Total flavonoids of rhizoma drynariae improved the osteogenic and pro-angiogenic capacities of BMSCs to accelerate long bone regeneration.

Total Flavonoids of Rhizoma Drynariae (TFRD) possess the ability to enhance bone regeneration by promoting angiogenesis-osteogenesis coupling, but the underlying mechanisms remain poorly understood. This study aimed to investigate the influence of TFRD on the coordination of osteogenic and pro-angiogenic properties of bone marrow mesenchymal stem cells (BMSCs) during long bone regeneration and further elucidate the underlying mechanism. We initially assessed pharmacological effects of TFRD in mouse monocortical tibial defect (MTD) model by utilizing micro-CT, histopathology and immunofluorescence imaging. Subsequently, we extracted BMSCs from TFRD-treated mice and characterized the regulatory effects of TFRD on the behavior of BMSCs. We observed that TFRD treatment increased skeletal parameters, osteoblast number, vessel volume and perivascular osteoprogenitor population within the callus. In vitro analyses revealed that TFRD promoted the proliferation and osteogenic differentiation of BMSCs. Additionally, BMSC-conditioned medium from TFRD-treated mice enhanced the migration, proliferation and tube formation of endothelial cells (ECs) under hypoxia. TFRD increased the expression level of HIF-1α and its target genes in callus and hypoxia-cultured ECs. The results of YAP1/TAZ interference in ECs by using siRNA indicated that the enhancement of HIf-1α was through YAP1/TAZ inhibition. Our findings suggest that YAP1/TAZ/ HIf-1α pathways involved in indirect regulation of TFRD on angiogenesis through BMSCs paracrine pathways.