Short-term low-protein feeding accelerated skin wound healing by promoting re-epithelialization, inflammation resolution, granulation tissue formation and remodeling in largemouth bass, Micropterus salmoides.

The present study evaluated the effect of short-term feeding with graded dietary protein levels on skin wound healing in largemouth bass (Micropterus salmoides). Three isolipidic diets containing 48% (P48), 52% (P52), and 56% (P56) crude protein were fed to fish (initial mean weight 13.00 g) for 5 weeks, followed by a standardized mechanical skin-wounding challenge. Wound repair was assessed at 1, 3, and 7 days post-wounding (dpw). The P52 diet supported better growth performance than the P48 diet. However, P48 accelerated wound closure and promoted more advanced histological repair, characterized by earlier re-epithelialization, more efficient necrotic tissue clearance, reduced wound bed area, and a thinner, more mature neo-epidermis. At the molecular level, P48 induced early upregulation of re-epithelialization-related genes, including mmp2, mmp9, and egf, accompanied by stronger MMP9 immunohistochemical signals. P48 was also associated with rapid inflammatory activation, shown by early increases in MPO, NAG, and LZM activities and il1b and tnfa expression, followed by faster inflammatory resolution and sustained il10 upregulation. In addition, P48 showed higher antimicrobial-defense-related markers and stronger extracellular-matrix-, angiogenesis-, and collagen-associated responses, as evidenced by higher expression of hamp, prf, fn1, lamb2, vegf, shh, and col1a1, stronger CD31-positive immunofluorescence signals, and greater collagen fiber accumulation. Western blotting further showed that FN1, SHH, and CCN1 protein responses were broadly consistent with their corresponding transcript-level patterns. Temporal response analysis further indicated a coordinated transition from early epithelial and inflammatory responses to later repair and remodeling responses. Correlation analysis showed that reduced wound area was significantly and negatively associated with both ccn1 transcript abundance and CCN1 protein abundance. These findings indicate that short-term low-protein feeding enhances skin wound healing and may represent a stage-specific nutritional strategy for farmed largemouth bass.