3D-printed microfibers encapsulating stem cells in scaffold with tri-culture and two-stage metformin release for bone/vasculature/nerve regeneration in rats.

Abstract

Regeneration of critical-sized bone defects remains a major clinical challenge. Solely promoting osteogenesis is inadequate, because vasculature and neural innervation are critical for establishing the bone regenerative microenvironment. For the first time, the present study developed 3D bio-printed hydrogel microfibers (aMF) encapsulating human periodontal ligament stem cells (hPDLSCs) in a tri-culture system in calcium phosphate cement (CPC) scaffold with a two-stage metformin release for regeneration of nerve, vasculature, and bone. This tri-culture system consisted of hPDLSCs, human umbilical vein endothelial cells (hUVECs), and pericytes (PCs). Moreover, we employed 3D-bioprinted aMF in CPC scaffold with a controlled two-stage release system for metformin release to promote bone, vasculature, and nerve regeneration. Our innovative construct increased the regenerated amounts of bone, vasculature and nerve significantly by 2.5-fold, 3-fold, and 3.5-fold, respectively, than control group, in cranial defects in rats. This novel hPDLSCs tri-culture system in aMF-CPC scaffold with two-stage metformin release is highly promising for the regeneration of all three tissues of bone, vasculature, and nerves in a wide range of craniofacial and orthopedic applications.