Why do we get older when cells are always replicating?

A French woman named Jeanne Calment lived to be 122 years old, making her the oldest person in history. In fact, reaching this age is a challenge that very few, if any, people have been able to achieve.

The human body is not designed to live very long and is usually limited to the age of 90. So why do we age and what does aging really mean?

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Aging occurs when the body interacts with the external environment such as light, toxins in the air, water and diet, etc., causing changes in the structure and function of cells in the body. These changes will lead to a decline in function and then the gradual death of the entire body. Scientists have identified changes in genetics and changes in the ability of cells to regenerate themselves that cause the body to age.

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First, over time, our bodies accumulate genetic damage through DNA damage . This occurs naturally when DNA replicates, as well as in non-dividing cells. Organelles such as mitochondria are particularly susceptible to this damage. Mitochondria produce adenosine triphosphate, or ATP , the primary source of energy for all cellular metabolism, and they regulate many other cellular activities and play a key role in regulating cell death. If mitochondrial function is impaired, cells and organs will eventually fail.

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Other changes occur through gene expression. Genes that are less expressed in infants become more active in older adults, leading to the development of age-related degenerative diseases such as Alzheimer's.

It's true that cell replication slows down as we age . The DNA in our cells is wrapped around chromosomes, each of which has two protective regions at the ends called telomeres. These ends get shorter every time a cell duplicates. When telomeres get too short, the cell stops replicating and dies, slowing down the body's ability to repair itself. A process that stops a cell's life cycle when it's in danger, such as when cancer cells grow too large. But this reaction happens more often as we age, stopping cells from growing and reducing their ability to replicate.

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Aging also affects stem cells, which are located deep in our tissues and have the ability to replicate indefinitely to replace other cells. As we age, the number of stem cells decreases and they lose their ability to regenerate, affecting tissue regeneration and maintaining the original functions of our organs.

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Other changes revolve around how cells function. As they age, they lose the ability to regulate proteins, leading to a buildup of toxic substances. Communication between cells also slows down, eventually disrupting the body's ability to function properly.

There is much we still don't understand about aging . Ultimately, will our lives be extended by diet, exercise, drugs, or something else? Will future technologies like cell-editing nanobots or gene therapy extend our lives? And do we really want to live longer?