What is cellular senescence?

It is a state in which a cell permanently stops dividing but stays alive and active; it accumulates with age and influences surrounding tissue.

Why does the body repair itself less well with age?

Stem-cell pools decline in number and function over time, and cells accumulate damage, so the capacity for renewal and regeneration decreases as an organism ages.

Aging and Developmental Decline

How the developmental continuum extends into the progressive decline of aging, including cellular senescence and the loss of regenerative capacity.

Definition

Aging is the progressive, time-dependent decline in the function and maintenance of cells and tissues; developmental decline refers to the loss of growth, renewal, and regenerative capacities that accompanies the later stages of an organism's life history.

Scope

This topic treats aging as the later part of the life history that developmental biology helps explain: cellular senescence, the gradual loss of tissue and stem-cell function, and the molecular changes associated with growing old. It connects developmental mechanisms to the decline in maintenance and repair, framing the biology of aging without offering medical guidance.

Core questions

How does the developmental program connect to the later decline of aging?
What is cellular senescence, and what roles does it play?
Why does regenerative and stem-cell capacity decline with age?
What cellular changes are characteristic of aging tissues?

Key concepts

Cellular senescence
Telomere attrition
Stem-cell exhaustion
Loss of regenerative capacity
Genomic and epigenetic changes with age

Key theories

Hallmarks of aging: Aging is associated with a recurring set of cellular and molecular changes — including genomic instability, telomere attrition, cellular senescence, and stem-cell exhaustion — that together account for the functional decline of tissues over time.

Mechanisms

Aging tissues accumulate a characteristic set of changes. Cellular senescence is a state in which cells permanently stop dividing while remaining metabolically active and secreting signals that affect their neighbours; it can limit damaged-cell proliferation but also contributes to tissue ageing. Telomeres, the protective ends of chromosomes, shorten with division and can trigger senescence. Stem-cell pools decline in number or function, reducing the capacity for renewal and repair. These cellular changes, together with accumulating genomic and epigenetic alterations, are reflected in the progressive loss of tissue maintenance that defines developmental decline at the end of the life history.

Clinical relevance

The biology of senescence and stem-cell decline underlies age-related loss of tissue function and is studied as a route to understanding age-associated disease and impaired repair. This entry is educational and does not provide medical guidance.

History

The observation that normal cells divide only a limited number of times before entering senescence reframed aging as having a cellular basis; subsequent work linked telomeres, genome maintenance, and stem-cell function to the decline of tissues with age.

Key figures

Leonard Hayflick

Seminal works

lopezotin2013
gilbert2016

Frequently asked questions

What is cellular senescence?: It is a state in which a cell permanently stops dividing but stays alive and active; it accumulates with age and influences surrounding tissue.
Why does the body repair itself less well with age?: Stem-cell pools decline in number and function over time, and cells accumulate damage, so the capacity for renewal and regeneration decreases as an organism ages.