Suppression of Vitamin D Receptor and Induction of Retinoid X Receptor Alpha Expression During Squamous Differentiation of Cultured Keratinocytes
TLDR As skin cells mature, vitamin D receptor levels decrease while retinoid X receptor α levels increase.
The study investigated the expression of Vitamin D Receptor (VDR) and Retinoid X Receptor α (RXRα) during the squamous differentiation of cultured keratinocytes. It found that VDR expression was suppressed while RXRα expression was induced during differentiation. Factors such as cell density, extracellular calcium levels, and treatments with EGF, KGF, TPA, and IFN-γ influenced these patterns. EGF and KGF prevented VDR downregulation, while high calcium and TPA promoted VDR suppression and RXRα induction. The responsiveness of keratinocytes to Vitamin D was reduced under conditions of postconfluence, high calcium, and TPA treatment, but not by IFN-γ. These findings highlighted the complex regulatory mechanisms governing keratinocyte differentiation and the roles of VDR and RXRα in this process.
