Intermittent PTH induces cartilage healing after experimentally induced TMJ degeneration

Purpose Our data suggest that intermittent parathyroid hormone administration (PTH) may exert chondrogenerative effects on the cartilage of the temporomandibular joint (TMJ), however, it is not known whether PTH could prevent/reverse TMJ degeneration. Our aim was to evaluate the role of PTH in an experimental mouse model of this condition.Methods The triple collagen transgenic mice (Col1a1/Col3.6-tpz × Col2a1/Col2-cyan × Col10a1/Col10-mCherry) were used. Metal tubes were bonded to the incisors of 6-week-old male mice to induce an anterior crossbite and TMJ degeneration. The mice then received daily injections of PTH or saline solution (control groups) for 2 weeks.Results We observed a substantial decrease in TMJ cartilage thickness in Degeneration Control mice compared to Control. However, mice receiving PTH injections presented with increased cartilage thickness and proteoglycan distribution compared to Degeneration Control. There was a decrease in Col1a1 and an increase in Col10a1 positive cells in the TMJ cartilage of Degeneration Control mice compared to Control group, effect reversed by PTH treatment. Additionally, we observed increased markers for osteoarthritis in Degeneration Control mice compared to control, but mice receiving PTH injections presented with increased chondrocyte proliferation and decreased degeneration markers.Conclusions Intermittent PTH treatment following experimental TMJ degeneration increased cartilage thickness, proteoglycan distribution, and chondroprogenitor proliferation while reducing markers of osteoarthritis in TMJ cartilage.