The Cell Biology of Aging

The distinction between the effects of aging as a chronological process and diseases whose prevalence increase with advancing age remains blurred. Conditions once thought to be inevitable companions of old age are now known to in fact be pathological in origin and thus possibly treatable and preventable. One example is senile dementia, no longer the mysterious fate of the very old, but often a clinical manifestation of arteriosclerotic or biochemical brain disease. Further research may elucidate the mechanisms underlying aging and their possible connection to agerelated diseases, leading to the development of medical techniques that delay the onset and progression of symptoms. While it may not lead to actual extension of the human life span, such knowledge could reduce the prevalence and impact of chronic conditions that affect many elderly persons and drain our health care resources, allowing marked improvement in the general well-being and productivity of the growing elderly segment of the population. The cell is the physiological building block in all higher organisms, including humans. Any investigation of mechanisms underlying the aging process must therefore look at how different cell types are altered over time to produce the structural and biochemical changes normally associated with aging. Numerous biological signs of aging have already been identified in cells both within the human organism and grown on artificial media. This section reviews the theories and evidence concerning mechanisms underlying biological aging.