Hyaluronic acid (HA) injection is widely used in the treatment of temporomandibular joint (TMJ) osteoarthritis (OA). Proteoglycan 4 (PRG4) is another joint lubricant that protects surface of articular cartilage. But few studies had explored the role of HA in regulation of PRG4 expression in TMJ OA. In this study, the effects of HA on the expression of PRG4 in osteoarthritic TMJ synovial cells were investigated in hypoxia, which was similar to the TMJ physiologically.
Synovial cells were isolated from the TMJ OA patients and were treated with or without HA under normoxia or hypoxia for indicated time periods. The proliferation of synovial cells was measured using Cell Counting Kit-8 (CCK-8). The gene expression of HAS2, VEGF, and PRG4 was detected by quantitative real-time PCR, and the secretion of PRG4 and VEGF was assayed by enzyme-linked immunosorbent assay (ELISA). Immunofluorescence was used to examine the protein expression of hypoxia-induced factor-1α (HIF-1α).
Hyaluronic acid markedly increased the proliferation of osteoarthritic synovial cells in hypoxia. The expression of HAS2 and PRG4 mRNA of osteoarthritic synovial cells under hypoxia was enhanced by HA treatment. However, HA had no effect on reducing the VEGF and HIF-1α expression in synovial cells in hypoxia.
Hyaluronic acid could promote the expression of HAS2 and PRG4, but could not modulate HIF-1α and VEGF expression of TMJ osteoarthritic synovial cells in hypoxia.