Magnesium Ions Induce Endothelial Cell Differentiation into Tip Cell and Enhance Vascularized Bone Regeneration.

Vascularization has been considered an essential strategy for bone regeneration and can be promoted by magnesium ions (Mg²⁺). During angiogenesis, the differentiation of endothelial cells (ECs) into tip cell is a critical step since it controls the growth direction and pattern of new vascular sprouts. While several studies have noted the pro-angiogenic effects of Mg²⁺, however, their specific influence on tip cell formation is unclear. Therefore, this research seeks to examine the impact of Mg²⁺ on tip cells and elucidate the potential mechanisms involved. The results reveal that Mg²⁺ shows good compatibility and stimulates ECs to migrate and invade in vitro. Moreover, Mg²⁺ enhances EC spheroids sprouting and elevates the expression of genes linked to tip cells. The underlying mechanisms are that Mg²⁺ facilitates tip cell differentiation via the VEGFA-VEGFR2/Notch1 signaling pathway crosstalk and promotes migration and filopodia formation of tip cells and proliferation of stalk cells by inducing YAP nuclear translocation, culminating in the maturation of vascular networks. Furthermore, EC spheroids stimulated by Mg²⁺ load in hydrogel enhance vascularized bone regeneration in vivo. These findings enrich the understanding of how Mg²⁺ influence blood vessel formation and provide practical strategies for the development and design of magnesium-based biomaterials.