What’s preventing human longevity?
A look into neural aging.
Don’t you wish you could live forever? Me too. Unfortunately, we can’t…at least not yet.
The current global life expectancy is 72.0 years. You can spend as much as 29 years in school. The rest of the time is spent working, and then somewhere at the end you retire.
If we increased our human life span, this entire cycle would change. Seventy would be the new forty (hopefully) and you’d have so much more time to vacation…or solve problems. So, what really affects our life span? It’s a combination of genetics, environment, and lifestyle.
Scientists are currently studying nonagenerations, centenarians, semi-centenarians, and supercentenarians. Which are are just fancy words for saying people in their 90s, 100s, and people above 110. What similarities do they share? They’re nonsmokers, not obese, and cope well with stress.
Winning the genetic lottery.
My first thought was, what about their genetics? Are some of us just luckier than the rest? Only a little bit. It’s estimated that about 25% of the variation in human life span is determined by genetics.
These gene variants are found in the basic maintenance and function of the body’s cells. This includes DNA repair, maintenance of telomeres, and protection caused by free radicals. Other genes that are associated with blood lipid levels contribute significantly to longevity because they reduce the risk of heart disease, stroke, and insulin resistance.
It’s true, some people are just more genetically fit to live longer than others. However, with emerging technology including gene-editing, we can alter individual DNA to optimize for a longer life.
It’s crazy to think about, but it’s all possible through the use of technology such as CRISPR-Cas9. Creations such as CRISPR help researchers remove, add, or alter parts of the genome.
Great, so in a few years we can start increasing human longevity. This got me thinking. If your body can live longer, it doesn’t necessarily your brain won’t continue to degenerate.
Life span != health span.
Neural aging is the process in which your neural cells in the brain and nervous system deteriorate structurally and functionally over time. This degeneration is associated with a decline in sensory, motor, and cognitive functions of the brain. As you grow older, your brain shrinks in size.
Changes at the level of individual neurons contribute to shrinkage and cortical thinning. Neurons shrink and retract their dendrities and the myelin that wraps around axons deteriorates. The formation of new neurons (neurogenesis) also declines with age.
When the brain starts to deteriorate its due to causes elsewhere in the body. High blood sugar from diabetes degrades blood vessels. Cholesterol induces blockage of small blood vessels in the brain. While high blood pressure can burst or plug vessels.
If we increase life span, we also have to increase health span. We can’t live longer when diseases like Alzheimer’s and cancer still exist. Why? People that are older are more susceptible to these diseases.
Solving half of the problem.
I can’t give you the cure to all of these diseases…not yet at least. Instead, I want to talk to you about a potential solution the other half of the problem. Using stem cells to prevent neural aging.
Stem cells are essentially special human cells that can develop into a variety of cell types. They can turn into muscle cells, skin cells, immune cells, and most importantly, nervous cells.
Stem cells can keep dividing as long as they’re alive, that means they’re self-renewinng. What’s important is that they can create other stem cells and become multiple types of even more specialized cells.
Neural stem cells (NSCs) are self-renewing, multipotent cells. They create radial glial progenitor cells that generate neurons and glia for the nervous system during embryonic development.
Researchers have found that neural cells in the hypothalamus which regulates hunger, sleep, and body temperature orchestrate the body’s aging process. These cells begin to diminish with age. This is where stem cell replacement therapies can be used.
Cells, which keep on giving.
The two primary replacement strategies involve transplantation of exogenous tissue and activation of proliferation of endogenous cells. Exogenous tissue is derived externally whereas endogenous cells reside inside specific tissues. The advantage of endogenous stem cells is that they mitigate the risk of rejection and infection.
Transplanted NSCs can be used to directly replace lose tissue from aging. Implants of genetically engineered cells can be used to secrete factors which promote longevity, renewal, and proliferation in the brain.
Using stem cell replacement therapies may not only help you live longer, but help maintain the health of your brain. This all requires an understanding of the complex relationships between neural stem cells and the more restricted neural and glial progenitor cells.
People that currently benefit from the use of stem cell therapies include those with spinal cord injuries, type 1 diabetes, Parkinson’s disease, amyotrophic lateral sclerosis, Alzheimer’s disease, heart disease, stroke, burns, cancer and osteoarthritis.
With the combination of the right gene-editing techniques and stem cell therapies, we soon enough will increase human longevity while also increasing the human health span.
Seventy might just become the new forty.