Epithelial resealing.

Epithelia have the essential role of acting as a barrier which protects living organisms and its organs from the surrounding milieu. Therefore, it is crucial for epithelial tissues to have robust ways of maintaining its integrity despite the frequent damage caused by injury, inflammation and normal cell turnover. All epithelia have some capacity to repair themselves. However, the wound-healing process differs dramatically between the developmental stage and the type of tissue involved. In this review, we will not analyse all aspects of wound healing; instead we will focus on the capacity which several simple epithelial tissues have to reseal small discontinuities very rapidly and efficiently, a process that we call epithelial resealing. We will start by describing the initial experiments which demonstrated the existence of a purse string mechanism to repair embryonic wounds and we will compare this mechanism with embryonic morphogenetic movements which resolve epithelial discontinuities that arise during the normal course of development. We will then discuss other contexts in which epithelia resealing occurs, both in cell culture systems and in adult tissues, and which suggest that at least some of the mechanisms that regulate epithelial resealing may be conserved, acting in several types of simple epithelia, both in embryos and in adults, and across species.