The effect of differentiation stage of amniotic fluid stem cells on bone regeneration.

Bone tissue engineering strategies require cells with high proliferative and osteogenic potential as well as a suitable scaffold to support the development of these as they form new bone tissue. In this study, we evaluated whether the differentiation stage of amniotic fluid stem cells (AFSC) could enhance the regeneration of critical sized femoral defects in a rat model. For this purpose, AFSC were seeded onto a starch-poly(ε-caprolactone) (SPCL) scaffold and were cultured in vitro in osteogenic culture media for different periods of time in order to obtain: i) undifferentiated cells, ii) cells committed to the osteogenic phenotype and iii) "osteoblast-like" cells. In vitro results indicate that AFSC were considered to be osteogenically committed by the end of week 2 and osteoblastic-like after week 3 in culture. Constructs composed of AFSC-SPCL scaffolds from each differentiation stage were implanted into critical sized femoral defects. The quality of new tissue formed in the defects was evaluated based on micro-CT imaging and histological analysis of constructs retrieved at 4 and 16 weeks after implantation. In vivo formation of new bone was observed under all conditions. However, the most complete repair of the defect was observed after 16 weeks in the animals receiving the SPCL scaffolds seeded with osteogenically committed AFSC. Furthermore, the presence of blood vessels was noted in the inner sections of the scaffolds suggests that these cells could potentially be used to induce bone regeneration and angiogenesis in non-union bone defects.