Isolation, characterization, and in vitro culture of larval and adult epidermal cells of the frog Xenopus laevis.

Methods for the isolation and in vitro culture of larval and adult Xenopus laevis epidermal cells have been developed. Epidermal cells of stage 52-54 tadpoles and adult epidermal cells were enzymatically dissociated and purified (98%) by Percoll-density centrifugation and unit-gravity sedimentation. Both cell types attached on fibronectin-coated dishes and proliferated for 1 wk when the proper medium was used. There were four significant differences between larval and adult cells: a) Adult cells had a greater buoyant density than larval cells. b) Keratin synthesis patterns were markedly different. c) A combination of medium F12 and Eagle's minimum essential medium was optimal for growth of larval cells whereas MCDB151 medium was optimal for adult cells. d) Adult cells needed fetal bovine serum (greater than 5%) whereas larval cells grew without fetal bovine serum. In contrast to these differences, larval and adult cells had two similar properties: a) Insulin had a potent effect on the growth of both cells, and b) The optimal Ca++ concentration for cell growth was quite low for both cell types; 0.1 mM for larval cells and below 0.05 mM for adult cells. These results suggest that low Ca++ levels are essential for both cornifying (adult) and uncornifying (larval) amphibian keratinocytes. The culture techniques described herein for larval and adult epidermal cells provide a new in vitro model for analyzing development of the epidermis during amphibian metamorphosis.