The supplementation of mannan oligosaccharide in diet promotes the skin wound healing of juvenile turbot, Scophthalmus maximus

A 30-day feeding trial was conducted to investigate the effects of the supplementation of mannan oligosaccharide (MOS) in the diet on the skin wound healing process of juvenile turbot (Scophthalmus maximus). Two groups of diets were formulated, the control diet (CON) and the control diet supplemented with 0.16 % MOS (MOS), which were fed to the turbot separately. Each group had 3 replicates, with 20 fish per replicate. At the end of the feeding trial, all the fish were weighed and counted. Then four fish per tank were randomly selected for sampling, and the skin of the rest fish was wounded by a biopsy punch. The wounded fish continued to be fed as usual with the same diets respectively, and then sampled again at the 1, 3, and 7 day(s) post wounding (dpw). The results by image analysis showed that the wound closure rate of wounded fish was significantly improved by the supplementation of dietary MOS. As for the results of gene expression, dietary MOS promoted the expression of pro-inflammatory factors (il-1β & tnf-α) and decreased the expression of anti-inflammatory factors (tgf-β1 & il-10). It also enhanced the expression of genes related to re-epithelialization (mmp-9, fgf2, tgf-β1, rock1), as well as new tissue formation and remodeling (fn1, lamb2, col1-α, vegf). Furthermore, dietary MOS promoted re-epithelialization, cell proliferation, collagen deposition, and angiogenesis according to the histomorphological observation. In addition, the supplementation of MOS modified the communities of skin microbiota, decreasing the abundance of Rolstonia, Pseudomonas, and Aeromonas, while increasing the abundance of Pseudoalteromonas luteoviolacea and Shewanella colwellianav. In conclusion, the supplementation of dietary MOS (0.16 %) can promote the re-epithelialization and the recruitment of inflammatory cells, stimulate ECM biosynthesis and angiogenesis, modify the communities of skin microbiota, and ultimately promote the skin wound healing process.