Sekundarna osteoporoza je komplikacija dugoročne terapije heparinom. Istražili smo ulogu heparina u BMP6 signalnom putu i osteogenoj aktivnosti in vitro korištenjem stanične linije mioblasta miša C2C12-BRE-Luc i in vivo u dva modela osteoporoze u miševa. BMP6 specifično veže heparin koji inhibira BMP6-potaknutu fosforilaciju Smad1/5/8 u C2C12-BRE-Luc stanicama. Predtretman kloratom i heparinazom III inhibira BMP6 signalizaciju, za koju su N- i O-sulfatne strukture neophodne. Heparin inhibira BMP6-potaknuti izražaj alkalne fosfataze i osteokalcina. U potkožnom testu heparin ovisno o dozi inhibira BMP6-inducirano formiranje nove kosti i hrskavice. U modelu osteoporoze nakon menopauze heparin ovisno o dozi inhibira sposobnost BMP6 za poboljšanje kvalitete kosti, što je pokazano pomoću DEXA-e i μCT-a. U modelu heparinom inducirane osteoporoze istovremeno tretiranje s BMP6 sprječava negativan učinak heparina na kosti, što je pokazano nepostojanjem značajne razlike u BMD i parametrima spužvaste kosti u odnosu na kontrolne životinje. Ovi rezultati pokazuju po prvi puta da vezivanje heparina za BMP6 može doprinijeti razvoju heparinom inducirane osteoporoze te da terapija heparinom u kombinaciji s BMP6 može spriječiti heparinom induciranu osteoporozu.

Secondary osteoporosis is a complication of long-term heparin therapy. We investigated the role of heparin in BMP6 signaling and osteogenic activity in vitro in C2C12-BRE-Luc mouse myoblast cell line and in vivo in two osteoporosis models in mice. BMP6 specifically binds to heparin, which inhibits BMP6-induced phosphorylation of Smad1/5/8 in C2C12-BRE-Luc cells. Pretreatment with chlorate and heparinase III inhibits BMP6 signaling, for which the N-and O-sulfate structures are necessary. Heparin inhibits BMP6-induced expression of alkaline phosphatase and osteocalcin. In the subcutaneous test heparin dose-dependently inhibits BMP6-induced formation of new bone and cartilage. In the model of postmenopausal osteoporosis heparin dose-dependently inhibits the ability of BMP6 to improve the quality of the bone, as shown by DEXA and μCT. In the model of heparin-induced osteoporosis simultaneous treatment with BMP6 prevents the negative effect of heparin on bone, as shown by the lack of significant differences in BMD and trabecular bone parameters compared to control animals. These results show for the first time that binding of heparin to BMP6 may contribute to the development of heparin-induced osteoporosis and that heparin therapy in combination with BMP6 can prevent heparin-induced osteoporosis.