Feeder cell–dependent primary culture of single blastula–derived embryonic cell lines from marine medaka (Oryzias dancena)

Fish embryonic stem cells (ESCs) are derived from blastomeres that have been cultured from blastula embryos. The most widely used method for derivation of fish ESCs is the culture of blastomeres that have been isolated from approximately 10 blastula embryos under feeder-free conditions. However, this method leads to intercellular genetic heterogeneity among the cultured cells, which is a major obstacle to the development of stable ESC culture conditions. In this study, to establish ESC lines with intercellular genetic homogeneity at the early stage of culture, we attempted to derive embryonic cell lines from single blastula–derived blastomeres of marine medaka (Oryzias dancena) in a feeder cell culture system. Using basic fibroblast growth factor–expressing feeder cells during primary culture, we successfully established 22 single blastula–derived embryonic cell lines that could be subcultured more than 20 times. In contrast, we were unable to efficiently derive cell lines using wild-type feeder cells and under feeder-free conditions. The established cell lines exhibited ESC-like cell characteristics in terms of alkaline phosphatase activity, pluripotency-related gene expression, and embryoid body formation. The results of this study will contribute to the development of methods for derivation of fish ESCs.