Known as a center of the goldfish industry, the city of Yatomi, Aichi Prefecture, is exploring a medical spinoff from the bubble eye goldfish.
Experts believe the fluid in sacs beneath the eyes could be a cell growth stimulant with valuable uses in medical research.
The research is being conducted at the Aichi Fisheries Research Institute’s inland water fisheries research center, which has a tuition center in Yatomi.
Yatomi and the city of Yamatokoriyama in Nara Prefecture are both known as centers of goldfish breeding. However, as with other industries, goldfish breeding experts are aging.
The number of goldfish produced in Yatomi hit a peak in 1975 of 71.57 million and has been decreasing since then, falling to 8.53 million in 2015.
The city has been looking into developing business opportunities for goldfish other than as an ornamental fish. In 2007, it launched joint research with Satohiko Araki and other researchers from Nagoya University Graduate School of Science’s Sugashima Marine Biological Laboratory in Toba, Mie Prefecture.
The research is aimed at replacing the widely used fetal bovine serum (FBS).
Using the fluid from goldfish is considered highly safe as humans share fewer common illnesses with fish than with cows.
Moreover, FBS may contain harmful elements such as prions, which can lead to bovine spongiform encephalopathy and its human equivalent.
However, the amount of fluid that can be extracted from a wild fish is a small fraction of its body weight, which means a great number have to be sacrificed.
The researchers eventually started examining bubble eye goldfish, which were developed through crossbreeding mutated crucian carp.
Using a syringe, they can extract 40 milliliters of fluid, close to 30 percent of the fish’s body weight, from a mature goldfish measuring roughly 10 cm.
The sacs deflate once they are empty but fill up again in a few months, allowing researchers to extract fluid from the same fish repeatedly.
The fluid has been shown to stimulate the growth of human cells.
An experiment was conducted to compare how many vascular endothelial cells grow in 10 days using a cell culture solution containing fluid from a bubble eye, compared with an FBS solution and one lacking a growth stimulant.
The results showed that the bubble eye batch was 1.14 times more effective than the FBS solution, and 4.89 times more than the third one.
The researchers acquired a patent for this cell growth technology in December.
Meanwhile, there remain issues to be resolved before the fluid can be put to practical use.
Cells from human skin and organs increase by attaching themselves to surrounding cells.
To culture cells artificially, the stimulant must have strong properties of adhesion so the cells can attach themselves to the basic container.
However, the fluid from bubble eye goldfish is not as adhesive as FBS.
The researchers believe its adhesion can be improved if the surface of the container is treated or if activated carbon is added.
“Cell culture is essential to many aspects of the medical industry, from the diagnosis of illnesses and the development of drugs to gene therapy and regenerative medicine,” said researcher Junpei Arakawa of the institute.
“We hope that the fluid sacs of artificially created ornamental fish can be useful in the medical field,” he added.
The bubble eye goldfish has been around since the Qing dynasty. It was treated as a closely guarded treasure in China.
The fish were imported to Japan for the first time in 1958. They are now widely available in pet stores at a cost of about ¥1,000 each.
This section, appearing Tuesdays, features topics and issues from the Chubu region covered by the Chunichi Shimbun. It is appearing on Wednesday this week because Tuesday was a press holiday. The original article was published on Oct. 3.