Establishment and utilization of striped catfish skin epithelial cell line to study host-pathogen interaction

The scaleless striped catfish (Pangasianodon hypophthalmus) is an economically important aquaculture species but is frequently infected by Aeromonas hydrophila (AH), causing substantial economic losses. Fish skin mucosa plays a protective role by initiating inflammatory responses to AH challenge. However, how the skin epithelial cells, the outermost defensive layer of skin tissue, respond and interact with AH remains unknown. This study aims to establish a skin epithelial cell line from striped catfish and investigate the response of skin epithelial cells under AH challenge. Skin epithelial cells were isolated and subcultured at optimal temperature and serum concentration, and epithelial properties were confirmed by the epithelial marker cytokeratin. The established skin epithelial cell line was inoculated with or without AH to evaluate survival and immune responses. We found cells survived at a tissue-damaging concentration of AH and showed an extremely higher immune response. Moreover, the presence of mucus and its microbiome may regulate AH-induced immune response, suggesting a complexity of skin-AH interaction in vivo. In conclusion, this study successfully established a striped catfish skin epithelial cell line and utilized it to characterize the outermost skin epithelial responses to AH in the presence of the mucus microbiome. By employing this cell line, new insights into epithelial-level immune interactions with pathogens were provided.