biostudies-literatureVilla-Diaz LGNIGMS NIH HHS641-51https://www.ebi.ac.uk/biostudies/studies/S-EPMC3133563biostudies-literatureUnknown18(4)Human embryonic stem cell (hESC) culture is routinely performed using inactivated mouse embryonic fibroblasts (MEFs) as a feeder cell layer (FL). Although these cells maintain pluripotency of hESCs, the molecular basis for this is unknown. Objectives of this study were to determine whether timing between MEF inactivation and their use as a FL influenced hESC growth and differentiation, and to begin defining the mechanism(s) involved. hESCs were plated on MEFs prepared 1 (MEF-1), 4 (MEF-4), and 7 (MEF-7) days earlier. hESC colony morphology and Oct3/4 expression levels were evaluated to determine the influence of different FLs. Significant enhancement of hESC growth (self-renewal) was observed on MEF-1 compared with MEF-4 and/or MEF-7. Conditioned media (CM) collected from MEF-1 supported sStem cells and developmentAnalysis of the factors that limit the ability of feeder cells to maintain the undifferentiated state of human embryonic stem cells.PMC3133563P20 GM-069985Villa-Diaz LGSmith GDPacut CSlawny NAO'Shea KSDing JfalseAnalysis of the factors that limit the ability of feeder cells to maintain the undifferentiated state of human embryonic stem cells.Human embryonic stem cell (hESC) culture is routinely performed using inactivated mouse embryonic fibroblasts (MEFs) as a feeder cell layer (FL). Although these cells maintain pluripotency of hESCs, the molecular basis for this is unknown. Objectives of this study were to determine whether timing between MEF inactivation and their use as a FL influenced hESC growth and differentiation, and to begin defining the mechanism(s) involved. hESCs were plated on MEFs prepared 1 (MEF-1), 4 (MEF-4), and 7 (MEF-7) days earlier. hESC colony morphology and Oct3/4 expression levels were evaluated to determine the influence of different FLs. Significant enhancement of hESC growth (self-renewal) was observed on MEF-1 compared with MEF-4 and/or MEF-7. Conditioned media (CM) collected from MEF-1 supported s2009-01-01T00:00:00Z2009 May2026-04-28T21:30:07.182Z2026-04-07T14:42:16.715ZS-EPMC31335631876473510.1089/scd.2008.0010