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REGENERATIVE BIOLOGY
There is conflicting evidence about which cell type is responsible for liver regeneration following damage. It emerges that duct-like progenitor cells arise from hepatocytes after liver damage, a finding that reconciles previous data.
Prometheus, a Titan in Greek mythology, is said to have been condemned by Zeus to have his liver plucked out by an eagle every day for eternity, only to have the organ grow back each night. In real life, as in the myth, the liver has remarkable regenerative potential, but the precise mechanism by which liver cells repopulate the tissue following damage remains unknown. Writing in Cell Stem Cell, Tarlow et al.1 report that, following liver damage, transplanted liver cells called hepatocytes are converted into another liver cell type, the ductal progenitor cell, which then proliferates and differentiates back into a functional hepatocyte to replenish the tissue.
The liver is the largest internal organ in the human body, and is responsible for many metabolic and detoxification activities. It is composed mainly of bile-duct cells and hepatocytes, which work in conjunction with other, less-populous cell types. But the cell type responsible for repopulation of the tissue after damage has been an area of active debate.
Some studies2,3 in mice have indicated that hepatocytes are the major drivers of liver regeneration. However, other studies in mice4, rats5 and zebrafish6 have found that, following blockade of hepatocyte regeneration, damage activates a response that involves progenitor cells7. These liver progenitor cells have been shown to derive from ductal cells7 or to arise from an as-yet-unidentified cell8,9. To add complexity to this already conflicting set of reports, a stream of...