<scp>P2Y₂</scp> Inhibition Modifies the Anabolic Response to Exercise in Adult Mice

As the aging population continues to grow, the incidence of osteoporotic fractures increases and is compounded by our lack of therapeutic strategies that increase bone formation. Although exercise and physical activity play a key role in maintaining bone mass throughout our lives, the loads and exertion required to elicit an anabolic response becomes exceedingly difficult to achieve with age. Based on previous work, the P2Y₂ receptor offers a unique therapeutic target to increasing bone mass by modifying the mechanotransduction. Others have also shown P2Y₂ to have a negative effect on osteoblast function. However, the extent to which inhibiting P2Y₂ pharmaceutically improves bone mass or the mechanotransduction of bone remains unknown. Our central hypothesis for this study states that inhibiting P2Y₂ activity can enhance the anabolic response to loading in an aging population. To test this hypothesis, the anabolic response to exercise was examined by treating adult mice, which typically display a minimal response, with the P2Y₂ inhibitor AR-C118925XX (ARC). Our findings from this study demonstrate that ARC treatment of adult mice increases periosteal bone formation in response to exercise. The enhanced response to exercise was characterized by a reduction in osteocytes' induction of osteoclast activity. Endocortical bone formation also increased with treatment independently of exercise, providing gains in mechanical strength and tissue level properties. Overall, inhibiting P2Y₂ activation has a beneficial effect on bone formation and the anabolic response to loading, namely by limiting osteoclast activation.