Endothelial PIEZO1 activation impairs osteogenesis via GREM1-mediated inhibition of BMP signaling

To investigate the effects and underlying mechanisms of systemic PIEZO1 activation on the bone vasculature and osteogenesis.

Three-week-old C57BL/6J male mice were intraperitoneally injected with Yoda1, and changes in bone microstructure and vasculature were assessed via micro-CT and immunofluorescence. MC3T3-E1 osteoprogenitors and endothelial cells (human umbilical vein endothelial cells, HUVECs and human bone marrow microvascular endothelial cells, hBMECs) were treated with Yoda1 in vitro. Gene expression analysis, alkaline phosphatase (ALP) assays, and RNA sequencing were performed to assess osteogenic activity and endothelial identity, respectively. Alterations in the osteogenic-promoting function of endothelial cells upon PIEZO1 activation were evaluated by treating MC3T3-E1 cells with endothelial-conditioned media.

Systemic Yoda1 administration reduced the abundance of CD31^hiEMCN^hi-type H vessels and disrupted trabecular bone microarchitecture. Yoda1 suppressed osteogenic gene expression and ALP activity in MC3T3-E1 cells, even at low concentrations. RNA-seq of Yoda1-treated hBMECs revealed a transcriptional shift toward an l-type endothelial phenotype and upregulation of the expression of BMP antagonists, including GREM1. Functional rescue assays confirmed that endothelial-derived GREM1 inhibits BMP4-induced osteogenic differentiation via paracrine signaling.

Our study reveals a dual role of PIEZO1 in bone biology, demonstrating that its activation disrupts vascular-osteogenic coupling and suppresses osteoblast differentiation through the PIEZO1-GREM1-BMP4 axis. These findings suggest that caution should be taken when targeting PIEZO1 for bone regeneration and highlight the importance of dose and duration in therapeutic applications.