In adult mammals, the liver is the most regenerative organ, capable of significant regrowth following injury. Why is this the case? Researchers here point to a small subset of liver cells in mice that are distinguished by telomerase expression, and while mice and humans have quite different telomerase and telomere dynamics, indirect evidence suggests that a similar population may exist in our species. Significant telomerase expression is the characteristic of stem cells that allows for unlimited replication: telomerase acts lengthen telomeres, the caps at the ends of chromosomes that shorten with each cell division. When too short, cells enter senescence or destroy themselves. Lacking telomerase, the vast majority of cells can only divide a set number of times.
This segregation between a few privileged stem cells and the vast mass of restricted somatic cells is the primary strategy by which multicellular life keeps the incidence of cancer to a manageable level. Mutations occur constantly, and evolution requires mutation, even when harmful to individuals, but it is much harder for mutational damage to cause somatic cells to run amok, given their inherent limitations. Unsurprisingly then, researchers are interested in the source of the liver’s regenerative capacity