Epidermis as a secretory tissue: an in vitro tissue model to study keratinocyte secretion.

In addition to protective functions, keratinocytes secrete a variety of effector molecules that may have local or distant effects. To explore the secretory activity of keratinocytes we have developed a two-chamber culture model in which a fully differentiated stratified epithelium is present in the upper chamber and secreted protein is collected in a lower chamber. A collagen matrix is not used and during collection of secreted protein, 3T3 feeder cells are absent. Keratinocytes secrete protein at the rate of 0.67 microgram/h/10(6) cells, encompassing a molecular weight range from several kD to over 180 kD. Secretion is an unexplored area of keratinocyte biology and this model will allow investigation of this activity.