Spreading, proliferation, and differentiation of the epidermis after wounding a Cichlid fish,Hemichromis bimaculatus

Abstract

A large superficial wound has been experimentally provoked in the cichlid fish Hemichromis bimaculatus to study the interactions between the epidermal cells and the substrate on which they spread, on the one hand, and the restoration of the subepidermal tissues and the epithelial-mesenchymal interactions preceding scale regeneration, on the other hand. The re-epithelialization process, e.g., migration, spreading, differentiation, and proliferation of the epidermal cells, has been followed step by step, using light, scanning and transmission electron microscopy, and tritiated thymidine incorporation, until complete reorganization of the healing epidermis. Wound healing is fast (500 microm/hr) and proceeds centripetally from the wound margins. The epidermal cells spread on a wound surface which is composed of two different matrices: the remains of basement membrane materials covering the scale-pockets, and collagen fibrils of cut dermal strips. Even though both matrices favour cell spreading and attachment, migrating cells show a different behaviour. The re-epithelialization of the wound follows an orderly sequence similar to amphibian and mammalian wound healing, i.e., a "leap frog" mechanism of cell locomotion involving three epidermal layers. The basal layer cells, which spread on the substrate, and the superficial layer cells which protect the epidermis, differentiate first. Whatever the type of substrate over which the epithelium spreads (basement membrane material or collagen fibrils), the epidermal basal layer cells differentiate as soon as they become attached. The incorporation of tritiated thymidine has revealed that there is no proliferation in the healing epidermis until after complete closure of the wound, but that the rapid re-epithelialization of the large surface requires the recruitment of epidermal cells at the wound margins. The present study offers new data on the dynamics of re-epithelialisation and on the resistance of cichlid skin to such wounds. It is also clearly shown that the epidermal basal layer cells differentiate rapidly, a step which is interpreted as the first stage of epithelial-mesenchymal interactions that will lead to scale regeneration.

Re-epithelialization of cutaneous wounds in adult zebrafish combines mechanisms of wound closure in embryonic and adult mammals

“…Time-lapse in vivo imaging of Tg(krt4:GFP) fish, where the superficial epidermal cells are labelled with GFP, revealed that partial-thickness wounds close very rapidly with a speed of ∼500 µm/h (Fig. 1D), in line with previously reported rates for partial-thickness wounds in the cichlid fish Hemichromis bimaculatus (Quilhac and Sire, 1999). By contrast, full-thickness wounds closed more slowly (∼250 µm/h; Fig.…”

Skin development in bony fish with particular emphasis on collagen deposition in the dermis of the zebrafish (Danio rerio).

“…In addition, in providing a larger epidermis surface the microridges probably improve the efficiency of the secretion at the cell surface (Whitear, 1970(Whitear, , 1990. The upper cell layer, through its rich content in microfilaments, probably keratin filaments, also ensures the animal with protection against osmotic shocks, as shown during wound healing (Quilhac and Sire, 1999). These outer epidermal cells are not renewed periodically, but are individually replaced when dead.…”

“…Most cells of this intermediate region remain, however, undifferentiated. They serve as a reservoir to replace dead cells in each of the epidermis regions and they can divide rapidly when necessary, during wound healing for instance (Quilhac and Sire, 1999). The third, deep region of the epidermis is composed of a single cell layer (the basal layer), the main function of which is to keep the epidermis attached to the underlying dermis by means of anchoring structures (hemidesmosomes) attached to the basement membrane.…”

Histopathology and Wound Healing in Oxytetracycline Treated Oreochromis niloticus (L.) Against Aeromonas hydrophila Intramuscular Challenge

“…These results corroborate the findings of Ashley et al [31], who described a temporal precedence of epidermal over dermal repair. Quilhac and Sire [32] also observed a rapid differentiation of the epidermal basal layer cells during the re-epithelialization process after wounding of a cichlid fish. The depression at the site of injection during the recovery period is an indication that the tissue re-growth or dermal repair had not reached steady state levels.…”