Hedgehog signal expression in articular cartilage of rat temporomandibular joint and association with adjuvant‐induced osteoarthritis

Objective The aim of this study was to investigate the changes in hedgehog (Hh) expression and its possible effects on cartilage degeneration in adjuvant-induced temporomandibular joint osteoarthritis (TMJOA) of rats. Methods Forty-eight male Sprague–Dawley rats were randomly divided into experimental osteoarthritis (OA) and sham control groups. The bilateral TMJs of six rats from each group were harvested at three, seven, 14, and 28 days. Histological changes in condylar cartilage were assessed by hematoxylin and eosin, toluidine blue, and safranin O staining. The expression of Hh signal-related proteins including Indian hedgehog (Ihh), patched-1 (Ptch1), smoothened (Smo), glioma-associated oncogene homologue1 (Gli1) in cartilage was assessed by immunohistochemistry and Western blot. The protein expression of matrix metalloproteinase-13 (MMP-13), type X collagen, and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5) in cartilage was evaluated by Western blot. Results The histological analysis showed marked cartilage degeneration in adjuvant-induced OA groups, including reduced cartilage cellular density, thinner and degraded cartilage, and decreased proteoglycan content in the extracellular matrix. Compared with matched control groups, the expression of Ihh, Ptch1, Smo, and Gli1 in the OA groups was higher in a time-dependent manner. The protein levels of MMP-13, type X collagen, and ADAMTS-5 were substantially increased in OA cartilage compared with those in matched control rats. Conclusion These results indicate that the activation of Ihh signaling may be correlated with pathological changes of condylar cartilage in adjuvant-induced TMJOA.