cancer geneticist ronald a. depinho and his colleagues published research on mice where telomerase activity was first genetically removed. then, after the mice had prematurely aged, they restored telomerase activity by reactivating the telomerase gene. as a result, the mice were rejuvenated: shrivelled testes grew back to normal and the animals regained their fertility. other organs, such as the spleen, liver, intestines and brain, recuperated from their degenerated state. "[the finding] offers the possibility that normal human aging could be slowed by reawakening the enzyme in cells where it has stopped working" says ronald depinho. however, activating telomerase in humans could potentially encourage the growth of tumours.