Establishment of spontaneously immortalized Japanese eel muscle-derived preadipocyte cell lines for cultured seafood production.

The lack of immortalized fat cell lines is a significant bottleneck for cultured seafood production. Here, we report three spontaneously immortalized cell lines (JE-KRT224, JE-EK9, and JE-F1140) from the muscle of juvenile Japanese eel (Anguilla japonica) capable of robust lipid accumulation. These lines exhibit stable proliferation with good population doubling times and have been cultured for over 120 population doubling levels, indicating spontaneous immortalization. They efficiently absorbed exogenous fatty acid (oleic acid), accumulated intracellular lipids, and developed a fatty acid profile comparable to that of native eel meat. Furthermore, all lines successfully differentiated into adipocytes using standard induction conditions. They expressed the mesenchymal marker vimentin, key mesenchymal stem cell markers (CD29, CD73, CD105), and adipogenic markers (PPARG, FABP4), supporting their characterization as preadipocytes likely derived from mesenchymal stem cells. These novel cell lines represent a valuable resource for advancing fish adipogenesis research and developing multi-component cultured eel meat.