Epimedium-derived flavonoids promote osteoblastogenesis and suppress adipogenesis in bone marrow stromal cells while exerting an anabolic effect on osteoporotic bone

BackgroundEpimedium-derived flavonoids (EFs) have been reported to prevent bone loss in ovariectomized (OVX) rats and late postmenopausal women but the underlying mechanism of the anabolic effect is unknown.ObjectiveThis study aimed to investigate the effect of EFs on osteoporotic bone using histomorphometry and on osteoblastogenesis/adipogenesis of bone marrow stromal cells (BMSCs).Methods11-month-old female Wistar rats were divided into Sham, OVX, Sham + soluble vehicle (Sham + SV), OVX + SV and OVX + EFs (10 mg/kg/day) groups. 3 months after surgery, rats from the first two groups were euthanized to verify the establishment of OVX-induced osteoporosis. Other groups were orally treated with either daily SV or EFs for 4 months. At sacrifice, serum was analyzed for the levels of osteocalcin and TRACP 5b, BMD in the proximal femur was measured by pQCT. Static and dynamic bone histomorphometry was performed in proximal tibiae with microCT and undecalcified sections, respectively. The effect of EF treatment on differentiation of rat BMSCs was assessed by colony formation assays and gene expression analysis, respectively. Gene expression, ALP activity and adipocyte numbers were determined in differentiating human BMSCs after exposure to conditioned serum from SV- or EFs-treated OVX rats.ResultsThe serum level of osteocalcin was higher and TRACP 5b was lower in EFs versus SV-treated OVX rats. BMD, BV/TV, Tb.N and Conn.D in EFs-treated OVX rats were significantly greater than those of SV-treated OVX rats. Bone histomorphometric parameters OS/BS, MAR, and BFR/BS were significantly higher in EFs versus SV-treated OVX rats. EFs significantly increased osteogenesis and decreased adipogenesis of BMSCs, as evidenced by CFU-ALP and CFU-Adipo assays, respectively. The mRNA level of Runx2 and bone sailoprotein was significantly higher while PPARγ2 was significantly lower in BMSCs from EFs-treated versus SV-treated OVX rats. ALP activity and Runx2 mRNA was significantly higher while adipocyte number and PPARγ2 mRNA was significantly lower in human BMSCs after exposure to conditioned serum from EFs versus SV-treated OVX rats.ConclusionEFs exerted anabolic effect on osteoporotic bone by concomitantly promoting osteogenic and suppressing adipogenic differentiation of BMSCs.