Cells go through a natural life cycle which includes growth, maturity, and death. This natural life cycle is regulated by a number of factors, and the disruption of the cycle is involved in many disease states. For example, cancer cells do not die the way normal cells do at the end of their life cycle. Here we look at the various processes by which cells age and die, both programmed and unprogrammed.

 

Cellular senescence is part of the normal aging of a diploid cell where it loses its ability to divide. Some sources suggest that senescence occurs via programmed gene expression changes, or that it is a result of an accumulation of DNA double strand breaks or toxins. Cellular senescence is easily detected by measuring Senescence Associated ß-galactosidase (SA-ß-gal), a hydrolase enzyme that catalyzes the hydrolysis of ß-galactosidase into monosaccharides only in senescent cells.

 

Programmed cell death happens naturally as a result of a cascade of signals within the cell itself. The most common form of programmed cell death, apoptosis, plays an important role in population control and prevents massive cell growth which could lead to a possible tumor. In embryogenesis, apoptosis allows the digits of our fingers and toes to acquire their normal shape that is instead of having webbed hands and feet. The cell is ultimately triggered to commit suicide when the correct internal signals are activated.

 

Anoikis is a specific type of apoptosis that is induced by the lack of correct cell attachment to the extracellular matrix (ECM). The importance of anoikis can be seen when cancer cells metastasize and are able to survive independently within the body without any direct attachment to the ECM.

 

Autophagy is another type of programmed cell death in which a cell’s own internal machinery is degraded by its lysosomes. It is theorized that this process may occur for reasons of self-preservation of the organism or to allow the organism to conserve resources to be allocated elsewhere in the body.

 

In contrast to programmed cell death, necrosis is the premature death of cells and living tissue caused by external factors such as trauma, infection, or toxins. Usually necrotic cells are not eliminated from the body the way apoptotic cells are, because the signaling pathways activated during apoptosis are not activated during necrosis.

Ageing or aging (see spelling differences) is the process of becoming older. The term refers especially to human beings, many animals, and fungi, whereas for example bacteria, perennial plants and some simple animals are potentially biologically immortal. In the broader sense, aging can refer to single cells within an organism which have ceased dividing (cellular senescence) or to the population of a species (population ageing).

 

In humans, aging represents the accumulation of changes in a human being over time, encompassing physical, psychological, and social changes. Reaction time, for example, may slow with age, while knowledge of world events and wisdom may expand. Aging is among the greatest known risk factors for most human diseases: of the roughly 150,000 people who die each day across the globe, about two thirds die from age-related causes.

 

Last Updated on: Nov 27, 2024