Targeting loop3 of sclerostin preserves its cardiovascular protective action and promotes bone formation

Sclerostin negatively regulates bone formation by antagonizing Wnt signalling. An antibody targeting sclerostin for the treatment of postmenopausal osteoporosis was approved by the U.S. Food and Drug Administration, with a boxed warning for cardiovascular risk. Here we demonstrate that sclerostin participates in protecting cardiovascular system and inhibiting bone formation via different loops. Loop3 deficiency by genetic truncation could maintain sclerostin's protective effect on the cardiovascular system while attenuating its inhibitory effect on bone formation. We identify an aptamer, named aptscl56, which specifically targets sclerostin loop3 and use a modified aptscl56 version, called Apc001PE, as specific in vivo pharmacologic tool to validate the above effect of loop3. Apc001PE has no effect on aortic aneurysm and atherosclerotic development in ApoE(-/-) mice and hSOST(ki).ApoE(-/-) mice with angiotensin II infusion. Apc001PE can promote bone formation in hSOST(ki) mice and ovariectomy-induced osteoporotic rats. In summary, sclerostin loop3 cannot participate in protecting the cardiovascular system, but participates in inhibiting bone formation. Antibodies targeting sclerostin can ameliorate postmenopausal osteoporosis but present some cardiovascular risk. Here the authors show that the cardiovascular and skeletal effects of sclerostin are mediated by different loops, suggesting ways to preserve the positive effects on bone formation while avoiding the negative cardiovascular consequences.

Automated summary

This study demonstrates that sclerostin has different mechanisms in protecting the cardiovascular system and inhibiting bone formation. By targeting sclerostin loop3, a drug can promote bone formation without affecting the cardiovascular system.