Melanocytes comprise from 5% to 10% of the cells in the basal layer of epidermis.

When miR-203 is expressed prematurely, basal cells diminish their proliferative potential; and when it is absent, proliferation is no longer restricted to the basal layer of epidermis.

CD44 is collocated with HA in the basal layer of epidermis where additionally it has been shown to be preferentially expressed on plasma membrane facing the HA-rich matrix pouches.

Hyperplasia may be due to any number of causes, including increased demand (for example, proliferation of basal layer of epidermis to compensate skin loss), chronic inflammatory response, hormonal dysfunctions, or compensation for damage or disease elsewhere.