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Whale neurons unveil risk of environmental pollution: Japan-led research

Mari Ochiai is seen holding a paper on the direct reprogramming of somatic cells from melon-headed whales into neurons at Ehime University in Matsuyama, Ehime Prefecture, on Oct. 4, 2021. She visited the Ibaraki Prefecture city of Hokota immediately after melon-headed whales were stranded there. (Mainichi/Nobuto Matsukura)

MATSUYAMA, Ehime -- A research group has succeeded in directly reprogramming somatic cells from melon-headed whales into neurons for the first time -- a development that is likely to contribute to research on neurotoxicity in marine mammals and show how pollutants affect them.

    The findings by the research group led by Mari Ochiai, assistant professor of environmental toxicology at Ehime University Center for Marine Environmental Studies, were published in the American academic journal Environmental Science & Technology.

    According to the publication, the research group in 2015 cultivated fibroblasts, or connective tissue cells, using the individual tissue of melon-headed whales, after about 160 of them became stranded on the coast of the Ibaraki Prefecture city of Hokota.

    After several weeks of treating the cells with a solution mixed with low molecular weight compounds, the group obtained cells with a morphology similar to that of neurons. Methods including gene expression analysis revealed that they were artificially induced neuronal cells.

    Direct reprogramming, or the converting of somatic cells into other forms without the need to transition through induced pluripotent stem (iPS) cells, is attracting attention in fields including fundamental research and regenerative medicine. The group's research marked the first time for whale cells to be reprogrammed directly.

    The group then exposed these reprogrammed cells to substances called hydroxylated polychlorinated biphenyls (OH-PCBs), which are metabolized from polychlorinated biphenyls (PCBs), a common type of environmental pollutant. After 24 hours, over 80% of the reprogrammed neurons had self-destructed in a process called apoptosis. Exposure to OH-PCBs may have disrupted the cells.

    Apoptosis is a mechanism which kills cells that are severely damaged or detrimental to the body's own existence. It plays a role not only in the formation of human fetal limbs, and the disappearance of webbed cells, but also in the removal of cells infected with a virus or having genetic abnormalities, such as being cancerous.

    Persistent organic pollutants such as PCBs released into the environment have spread throughout the world, and a survey by Ehime University found 265 types of organic pollutants in marine mammals in the 1990s. The research group also detected PCBs in the brains of melon-headed whales that were stranded in Ibaraki, including the ones they examined.

    After studying marine biology at the University of California, Santa Cruz, Ochiai enrolled in Ehime University's graduate school in 2009, and has continued to analyze contaminants remaining in orcas and dolphins.

    Ochiai said, "Pollutants may cause issues other than apoptosis. We would like to explore complex contamination cause by various substances, and apply this toxicity evaluation technology to other marine mammals."

    (Japanese original by Nobuto Matsukura, Imabari Local Bureau)

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