Bioprinted Scaffold Remodels the Neuromodulatory Microenvironment for Enhancing Bone Regeneration

Herein, a 3D bioprinted scaffold is proposed, containing a calcitonin gene-related peptide (CGRP) and the beta-adrenergic receptor blocker propranolol (PRN) as a new method to achieve effective repair of bone defects. By leveraging the neuromodulation mechanism of bone regeneration, CGRP and PRN loaded mesoporous silica nanoparticles are added into a hybrid bio-ink, which initially contains gelatin methacrylate, Poly (ethylene glycol) diacrylate and bone marrow mesenchymal stem cells (BMSCs). Subsequently, the optimized bio-ink is used for 3D bioprinting to create a composite scaffold with a pre-designed micro-nano hierarchical structure. The migration and tube formation of human umbilical vein endothelial cells (HUVECs) can be promoted by the scaffold, which is beneficial to the formation of a new capillary network during the bone repair process. With the release of CGRP from the scaffold, the secretion of neuropeptides by sensory nerves is simulated. Meanwhile, the release of PRN can inhibit the binding process of catecholamine to beta-adrenergic receptor, co-promoting the osteogenic differentiation of BMSCs with CGRP and silicon ions, which will effectively enhance bone repair of a critical-sized cranial defect in a rat model. In conclusion, this study provides a promising strategy for bone defect repair by understanding the neuromodulatory mechanisms during bone regeneration.