Derived from the Latin term “senex,” meaning “old,” senescence refers to the aging of cells in our bodies and its impact on our health. While senescence isn’t all bad news, it’s typically irreversible. Cellular senescence is important to understand as it is one of the hallmarks of aging.

Two images of a woman as her younger face and her older face
Maggie Aime, MSN, RN
Written by Maggie Aime, MSN, RN Medical Writer

Key takeaways:

  • Senescence is a natural process where cells in our bodies stop dividing. When these cells don’t die as they should, they accumulate and can cause inflammation and a weak immune system.
  • While senescence can trigger inflammation, it also plays important roles in normal development and limiting tumor growth.
  • Overactive genes, excessive stress or damage, and the natural aging process can cause senescence.
  • Although cellular senescence is typically irreversible, recent studies suggest that certain interventions, like senolytics, can selectively remove senescent cells and potentially improve health.
  • Senescent cells may play a role in Alzheimer’s disease and skin aging. Removing these cells has shown some benefits in animal models. However, more research is needed for conclusive evidence.

Next time you look in the mirror, take a closer look at your skin. Did you know that aging doesn’t just affect how your skin looks but also the cells in your body?

It’s called senescence, a natural part of our bodies’ development and aging.

But is senescence good or bad? Can it be reversed? Does it cause Alzheimer’s? Keep reading to uncover what senescence is about.

What is Senescence?

The word senescence comes from the Latin term “senex,” which means “old” and is related to biological aging.

Senescence can be described at different biological levels including: organismal senescence and cellular senescence.

Organismal senescence is aging of a whole organism, like a human being, and is associated with an increase in death rate and decrease in physiological potential to bear children (fecundity).

Cellular senescence contributes to organismal aging and specifically refers to the process of aging that happens to the cells in our bodies and its impact on our health and functioning.

Cellular senescence can be a problem when cells stop dividing, but don’t die as they should.

Generally, our immune system is supposed to get rid of old cells through a process called apoptosis. But, as we get older, our bodies may not be able to remove these damaged cells as efficiently.

Instead, these senescent cells stick around and release chemicals that can trigger inflammation. Even a small number of these senescent cells can cause harm to nearby healthy cells.

Think of a spoiled fruit in a bowl that can spoil the rest. This can lead to a weakened immune system and other health problems.

Is Senescence Good or Bad?

Although senescent cells can trigger inflammation, they can be beneficial. Cellular senescence helps keep our body balanced and can act as a protective mechanism to slow tumor growth.

Senescent cells produce a set of molecules and compounds known as the senescent secretome, which actually serve important functions throughout different stages of life. These substances contribute to processes such as the development of embryos, giving birth, and wound healing.

In simple words, senescence can be good for our bodies. The problem occurs when senescent cells pile up, which can happen as we age. This can contribute to chronic inflammation and diseases like cancer.

What Are the Different Types of Cellular Senescence?

Scientists have discovered various types of cellular senescence. They include oncogene-induced senescence, stress-induced premature senescence, and classical replicative senescence.

  • Oncogene-induced senescence happens when oncogenes – mutated genes that can cause cancer – become too active, causing cells to divide quickly and potentially form tumors. In response, cells activate tumor-suppressing pathways that trigger cellular senescence. This type of senescence safeguards against uncontrolled cell growth that could lead to cancer.
  • Stress-induced premature senescence happens when cells experience excessive stress or damage. This can be due to factors like exposure to harmful substances or prolonged inflammation. The cells respond by entering senescence early, serving as a protective mechanism for the body.
  • Classical replicative senescence is a result of the normal aging process. Cells have a limited number of times they can divide, called the Hayflick limit. Once this limit is reached, the cells stop dividing and enter senescence. This type of senescence contributes to the natural aging of our bodies.

Can Senescence be Reversed?

Cellular senescence is typically irreversible. Once a cell enters a senescent state, it can’t divide or perform its normal functions.

However, recent research has suggested that certain interventions may be able to affect some aspects of cellular senescence.

For example, studies have shown that senescent cells can be selectively removed from tissues using drugs or other compounds. This approach has shown promise in preventing age-related diseases and improving overall health in animal models.

Researchers have been studying senolytics, and they have found encouraging outcomes in treating aging and various diseases.

Initial tests conducted on humans using a combination of Dasatinib and Quercetin have shown reduced accumulation of senescent cells in the fat tissue of patients with diabetic kidney disease. Additionally, these treatments have led to improved physical function in patients with idiopathic pulmonary fibrosis.

Clinical trials are underway to test other types of senolytics, including the flavonoid Fisetin and BCL-xL inhibitors. These new treatments could help fight against age-related diseases and health problems caused by senescence.

What About Senescence and Alzheimers?

Aging is the most significant risk factor for late-onset Alzheimer’s disease (LOAD), which is responsible for over 95% of Alzheimer’s cases.

Scientists are still unsure why aging makes us more susceptible to LOAD. However, they believe cellular senescence may play a role in aging-related diseases like Alzheimer’s.

In the brains of Alzheimer’s patients and animal models, scientists have found senescent astrocytes, microglia, endothelial cells, and neurons.

When senescent cells are removed through genetic methods or medications, it improves memory and reduces the harmful effects of proteins called β-amyloid and tau in mice with the disease.

This suggests that cellular senescence is closely linked to the development and progression of Alzheimer’s disease.

Despite these findings, we still don’t fully understand how senescent cells contribute to Alzheimer’s.

Researchers continue to study this topic, and they believe that getting rid of senescent cells could be a promising way to treat age-related diseases like Alzheimer’s.

Does Senescence Cause Skin Aging?

Studies have shown cellular senescence can cause aging in many organs, including the skin.

Senescent cells accumulate in different parts of the skin as we age and contribute to many of the changes we see during aging. When these cells are added to lab models of skin, it mimics the changes seen in the skin.

Researchers have tried removing senescent cells to see if it slows down skin aging, but the results are inconclusive.

Some studies have shown benefits, but more specific research is needed.

FAQs:

What happens when a cell reaches senescence?

When a cell reaches senescence, it stops dividing and undergoes permanent growth arrest. It can release substances that have both beneficial and harmful effects on the surrounding cells and tissues.

Which hormone prevents senescence?

No hormone has been shown to prevent senescence completely. However, certain hormones, such as growth hormone and insulin-like growth factor 1 (IGF-1), have been associated with regulating cell growth and maintaining tissue health, indirectly influencing the senescence process.

What is the cause of senescence?

Senescence is a natural part of the aging process. Other factors like exposure to harmful substances, stress, and damage can also contribute to senescence. So, while aging is the main cause, other factors can also play a role in triggering senescence.

Can senescence be prevented?

Senescence cannot be completely prevented. However, researchers are exploring ways to slow or delay the onset of senescence. Some strategies include reducing oxidative stress and promoting healthy lifestyle habits such as exercise and a balanced diet.

Does senescence cause disease?

Senescence itself does not cause disease, but it can contribute to age-related diseases. When cells become senescent, they can secrete molecules and proteins that can cause inflammation and tissue damage. This damage can accumulate over time and contribute to diseases such as neurodegenerative disorders, heart disease, and cancer.

Final Thoughts

Cellular senescence is a complex process that plays a crucial role in our bodies. It can be both beneficial and detrimental.

There are new and exciting developments in senolytics that could help get rid of senescent cells and fight against aging-related health problems.

But, there is still a lot we don’t know, and more research is needed to fully understand it.

Maggie Aime RN

Maggie Aime, MSN, RN

Maggie Aime, MSN, RN is a freelance health, wellness, and medical personal finance writer. Her extensive nursing experience includes oncology, kidney transplant, cardiology, and home health. Read more about her work at www.thewritern.com.

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