We all age. It is inevitable, or so we have always been told. People have been searching for the “fountain of youth” for centuries, but scientists this month were able to reverse the ageing process in some older human cells. Whether you believe ageing is inevitable or could be avoided with an apple a day, what does this research mean and why do we age?
This was one of the first riddles I heard: In the morning I have 4 legs, in the afternoon I have 2, and in the evening I have 3. What am I? The answer is ageing. You begin as a baby (4 legs), age to an adult (2 legs), finally becoming old and in need of a cane (3 legs). We all age and we’ve all heard of our biological clock, but what is it exactly? The true definition of the biological clock is the body’s way of measuring time. It does not rely on day and night, but instead habits, our age, and chemical changes in the body. However, it is also used to refer to a woman’s fertility (e.g. the biological clock is ticking = you’re getting older, you don’t have many eggs left, get on with it). If we could slow the ‘biological clock’ down, would this mean a longer fertility window?
It may seem like a straightforward question, but what is ageing? We are an ageing population, living longer on average than ever before. Between 2015-2050 the World’s population of over 60’s will ~double from 12% to 22%, and by 2020 there will be more over 60’s than under 5’s. An increased average lifespan is due to better healthcare, technology, housing, and knowledge of diet, to name but a few causes. On a biological level, ageing is caused by molecular and cellular damage to our cells over a lifetime. This damage leads to a gradual decline in physical and mental ability, and an increased risk of contracting illness, ultimately leading to death. Some 90 year olds are able to walk unaided, whilst some 70 year olds struggle. This is partly genetics, partly life experience (e.g. job, diet etc.), but ultimately, we all age.
The ‘fountain of youth’ has been sought for centuries, but in recent history, research has made steps to deduce exactly what happens to our cells as we age. What has research done to halt ageing? Some research groups believe a key to the ageing process may lie in the accumulation of senescent cells (i.e. cells that can no longer replicate/divide) in organs. This is thought to happen when DNA is damaged, when there is inflammation, or damage to the protective ends (telomeres) of chromosomes (i.e. found in the nucleus of our cells and contain our genetic information), or when the cell can no longer turn genes on and off as required. Researchers at the University of Exeter, medical school (UK) have managed to reverse this ageing process in some older human cells by delivering hydrogen sulfide (H2S) (i.e. the molecule that causes the rotten eggs smell) to mitochondria (i.e. the part of the cell responsible for producing energy), preventing cells from becoming senescent. This enables the cells to continue dividing, as younger cells would. It has been hypothesised that delivering H2S to mitochondria increases the number of some splicing factors (i.e. proteins that aid in switching genes on and off in response to environmental changes). Splicing factors are potentially fundamental to the ageing process as their numbers decline as we age. The results showed introduction of H2S boosted the amount of two splicing factors which are connected to cells becoming senescent, therefore reducing the number of cells which reached this ageing mechanism.
This research may seem odd, trying to prevent something we’ve always assumed inevitable, however, by understanding the mechanisms which underpin ageing we can understand more about the process our bodies undergo as we grow old. Even if we could live forever, would we want to? The Earth is not made for our ever growing population, and whilst housing is scarce and food unable to support the increase in population, maybe we shouldn’t plan on being around forever. Research such as this divides opinion, but it also engages more people in the paths of scientific discovery. By understanding what causes ageing and what could halt it, we may have more of an idea as to what makes us human.