Intermittent PTH Therapy is Anabolic in TMJ in Young Mice

Objective: Intermittent PTH treatment is a common therapy for the treatment of osteoporosis and unlike other osteoporosis therapies is able to cause an anabolic response in the periosteum.  The temporomandibular joint is composed of the mandibular condyle, the articular portion of the temporal bone and a disc that are covered by fibrocartilage.  Unlike other joints, the cartilage of the mandibular condyle is derived from periosteum.  Therefore, the goal of this study was to examine if similar to bone, intermittent PTH therapy is anabolic in the temporomandibular joint (TMJ). 

Method: Intermittent PTH (80μg/kg) or vehicle was injected to young mice (6-7 weeks old male C57BL/6) once a day for fourteen days.   Gene expression of chondrocyte maturation markers, proliferation, condylar cartilage thickness and micro-CT analysis was evaluated in the mandibular condyle from both treatment groups. 

Result: In young growing mice, intermittent PTH therapy caused a significant increase in the mandibular condylar cartilage thickness and   VEGF expression compared to vehicle treated controls.  Further PTH treatment caused a significant decrease in OPG expression. And in the subchondral bone, PTH treatment caused a significant decrease in bone volume compared to vehicle treated group.

Conclusion: Intermittent PTH treatment (80μg/kg/day) caused increased condylar cartilage thickness but a decrease in mandibular condylar bone density in young growing mice.