3T3-J2 Irradiated Feeder Cells are optimized to support epithelial cell expansion in Conditional Reprogramming (CR) Medium (Catalog #100-0352; Liu X et al. 2012; Liu X et al. 2017; Suprynowicz FA et al.). The cells are mitotically inactivated by radiation, but maintain metabolic activity. 3T3-J2 Irradiated Feeder Cells are cryopreserved and can be used directly for seeding epithelial cells without plating in advance. Each vial contains 2 - 3 x 10^6 cells and can be used to seed up to three T-25 cm2 flasks or one T-75 cm2 flask. 3T3-J2 Irradiated Feeder Cells are intended for Research Use Only.