Preparation of Mouse Embryonic Fibroblast Feeder Cells

MEFs are primary cells derived from day-13.5 fetuses that do not continue to proliferate indefinitely. Once the cells begin to senesce they lose their capacity to support undifferentiated growth and proliferation of hPSCs, so they are used optimally between passage 4 and passage 7. Usually large batches are made, tested, and cryopreserved so that this process needs to be repeated only occasionally.