Deferoxamine released from poly(lactic-co-glycolic acid) promotes healing of osteoporotic bone defect via enhanced angiogenesis and osteogenesis.

The regeneration capacity of osteoporotic bones is generally lower than that of normal bones. Current methods of osteoporotic bone defect treatment are not always satisfactory. Recent studies demonstrate that activation of the hypoxia inducible factor-1α (HIF-1α) pathway, by genetic methods or hypoxia-mimicking agents, could accelerate bone regeneration. However, little is known as to whether modulating the HIF-1α pathway promotes osteoporotic defect healing. To address this problem in the present study, we first demonstrated that HIF-1α and vascular endothelial growth factor expression levels are lower in osteoporotic bones than in normal bones. Second, we loaded poly(Lactic-co-glycolic acid) (PLGA) with the hypoxia-mimetic agent deferoxamine (DFO). DFO released from PLGA had no significant effect on the proliferation of mesenchymal stem cells (MSCs); however, DFO did enhance the osteogenic differentiation of MSCs. In addition, DFO upregulated the mRNA expression levels of angiogenic factors in MSCs. Endothelial tubule formation assays demonstrate that DFO promoted angiogenesis in human umbilical vein endothelial cells. Third, untreated PLGA scaffolds (PLGA group) or DFO-containing PLGA (PLGA + DFO group) were implanted into critically sized osteoporotic femur defects in ovariectomized rats. After treatment periods of 14 or 28 days, micro-CT, histological, CD31 immunohistochemical, and dynamic bone histomorphometric analyses showed that DFO dramatically stimulated bone formation and angiogenesis in a critically sized osteoporotic femur defect model. Our in vitro and in vivo results demonstrate that DFO may promote the healing of osteoporotic bone defects due to enhanced angiogenesis and osteogenesis.