Hallmarks of Aging

Altered Extracellular Matrix

Age-related changes in the extracellular matrix — cross-linking, fibrosis, elastin loss — that impair tissue function and reciprocally alter cell behaviour.

Altered Intercellular Communication

Age-related changes in hormonal, neuronal, and immune signalling between cells and tissues.

Cellular Senescence

Stable cell-cycle arrest accompanied by a pro-inflammatory secretome (the SASP) that propagates dysfunction to neighbouring tissue. Senescent-cell burden rises with age and drives inflammaging.

Chronic Inflammation

Persistent low-grade systemic inflammation ("inflammaging") that accelerates most major age-related diseases.

Deregulated Nutrient-Sensing

Loss of homeostasis in the insulin/IGF-1, mTOR, AMPK, and sirtuin pathways that translate nutrient state into growth and repair decisions.

Disabled Macroautophagy

Decline in the bulk recycling pathway that engulfs and degrades cellular components, especially damaged mitochondria and protein aggregates.

Dysbiosis

Age-related shift in gut microbial composition and function, with knock-on effects on metabolism, immunity, and the brain.

Epigenetic Alterations

Age-related changes in DNA methylation, histone modifications, and chromatin remodelling that drift cells away from youthful gene-expression patterns.

Genomic Instability

Accumulation of DNA damage over the lifespan, driven by both endogenous and environmental insults.

Loss of Proteostasis

Decline in the cell's ability to fold, refold, and degrade proteins, leading to accumulation of misfolded and aggregated species.

Mechanical Aging

Proposed hallmark: age-related changes in tissue mechanical properties (stiffness, elasticity, viscoelasticity) that drive dysfunction independently of molecular hallmarks.

Metaflammation

Metabolically-driven chronic low-grade inflammation — a distinct sub-phenotype of inflammaging arising from adipose tissue, gut, and metabolic organs.

Mitochondrial Dysfunction

Age-related decline in mitochondrial bioenergetics, biogenesis, and quality control, with downstream effects on ROS, inflammation, and cell death.

Splicing Dysregulation

Proposed candidate hallmark of aging: mis-regulation of pre-mRNA splicing accumulates with age, producing dysfunctional protein isoforms and driving multiple age-related diseases.

Stem Cell Exhaustion

Decline in the number and regenerative capacity of tissue-specific stem cells, impairing replacement of dying or damaged cells.

Telomere Attrition

Progressive shortening of chromosomal end-caps with each cell division, triggering senescence or apoptosis.