Abstract
Reepithelialization of skin which comprises epidermis and dermis has not been fully elucidated due to the complexity of the participants as well as the interactions therein. In this study, the intrinsic roles and behaviors of epidermis itself during wound closure on neonatal rat skin were explored by developing and utilizing a novel in vivo wound model, termed “shallow incisional wound” in which the injury of dermis was minimized. The shallow wounds were closed by 12 h postwounding (PW) by the migration of the wound-marginal epidermal sheets in which activated myosin light chain (p-MLC) was predominantly detected at the lateral plasma membrane of individual cells. By local administration of Rho-associated protein kinase (ROCK) inhibitor Y27632, p-MLC disappeared at the wound margin and wounds were not closed by 12 h PW. Inhibition of Rac 1 by NSC23766 also resulted in hold of wound closure by 12 h PW, though NSC23766 somewhat slowly acted on p-MLC expression. These results suggest that, without joining of dermis, epidermal cells have a potential ability of closing wounds by active epithelial sheet movement integrated by Rho family small GTPases-dependent extension and contraction of the individual cell bodies.
Highlights
Skin is located at the outermost layer of multicellular organisms, and plays a definite role in the maintenance of homeostasis [1,2]
A series of our previous study showed that full-thickness excisional wounds made on neonatal rats were covered with quick reepithelialization by the marginal epidermis, and that immunohistochemical analyses using anti-keratin and cadherin antibodies could discriminate the major cell populations of the epidermal cells covering the wounds into the basal cell-derived “leading edge cells” and “immature spinous cells” [4,5]
The results from these analyses suggest that the myosin phosphorylation which drives the contraction of cells located at the lower part of epidermis may be a prerequisite for the centripetal epidermal migration, i.e., the closure of the shallow incisional wounds, on neonatal rat skin
Summary
Skin is located at the outermost layer of multicellular organisms, and plays a definite role in the maintenance of homeostasis [1,2]. The balance between activities of these two Rho small GTPases is considered to be critical for migration and formation of cells, and the actions of Rac 1 and Rho A antagonize and downregulate each other [10,11,12,13] These findings were largely based on analyses using culture systems in vitro, and validation in vivo is poorly made except for only a few instances [10,14]. The experimental results obtained in this study strongly support the possibility that wound closure could be executed by the active migration of the only epidermis, independently of dermis, on neonatal rat skin
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