Growing a stratified, cornified primary culture of rat keratinocytes with epidermis-like water permeation barrier function.

The culture of cutaneous keratinocytes grown on a Puropore nylon microporous membrane at the air-liquid interface has been shown to be similar to the epidermis in a number of molecular and morphologic characteristics but to exhibit a significantly greater degree of tritiated water permeation. Various culture conditions have been altered in an effort to improve the water barrier properties. A Kp value in the range of 5.5 +/- 1.6 x 10(3) has been obtained for 79% of the cultures a) by plating 0.9 x 10(6) viable basal cells on a piece (13-mm diameter) of membrane for 7 days of submerged growth, b) by placing two membranes on two stacked glass fiber filters (47-mm extra-thick) in a culture dish (60 mm) for 14 days of growth at the air-liquid interface, c) by replacing the growth medium, i.e., 1 ml of complete minimum essential medium (CMEM) every 24 h after lifting, d) by using 10% fetal bovine serum (FBS) in the CMEM during the submerged culture period and 15% FBS in the CMEM during the lifted culture period, and e) by adding a dialysis membrane on top and a Puropore nylon membrane below the culture when the cultures were inserted in the permeation cell for testing. The percentage of cultures with this value for Kp can be increased to 90% if only cultures with yellow, smooth, and shiny surfaces are tested. This system should be useful as a replacement for skin in testing the cutaneous permeation of some chemicals.