Enhancement of BMP-2-mediated angiogenesis and osteogenesis by 2-N,6-O-sulfated chitosan in bone regeneration

Sulfated polysaccharides are attractive semi-synthesized materials that can be used as a mimic of heparan sulfate to modulate the protein activity and other physiological processes. In this study, we employed sulfated chitosan to enhance the angiogenic capacity of bone morphogenic protein-2 (BMP-2). Bone marrow stromal cells (BMSCs) cultured in a combination of BMP-2 and 2-N,6-O-sulfated chitosan (SCS) group exhibited a higher cell viability and sprouting ability. The cells also secreted more VEGF and NO. The expression patterns of angiogenic and osteogenic genes were analyzed, and VEGFR2 signaling was found to play a role in the enhancing effect of SCS. The chick embryo chorioallantoic membrane (CAM) assay revealed an enhanced angiogenic effect of BMP-2 when SCS was involved. In addition, we investigated angiogenesis and osteogenesis in mouse using a BMP-2-induced ectopic bone model. Histological and immune-staining analysis revealed that both bone and vascular tissue were enhanced when SCS was added. These data prove that SCS can improve the angiogenic potential of BMP-2 and thus lead to better bone regeneration.