HIF-1α expression is associated to cell proliferation and ECM production in temporomandibular joint osteoarthritis.

Temporomandibular joint osteoarthritis (TMJOA) is a complex joint disorder characterized by progressive degradation of the cartilage matrix and apoptosis of chondrocytes; however, hypoxia-inducible factor 1α (HIF-1α) serves a positive role in maintaining the stability of the articular cartilage matrix. Therefore, the present study aimed to determine the expression levels of HIF-1α in the cartilage tissue of rats with TMJOA, and to explore its association with the proliferation of chondrocytes and the formation of cartilage matrix. Experimental animals were subjected to occlusal interference treatment for periods ranging from 2 to 10 weeks to induce osteoarthritis (OA)-like pathological changes. Subsequently, various histochemical methods were employed to systematically evaluate the degree of articular cartilage damage in the TMJOA rat model. The expression levels of HIF-1α, proliferating cell nuclear antigen (PCNA), collagen type II (COLII) and aggrecan in cartilage tissues of rats with OA were analyzed using immunohistochemistry and immunofluorescence techniques. Western blotting and immunofluorescence were used to quantify the expression levels of HIF-1α, PCNA, Aggrecan and COLII in primary chondrocytes under hypoxic conditions (1% O2). EdU was used to assess the chondrocyte proliferation. From week 4 onward, a reduction in HIF-1α expression levels were detected in the lesioned cartilage of the TMJOA rats. Furthermore, the percentage of HIF-1α-positive chondrocytes was found to be significantly negatively associated with the OA score. This study demonstrated that the expression pattern of HIF-1α was consistent with cell proliferation and extracellular matrix production, and was negatively correlated with the severity of condylar cartilage degeneration.