Cellular Aging - Definition and Causes

Introduction

Soon after birth, the cellular aging process begins; as cells multiply, divide, and increase in size, they age too. The body has planned a process to replace these aging cells with newer cells. Aging is one of the periods in the cell life cycle. The regulation and subsequent breakdown of cellular processes represent a programmatic decision by the cell to either continue or abandon maintenance procedures with age.

What Is Cellular Aging?

Cellular aging is referred to as cellular senescence. Cellular aging is a defense mechanism of the cell to prevent further damage. The cell becomes incapable of re-entering the cell cycle. The aging cell is larger when compared to surrounding cells. Older cells do not divide further. Cell division of aging cells can lead to some errors and can harm themselves or the surrounding tissues. It takes around six weeks for a normal cell to turn into a senescent, aging cell.

What Causes Cellular Aging?

DNA - Deoxyribonuclease replication is an important part of the cell life cycle. The body has specific triggers involved, which stop the replication process. These triggers are present within the aging cell or from the environment. Cell aging takes place as a physiologic as well as a pathologic response. Cell aging can also be linked to overnutrition. The following are the causes of cellular aging:

• DNA Damage: Every cell consists of chromosomes. These chromosomes have all the genetic information. The end of these chromosomes is called a telomere. After each replication cycle, the telomere shortens. Without telomere, cell replication is unstructured and dangerous. Ultraviolet rays or UV rays can cause DNA damage. So cells are altered to maintain the genetic code.

• Oxidative Stress: The reactive oxygen species in a cell's environment can lead to replication errors. Cellular replication discontinues in the presence of such reactive oxygen species. Oxidative stress acts as a trigger for cell aging.

• Reduced Autophagy: Autophagy is a self-destructive process. A cell and its components fail as the cell ages. A cell self-digests its products in a process called autophagy. A cell consists of digestive enzymes called lysozymes. These lysosomes are responsible for breaking down damaged cell components. This increases protein levels within the cell and hampers replication. This process triggers aging.

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What Is the Difference Between Apoptosis and Cellular Aging?

An aging cell loses its ability to replicate. They can perform their original function. They are less efficient and less productive. However, apoptosis is programmed cell death. Older cells apoptose, but not all aging cells apoptose. Apoptosis is triggered to control the replication of poorly structured cells.

What Causes Premature Cellular Aging?

Cellular aging cannot be controlled. Some activities can act as triggers for premature aging. Following are the activities:

• Smoking.

• Drug use.

• Stress.

• Sunburns and tanning.

• Obesity.

What Are the Physiologic Roles of Senescence?

Cellular aging affects tissue homeostasis. Cellular aging also plays an important role in tissue remodeling and wound healing; it acts as a protective stress response. During repair, excessive connective tissue formation triggers fibrosis. Accumulation of extracellular proteins leads to the formation of scars, unstable structures, and non-functional tissue. It acts as an anti-cancer phenomenon and limits the malignant transformation of cells. If aging cells accumulate, it leads to age-related diseases. The aging of cells is required for the proper development of embryos and tissue repair. In cancer, cell aging helps to prevent tumor formation.

What Are Age-Related Diseases?

All organisms exhibit loss in tissue and function over a period. This leads to age-related diseases. Markers of aging accumulate in the tissues triggering the diseases mentioned below.

• Atherosclerosis: Accumulation of lipoproteins in the arteries activates certain smooth muscle cells. These cells trigger an inflammatory response. These cells form a wax-like substance called plaque. The smooth muscle cells and endothelial cells from this plaque release aging markers. Thus, the gaining of cells acts as a protective barrier against atherosclerosis.

• Osteoarthritis: Osteoarthritis is decreased function of the synovial joint due to degeneration of cartilage between the joint, presence of bony projections, inflammation, and thickening of ligaments. These changes cause pain and difficulty in moving. The cartilage-forming cells called chondrocytes secrete extracellular matrix for the maintenance of the cartilage between the joints. They also release aging markers. Chondrocytes lose this ability over time. Transplantation of aging markers through ear cartilage helps with the treatment of osteoarthritis.

• Osteoporosis: Osteoporosis occurs due to a change in bone turnover rate. In osteoporosis, bone resorption is more than bone formation. This leads to a decrease in bone density and strength, which increases the risk of fracture. Aging bone cells activate osteoclast and bone-resorbing cells and stimulate bone resorption.

• Glaucoma: Glaucoma is a condition in which blindness occurs due to progressive degeneration of the optic nerve. This occurs due to increased pressure in the eye, followed by the death of retinal cells. The role of aging cells in glaucoma development is unclear.

• Cancer: Cellular aging has oncogenic signal transduction. This is a response that inhibits the conversion of cells into malignant cells. Drugs used in chemotherapy and radiation can induce the aging of cancer cells. Aging controls proliferation and prevents the spread of cancer.

How Can We Prevent Cellular Aging?

We cannot completely stop aging; however, we can slow down the process. Following are the ways we can follow:

• Healthy Diet: A well-balanced and nutritious diet helps against damage and repair.

• Stress Management: Managing stress well by means of meditation, yoga, and indulging in hobbies will reduce stress hormones.

• Exercise: Regular exercise and lifestyle modifications help us against chronic diseases and build strong cells and tissues.

• Avoid Exposure to the Triggering Agents: Limited exposure to the sun and pollutants and the use of protective gear can control aging.

• Prevention Is Better Than Cure: Routine health checkups and management of weight, diet, and blood pressure keep the risk factors under control.

Conclusion

Aging cells stop division; aging protects against tumor formation and regulates cell division, and enters senescence after damage. It occurs due to DNA damage, oxidative stress, or autophagy. Cellular aging plays a vital role in age-related diseases.