Effects of retinoic acid and other retinoids on the gowth and differentiation of 3t3 supported human keratinocytes

Using mitomycin C treated 3T3-Swiss fibroblasts as feeder cells, human keratinocytes derived from infant foreskins were subcultured in the presence ofrans-retinoic acid (RA) and other retinoids. At 1 μg/ml (3×10−6 M) and higher RA concentrations planting efficency was markedly reduced. Addition of retinoids to 1 μ/ml after colonies wereestablished produced no change in the rate of cell production, but caused differentiated cells to be sloughed earlier than in control cultures. Electron microscopy showed wider extra cellular spaces that contained numerous villi, increased numbers of microvilli at the surfaces of the outermost cells, and decreased number of cell layers all of which were consistent with the observed desquamatory effects of RA. Retinoic acid also extended the time during which cell population increased so that RA treated cultures produced more cells than control cultures over their respective lifetimes.