Photo Source: https://www.researchsquare.com/article/rs-6836543/v1
To sustainably supply the endangered Japanese eel, the development of cell-cultured eel is expected. However, there have been no spontaneously immortalized adipocyte cell lines in fish species, and the foundation for reproducing fat tissue has been limited.
Under these circumstances, a research group from the Tokyo Metropolitan Industrial Technology Research Institute (Dr. Eriko Kishino) and Kitasato University (Associate Professor Daisuke Ikeda) successfully established three spontaneously immortalized preadipocyte cell lines (JE-KRT224, JE-EK9, JE-F1140) from Japanese eel muscle tissue.
The paper, titled “Establishment and characterization of spontaneously immortalized Japanese eel muscle-derived preadipocyte cell lines for cultured seafood production,” was published as a pre-peer-review preprint on Research Square, a research publication platform.
Kitasato University also succeeded in establishing a spontaneously immortalized myoblast cell line JEM1129 from Japanese eel muscle tissue in August last year. With this latest achievement, researchers have taken a step closer to realizing cultured meat that resembles “fatty” grilled eel (kabayaki).
Regarding this development, Associate Professor Ikeda commented to Foovo as follows:
“In this study, we successfully established the world’s first preadipocyte cell line derived from Japanese eel, and clarified its fat accumulation and differentiation capabilities.
By combining these with previously established myoblast cell lines, we expect to achieve tissue architecture similar to that of actual eel meat. Going forward, we will focus on establishing large-scale culture technology, which is essential for commercialization, and further advance research toward edibility.”
Establishment of three cell lines with fat differentiation, lipid accumulation, and fatty acid uptake capabilities
Source: Establishment and characterization of spontaneously immortalized Japanese eel muscle-derived preadipocyte cell lines for cultured seafood production
All three cell lines differentiated into adipocytes in mammalian cell adipogenic differentiation medium, and lipid droplet formation was confirmed by Oil Red O staining after 10 days of culture.
The three lines have achieved more than 120 cumulative cell doublings (120 PDL) to date, confirming immortalization. The population doubling time (PDT) averaged approximately 20 hours, which is faster compared to other fish species such as sea bass (approximately 30 hours).
Furthermore, when cultured in oleic acid-containing medium, higher fatty acid uptake was confirmed compared to medium without oleic acid. While no significant difference was observed between the two groups after one week of culture, lipid accumulation within cells was observed in the oleic acid-supplemented medium after 3 weeks, showing a significant increase. This confirmed that all three lines possess both lipid uptake and accumulation capabilities.
Source: Establishment and characterization of spontaneously immortalized Japanese eel muscle-derived preadipocyte cell lines for cultured seafood production
Eels are high-fat fish containing approximately 20% lipids, and these lipids play a key role in their unique flavor and texture.
In all three cell lines, the composition of accumulated fatty acids generally matched the fatty acid profile of Japanese eel muscle, suggesting potential for flavor reproduction.
Additionally, the three cell lines formed multilayer structures in vitro, indicating the potential to achieve three-dimensional tissue without a scaffold. Furthermore, the use of an appropriate scaffold for cell adhesion may enable more efficient three-dimensional culture.
Furthermore, even in standard medium, the cells simultaneously expressed mesenchymal stem cell markers (CD29, CD73, CD105) and vimentin, the adipogenic transcription factor PPARG, and the lipid-binding protein FABP4. This molecularly confirmed that all three lines are preadipocytes derived from mesenchymal stem cells within muscle tissue.
Optimization of culture medium is a challenge for co-culture and low-cost design
On the other hand, for practical implementation, the development of food-grade, low-cost media is required.
For JE-KRT224 culture, medium containing 10% FBS was optimal, and the cells did not proliferate in serum-free conditions. Additionally, this study used reagents such as insulin and dexamethasone for adipogenic differentiation induction, which are not expected to be used in food applications.
The paper points out that low/serum-free media for fish and media that can co-culture fish-derived myoblasts and preadipocytes have not yet been established, and the development of edible, low-cost FBS-free alternative media is a future challenge.
The preadipocyte cell lines established in this study are promising as a lipid source necessary for constructing high-fat Japanese eel-like tissue, and the three-dimensional construction of cultured eel meat has become realistic through combination with myoblast cell lines.
The fact that Japan, the world’s largest consumer of eel, has produced the world’s first spontaneously immortalized preadipocyte cell line derived from Japanese eel is highly significant. It marks an important step forward that will help accelerate future commercialization.
This article is an English translation of a Foovo article, published with permission from Foovo.
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