What is aging and can we reverse it?
What causes aging?
What roles do stem cells play in aging?
We can hate it or embrace it, but we all know the hallmark signs: wrinkles, physical weakness, slowed healing, and much more. Unfortunately, some of the most common and detrimental diseases also appear with age, such as cardiovascular disorders, neurodegenerative diseases, and cancer.
So, have you ever stopped to wonder what is happening at a cellular level when we age?
Because of the direct correlation between aging and such common diseases, scientists have put a lot of work into understanding how the body ages. Turns out, there are multiple interrelated mechanisms of aging! And here's the good news: these mechanisms can often be interfered with to reverse or slow aging at the cellular level.
It is therefore conceivable that if we can slow or reverse aging, we can also prevent ourselves from contracting age-related diseases, and as a positive side note, stay looking young and rejuvenated.
An interesting finding is that aging can actually be "contagious" between tissues and organs [1,2,3]. For instance, if aging is accelerated in the liver from excessive drinking, cells can communicate to induce aging-specific deterioration in, say, the heart. So, this process should be able to go the other way, right? Yes, in fact, lifespan extending manipulations to one tissue can slow the aging process in other tissues through cell-to-cell communications .
So, what exactly is cellular aging? Scientists define aging as a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death . The most general cause of aging is widely accepted as the accumulation of cellular damage over time. This cellular damage can be caused by sun exposure (which is why you should ALWAYS wear sunscreen), damage by free radicals, genetic abnormalities, and nutritional imbalance.
Throughout this post and the next, we will talk about four specific mechanisms of aging:
Each mechanism has been experimentally proven to affect aging and provide venues in which we can potentially engineer interference with the aging process.
Cellular damage doesn't just happen by external factors, it also happens naturally over time through DNA alterations. Our bodies are in constant need of new cells, either to replace old or damaged cells, or to grow as a whole. These new cells come from a process of cell division, in which one cell doubles by dividing into two, which then divides into four, and so on .
This process of division can only happen around 50 to 60 times until the original cell dies, which may lead you to wonder why we don't just run out of cells . This is where stem cells come into play.
Stem cells are like a stockpile of cells that have the potential to divide into any type of tissue, such as a skin cell, a heart cell, a liver cell, etc.. You may recognize stem cells as a recent buzzword and now you know why: They have the potential to create young, healthy cells with a fresh copy of DNA to replace old and damaged ones. Not surprisingly, our stem cells lose their vitality and become exhausted over time, leading to the observable decline in the regenerative capacity of the human body with age .
Since all cells need to contain a copy of our DNA, each time that our cells divide, a new copy of our genome needs to be made. It is predicted that there are over three billion base pairs in the human genome and that humans have approximately 10 trillion cells at any given point .
Just like you might make a mistake if you tried to copy three billion letters, so do the proteins that replicate our DNA, and we call these mistakes "replication errors" . If these DNA alterations affect essential genes, the resulting cells can be dysfunctional and may jeopardize the health of the tissue. This is of special detriment if the DNA damage impacts the functional ability of stem cells, since they allow for tissue renewal in the body .
Luckily, our bodies have evolved to develop DNA repair mechanisms to fix these replication errors if they occur. It has been shown that deficiencies in these DNA repair mechanisms lead to accelerated aging . There has also been experimental evidence that proves that artificial reinforcement of these DNA repair mechanisms may delay aging and enhance protection against age-related diseases, such as cancer . This provides one area in which we can enhance our bodies to increase our health span.
As always, thank you for listening and stay tuned for three more mechanisms of cellular aging that could serve as the basis for age reversal.
We hope you have enjoyed the reading and we would love to hear your comments!
1. Lopez-Otin C, Blasco MA, Partridge L, Serrano M, Kroemer G. The Hallmarks of Aging. Cell [Internet]. 2013 Jun 6 [cited 2018 Aug 20];153(6):1194'217. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3836174/
2. Nelson G, Wordsworth J, Wang C, Jurk D, Lawless C, Martin?Ruiz C, et al. A senescent cell bystander effect: senescence-induced senescence. Aging Cell [Internet]. 2012 Apr 1 [cited 2018 Aug 22];11(2):345?9. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1474-9726.2012.00795.x
3. Droujinine IA, Perrimon N. Defining the interorgan communication network: systemic coordination of organismal cellular processes under homeostasis and localized stress. Front Cell Infect Microbiol [Internet]. 2013 Nov 19 [cited 2018 Aug 22];3. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832798/
4. How cells and tissues grow [Internet]. Cancer Research UK. 2014 [cited 2018 Aug 20]. Available from: https://www.cancerresearchuk.org/about-cancer/what-is-cancer/how-cancer-starts/how-cells-and-tissues-grow
5. Chat Q&A: How much DNA is in our body? [Internet]. National Human Genome Research Institute (NHGRI). [cited 2018 Aug 20]. Available from: https://www.genome.gov/
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