Mathematical-model-guided development of full-thickness epidermal equivalent

Epidermal equivalents prepared with passaged keratinocytes are typically 10-20 μm thick, whereas intact human epidermis is up to 100 μm thick. Our established mathematical model of epidermal homeostasis predicted that the undulatory pattern of the papillary layer beneath the epidermis is a key determinant of epidermal thickness. Here, we tested this prediction by seeding human keratinocytes on polyester textiles with various fiber-structural patterns in culture dishes exposed to air, aiming to develop a more physiologically realistic epidermal model using passaged keratinocytes. Textile substrate with fiber thickness and inter-fiber distance matching the computer predictions afforded a three-dimensional epidermal-equivalent model with thick stratum corneum and intercellular lamellar lipid structure. The basal layer structure was similar to that of human papillary layer. Cells located around the textile fibers were proliferating, as indicated by BrdU and YAP (Yes-associated protein) staining and expression of melanoma-associated chondroitin sulfate proteoglycan. Filaggrin, loricrin, claudin 1 and ZO-1 were all appropriately expressed. Silencing of transcriptional coactivator YAP with siRNA disturbed construction of the three-dimensional structure. Measurement of trans-epidermal water loss (TEWL) indicated that the model has excellent barrier function. Our results support the idea that mathematical modeling of complex biological processes can have predictive ability and practical value.