Exosome-mediated Piezo1 activation in 3D-printed titanium scaffolds promotes repair of femoral head osteonecrosis.

Osteonecrosis of the femoral head (ONFH) is a debilitating bone disorder characterized by ischemic degeneration with limited therapeutic options. Piezo1, a mechanosensitive ion channel, transduces physical stimuli into intracellular signals regulating osteogenesis and angiogenesis. Here, we developed a 3D-printed Ti6Al4V scaffold conformally coated with photocrosslinked hyaluronic acid hydrogel that retains and releases Piezo1-engineered exosomes (P-Exos), forming a hybrid construct (P-Exos@HAMA/Ti) with cancellous-bone-like stiffness and sustained bioactivity. In vitro studies demonstrated that P-Exos enhanced BMSC viability, migration, and osteogenic differentiation (ALP/ARS; Runx2, Osterix, OCN) while promoting endothelial proliferation and network formation (CD31, VEGFA). RNA-seq and mechanistic validation revealed Ca2+-responsive YAP1/β-catenin signaling, characterized by elevated intracellular Ca2+ levels, upregulated YAP1/β-catenin expression, and nuclear localization, underpinning the scaffold's osteo-angiogenic synergy. In a rat ONFH model, P-Exos@HAMA/Ti restored trabecular architecture and bone volume, improved micro-CT indices (increased BV/TV, Tb.N, Tb.Th; decreased Tb.Sp), and enhanced osteogenic/angiogenic marker expression, alongside superior locomotor recovery. This multifunctional platform couples mechanical stabilization with Piezo1-mediated mechanotransduction, establishing a pro-regenerative niche integrating biomechanical support with sustained exosomal signaling for effective repair of ischemic bone defects.