Dietary supplementation with a multi-strain yeast fraction enhances skin wound healing in zebrafish (Danio rerio)

Abstract

Mechanical skin lesions are a persistent issue under aquaculture operations compromising fish health and robustness. Using an established zebrafish model, the study compared the potential skin wound healing benefit of dietary supplementation with a single-strain yeast fraction rich in β-glucans (β-glucan diet) or with a multi-strain yeast fraction (MsYF). Adult zebrafish were divided into four triplicated groups (12 tanks; 25 fish/tank) as negative control (unwounded-basal diet); control (wounded-basal diet), β-glucan (wounded-β-glucan diet), and MsYF (wounded-MsYF diet) and, following 7-week of nutritional preparation, inflicted with a full-thickness skin wound using a biopsy punch. Wound healing was assessed macroscopically by measuring wound surface area (18 fish individually tracked/group) until full healing within 4 weeks; as well as by histopathological diagnostic, transcriptional and immunoblotting analysis at the wound site at 1, 4 and 9 day post-wound (dpw) over the early healing phase (re-epithelization and inflammation). Following an initial expansion, wound closure was first measured at 4 dpw in the β-glucan and MsYF groups showing a positive and significantly higher daily wound closure rate compared to the control. Later at 16 dpw, cumulative and daily wound closure were significantly higher in the MsYF compared to the β-glucan and control groups. Enhanced gross wound healing was confirmed by histopathological diagnosis of mitigated inflammation, earlier re-epithelization and significantly enhanced granulation tissue synthesis in the MsYF group. Targeted transcriptomic and proteomic markers documented an early up-regulation of matrix metalloproteinases and a dampening or quicker resolution of inflammatory and cellular stress markers in the healing tissues of the MsYF compared to the control group while the β-glucan diet overall elicited intermediary results. Overall, this study demonstrates that dietary supplementation with a yeast-based functional compound can modulate fish immune response in wound healing and promote early wound closure indicating a role for skin health management under aquaculture operations.