Inhibition of angiogenesis impairs bone healing in an in vivo murine rapid resynostosis model

Biologics can improve bone formation, but may diffuse away from sites of therapeutic need. We developed a click‐chemistry hydrogel that rapidly polymerizes in situ to control delivery of biologics during post‐suturectomy resynostosis in 21‐day‐old male mice. Here, we used this model to determine the role of angiogenesis in post‐suturectomy resynostosis and examine whether controlled release of angiogenesis inhibitors could delay bone regeneration. Hydrogels [DB‐co‐PEG/poly (TEGDMA)‐co‐(N3‐TEGDMA)] were produced containing anti‐angiogenic compounds [anti‐VEGFA‐antibody or hypoxia inducible factor 1α‐inhibitor topotecan]. Bioactivity in vitro was assessed by tube length and branching points of endothelial cells in hydrogel‐conditioned media. In vivo effects were examined 14 day post‐suturectomy, based on the temporal analysis of angiogenic mRNAs during resynostosis following posterior frontal suture removal. MicroCT was used to quantify angiogenesis in contrast‐agent‐perfused blood vessels and bone defect size in defects receiving hydrogel, anti‐VEGFA/hydrogel, or topotecan/hydrogel. Shorter endothelial tube length and less branching were seen in inhibitor‐conditioned media (topotecan > AbVEGFA). In vivo , both compounds inhibited angiogenesis compared with hydrogel‐only. Anti‐VEGFA/hydrogel reduced resynostosis compared with empty defects, but topotecan/hydrogel blocked bone regeneration. We demonstrate that anti‐angiogenic compounds can be incorporated into a spontaneously polymerizing hydrogel and remain active over 14 days in vitro and in vivo . Moreover, bone formation can be delayed by inhibiting neovascularization, suggesting possible use as a therapeutic to control resynostosis following suturectomies and potential applications in other conditions where rapid osteogenesis is not desired. © 2017 Wiley Periodicals Inc. J Biomed Mater Res Part A: 105A: 2742–2749, 2017.