Directed differentiation of BMSCs on structural/compositional gradient nanofibrous scaffolds for ligament-bone osteointegration

Nanofibrous scaffolds with structural and compositional gradients exhibit great potential to modulate zonal differentiation of stem cells for the regeneration of soft-to-hard tissue interface. Here, the response of bone marrow stem cells (BMSCs) to electrospun gradient nanofibrous scaffolds was investigated to demonstrate their potential capabilities for interfacial tissue regeneration. The electrospun scaffolds showed gradient distribution of BMP-2/nanoHA contents and the fiber orientations gradually changed from random to align. Biomimetic mineralization demonstrated that calcium and phosphorus elements can deposit onto the surface of the nanofibers in a gradient manner similar to nanoHA content. BMSCs cultured on the gradient nanofibrous scaffolds exhibited high cell viability and cell morphology gradually changed from disorder to highly align similar to the underlying fiber orientation. BMP-2/nanoHA content gradients in the nanofibrous scaffolds were found to effectively promote the zonal expression of bone-specific genes like osteocalcin (OCN), Runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP). Immunofluorescent staining of osteopontin (OPN) and OCN further confirmed osteoblastic phenotypic maturation on the regions of the scaffolds with a higher level of nanoHA and BMP-2 contents after cultured 28 days. These results indicated that the gradient nanofibrous scaffolds enable to guide zonal differentiation of BMSCs in vitro, which might be useful to realize multitissue regeneration in one construct for the regeneration of soft-to-hard tissue interface.