Effect of Vitamin A Acid on Homeostasis and Differentiation of Epidermal Cells Cultured on Collagen

Abstract

Cultured guinea pig epidermal cells were treated with vitamin A acid (VA; 2, 5, 10 μg/ml) and controlled by autoradiography and histochemical methods. Cells attached to the bottom of the plates were counted and their number correlated with the number of cells sloughed off into the medium (A/D ratio). VA reduced the size of multilayered cell colonies, favoured cell spreading and accelerated confluence. It altered the mode of shedding since the cells sloughed off into the medium as isolated cells rather than cell complexes, as in untreated controls. It increased the A/D ratio in early cell cultures and decreased the A/D ratio in late cell cultures. The higher the concentration of VA, the earlier and more prominent was the decrease of the A/D ratio. Low concentration of VA (2 μg/ml) given once at seeding favoured the formation of keratohyalin and cornifíed envelopes whereas high concentrations (5, 10μg/ml) given continuously prevented their formation and caused mucoid vacuolar degeneration of single cells. VA inhibited complete keratinization in all cases, but appeared to allow pre-keratinization, particularly at low concentrations. The results indicate that VA controls epidermal homeostasis in vitro by its influence on both proliferation and shedding. Its effect on the markers of differentiation is heterogeneous since it prevented keratinization in every case, but induced keratohyalin formation under certain conditions.

Lung organoid culture

“…Such an effect can be expected due to the known action of retinoids on the epithelium [38,111,141,1861. It seems that this cell type is more vulnerable than the epithelium.…”

“…The opposite effect of an inhibition of pneumocyte type I1 differentiation without any detectable effects on the connective tissue was achieved only by the retinoids. Such an effect can be expected due to the known action of retinoids on the epithelium [38,111,141,1861.…”

Regulation of the expression of epidermal keratinocyte proliferation and differentiation by vitamin A analogs

“…Retinoic acid has been shown to stimulate adult guinea pig keratinocyte proliferation during the first 24-60 h of culture [12][13][14], possibly by altering the plating efficiency and cell surface properties of the freshly trypsinized cells. After this initial effect, retinoic acid appears to affect the differentiation of the keratinocytes, primarily by influencing the attachement/ detachment ratio of the keratinocytes [9][10][11] and by decreasing keratin [7] and cell envelope formation [8]. Retinoids (vitamin A analogs) other than retinoic acid, however, appear to have different effects on in vitro keratinocytes [15].…”

Analysis of the expression pattern of the carrier protein transthyretin and its receptor megalin in the human scalp skin and hair follicles: hair cycle-associated changes

“…The upregulation of the two proteins in anagen VI hair follicles as well as their striking downregulation in catagen hair follicles suggest their essentiality in anagen maturation and maintenance. This might be accomplished by inducing keratinocyte proliferation and differentiation via internalization of many important biomolecules including vitamin A, which was found to control keratinocyte homeostasis in vitro by its influence on both proliferation and shedding (Mahrle and Gray 1983). This is further supported by the findings of Billoni et al (1997) that the retinoid-X-receptor-alpha is expressed in human hair follicle and that retinoid-Xreceptor agonist CD2425 stimulates hair growth and survival in vitro, and the finding of Bazzano et al (1993) that topical application of all-trans retinoic acid and other retinoids prolonged the anagen phase in mice (C 3 H mouse The immunoreactivity score (IR-score) was calculated by multiplying the percentage of positive cells (PP%) and the staining intensity (SI)…”