The cells of our body get damaged due to injury, disease, or other stress factors from our environment or from within our cells. Ideally, our immune system clears out these damaged cells through the process of apoptosis which is a natural cellular housekeeping process to remove damaged cells. However, as our bodies age, this process becomes less effective in the removal of these damaged cells causing them to build up and have a negative effect on our health.
Extensive research is being carried out to understand a cellular state called senescence with the goal of slowing the aging process and to increase the active and healthy years of life.
What is Cellular Senescence
The process in which the division and growth of cells stops but the cell does not die is known as cellular senescence. This feature makes the senescent cells unique. These cells, instead of being removed from the body, remain and release chemicals triggering inflammation. Just like a single moldy fruit can destroy an entire bowl full of fruit, very few senescent cells present in the body can persist and extend the inflammation to the neighboring and distant cells around the body and harm them.
However, its important to note that not every senescent cell causes harm. It can depend on what part of our life stage they occur in and also the quantity of these cells in our body. Some of these cells release compounds and molecules known as the senescent secretome, essentially the laundry list of chemicals that are secreted by senescent cells and that play an important but useful role in different life stages such as the development of an embryo, childbirth, and the healing of wounds.
What happens in cells undergoing senescence?
During a normal cell cycle, our cells enter into the phase where the cell cycle stops and the cells die a normal death and are removed from the body. However, in senescence, our normal cells enter into the phase of cell arrest, they undergo a shift in form and function where they stay active metabolically without undergoing the process of cell death.
Normally, significant structural changes occur in a cell undergoing senescence. Such cells become enlarged, flat, and sometimes, they present with enlarged or multiple nuclei.
What causes cellular senescence?
Different types of stress and developmental stages can trigger senescence in our bodies. External and internal stimuli both can be a cause. Radiation, mutation of the genes capable of causing cancer, oxidative and genotoxic stress, mitochondrial dysfunction, signals of tissue damage or inflammation, nutrient deprivation, chemotherapeutic agents, changes in the structure of telomeres and its progressive shortening are some of the reasons behind the development of senescent cells.
Do senescent cells play other roles in the body?
Many scientific studies have demonstrated that senescence can influence disease and aging as well as many normal physiologic functions of our body. Indeed, there is a role of senescence during our development and, also it can be engaged in the tissue remodeling of our body. It is observed that senescent cells are transiently induced during the process of wound healing and help to restore the tissue to its original and normal state. Moreover, it is also a potent anti-cancer mechanism that limits the division of cancerous cells.
How our body is affected by cellular senescence.
As our age increases so do the number of cells undergoing the process of senescence. With age, our immunity system becomes less functional, and this causes the senescent cells to gather and affects healthy cells. As the numbers of these cells build up in our body then it negatively affects our health. It has an influence on our ability to tolerate illness and stress and recover from injuries. Also, our ability to learn new things is affected because the senescence in our brain can damage cognitive functions.
We now know that a number of age-related diseases are connected to cellular senescence. Diabetes, cardiovascular diseases, cancer, stroke, osteoporosis, osteoarthritis, Alzheimer’s disease, and dementia to name a few. Besides, a decrease in eyesight, thinking ability, and mobility can also be linked with it. Scientific investigations are also being carried out to find a link between the appearance of wrinkles on the face and sagging skin caused by senescence cells in our skin .
The bottom line.
The interest in the role of senescence in the development of a multitude of conditions and diseases is growing. Researchers are exploring the mechanisms regulating the connection between aging, inflammation, disease, and senescence. Investigations to identify, explore and classify differences between the senescence cells throughout the human body are ongoing and in the future new therapies will be developed that may target specific tissues that are being disproportionally affected by senescence with the goal of specific therapies to slow aging.