Developing tissue-engineered bone with pre-vascularization and innervation using a bottom–up approach involving MSC/EPC/SC microtissues

The regeneration of bone tissue depends on the harmonious interaction between blood vessels and nerve fibers, both essential for various physiological and pathological functions in the skeletal system. The key to mimicking the structure and function of natural bone lies in integrating angiogenesis and neurogenesis processes to prepare vascular-nerve-tissue-engineered bone (TEB). Unlike traditional strategies for constructing vascular nerve TEB (such as adding growth factors or cells to scaffolds or preparing composite scaffolds), this study employs a bottom-up approach, using modular microtissue units to construct novel vascular nerve TEB. Initially, vascular-nerve-bone microtissues composed of bone marrow mesenchymal stem cells, endothelial progenitor cells (EPCs), and Schwann cells (SCs) were generated through three-dimensional coculture in microporous array plates. These vascular-neural-bone microtissues were then encapsulated as modular building blocks within gelatin methacrylate (GelMA) hydrogels to construct large-scale vascular-neural TEB. The microtissue-based vascular-neural-TEB construction protocol demonstrated feasibility at the molecular, cellular, and tissue/organ levels. Research findings indicate that the GelMA/MSC/EPC/SC vascular-neural-TEB possesses concurrent capabilities for angiogenesis, neurogenesis, and osteogenesis during bone repair. These findings provide novel insights for the construction of multifunctional bone grafts and lay the foundation for the clinical treatment of bone defects.