Aging Breakthroughs: Senescent Cell Removal
As we age, everything slows down. We move slower, our joints don’t function as well, our eyesight gets worse, and we become more prone to disease. A lot of the reason all of this happens is due to senescent cells. But a brand new study is showing that we might not have to live with the cells that cause aging! It may be possible to remove them using the healthy cells inside of our bodies.
What are Senescent Cells?
Source: National Institute of Aging
Senescent cells are stressed cells that can no longer divide. When we are younger, our bodies clear these cells through a process called apoptosis, but as we age our bodies aren’t as effective at this.
Although senescent cells no longer divide, they aren’t completely dead. For that reason, they are also called “zombie cells.” They stay in the body and continue to release chemicals. These chemicals can trigger inflammation. When these cells come into contact with healthy cells, they overtake them causing inflammation or even disease to spread.
As we get older, we accumulate more senescent cells. The immune system becomes less efficient and people become more prone to illness and disease. This process also slows down our ability to heal from injury or even learn, since senescent cells do exist in the brain.
Some of the disorders that have been connected to cellular senescence include:
Alzheimer’s and Other Dementias
Senescent cells are also linked to what we consider normal aging, such as declining eyesight, slower mobility, and declining mental sharpness.
Cellular senescence was discovered in the 1960’s when scientists studying cell samples found that there is a limit on the number of times a cell can divide. Although we’ve known about it for about 60 years, interest in researching cellular senescence is just now taking off.
Can you prevent senescent cells?
Unfortunately senescent cells are a part of life and we all have them. All cells have a lifespan and eventually become senescent. In fact, people of all ages have senescent cells, even babies and young children. The difference is that those with a strong immune system will have the cells cleared out quickly so they do little to no damage. Older people or those with weak immune systems don’t respond as fast, allowing the zombie cells to overtake healthy cells.
Not all senescent cells are bad. For example, if you cut yourself and damage your skin, the senescent cells are what signal your immune system to help you heal. In other cases, a cell that has become cancerous could become senescent on its own in order to warn the immune system to clear it out.
What are senolytics?
Senolytics are drugs that help clear out senescent cells. Because this is a new area, scientists are still learning about what certain drugs can do. Several senolytics are in development as both prescription drugs and over the counter supplements.
The two senolytic compounds that are being studied are dasatinib and quercetin. Dasatinib was developed as a cancer drug and it was approved for use in humans. Quercetin occurs naturally in some fruits and vegetables. Both of these compounds work by keeping senescent cells alive. A 2019 study used people suffering from kidney disease as subjects. When administered the combination of dasatinib and quercetin for only three days, senescent cells were reduced.
A 2015 study found another compound, navitoclax, was also effective in clearing senescent cells from mice that had been exposed to harmful levels of radiation. It also replenished stem cells that had gone senescent. Since our stem cells make other cells, this information could be used to further study rejuvenation.
At this time, no prescription drugs have been approved specifically as senolytics. There are several over the counter supplements, but it is hard to say whether or not they work given the barrier to entry to the supplement market is low.
Several biotechnology companies have had limited success with developing senolytics. One of the challenges is to create compounds that target only the senescent cells, and not healthy ones. We need some level of senescent cells as well, so killing them all could do more harm than good.
Immunotherapy Could Target Senescent Cells
The body has its own healing mechanisms in the immune system. But once the system is weakened, it’s harder to fight disease. Scientists are working to find ways to strengthen the immune system which could have the bonus effect of attacking senescent cells.
A 2021 study out of the University of California San Francisco explains how senescent cells could be removed using the body’s own defenses.
One type of cell we have is called Natural Killer cells, or NKs. Their job is to target other cells carrying viruses or even tumors, and kill them. As we get older, these cells become less active and aren’t as effective. That is part of the reason that it’s easier to get sick as we age.
Finding ways to stimulate NKs could have far reaching benefits. Instead of directly targeting senescent cells with drugs, they’re looking for ways to target NKs. These cells are easier to find because they have a receptor that no other cell in the body has. Studies using mice showed a significant reduction in senescent cells when the NK cells were primed to eliminate them.
Because the study of senescent cells is relatively new, more studies are being done all the time. With the new information about how NK cells could be stimulated to remove senescent cells, human trials could soon be underway.
The Qyral team will follow these developments and release them as they become available.