INTRODUCTION

Embryonic stem cells (ESCs) provide an attractive cell source for basic research and disease treatment. Currently, the common culture system for mouse ESC requires mouse embryonic fibroblast (MEF) as a feeder layer supplemented with leukemia inhibitory factor (LIF). The drawbacks associated with MEF and the cost of LIF have motivated exploration of new feeder cell types to maintain self-renewal of mouse ESCs without the need of exogenous LIF. However, why these feeder cells could maintain ESCs at the undifferentiated state independent of exogenous LIF is unclear.

METHODS

We derived mouse ESC lines using human foreskin fibroblast (HFF) in the absence of exogenous LIF. We also examined the dependence of HFF on the JAK-Stat3 pathway to maintain ESC identities and explored the potential molecular basis for HFF to support self-renewal of ESCs.

RESULTS

HFF supported mouse ESC self-renewal superiorly to MEFs. Using the HFF system, multiple lines of mouse ESCs were successfully derived without addition of exogenous LIF and any small molecular inhibitors. These ESCs had capacities to self-renew for a long period of time and to differentiate into various cell types of the three germ layers both in vitro and in vivo. Moreover, the ESCs participated in embryonic development and contributed to germ cell lineages in the chimeric mouse. At a molecular level, HFF was dependent on the JAK-Stat3 pathway to maintain ESC self-renewal. The high level of interleukin-6 (IL-6) produced by HFF might be responsible for the exogenous LIF-independent effect.

CONCLUSION

This study describes an efficient, convenient and economic system to establish and maintain mouse ESC lines, and provides insights into the functional difference in the support of ESC culture between MEF and HFF.