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.

To evaluate the potential of three stem cells for cell therapy and tissue engineering applications, the biological behavior and osteogenic capacity of the newly introduced cord-blood-derived, unrestricted somatic stem cells (USSC) were compared with those of mesenchymal stem cells isolated from bone marrow (BM-MSC) and adipose tissue (AT-MSC). There was no significant difference between the rates of proliferation of the three stem cells. During osteogenic differentiation, alkaline phosphatase (ALP) activity peaked on day 7 in USSC compared to BM-MSC which showed the maximum value of ALP activity on day 14. However, BM-MSC had the highest ALP activity and mineralization during osteogenic induction. In addition, AT-MSC showed the lowest capacity for mineralization during differentiation and had the lowest ALP activity on days 7 and 14. Although AT-MSC expressed higher levels of collagen type I, osteonectin and BMP-2 in undifferentiated state, but these genes were expressed higher in BM-MSC during differentiation. BM-MSC also expressed higher levels of ALP, osteocalcin and Runx2 during induction. Taking together, BM-MSC showed the highest capacity for osteogenic differentiation and hold promising potential for bone tissue engineering and cell therapy applications.