Rikurzhen touched on a topic I find very interesting. Here’s information that I hope others will find informative.

Here are a couple of sites for information on aging:

SENS (Strategies for Engineered Negligible Senescence)

Flow Chart of Biochemical and Physiological Interactions in Human Aging

Here’s my rough synopsis (you really should read the SENS site):

Aging is several processes occurring at the same time:

DNA damage. Mainly in mitochondria.

Body system changes. Changing hormonal levels. Changes in the brain’s regulation of body homeostatis. Different gene expression patterns in body tissues. Cell receptor responses change. (Possibly pre-programmed system changes as a delayed result of puberty.)

Organ changes. Various organs function with less efficiency. The immune system undergoes a significant decline.

Stem cells lose regenerative ability. (May be related to telomer shortening.)

Accumulation of cellular garbage.

Protein cross-linkage in extra-cellular protein. (Hardening of the arteries.)

Arguments against systemic DNA damage being the main driver of aging:

Except for certain mitochondrial diseases, most mitochondria continue operating with good efficiency.

For the tissues tested, aging seems to occur at the same rate in all tissues. DNA damage occurs much more frequently in some tissues, e.g., retina of the eye. If DNA damage drives aging, I’d expect certain tissues to be “older” than others.

Article: A Global View of Gene Expression in the Aging Kidney

Article: Young blood revives aging muscles, Stanford researchers find

While I believe all of the above aging factors play a role, I think the main driver is a body system affect. It could be the brain’s regulation of body homeostasis changes. (Perhaps genetically programmed changes or perhaps just cumulative failure of feedback systems.)

It could be a central reservoir of special stem cells with the ability to differentiate into all cell types loses its regenerative abilities. (Such stem cells may have recently been found in bone marrow. Article )

If aging is mainly a general system failure, it could still be driven by DNA damage. But it wouldn’t be global DNA damage. It would be DNA damage in specific cells such a special stem cells or special neurons involved in regulating body systems. Replacing or fixing those cells might reverse some aspects of aging.