Epidermal‐dermal and fibronectin cell‐interactions during fish scale regeneration: immunofluorescence and TEM studies

Abstract

Summary— Fibronectin (FN) immunolocalization and ultrastructural observations of epidermal‐dermal cell interactions during skin regeneration of the cichlid fish Hemichromis bimaculatus after scale removal were carried out for a healing period of 48 h. On control samples after scale removal, FN was localized on the surface of a thin cellular sheet, the scale‐pocket lining (SPL), separating the dermis from the scale‐associated cells. A layer of extracellular matrix, constituting a basement membrane, was observed on the SPL surface. Study of wound healing showed that in less than 1 h epithelial cells spread rapidly over the undamaged SPL surface on which FN was still present after the scale was removed. It appeared that this FN can be damaged or lost if the area is exposed to the exterior water for more than one hour. When epithelial continuity was re‐established, an epithelial‐SPL space was formed and was progressively filled by an electron‐dense extracellular matrix. No basement membrane was defined until both tissues were separated by dermal cells about 30 h after the wound was inflicted. FN is detected in the epithelial‐SPL interface from 12 h to 30 h after scale removal. Therefore, in normal skin, specific localization of FN in the interface between the scale‐associated cells and the outer surface of the SPL cells can be implicated in the attachment between the scale and the SPL surface favoring a flexibility of scale movement during swimming. In addition, FN could play an important role as a major extracellular matrix protein during wound‐healing after scale removal.