Nanohydroxyapatite-Coated Electrospun Poly(<scp>l</scp>-lactide) Nanofibers Enhance Osteogenic Differentiation of Stem Cells and Induce Ectopic Bone Formation

A combination of calcium phosphates with nanofibrous scaffolds holds promising potential for bone tissue engineering applications. In this study, nanohydroxyapatite (n-HA) was coated on the plasma-treated surface of electrospun poly(l-lactide) (PLLA) nanofibers and the capacity of fabricated scaffolds for bone formation was investigated in vitro using human cord blood derived unrestricted somatic stem cells (USSC) under osteogenic induction and in vivo after subcutaneous implantation. PLLA and n-HA-coated PLLA (n-HA/PLLA) scaffolds exhibited a nanofibrous structure with interconnected pores and suitable mechanical properties. These scaffolds were also shown to support attachment, spreading, and proliferation of USSC, as shown by their flattened normal morphology and MTT assay. During osteogenic differentiation, significantly higher values of ALP activity, biomineralization, and bone-related gene expression were observed on n-HA/PLLA compared to PLLA scaffolds. Subsequently, these markers were measured in higher amounts in USSC on PLLA nanofibers compared to TCPS. According to the in vivo results, ossification and formation of trabeculi was observed in the n-HA/PLLA scaffold compared to PLLA. Taking together, it was shown that nanofibrous structure enhanced osteogenic differentiation of USSC. Furthermore, surface-coated n-HA stimulated the effect of nanofibers on the orientation of USSC toward osteolineage. In addition, the n-HA/PLLA electrospun scaffold showed the capacity for ectopic bone formation in the absence of exogenous cells.