Physiological and retinoid-induced proliferations of epidermis basal keratinocytes are differently controlled

The 2002 study explored how retinoic acid (RA) and its receptors (RARs) affect the proliferation of basal keratinocytes in the epidermis. It was discovered that the normal renewal of keratinocytes does not require RAR-mediated signaling, as evidenced by the maintenance of proliferation in mice lacking RARα, RARβ, and RARγ. However, RA-induced epidermal hyperplasia was found to depend on RXR/RARγ heterodimers, with RXRα/RARγ being necessary for this process, while RXRα/RARα heterodimers were not. The study also indicated that RARγ plays a crucial role in the suprabasal layers for RA-induced hyperplasia, and there is some functional redundancy among the RARs and RXRs. The specific number of mice used in the study was not mentioned in the summary.