Zinc Silicate/Nano-Hydroxyapatite/Collagen Scaffolds Promote Angiogenesis and Bone Regeneration via the p38 MAPK Pathway in Activated Monocytes
Yue Song, Hao Wu, Yi Gao, Junqin Li, Kaifeng Lin, Bin Liu, Xing Lei, Pengzhen Cheng, Shuaishuai Zhang, Yixiao Wang, Jinbo Sun, Long Bi, Guoxian Pei
Abstract
Recent studies show that biomaterials are capable of regulating immune responses to induce a favorable osteogenic microenvironment and promote osteogenesis and angiogenesis. In this study, we investigated the effects of zinc silicate/nanohydroxyapatite/collagen (ZS/HA/Col) scaffolds on bone regeneration and angiogenesis and explored the related mechanism. We demonstrate that 10ZS/HA/Col scaffolds significantly enhanced bone regeneration and angiogenesis in vivo compared with HA/Col scaffolds. ZS/HA/Col scaffolds increased tartrate-resistant acid phosphatase (TRAP)-positive cells, nestin-positive bone marrow stromal cells (BMSCs) and CD31-positive neovessels, and expression of osteogenesis (Bmp-2 and Osterix) and angiogenesis-related (Vegf-α and Cd31) genes increased in nascent bone. ZS/HA/Col scaffolds with 10 wt % ZS activated the p38 signaling pathway in monocytes. The monocytes subsequently differentiated into TRAP+ cells and expressed higher levels of the cytokines SDF-1, TGF-β1, VEGF-α, and PDGF-BB, which recruited BMSCs and endothelial cells (ECs) to the defect areas. Blocking the p38 pathway in monocytes reduced TRAP+ differentiation and cytokine secretion and resulted in a decrease in BMSC and EC homing and angiogenesis. Overall, these findings demonstrate that 10ZS/HA/Col scaffolds modulate monocytes and, thereby, create a favorable osteogenic microenvironment that promotes BMSC migration and differentiation and vessel formation by activating the p38 signaling pathway.