Low Ca2+ stripping of differentiating cell layers in human epidermal cultures: an in vitro model of epidermal regeneration.
An in vitro model of the epidermal regeneration process is described. Incubation of multilayered, keratinizing cultures of human epidermal cells in Ca2+-free medium for 72 h results in a complete stripping of all suprabasal layers. When the Ca2+ stripped cultures are refed normal Ca2+ medium a reproducible series of morphologic and cell kinetic changes takes place. It is suggested that these changes represent a general pattern of regeneration after epidermal wounding. After an initial lag phase the regenerative response is principally effected by a recruitment to the proliferating pool of cells with a high rate of DNA synthesis. The cells seem to be programmed to rapid differentiation. Studies with cholera toxin suggest that this adenylate cyclase-stimulating agent is able to induce significant changes in the regenerative process causing a prolonged, but less intense, proliferative response leading to lateral growth rather than to rapid differentiation.