Establishment of a novel macrophage-like cell line from the head kidney of Larimichthys crocea: A useful cell model for investigating host-pathogen interactions.

Abstract

A novel cell line (LYC-hK) was established from the head kidney of large yellow croaker (Larimichthys crocea), a major marine aquaculture fish species in China. The cell line has been continuously subcultured for over 100 passages and exhibits stable morphology, transitioning to fibroblast-like. Specifically, it exhibits a transition toward epithelium-like phenotype at high density. Karyotype analysis verified the stability of the diploid chromosome: approximately 50 % of the cells retained 48 chromosomes at the 120th passage. Functionally, LYC-hK displayed robust macrophage-like activity, including reactive oxygen species production upon stimulation with lipopolysaccharide (LPS) or phorbol myristate acetate (PMA), and efficient phagocytosis of Nocardia seriolae and Pseudomonas plecoglossicida, followed by time-dependent intracellular bacterial clearance. Gene expression profiling revealed high transcript abundance of macrophage-specific marker genes, including CD68, mpeg1, CD209/DC-SIGN, and CD302, alongside strong induction of the pro-inflammatory cytokines IL-1β and IL-8 upon bacterial challenge. Notably, high-level expression of the CD34 gene was also detected which implies that the LYC-hK might possess hematopoietic progenitor-like properties. Furthermore, successful transfection of the LYC-hK cells with the pEGFP-C2 plasmid confirmed the line's suitability for studies involving exogenous gene expression. Collectively, these findings indicate that LYC-hK is a stable macrophage-like cell line, providing a valuable in vitro model for studies of host-pathogen interactions and functional genomics in teleost fish.