First, let’s think about the question ‘Why do we age?’ In short, it’s because cells can only play an active role in our bodies for a certain length of time before they reach retirement. As more of our cells come out of active service, we physically age. And just as we use our birthdays to count down to retirement, so our cells have an internal clock that ticks down towards the end of active service. Once the counter hits zero, the cell is relieved of duty.
So how does this counter work? Each of our cells contains a set of chromosomes: packages of DNA that store all the genetic information needed to tell our bodies how to grow and operate. Every time a cell divides to replace the old ones, it must copy all of its chromosomes so that both daughter cells have their own full set. But the copying process isn’t perfect: each time a chromosome is copied, a tiny amount of DNA is lost from each end. This is how the cells keep count: the ends of each chromosome are used as a measuring stick. As the years pass, the chromosome shrinks, its ends gradually eroded until a certain critical length is reached. At this point, the chromosome becomes too short to be copied: the cell has reached the end of its useful life.
The obvious follow-up question is: is it possible to override this ageing process? Well, one option appears to be the use of stem cells. Stem cells are like new-born babies: they have yet to be adulterated by their surroundings and have the potential to follow one of many career paths – from nerve, brain or heart cell to skin cell. Stem cells are present in each one of us and play a vital role in maintaining our organs and tissues. Stem cells act as the raw material for running repairs; damaged cells are actively destroyed and replaced by the children of stem cells.
The promise held by stem cells in our quest against ageing lies in the potential of these cells to be ‘groomed’ towards a particular destiny – artificially creating replacement cells for the old ones. Once we have mastered this grooming process, perhaps we will be able to use stem cells to grow new tissues or organs on demand. Just as we might replace a worn out car tyre or pair of brake pads, the hope is that we will be able to remove worn out or damaged organs, and replace them with shiny new ones.
It’s early days, but the use of stem cells does seem to be a potential way to at least slow the ageing process, if not stop it completely.
Answered by Jon Crowe.
Image credit: Petras Gagilas on flickr
For a run-down of some more unusual avenues in anti-ageing research, take a look at 5 Crazy Ways Science Is Trying To Make You Live Forever.
You can read more on this in an article I wrote for issue 4 of Guru.