Single-cell transcriptomics reveals cellular heterogeneity and cell-cell communication networks in free gossypol-induced enteritis in juvenile largemouth bass (Micropterus salmoides).

This study utilized single-cell transcriptomics to reveal the cellular heterogeneity and cell-cell communication networks in free gossypol-induced enteritis in juvenile largemouth bass (Micropterus salmoides). Four isonitrogenous and isolipidic diets were formulated: a fishmeal-based control (FM) and three diets supplemented with 150, 300, or 600 mg/kg gossypol acetate (FG150, FG300, or FG600). Healthy fish (14.80 ± 0.10 g) were randomly assigned to four groups (four replicates of 25 fish each) and fed for eight weeks. Results showed that increasing dietary FG progressively impaired growth performance and intestinal health. Compared to FM group, FG600 group exhibited lowest growth performance; reduced plica height/ width, muscular layer thickness, and goblet cell numbers; elevated serum lipopolysaccharide and D-lactic acid; decreased serum phosphatase activities; lowest intestinal total antioxidant capacity; downregulated tight-junction genes (such as zo-1, zo-2, occludin, and claudin15); upregulated pro-inflammatory cytokines (tnf-α, il-1β, il-8, and nf-κb1); and increased abundance of potentially pathogenic bacteria (Aeromonas and Vogesella). Single-cell transcriptomic identified nine intestinal cell types, including epithelial cells, B cells, macrophages, and others. In FG600 group, proportions of epithelial cells, macrophages, and B cells in the G1 phase decreased, along with reduced communication strength/ probability among neuroendocrine cells, M1 macrophages and mature B cells. Pseudotime analysis identified branch point 1 as a critical immune-related node in epithelial differentiation. In conclusion, FG impairs growth performance and intestinal health in juvenile largemouth bass, likely by increasing abundance of potential pathogens, disrupting neuroendocrine-immune cell communication; activating macrophages/ B cells, inducing inflammation, inhibiting epithelial repair, and compromising intestinal barrier function.