Promotion of Dentin Regeneration With Nanofibrous Microspheres in Combination With Sequential Delivery of BMP-2/SDF-1

Objectives: The aim of this study was to investigate the effects of PLLA nanofibrous microspheres (NF-MS) as cell delivery carrier in combination with sequential delivery of BMP-2/SDF-1 on the induction of dentin regeneration.


Methods: Stem cells of apical papilla (SCAP) were treated with SDF-1 for migration and proliferation test. The CXC chemokine receptor 4 (CXCR4) for SDF-1 in cultured SCAP were examined using reverse-transcription polymerase chain reaction (RT-PCR) and flow cytometric analyses. SCAP were treated with BMP-2 for odontogenic differentiation by measuring alkaline phosphatase activity (ALP), odontogenic gene expression levels and mineralized nodule formation. Injectable NF-MS, which mimic the physical architecture of collagen fibers on the nano scale, were fabricated by combining thermally-induced phase separation techniques with an emulsification process. BMP-2/SDF-1 PLGA microspheres were prepared using double emulsion method. SCAP cultured on NF-MS combining with sequential delivery of BMP-2/SDF-1system were implanted into subcutaneous pockets for dentin regeneration in vivo.

Results: SCAP harbored more intracellular CXCR4 and had fewer detectable CXCR4 on the cell surface. Although there was no obvious effect on SCAP proliferation, SDF-1significantly promoted a higher number of migrated cells; this effect was attenuated by anti-CXCR4 antibodies. BMP-2 enhanced odontogenetic differentiation-related gene expression and mineralized nodule formation in SCAP. BMP-2/SDF-1 microspheres were synthesized and optimized for sequential delivery. The results in vivo demonstrated sequential release of BMP-2/SDF-1 promoted more mineralization and osteodentin formation compared to a BSA-releasing control.

Conclusions: The NF-MS combined with sequential release of BMP-2/SDF-1 provides a preferable microenvironment for SCAP to regenerate dentin-like tissue. This study might serve as a feasible approach for directing SCAP into odontogenetic differentiation and present a first step in the development of a dental tissue enginnering strategy for apex regeneration of immature permanent teeth.