Nanofibrous spongy microspheres for the delivery of hypoxia-primed human dental pulp stem cells to regenerate vascularized dental pulp.

Dental pulp infection and necrosis are widespread diseases. Conventional endodontic treatments result in a devitalized and weakened tooth. In this work, we synthesized novel star-shaped polymer to self-assemble into unique nanofibrous spongy microspheres (NF-SMS), which were used to carry human dental pulp stem cells (hDPSCs) into the pulp cavity to regenerate living dental pulp tissues. It was found that NF-SMS significantly enhanced hDPSCs attachment, proliferation, odontogenic differentiation and angiogenesis, as compared to control cell carriers. Additionally, NF-SMS promoted vascular endothelial growth factor (VEGF) expression of hDPSCs in a 3D hypoxic culture. Hypoxia-primed hDPSCs/NF-SMS complexes were injected into the cleaned pulp cavities of rabbit molars for subcutaneous implantation in mice. After 4 weeks, the hypoxia group significantly enhanced angiogenesis inside the pulp chamber and promoted the formation of ondontoblast-like cells lining along the dentin-pulp interface, as compared to the control groups (hDPSCs alone group, NF-SMS alone group, and hDPSCs/NF-SMS group pre-cultured under normoxic conditions). Furthermore, in an in situ dental pulp repair model in rats, hypoxia-primed hDPSCs/NF-SMS were injected to fully fill the pulp cavity and regenerate pulp-like tissues with a rich vasculature and a histological structure similar to the native pulp. STATEMENT OF SIGNIFICANCE: Vascularization is key to the regeneration of many vital tissues. However, it is challenging to create a suitable microenvironment for stem cells to regenerate vascularized tissue structure. This manuscript reports a novel star-shaped block copolymer that self-assembles into unique nanofibrous spongy microspheres, which as an injectable scaffold recapitulate the cell-cell and cell-matrix interactions in development. Using a clinically-relevant surgical procedure and a hypoxic treatment, the nanofibrous spongy microspheres were used to deliver stem cells and successfully regenerate dental pulp with a rich vasculature and a complex histologic structure similar to that of the native dental pulp. The novel microspheres can likely be used to regenerate many other vascularized tissues.