Lipid composition of cultured murine keratinocytes

The current study was undertaken to determine whether a previously reported murine culture system is an acceptable model for the study of epidermal lipid metabolism. The lipid composition of primary neonatal mouse keratinocyte cultures was determined and compared with that of freshly isolated keratinocytes and whole epidermis. 14C-Labeled arachidonic acid (AA) and linoleic acid (LA) were added to cultures and the incorporation into specific lipids was assessed. The lipid composition of the cultures indicated that they were partially differentiated, which parallels the well-known incomplete keratinization seen in many keratinocyte culture systems. Of particular importance, the LA-rich uniquely epidermal lipids which may be of importance in water barrier function, acylglucosylceramide (AGC) and acylceramide (AC), were made by the cultures. Fatty acid analysis of total lipid, phospholipid, and AGC extracts revealed a significant decrease in LA content compared with the parent epidermis; this may have resulted from the low level of LA in fetal bovine serum, which was the serum source for these cultures. Labeled AA and LA were incorporated into the lipids of cultured keratinocytes in distinct patterns that were consistent with the fatty acid content of the lipids. Both AGC and AC showed preferential uptake of LA compared with AA. There was minimal labeling of non-linoleate-containing lipids and a low degree of conversion of labeled LA to AA. Considering the grossly different environment of the in vitro system compared with the in vivo state, the overall lipid composition was remarkably well maintained. Keratinocyte cultures should be of great value in the study of epidermal lipid metabolism.