Why do cells lose their ability to repair themselves over time?
Cells lose their repair capacity through a combination of declining energy stores, impaired DNA repair and the accumulation of 'burned-out' cells that secrete inflammatory substances. These are well-supported mechanisms, although it is still too early to act on them through supplements or therapies.
Cells have multiple systems for repairing damage: they fix damaged DNA, produce new power plants (mitochondria) and clear out broken components. All of these processes slow down as you age, and that has tangible consequences. One example: with ageing, levels of NAD+, a substance cells need to drive DNA repair and energy production, decline. Without sufficient NAD+, the repair enzymes function less effectively, which contributes to muscle weakness, metabolic problems and cognitive decline.
At the same time, so-called 'senescent' cells accumulate in tissues. These are cells that have permanently stopped dividing after damage or stress. They do not clear themselves away, but they do continuously secrete inflammatory substances. Those substances damage the surrounding healthy cells and have been linked to conditions such as liver fibrosis, atherosclerosis, diabetes and osteoarthritis. In animal research, removing senescent cells was shown to reduce the symptoms of these diseases and to extend lifespan. Whether the same applies to humans is still being investigated.
Senescent cells are not always harmful, however. During wound healing and early development they play a temporarily useful role. The problem only arises when they accumulate permanently, as happens with ageing: at that point they actually inhibit repair and sustain a low-grade inflammation.
The cell's power plants, the mitochondria, also begin to function less well with ageing. The production of new mitochondria decreases, making the cell less resilient in the face of damage. In the skin there is an additional factor: the skin's support cells (fibroblasts) lose their biomechanical properties, and the skin's immune system weakens. This makes it harder to fight infections and close wounds, and increases the risk of chronic, non-healing wounds.
An interesting insight comes from research into naked mole rats, animals that live remarkably long lives. They possess a modified version of a DNA-surveillance protein that strengthens the repair process rather than slowing it down. Just a small adjustment to that protein was sufficient in cells to slow ageing. Whether something like this could ever be applied in humans remains speculative for the time being.
Claims are based on combinations of animal and human studies (PMID 30648461, 32555459, 32993416, 33353981, 41066557, 32279443, 33296633, 25473038). Most mechanistic findings are robust, but for repair interventions (NAD+, senolytic therapies) the evidence in humans is still limited or absent.
Can DNA damage in your cells repair itself?
Your cells repair DNA damage continuously and systematically, but the system is not infallible: chronic overload or a defect in the repair pathways increases the risk of cancer and age-related diseases.
Why do some cells stop dividing as you age?
Cells stop dividing as a protection against damage and cancer, but the accumulation of such stopped cells contributes over the years to inflammation and age-related diseases. Drugs that target this are promising in animal research, but are not yet ready for use outside clinical studies.
Why are cells damaged when you don't get enough oxygen?
Oxygen deprivation damages cells through a chain of mechanisms: energy deficit, overstimulation of nerve cells, and an assault by free radicals, partly triggered precisely when blood flow is restored. How severe the damage turns out to be depends on how long and how serious the deficit is.
How does air pollution damage your cells from the inside?
Air pollution damages your cells from the inside through oxidative stress: fine particulate matter causes an excess of harmful oxygen molecules that attack your DNA, energy factories, and immune system. Protection begins with limiting exposure, because the damage occurs at the cellular level.
Why do damaged proteins accumulate in your cells as you age?
As you age, several systems that clear away damaged proteins weaken simultaneously and amplify each other's failure. This is one of the central mechanisms behind age-related diseases, but how to stop it in a targeted way is still actively being researched.
What is apoptosis and why is it beneficial for cells to clean themselves up?
Apoptosis is an indispensable clean-up mechanism that keeps your body healthy, but balance is everything: too little increases the risk of cancer, too much damages the brain and other vulnerable tissue.