All-trans retinoic acid differentially suppresses the expression of differentiation genes in human epidermal keratinocytes in vitro

초록

Retinoids (vitamin A and its analogs) have been shown to regulate epithelial cell growth and differentiation. The modulation of genes involved in epidermal differentiation by retinoids offers the opportunity to exploit differential expression in various dermatoses. Normal human epidermal keratinocyte (NHEK) cells were grown in 0.05 mM calcium. At confluency, the calcium concentration was raised to 1.2 mM and all-trans retinoic acid (atRA) at 1 10 - 8 to 1 10 - 6 M was added. RNA was isolated at 1, 2, 3, 4, 6, and 8 days after treatment. RT-PCR of total RNA done during the exponential phase of the PCR reaction showed decreased expression of keratin 1 (K1), K10, loricrin (Lor), profilaggrin (PF), small proline rich protein 1 (SPR1), SPR2, transglutaminase 1 (TGase1) and TGase3, but not involucrin (Inv), TGase2, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Kinetic analyses showed decreased expression of: TGase1, TGase3 and K10 after 1 day; Lor, SPR1 and SPR2 after 2 days; and PF after 3 days. This experimental system shows that the various differentiation genes are in fact regulated differently by atRA. Moreover, it affords an opportunity to explore the effects of receptor-selective retinoids in a single culture system to specifically investigate the expression of individual epidermal differentiation genes.