7 Mechanisms Causing Ageing.

The seven types of aging damage

By Aubrey David Nicholas Jasper de Grey

Main article: Strategies for Engineered Negligible Senescence

De Grey proposed the following types of aging damage:

1. Mutations – in chromosomes causing cancer due to nuclear mutations/epimutations:These are changes to the nuclear DNA (nDNA), the molecule that contains genetic information in eukaryotes, or to proteins which bind to the nDNA. Certain mutations can lead to cancer, and, according to de Grey, non-cancerous mutations and epimutations do not contribute to aging within a normal lifespan, so cancer is the only endpoint of these types of damage that must be addressed.
   

2. Mutations – in mitochondria:Mitochondria are components in eukaryotic cells that are important for energy production. They contain their own genetic material, and mutations to their DNA can affect a cell's ability to function properly. Indirectly, these mutations may accelerate many aspects of aging.
   

3. Junk – inside of cells, aka intracellular aggregates:Cells are constantly breaking down proteins and other molecules that are no longer useful or which can be harmful. Those molecules which can't be digested simply accumulate as junk inside of cells. Atherosclerosis, macular degeneration and many kinds of neurodegenerative diseases (such as Alzheimer's) are associated with this problem.
   

4. Junk – outside of cells, aka extracellular aggregates:Harmful junk protein can also accumulate outside of cells. The amyloid senile plaque seen in the brains of Alzheimer'spatients is one example.[41]
   

5. Cells – too few, aka cellular loss:Some of the cells in bodies cannot be replaced, or can be replaced only very slowly – more slowly than they die. This decrease in cell number causes the heart to become weaker with age, causes Parkinson's disease, and impairs the immune system.
   

6. Cells – too many, aka cellular senescence:This is a phenomenon where some cells can no longer divide, but also do not die and let others divide. They may also do other things that they're not supposed to, like secreting proteins that may be harmful. Cell senescence has been proposed as cause or consequence of diabetes mellitus type 2.[42] Immune senescence is also caused by this.[citation needed]
   

7. Extracellular protein crosslinks:Cells are held together by special linking proteins. When too many cross-links form between cells in a tissue, the tissue can lose its elasticity and cause problems including arteriosclerosis and presbyopia.[25][43] NB: The critics single out three proposed therapies for criticism: somatic telomerase deletion, somatic mitochondrial genome engineering, and the use of transgenic microbial hydrolase.[48]