The effect of 3T3 fibroblasts on the expression of anchorage independence and cornification of oral keratinocytes

Relationship between the proliferation of keratinocytes cultured in vitro and prostaglandin E2

In the growth of keratinocytes "in vitro", PGE2 seems to play an important role. We have shown that in fibroblast-keratinocyte co-cultures, indomethacin, employed at concentrations which inhibit the PGE2 synthesis, reduced the proliferation of epidermal cells. This effect was reversed by an exogenous PGE2 addition to the culture media. To better understand the relationship between keratinocytes and the autacoid, we have tested PGE2 at various concentrations in different cultural conditions, that is, epidermal cells were grown on a 3T3-J2 feeder layer, without fibroblasts and with a 3T3-J2 conditioned medium. We observed an increase in keratinocyte proliferation induced by the autacoid alone in the presence of fibroblasts, while a severe inhibitory effect was relieved when dermal cells or the conditioning medium were absent. The lack of fibroblasts and their products in the culture medium modified the morphology of keratinocytes cultured in vitro. PGE2 induced significant morphological and morphometrical variations only if added to the conditioning medium. The autacoid decreased the expression of 66 kDa protein, if cells were grown in the presence of fibroblasts or with conditioning medium, whereas it completely inhibited this keratin and those of 60, 54 kDa if cells were cultured only with a basal medium. From morphometrical and electrophoretical data we can suppose that PGE2 inhibits cell differentiation. Thus PGE2 action on keratinocytes seems to be strictly related to the presence of dermal cells.

Inhibited morphological terminal differentiation and enhanced proliferation of cultured mouse epidermal cells at different concentrations of dimethyl sulphoxide

Dimethyl sulphoxide (DMSO), at concentrations of 1-2%, induces terminal differentiation in several different cell types in vitro and enhances the growth of newborn mouse epidermal cells in primary culture under conditions that also permit terminal differentiation. We have found that DMSO concentrations approaching 4% reversibly inhibited (with little overt toxicity) terminal differentiation of normal epidermal cells from newborn SENCAR mice. Cells cultured in medium containing 4% DMSO and calcium in excess of 1 mM did not stratify extensively or slough large amounts of keratinized debris into the medium as occurred in control cultures, nor did they form large numbers of squamous cells or keratin bundles, as revealed by light and electron microscopy. The number of detergent-insoluble cornified envelopes was similarly reduced. Long-term growth of epidermal colonies in secondary culture was optimum in 1% DMSO, this concentration also permitting normal terminal differentiation of these cells. Since DMSO had these effects on epidermal cells in vitro, it may also affect epidermal cell proliferation and terminal differentiation in vivo, an important consideration should DMSO ever be approved for topical use in the US.