It is reported that transforming growth factor beta1 (TGF-beta1) has the protective effects on the articular cartilage in osteoarthritis (OA). To investigate the significance of the expressions of matrix metalloproteinase 9 (MMP-9), TGF-beta1 mRNA and corresponding proteins in OA.
The specimens of articular cartilage and synovium were collected from voluntary donators, including 60 cases of OA (experimental group) and 20 cases of traumatic amputation, cruciate ligament rupture, discoid cartilage injury, and menisci injury (normal control group). The pathological changes were observed by HE staining. MMP-9 and TGF-beta1 protein expressions were detected by immunohistochemical technique, and the mRNA expressions of MMP-9 and TGF-beta1 were detected through in situ hybridization technique; and their correlation was analysed.
HE staining showed: shrinkage, necrosis, and irregular arrange of the articular chondrocytes, extracellular matrix fracture, hypertrophy and hyperplasia synovium, infiltration of lymphoid and mononuclear cells and proliferation of many small blood vessels in the experimental group; regular arrangement of the articular chondrocytes, the homogeneously staining matrix, and synovial tissue without chronic inflammation and significant proliferation in the normal control group. The mRNA and protein expressions of MMP-9 and TGF-beta1 were positive in 2 groups. The positive-stained cells included chondrocytes, synovial lining cells, and vascular endothelial cells, fibroblasts, and inflammatory infiltrated cells in subsynovial layer. The expressions of mRNA and corresponding protein of MMP-9 and TGF-beta1 in the experimental group were significantly higher than those in the normal control group (P < 0.01). There was a positive correlation between MMP-9 mRNA and protein expression (r = 0.924, P = 0.000), and between TGF-beta1 mRNA and protein expression (r = 0.941, P = 0.000) in the experimental group. There was a negative correlation between the expression of MMP-9 protein and TGF-beta1 protein (r = 0.762, P = 0.000), and between the expression of MMP-9 mRNA and TGF-beta1 mRNA (r = -0.681, P = 0.000) in the experimental group.
The higher expression of TGF-beta1 can protect articular cartilage by down-regulating the expression of MMP-9 of chondrocytes and synoviocytes in OA, which may delay the biological behavior of OA such as occurrence and progress, etc.