[Vidéo] The 9 Causes of Aging, Episode 7, Senescence – with Dr. Guilhem Velvé Casquillas

Senescence: definition

We will address a seventh identified cause of aging: cell senescence.

A senescent cell is an aging cell whose functions degrade, it stops dividing and its activity changes. They are zombie cells in our body, not quite dead, but unable to replicate. During this shift, a normal cell will start to change its metabolism and can, for example, start secreting pro-inflammatory molecules that will, in turn, signal to the surrounding cells that there is a problem. Through this mechanism, the first senescent cells can degrade the health of other cells and that’s when everything starts to go wrong.

Senescent cells accumulate with age in certain tissues, causing them to lose homogeneity and probably causing them to deteriorate even more rapidly.

However, senescence may have been selected as a mechanism to prevent the proliferation of cancer cells. Indeed, we have noticed that cancer cells do not have senescence mechanisms and are virtually immortal.

Senescence et immunity

Fortunately, senescent cells can be eliminated by the immune system. But of course, this requires an effective immune system. However, with age, the immune system becomes less effective, even as more and more cells become senescent. This inevitably leads to an accumulation of senescent cells in some of our tissues.

This mechanism, initially a defence mechanism, is therefore beneficial during youth. It protects the body from the proliferation of cancer cells, but requires an effective immune system to eliminate them and strong stem cells to replace them.

To sum it up, as the body ages, senescent cells accumulate due to the lack of stem cell renewal and a less effective immune system. And the accumulation of these latter weakens the surrounding tissues even more… another vicious circle.

In fact, when researchers have induced the self-destruction of senescent cells in old mice, they have observed a rejuvenation of these mice. At least our little presentation on senescence ends well.