Retinoids alter the direction of differentiation in primary cultures of cutaneous keratinocytes

Abstract

The effects of vitamin A on the morphological expression of differentiation were studied in cell cultures of cutaneous keratinocytes from the newborn rat. The cells were first cultivated in a medium containing 0.11 mM calcium until a confluent monolayer had been formed. Stratification and terminal differentiation were then triggered by raising the calcium concentration of the medium to 1.96 mM ('normal' culture). The rise in the concentration of calcium was coupled with the addition of retinol (RL) of retinoic acid (RAC) to the medium to produce an excess of vitamin A (high-retinoid culture). Delipidized serum was used to produce a deficiency of vitamin A (low-retinoid culture). The tissue organization and the ultrastructure of the keratinocytes in the stratified culture were the same as those seen in conventional cultures and skin explants. These stratified cultures expressed the morphological features of the epidermis of intact skin. The addition of RL or RAC to the medium enhanced features characteristic of the secretory epithelium, such as the formation of an extensive endoplasmic reticulum, an enlargement of the Golgi zone, and an increase in the number of vacuoles. At the same time, the addition of retinoids diminished features characteristic of the terminal differentiation of the stratified squamous epithelium, such as stratification and keratinization. Deficiency of vitamin A in the medium resulted in a culture with many differentiated layers. The differentiated cells of the low-retinoid cultures contained densely packed tonofilaments and synthesized products that reacted with the monoclonal antibody AE2 that is specific for keratin peptides which are markers of epidermal differentiation. In the cell culture system that is presented here, an excess of retinoids redirected epithelial differentiation from a stratifying and keratinizing epithelium towards a secretory epithelium. This system is a useful tool for elucidating the mechanisms responsible for the effect of vitamin A on the differentiation of epithelial cells.

Golgi-disturbing agents

“…The DNA-binding properties of the receptor are altered, which eventually cause a direct regulation of transcription of specific genes in a developmental and cell-specific manner. Besides these characteristics, retinoic acid exerts a change in the GA morphology: in cutaneous keratinocytes, application of retinoic acid results in an enlargement of the GA and the appearance of vacuoles (Brown et al 1985), whereas in human monocytic leukemia THP-1 cell lines, the GA was only moderately developed in parallel to abundant lysosomes and mitochondria in the cytoplasm (Hyodoh 1987).…”

Regulation of interleukin 1 and its receptor in human keratinocytes.

“…18). Addition of Ca2+ to an extracellular concentration of 1.2-2.0 mM or addition of phorbol 12-myristate 13-acetate (PMA) to keratinocyte cultures can induce or accelerate overlapping subsets of markers associated with squamous differentiation (19)(20)(21)(22)(23)(24), and retinoic acid (RA) can block or reverse the appearance of these markers (25)(26)(27)(28). Because keratinocyte cultures both produce IL-1 and respond proliferatively to its presence, we reasoned that IL-1 or IL-1 receptor (IL-1R) or both might be critically regulated as the cells cease to divide and commit to terminal differentiation in culture.…”

Golgi-Disturbing Agents Lead to the Elimination of Intracellular Toxoplasma gondii

“…Retinoic acid induces Golgi swelling [18], modifies the endocytic routing in cells and blocks new protein secretion [24]. The effects of BFA and RA on intracellular parasites were observed only after 5 hours of incubation.…”

“…Ultrastructural studies showed that cytotoxic effects in the presence of OA, Mon, BFA and RA affected Golgi structure and function [14,[17][18][19][20]. Mon induced complete endomembrane parasite disorganization, and enlargement of PVs containing parasites.…”