Methusalem’s mystery

摘要

Life is limited—at least for multicellular animals. The separation between differentiating somatic cells and the germ line also delineates the separation between mortality and eternal life. We are so tantalised by induced pluricellular stem cells, because they promise the option to cross this line. However, reprogramming of developmental potential is only part of the story; life leaves traces in a cell that exceed chromatin remodelling. These traces challenge cellular homeostasis, and with time, the cell will yield, a process whose manifestation in multicellular animals is familiar to all of us as ageing. It should be clear that ageing has to be separated from developmental potency; even plants, where induced pluripotency has been developed and biotechnologically exploited already for decades, undergo ageing. Is ageing more than the mere accumulation of life-related damage, or is it rather a predefined programme?A popular theory (Harman 1956) deduces ageing from oxidative damage by radicals, especially reactive oxygen species. This sounds like a fairly general mechanism—is it thus possible to arrive at a universal theory for ageing?