Increased levels of keratin 16 alter epithelialization potential of mouse skin keratinocytes in vivo and ex vivo

The process of wound repair in adult skin is complex, involving dermal cont raction and epithelial migration to repair the lesion and restore the skin' s barrier properties. At the wound edge, keratinocytes undergo many changes that engender an epithelialization behavior. The type II keratin 6 and typ e I keratins 16 and 17 are induced well before cell migration begins, but t he role of these proteins is not understood. Forced expression of human K16 in skin epithelia of transgenic mice has been shown to cause dose-dependen t skin lesions concomitant with alterations in keratin filament organizatio n and in cell adhesion. Here we show, with the use of a quantitative assay, that these transgenic mice show a delay in the closure of full-thickness s kin wounds in situ compared with wild-type and low-expressing K16 transgeni c mice. We adapted and validated an ex vivo skin explant culture system to better assess epithelialization in a wound-like environment. Transgenic K16 explants exhibit a significant reduction of keratinocyte outgrowth in this setting. This delay is transgene dose-dependent, and is more severe when K 16 is expressed in mitotic compared with post-mitotic keratinocytes. Variou s lines of evidence suggest that the mechanism(s) involved is complex and n ot strictly cell autonomous. These findings have important implications for the function of K16 in vivo.