Murine Keratinocyte Cultures Grown at the Air/Medium Interface Synthesize Stratum Corneum Lipids and “Recycle” Linoleate During Differentiation

In a recent investigation we showed that murine keratinocyte cultures grown at the air/medium interface in the presence of dermis exhibit morphologic differentiation comparable to that seen in vivo, including the formation of lamellar granules and stratum corneum intercellular lipid lamellae. In the present study, lifted cultures were found to more closely reproduce the lipid composition of the parent epidermal tissue than submerged cultures grown on plastic. In addition, the specific fatty acid profile of individual lipid classes in lifted cultures was, in general, remarkably well maintained in vitro. Acylceramides, which are highly enriched in linoleic acid in vivo, remained enriched in vitro; however, the linoleic acid content of the cultures was substantially lower than that in vivo, confirming previous reports of the relative essential fatty acid deficiency of standard culture media. As the lifted cultures differentiated over time, the lipid composition changed to reflect the formation of a stratum corneum with its different complement of lipids. Label from [U-14C] linoleic acid was specifically incorporated into linoleate-containing lipids during short pulses in both submerged and lifted cultures. Changes label distribution over a long chase period in lifted cultures indicated that linoleate was transferred from phospholipids to ceramides, providing evidence for the “recycling” of essential fatty acids in epidermis