Human iPS cell-derived fibroblast-like cells as feeder layers for iPS cell derivation and expansion.

Mouse embryonic fibroblasts (MEFs) are commonly used as feeder cells for the generation of human induced pluripotent stem cells (hiPSCs). However, medical applications of cell derivatives of hiPSCs generated with a MEF feeder system run the risk of having xeno-factor contamination due to long-term cell culturing under an animal factor-containing environment. We developed a new method for the derivation of human fibroblast-like cells (FLCs) from a previously established hiPSC line in an FLC differentiation medium. The method was based on direct differentiation of hiPSCs seeded on Matrigel followed by expansion of differentiating cells on gelatin. Using inactivated FLCs as feeder layers, primary human foreskin fibroblasts were successfully reprogrammed into a state of pluripotency by Oct4, Sox2 Klf4, and c-Myc (OSKM) transcription factor genes, with a reprogramming efficiency under an optimized condition superior to that obtained on MEF feeder layers. Furthermore, the FLCs were more effective in supporting the growth of human pluripotent stem cells. The pluripotency and differentiation capability of the cells cultured on FLC feeder layers were well retained. Our results suggest that FLCs are a safe alternative to MEFs for hiPSC generation and expansion, especially in the clinical settings wherein hiPSC derivatives will be used for medical treatment.