What is Cell Senescence?

While "senescence" can refer to the process by which our whole bodies become frailer as we age, it also has a more specialized meaning when it comes to individual cells. “Senescent” cells are one class of death-resistant cells, cells that overstay their welcome. They include cells that have suffered mutations and that, which the body has shut off, taking away the ability to reproduce in order to prevent them from growing out of control and becoming cancerous. They also include the key fat cells lining the inside of the gut that make obesity deadly, and defective immune cells that no longer protect the body against infection and even interfere with the ability of other immune cells to protect us. These cells stick around, releasing proteins that are dangerous to their neighbors and eventually cause disease.

How does the damage set in?

Cells are the basic building blocks of tissues. All cells experience changes with aging, a process known as cell senescence. They become larger and are less able to divide and reproduce. Among other changes, there is an increase in pigments and fatty substances inside the cell (lipids). Many cells lose their ability to function, or they begin to function abnormally.
An important cause of aging is death-resistant cells, cells that overstay their welcome. The senescent cells are the ones which have lost the ability to reproduce. These stick around, releasing proteins that are dangerous to their neighbors and eventually cause disease.

Resultant Diseases

Different kinds of death-resistant cells cause different problems. Death-resistant cells in the fat tissue of the gut contribute to Type II Diabetes Death-resistant immune cells make us more susceptible to infections that young people easily shake off, leading to huge numbers of deaths from the ‘flu and other infections in the elderly and allowing for the reactivation of shingles, the painful skin rash. Proteins secreted by senescent cells lining our organs help fuel the fires of cancer. And because cells are the fundamental structure composing our bodies, the deactivation of cells by senescence also contributes to cell loss and tissue atrophy.

Solution

Scientists are working on two main strategies to get rid of death-resistant cells. First is a “suicide gene” approach, in which a gene is introduced into the cells which will become active only when the cell becomes senescent. An alternative is to kill senescent cells from the outside, such as by stimulating the immune system to remove them or by designing “smart bomb” delivery systems that would recognize death-resistant cells and destroy them with drugs.