Properties of murine embryonic stem cells maintained on human foreskin fibroblasts without LIF

In embryonic stem (ES) cells, leukemia inhibitory factor (LIF)/STAT3, wnt and nodal/activin signaling are mainly active to control pluripotency during expansion. To maintain pluripotency, ES cells are typically cultured on feeder cells of varying origins. Murine ES cells are commonly cultured on murine embryonic fibroblasts (MEFs), which senesce early and must be frequently prepared. This process is laborious and leads to batch variation presenting a challenge for high-throughput ES cell expansion. Although some cell lines can be sustained by exogenous LIF, this method is costly. We present here a novel and inexpensive culture method for expanding murine ES cells on human foreskin fibroblast (HFF) feeders. After 20 passages on HFFs without LIF, ES cell lines showed normal expression levels of pluripotency markers, maintained a normal karyotype and retained the ability to contribute to the germline. As HFFs do not senesce for at least 62 passages, they present a vast supply of feeders.