Maintenance of mESCs by rodent hair follicle dermal cells. Rex-1 EGFP-transfected CGR8 mESCs were cocultured with PVG fibroblasts (a–c), DP (d–f), and DS (g–i) cells. The ESCs lost colony morphology (a), Rex-1-directed EGFP expression (b), and Oct4 expression (c) when cultured with skin fibroblasts. However, mESCs were effectively maintained in an undifferentiated state by coculture with follicular dermal cells, both DP and DS, displaying compacted colonies (d, g), eGFP expression under the control of Rex-1 (e, h), and high levels of Oct4 expression (f, i). RT-PCR analysis of CGR8 mESCs cocultured with rat DP and DS cells (j). PCR products obtained using primers specific for mouse GAPDH (control), Oct4, Nanog (markers of undifferentiated ES cells), LIF, BMP4 (involved in ES support), Nodal, Glu-R6, Brachyury, TTR, and AFP (markers of differentiation). Scale bars = 50 μm.