Skin and scale regeneration after mechanical damage in a teleost

Skin wound healing has been widely studied in mammalian models but the information on teleost cutaneous healing is sparse and frequently considered in the context of viral or bacterial infections or parasitic infestations in aquaculture. In the present study a detailed time course (0 h, 6 h, 1, 2, 3 and 4 days) coupled to morphology and gene expression analysis revealed rapid regeneration of skin without scarring in a marine teleost after a superficial wound caused by the loss of a large area of scales. The integrity of the integument, as assessed by quantification of extracellular matrix (ECM) gene transcripts (fn1a, colIα1, colVα2, colXα1, ogn1, ogn2, crtac1a, cyr61, pcna, krt2 and mmp9) was restored within 2 days. Epithelial-mesenchyme interactions assessed by expression of edar and shh were associated with epidermal closure, the re-establishment of the basement membrane and also scale eruption. Histological observations suggested tissue re-epithelialization was independent of inflammation and that transcripts representing the humoral and cellular elements of the immune response (mpo, cyba and csf1r, cd48 and cd200) were modulated in the early stages of sea bream (Sparus aurata) skin repair after injury. Overall, the results indicate that after superficial skin damage tissue reconstitution started immediately with re-epithelialization, followed by ECM deposition and finally tissue maturation, indicating that in the skin regenerative process, reconstitution of the physical barrier was the priority over other integument functions, including immune surveillance.