Kinetics of regression of epidermal hyperplasia in the the skin of mice following abrasion.

Previously, we reported the kinetics of epidermal production during the early phase of epidermal regeneration following abrasion in the skin of mice. We pointed out that following abrasion, epidermal regeneration is characterized by the production of a marked epidermal hyperplasia resulting in a massive overproduction of epidermis, amounting to over a fourfold increase in epidermal wet weight compared to normal. The purpose of this report is to present the kinetics of reduction of epidermal mass following the production of the epidermal hyperplasia as the epidermis returns to its normal thickness during the period of regression. After an almost six times increase in epidermal wet weight per unit area at 5 days after abrasion, epidermal wet weight per unit area begins to decrease gradually, approaching normal levels by 21 days. The gradual decline in epidermal wet weight is associated with a concomitant decrease in the number of nucleated epidermal cell layers, total and suprabasal nuclei per millimeter of interfollicular epidermis, and in the number of mitoses per 1000 nuclei.