Clopidogrel (Plavix®), a P2Y(12) receptor antagonist, inhibits bone cell function in vitro and decreases trabecular bone in vivo

Clopidogrel (Plavix®), a selective P2Y(12) receptor antagonist, is widely prescribed to reduce the risk of heart attack and stroke and acts via the inhibition of platelet aggregation. Accumulating evidence now suggests that extracellular nucleotides, signalling through P2 receptors, play a significant role in bone, modulating both osteoblast and osteoclast function. In this study, we investigated the effects of clopidogrel treatment on (1) bone cell formation, differentiation and activity in vitro; and, (2) trabecular and cortical bone parameters in vivo. P2Y(12) receptor expression by osteoblasts and osteoclasts was confirmed using qPCR and western blotting. Clopidogrel at 10µM and 25µM inhibited mineralised bone nodule formation by 50% and >85%, respectively. Clopidogrel slowed osteoblast proliferation with dose-dependent decreases in cell number (25-40%) evident in differentiating osteoblasts (day 7). A single dose of 10-25µM clopidogrel to mature osteoblasts also reduced cell viability. At 14 days, ≥10µM clopidogrel decreased ALP activity by ≤70% and collagen formation by 40%, whilst increasing adipocyte formation. In osteoclasts, ≥1µM clopidogrel inhibited formation, viability and resorptive activity. 20-week old mice (n = 10-12) were ovariectomised or sham treated and dosed orally with clopidogrel (1mg/kg) or vehicle (NaCl) daily for 4 weeks. DEXA analysis showed clopidogrel treated animals had decreases of 2% and 4% in whole body and femoral BMD, respectively. Detailed analysis of trabecular and cortical bone using microCT showed decreased trabecular bone volume in the tibia (24%) and femur (18%) of clopidogrel-treated mice. Trabecular number was reduced 20%, whilst trabecular separation was increased up to 15%. Trabecular thickness and cortical bone parameters were unaffected. Combined, these findings indicate that long-term exposure of bone cells to clopidogrel in vivo could negatively impact bone health. © 2012 American Society for Bone and Mineral Research.