With the advent of Science and scientific inventions in recent years, a phenomenon with significant potential has been discovered and observed almost everywhere. These scientific discoveries always intrigue the human imagination and stir the dominant ideas in it for its impossibility. One such idea is Life Extension—which extends the lifespan of humans or other organisms. When the lifecycle of the cells was discovered with its many stages, the question of life extension was also raised. Is it possible to remove dying cells to extend human lifespans indefinitely? However, before we can answer this question appropriately, it is essential to understand cellular senescence.
What is Cellular Senescence, and Why is It Important?
Cellular senescence is understood as a biological phenomenon responsible for cell division. The phenomenon is crucial to understanding the ageing process of cells. It was first observed by Leonard Hayflick and Paul Moorhead in the 1960s in human fetal fibroblasts. In cellular senescence, the growth of the cells is arrested over a while, and the cells become resistant to growth-stimulating hormones. DNA damage is a significant cause for cells to become unresponsive and crawl towards their eventual demise. It is generally accepted that this is the fate of all cells unless they transform themselves into malignant forms and keep replicating without stopping, something like cancerous cells. When the cells become unresponsive, they have been said to reach senescence.
Senescent cells are both metabolically and morphologically different from cells at other stages of their lifecycles. Senescent cells have a phenotype that induces inflammation. They show altered gene expression, besides their chromatin gesteasily reorganized and so on. The significant role that senescent cells play is of protection. Senescence does not let cells fall intoreplicating themselves and become malignant.
However, the accumulation of senescent cells is also associated with physiological conditions like age-related pathologies, tissue degeneration, and other inflammatory diseases. With age, the number of senescent cells in the body increases.
Why Does Accumulation of Senescent Occur at All?
There are quite a few reasons, all related to the body’s natural system, that foster the accumulation of senescent cells. Some of them are mentioned as follows:
- Cells must undergo an elimination process to avoid different types of fatal diseases. This process is called apoptosis process. However, aged cells don’t get self–appropriately eliminated;
- When senescent cells cannot go through apoptosis, they begin to accumulate in the body. In popular Science culture, such cells are also called zombie cells;
- These undead cells linger in the body, emitting signals that can cause inflammation, harm to healthy cells and also block growth or regenerative substances in the body.
How are Senescent Cells and Life Extension Connected?
A study published in 2018 discovered that old animals were able to live 36% longer and were also able to perform physical functions with more ease when senescent cells were removed from them. The mice were orally administered compounds that could remove senescent cells. Scientists further proclaimed this to be a discovery that would change the course of medicine forever.
Senescent cells keep accumulating and secrete toxins and inflammatory substances. Therefore,such positive results from their removal can be understood. The decline of health and onset of ageing through senescent cells was further explained when, in the same study, young mice had senescent cells transplanted in them. The young mice soon began to undergo degenerative ageing. Several more studies like these eventually gave rise to an entirely new area of scientific inquiry called senolytics—a worth studying scientific research.
What is Senolytics?
“Seno” means old cells that become harmful to the body by secreting toxic substances, and “Lytic” means to destruct. Therefore, Senolytics literally means the selective destruction or elimination or removal of old or senescent cells. The main achievement of Senolytic studies has been that they can come up with methods through which one can start getting rid of worn-out, severely metabolic and toxic senescent cells.
How are Senolytic Methods Able to Remove Senescent Cells?
Senolytic methods usually revolve around compounds that can remove senescent cells. Severaldiscoveries have been made of these compounds and their effectiveness over the years. The compounds by themselves are not enough. A tailor-made regime also has to be made for administering these compounds, either orally or by any other means most suited to the organism. The first Senolytic compounds that were discovered were Quercetin and Dasatinib. Quercetin is a naturally found compound, mainly in fruits and vegetables. However, Dasatinib is a drug that has been used for the treatment of leukaemia. These two compounds are used together to kill senescent cells in the body.
Are Senolytic Methods Effective in Humans?
While the concept of eliminating senescent cells for life extension is fascinating, and many Senolytic studies have shown remarkable results in animals, in humans, not much can be said concretely except that it is promising.
The first human trials were conducted in 2020 by Mayo Clinic in humans who had a lung disease known as idiopathic pulmonary fibrosis. The trials were conducted with the same Senolytic compounds used in animal testing: Quercetin and Dasatinib. A regimen of 1250 mg and 100 mg per day of Quercetin and Dasatinib, respectively, were followed. The patients showed slight physical improvements. For instance, they were able to walk faster by about 5%. However, these trials were conducted only for a brief period.
In conclusion, it can be said that these trials and also those conducted ever since have been entirely conclusive. By one factor or the other, these studies could not determine and also they could not even ensure overall improvements. They could only conduct trials with a small group of people with limited periods. Therefore, it can be said that cellular senescence in terms of life extension is still promising. It shows effectiveness to some extent, but there is still a need for a significant amount of in-depth research in the area to come up with the findings that can pave the way for a new dawn in the scientific research and innovation.