Types of aging damage and treatment schemes
Nuclear mutations/epimutations—OncoSENS
These are changes to the nuclear DNA (nDNA), or to proteins which bind to the nDNA. Certain mutations can lead to cancer.
This would need to be corrected by a cure for cancer, if any is ever found. SENS focuses on a strategy called "whole-body interdiction of lengthening telomeres" (WILT), which would be made possible by periodic regenerative medicine treatments.
Mitochondrial mutations—MitoSENS
Mitochondria are components in our cells that are important for energy production. Because of the highly oxidative environment in mitochondria and their lack of the sophisticated repair systems, mitochondrial mutations are believed to be a major cause of progressive cellular degeneration.
This would be corrected by allotopic expression—copying the DNA for mitochondria completely within the cellular nucleus, where it is better protected. De Grey argues that experimental evidence demonstrates that the operation is feasible, however, a 2003 study showed that some mitochondrial proteins are too hydrophobic to survive the transport from the cytoplasm to the mitochondria.[24]
Intracellular junk—LysoSENS
Our 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 accumulate as junk inside our cells, which is detected in the form of lipofuscin granules. Atherosclerosis, macular degeneration, liver spots on the skin and all kinds of neurodegenerative diseases (such as Alzheimer's disease) are associated with this problem.
Junk inside cells might be removed by adding new enzymes to the cell's natural digestion organ, the lysosome. These enzymes would be taken from bacteria, molds and other organisms that are known to completely digest animal bodies.
Extracellular junk—AmyloSENS
Harmful junk protein can accumulate outside of our cells. Junk here means useless things accumulated by a body, but which cannot be digested or removed by its processes, such as the amyloid plaques characteristic of Alzheimer's disease and other amyloidoses.
Junk outside cells might be removed by enhanced phagocytosis (the normal process used by the immune system), and small drugs able to break chemical beta-bonds. The large junk in this class can be removed surgically.
Cell loss and atrophy—RepleniSENS
Some of the cells in our bodies cannot be replaced, or can be only replaced very slowly—more slowly than they die. This decrease in cell number affects some of the most important tissues of the body. Muscle cells are lost in skeletal muscles and the heart, causing them to become frailer with age. Loss of neurons in the substantia nigra causes Parkinson's disease, while loss of immune cells impairs the immune system.
This can be partly corrected by therapies involving exercise and growth factors, but stem cell therapy, regenerative medicine and tissue engineering are almost certainly required for any more than just partial replacement of lost cells.
Cell senescence—ApoptoSENS
Senescence is a phenomenon where the cells are no longer able to divide, but also do not die and let others divide. They may also do other harmful things, like secreting proteins. Degeneration of joints, immune senescence, accumulation of visceral fat and type 2 diabetes are caused by this. Cells sometimes enter a state of resistance to signals sent, as part of a process called apoptosis, to instruct cells to destroy themselves.
Cells in this state could be eliminated by forcing them to apoptose (via suicide genes or vaccines), and healthy cells would multiply to replace them.
Extracellular crosslinks—GlycoSENS
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, presbyopia and weakened skin texture. These are chemical bonds between structures that are part of the body, but not within a cell. In senescent people many of these become brittle and weak.
SENS proposes to further develop small-molecular drugs and enzymes to break links caused by sugar-bonding, known as advanced glycation endproducts, and other common forms of chemical linking.