Aging is an interesting thing.

"Selenoproteins play a crucial role in protecting blood-forming stem cells from oxidative damage. A study in Blood found that disrupting selenoprotein production impairs immune cell development and accelerates aging-related changes. However, dietary Vitamin E may help restore these functions, offering potential strategies to combat age-related diseases." (ScitechDaily, The Secret to Healthy Aging? Scientists Uncover the Power of Selenoproteins)

Theoretically making immortal creatures is quite an easy thing. The system must simply change the DNA in the mitochondria and the cell's nucleus. The system can store DNA in the digital form. And then nanotechnology restores that damaged DNA to its original form. The system removes damaged DNA from mitochondria and the cell's nucleus. And then it injects that fresh DNA into them. The problem is this: there are very many cells in the human body.  

Aging is one of the things. That is under research. The question about aging is mortality built in our DNA.  Or, does mortality come because of the outside effects? The outside effects. Metabolism production, Radiation, and toxins cause damage to the DNA. There is programmed cell death in the DNA. But sometimes that thing doesn't work. That makes the damaged cells make the descendants. 

Those damages cause mutations in the descendant cells and mitochondria. The mitochondria are the power sources for the cells. And those things have their own DNA and their own decay process. The question is which ages or dies first the cell's nucleus or mitochondria. 

Mitochondria take their own chemical signal to decay when the cell begins its mitosis. Researchers have noticed that selenoproteins can resist aging. That thing means that those proteins have some kind of effect on the cell's nucleus. Or maybe those proteins can affect mitochondria and their division. The protein can also slow aging by removing the products that mitochondria produce in metabolism. 

The mice that have human genomes help to solve what is the outside effect's role. And what is encoded in human DNA? Things like the aging process are important when people make long-term space travel to Mars and beyond. Things like cosmic radiation can destroy the DNA from cells and mitochondria. And that can accelerate aging. The cell's nucleus DNA and the mitochondria DNA are things that control the cell's everyday actions. 

Sometimes the malfunction in the mitochondria DNA is one of the reasons for some hereditary diseases. That means the mitochondria are underpowered or overpowered. So the cell cannot have strength if mitochondria are low power or it uses its nutrients too fast and boils the cell if mitochondria have overpowered. If mitochondrial metabolism is too high, the ion pumps in the cell cannot remove metabolic waste. And they cannot pump nutrients in. 

The reason for aging is in the DNA damage. Things like retroviruses transfer DNA from other species into human genomes. If that outcoming DNA will be at the point that controls the programmed cell death that can turn a cell into a cancer cell. 

https://scitechdaily.com/new-humanized-mice-brings-scientists-closer-to-reversing-aging/

 https://scitechdaily.com/the-secret-to-healthy-aging-scientists-uncover-the-power-of-selenoproteins/