An enzyme called telomerase can slow, stop or perhaps even reverse the telomere shortening that happens as we age. The amount of telomerase in our bodies declines as we get older.
In 2009, the Nobel Prize for Physiology/Medicine was awarded to three scientists who discovered how telomerase impacts telomere length. Their work explained how the ends of DNA strands are protected by telomeres, and that telomeres are built by telomerase. Exposing human cells to telomerase slows cell ageing and allows cells to begin copying again. Activating telomerase can:
Help cells live longer and continue to function properly
Make old cells function as they did when they were younger (by changing gene expression to a younger phenotype)