engleski

BMP6 mechanism of action in the osteoporosis model of ovariectomized rats

Osteoporosis is a rare, but serious complication of the long-term heparin therapy. Around one third of patients receiving heparin have a reduction in bone density. In plasma, heparin binds to a number of different proteins, including circulating bone morphogenetic proteins (BMPs). BMP6 has a major role in promoting osteoblast differentiation and bone formation. Here we explored the role of exogenous heparin in BMP6 signaling. We treated C2C12- BRE-Luc cells with combination of BMP6 and heparin for different time points. By western blot and luciferase reporter assay, we show that BMP6-induced Smad1/5/8 phosphorylation was inhibited with heparin. BMP6 is known to induce C2C12 myoblast differentiation toward osteoblast phenotype. We incubated the cells with BMP6 with or without heparin for 24, 48 and 72 hours and measured the expression of early osteoblast markers, alkaline phosphatase (ALP) and osteocalcin (OC). After 48 and 72 hours of treatment, heparin statistically inhibited BMP6-induced ALP and OC gene expression. By using the ectopic bone formation assay in rats, we explored the effect of exogenous heparin on the BMP6-mediated osteogenic activity. We implanted heparin together with BMP6 on demineralized bone matrix (DBM) implants. Two weeks later, we could observe that implants containing the highest dose of heparin morphologically appeared smaller. We also show that BMP6 specifically binds to heparin. We incubated BMP6 with the heparin sepharose beads and BMP6 bound to the beads was detected. Altogether, we suggest that heparin-induced osteoporosis is a consequence, at least in part, of the heparin binding to circulating BMP6.

BMP6; osteoporosis

nije evidentirano