The Effects of Parathyroid Hormone and Bisphosphonate on the Cartilage and Subchondral Bone of the Temporomandibular Joint

Introduction:Parathyroid hormone increases bone strength primarily by stimulating bone formation, whereas Bisphosphonate, an antiresorptive drug, reduce bone resorption by blocking osteoclast activity. Here we examined the effects of alendronate (ALN), a type of bisphosphonate, and we also examine the effects of parathyroid hormone (PTH), which has an anabolic effect and increases bone remodeling when treated intermittently (I-PTH). I-PTH treatment leads to increased bone volume fraction, tissue density and trabecular thickness of the subchondral bone. I-PTH treatment also increases proteoglycan synthesis with a concomitant increase in mineralization of the Mandibular Condyle Cartilage (MCC). We hypothesize that combined treatment of I-PTH + ALN will have a chondroprotective effect on the cartilage of the Temporomandibular Joint (TMJ) Methods:Mice were divided into 4 groups; a control group, a PTH group, an ALN group, and a combined PTH and ALN group. Results:ALN combined with PTH, and alendronate alone, caused an increase in bone volume. I-PTH or ALN used individually increased cartilage thickness and cell proliferation while the combined treatment decreased this effect. Conclusion:The use of combined treatment of ALN and I-PTH showed a decrease in cell proliferation with an increase in bone volume butthere was no evidence of synergy between parathyroid hormone and alendronate. Bone formation increased as expected in the parathyroid hormone group but not in the combination therapy group