One-day treatment of small molecule 8-bromo-cyclic AMP analogue induces cell-based VEGF production for in vitro angiogenesis and osteoblastic differentiation.

Small molecule-based regenerative engineering is emerging as a promising strategy for regenerating bone tissue. Small molecule cAMP analogues have been proposed as novel biofactors for bone repair and regeneration and, while promising, the effect that these small molecules have on angiogenesis, a critical requirement for successful bone regeneration, is still unclear. Our previous research demonstrated that the small molecule cAMP analogue 8-bromoadenosine-3',5'-cyclic monophosphate (8-Br-cAMP) was able to promote initial osteoblast adhesion on a polymeric scaffold via cAMP signalling cascades. Here, we report that 8-Br-cAMP is capable of inducing in vitro cell-based VEGF production for angiogenesis promotion. We first demonstrated that treating osteoblast-like MC3T3-E1 cells with 8-Br-cAMP for 1 day significantly increased VEGF production and secretion. We then demonstrated that 8-Br-cAMP-induced cell-secreted VEGF is biologically active and may promote angiogenesis, as evidenced by increased human umbilical vein endothelial cells (HUVECs) migration and tubule formation. In addition, treatment of MC3T3-E1 cells with 8-Br-cAMP for as short as a single day resulted in enhanced ALP activity as well as matrix mineralization, demonstrating in vitro osteoblastic differentiation. A short-term 8-Br-cAMP treatment also addresses the concern of non-specific cytotoxicity, as our data indicate that a 1-day 8-Br-cAMP treatment scheme supports cellular proliferation of MC3T3-E1 cells as well as HUVECs. While the major concern associated with small molecule drugs is the risk of non-specific cytotoxicity, the short exposure treatment outlined in this paper provides a very promising strategy to mitigate the risk associated with small molecules.