The Science of Eliminating Aging

Shalizma Khandaker Orni

Sophomore

School of Life Sciences

Independent University, Bangladesh

March 23rd, 2019

Aging is a fairly normal physiological process that occurs in almost all living organisms. It is part of the fundamental cycle of life as we think of it. However, there are some species in this world that have somehow avoided this aging process completely. These biologically “immortal” animals, such as hydras, jellyfish, and possibly some lobsters, pose an interesting question: could it be possible to eliminate aging? To answer that question, we have to understand what brings about aging in the first place.

All cells in our body go through cell division, during which DNA replicates. Due to the nature of DNA replication, every time a chromosome is replicated, it loses some DNA at the very ends. This is where protective sequences of DNA called telomeres, come into play. The telomeres at the ends of chromosomes protect the chromosomal DNA (which harbors functionally important DNA sequences called genes, among others).  After each successful cell division, the telomeres get shorter and shorter until they are gone, and the cells stop dividing and are said to become senescent. These senescent cells can often persist without being replaced, leading to the tissue degeneration associated with aging, among other outcomes. Interestingly, stem cells and cancer cells produce an enzyme called telomerase which can lengthen the telomeres, allowing the cells to continue growing indefinitely. This enzyme helps lengthen the telomeres, and increased telomerase activity is associated with cancer.

IMDb

Another factor that accounts for aging is metabolism. Metabolism enables life itself, but toxic byproducts of respiration, such as reactive oxygen species, can damage and wear down cells. When this damage eventually builds up, it is associated with some the pathology that we see in aging individuals. The damages can be in the form of cellular atrophy, nuclear mutations, mitochondrial mutations and others.

Now that we have some understanding regarding the aging process, we can focus our attention on ways to possibly eliminate it. One idea that has persisted for a while now is to eliminate the senescent cells that characterize aging tissue. To that end, researchers at the Mayo Clinic in Rochester and the Scripps Research Institute in Jupiter, Florida, among other places, first identified six signaling pathways that various types of senescent cells rely on to prevent cell death and continue to persist. In early 2015, the team identified the first senolytic (drugs which kill senescent cells) based on inhibiting a pathway that senescent cells need for survival. Dasatinib, an FDA-approved chemotherapy drug, was found to eliminate human fat-cell progenitors that have turned senescent, while quercetin, a health-food supplement, was found to target senescent human endothelial cells. Many other senolytics have since been discovered.. The major difficulty right now is that these senolytic compounds only target particular cell types. Combination therapies are currently being considered and investigated.

Another method to prevent aging, that scientists at Harvard University, among other institutions, are researching have to do with a molecule called NAD+ (nicotinamide adenine dinucleotide). An important cofactor in several metabolic pathways for its ability to transfer electrons, NAD+ has been compared to a fountain of youth. As the body ages, the supply of NAD+ in the mitochondria diminishes, and this leads to oxidative damage of DNA and other cellular components by reactive oxygen species. The Harvard scientists are developing an “anti-aging” pill containing precursors for NAD+ synthesis in cells. NAD+ has been demonstrated to reverse signs of aging in mice, and a company called Elysium already sells an NAD+ boosting pill as a supplement, although they are now going through clinical trials in humans in order to be able to market it as an actual drug.

One final method (that we will talk about) that scientists are looking into is the concept of stem cells. Stem cells are the rejuvenating blocks of life, and have the ability to grow indefinitely and replace other cell types. Some types of stem cells persist in adults. For instance, hematopoietic stem cells found in our bone marrow continually replenish our blood cell populations. As we age, the regenerative ability of stem cells deteriorates, and the body becomes less capable of repair and recovery. Scientists are now considering implanting stem cells into aging individuals to restore their ability to heal or replace old tissue. This has been already been demonstrated to produce great results in mice, but clinical trials in humans are still pending.

In conclusion, as technology advances, we are getting closer and closer to achieving a state of longevity that far exceed any previous human generations. But the prospect of eliminating aging leaves us with a few existential questions. Firstly, would elimination of aging lead to an overwhelming overpopulation that far exceeds the carrying capacity of the planet? And if so, what measures can be taken in order to prevent that from happening? Should we even attempt trying to eliminate aging because of the possible complications that can arise from it? How would this affect culture, religious beliefs, and society? While there is only a thin chance that this will actually happen, we should still proceed with caution and awareness.

Shalizma is a sophomore in Biochemistry who wants to be a researcher and help humanity with my work. She is always open to trying new things and challenges which help her get out of her comfort zone. In short, she is just a girl chasing her dreams and having an amazing adventure while doing it.