014 Epiboly in Bioengineered Skin as a Novel Method for Studying Epidermal Migration and Determining Construct Viability

There are only a few models for studying epidermal migration in vitro, and their interpretation is made difficult by reliance on cell monolayers and the choice of a specific substrate. In this study, the process of keratinocyte migration and epiboly were investigated by using a bilayered bioengineered skin construct, consisting of human neonatal foreskin keratinocytes and dermal fibroblasts (Apligraf, Organogenesis, Canton, MA). At baseline, 6-mm punch biopsies of the construct were placed in serum-free media (AIM-V) or DMEM with or without 10% FBS. At varying time points the bioengineered skin samples were processed and analyzed by histology and immunostaining. By 72 hours, in a time-dependent manner, the epidermis had migrated over and enveloped the entire dermis (full epiboly). Full epiboly was partially inhibited by serum and was maximal in serum-free medium. Epiboly was preserved 5 days after stated expiration date and was equivalent to that seen in unexpired construct when stored at room temperature. The process of epiboly was downregulated in a dose-dependent manner by neutralizing antibodies to EGF and TGF-beta 1. The migrating epithelium was characterized by decreased keratinocyte proliferation (as per Ki67 immunostaining) and increased expression of vitronectin (epibolin). Increasing concentrations of antibodies of vitronectin blocked the process of epiboly, as did antibodies to the alpha5-betaV integrin receptor, which mediates vitronectin-driven keratinocyte locomotion. Interesting, epiboly was also blocked by preseeding human dermal fibroblasts on the dermal side of the construct. We propose that the process of epiboly in this model can be used to better understand and assess the mechanisms involved in keratinocyte migration and may be used as an assay for establishing construct functional viability.