Scientists today have focused on three key aspects of cellular senescence.
The first may explain why such a phenomenon would exist. Scientists note
that limiting the number of divisions a cell can undergo may serve to suppress
tumor formation and cancer. With each normal cell division, the possibility
of genetic mutation exists. Some of those mutations can make cells cancerous.
A finite life span for cells would reduce the likelihood that potentially
cancerous cells can survive.
A second important phenomenon associated with cellular senescence is
the many changes in function that occur in all cells as they approach
senescence. Many senescent cells stop functioning as they did when they
still had the capacity to divide. These hundreds of functional losses
that precede the loss of division capacity in normal cells mimic many
of the functional losses that occur in humans as we age, thus making the
study of these cells important in learning more about aging.
The third reason why studying senescent cells is important is that the
limit on their division capacity may directly govern the determination
of maximum human longevity.
Replicative senescence also plays an important role in the functioning
of all human systems, including, for example, the immune system. When
our bodies are confronted with infection, they produce white blood cells
called T lymphocytes that fight the infection. Those white blood cells
reproduce themselves time and again in order to win this battle. Cellular
or replicative senescence, however, limits those lymphocytes to a specific
number of reproductions. This may serve as one mechanism the body uses
to ensure that a proper balance is maintained between circulating white
blood cells and other components of the blood.
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