ROCK inhibition facilitates the generation of human-induced pluripotent stem cells in a defined, feeder-, and serum-free system.

Human-induced pluripotent stem cells (iPSCs) generated from human adult somatic cells through reprogramming hold great promises for future regenerative medicine. However, exposure of human iPSCs to animal feeder and serum in the process of their generation and maintenance imposes risk of transmitting animal pathogens to human subjects, thus hindering the potential therapeutic applications. Here, we report the successful generation of human iPSCs in a feeder-independent culture system with defined factors. Two stable human iPSC lines were established from primary human dermal fibroblasts of two healthy volunteers. These human iPSCs expressed a panel of pluripotency markers including stage-specific embryonic antigen (SSEA)-4, tumor-rejection antigen (TRA)-1-60, TRA-1-81, and alkaline phosphatase, while maintaining normal karyotypes and the exogenous reprogramming factors being silenced. In addition, these human iPSCs can differentiate along lineages representative of the three embryonic germ layers upon formation of embryoid bodies, indicating their pluripotency. Furthermore, subcutaneous transplantation of these cells into immunodeficient mice resulted in teratoma formation in 6 to 8 weeks. Our findings are an important step toward generating patient-specific iPSCs in a more clinically compliant manner by eliminating the need of animal feeder cells and animal serum.