CGRP-empowered stem cell sheet/short nanofiber sponge via enhancing neurovascular coupling for bone regeneration

Functional repair of critical-sized bone defects is highly dependent on the synergistic establishment of a neurovascularized microenvironment. However, current strategies face a critical bottleneck: the lack of effective coupling and synchronization between newly formed blood vessels and regenerating nerves. This "decoupling" results in immature vascular network and absent neurotrophic support, which subsequently limits osteogenic activity and ultimately leads to the formation of low-quality repair tissue with insufficient blood supply and neural innervation, severely restricting functional healing of bone defects. To address this challenge, we developed a calcitonin gene-related peptide (CGRP)-empowered composite delivery system consisting of stem cell sheets and short nanofiber sponges. The system was fabricated by embedding CGRP-loaded polydopamine microspheres into bone marrow mesenchymal stem cell sheets, which were then assembled with poly-L-lysine-modified short nanofiber sponges through electrostatic interactions. Multidimensional analysis of neural and vascular markers revealed that CGRP not only rapidly initiated angiogenesis and recruited neural ingrowth, but also synergistically interacted with endogenous CGRP secreted by newly formed nerves, thereby establishing a self-sustaining positive feedback loop that achieved tight coupling and coordinated regeneration of nerve-vessel-bone networks. This process enhanced osteogenic differentiation capacity through activation of the MAPK/ERK signaling pathway. Both in vitro and in vivo experiments demonstrated that this system effectively promoted the coordinated regeneration of neural, vascular, and bone tissues, significantly improving bone defect repair efficiency. This study provides a functional strategy with significant translational potential for overcoming clinical bottlenecks in neurovascularized bone regeneration.