detected in the diabetic group compared with the nondiabetic group. The results of Western blot analysis showed significantly higher levels of MMP-3, 13, 14, and TIMP-1 in the joint capsule of patients in the diabetic or nondiabetic groups compared with the control group. However, no significant differences of protein levels of them were observed between diabetic and nondiabetic groups. The findings of this study demonstrate the potential involvement of MMP-1 and 9 in the pathophysiology of diabetic FS. These findings may be helpful in identification of therapeutic targets for development of novel treatments for this protracted chronic fibrosing condition. [ABSTRACT FROM AUTHOR]