Mouse Embryonic Fibroblasts (MEF) are used to support the growth of mouse and human pluripotent stem cells. MEF not only provide a substrate for pluripotent stem cells to grow on, but also secrete critical growth factors to maintain stem cell pluripotency. MEF are isolated from mouse embryos and used at early passages. To serve as feeder cells, MEF must be treated with mitomycin C or by irradiation to prevent cell proliferation. The treated cells can also be used to generate conditioned medium for feeder-free culture of pluripotent stem cells. MEF-mt from ScienCell Research Laboratories are isolated from embryonic day 14 CD-1 mouse embryos. These cells have been treated with mitomycin C to prevent further cell division. They are cryopreserved at passage 3 and delivered frozen. Each vial contains 1 x 106 cells in 1 ml volume. MEF-mt are characterized by immunofluorescence with antibody specific to fibronectin. MEF-mt are negative for mycoplasma, bacteria, yeast, and fungi. MEF-mt are guaranteed to further culture under the conditions provided by ScienCell Research Laboratories; however, MEF-mt are not recommended for expanding as mitomycin C treatment prevents further cell proliferation. Recommended Medium It is recommended to use DMEM (Cat. #09221) supplemented with 10% fetal bovine serum (FBS, Cat. #0010, 0025, 0500) for culturing MEF-mt in vitro.