»How Long Can Our Lives Be Extended?«

The gerontologist Karl Lenhard Rudolph talks about the consequences of evolution

What happens to people when they age? Why do we get old and die?

Over the millions of years of evolution, most living organisms have been programmed to reach the pinnacle of their capabilities at the ages when they reproduce. Such organisms can be regarded as having completed their mission after they have reproduced and the next generation has reached maturity. The same is true of human beings. Our hard drive, by which I mean our genes and the way they are connected with one another, achieves optimal fitness between the ages of 25 and 40. Evolution doesn’t concern itself with what happens after that (except for the low evolutionary utility of the grandparents helping to bring up the grandchildren). So aging begins after the reproductive years have passed. The nerve cells in the brain begin to lose their plasticity and stop forming synapses, stem cells stop dividing, and the ability of organs to regenerate themselves decreases. Simultaneously, the number of mutations and defects increases. In the meantime, proteins clump together and toxic substances lead to chronic inflammation in nearly all body tissues. Aging begins when this loss of cell and organ functioning sets in.

»There’s a biological limit to life expectancy—100 years, or 120 at the most«

What happens to mental capabilities?

Mental development also follows this pattern, but not as clearly. The aging individual experiences a loss of creativity, but he or she also gains experience. There are some artists who didn’t write their greatest works or compose their best music until they were relatively old. In general, it’s true here as well that as people age, their ability to learn new things diminishes and their memory deteriorates.

Still, people keep living longer. At the beginning of April, an Italian woman named Emma Morano died at the age of 117. What are the limits of longevity?

I believe there’s a biological limit to life expectancy that I would say could be 100 years, or 120 at the most. We shouldn’t be fooled by the fact that the average life expectancy in Germany has doubled in the last 200 years from the mid-40s to the mid-80s and will likely increase to 90 by 2035. This increase is mostly due to illnesses being detected at an earlier stage of their development, improved treatments, and the fact that people live healthier lives. They have a better diet and enjoy better living and working conditions. All of this slows aging processes, but it doesn’t stop aging as such. The ageing process, which is launched by evolution to reduce the ability of all of our systems to function properly after our reproductive years are over, cannot be shut down that easily.

There are regions in which people live longer (see our report on page 46). Why is that? Can we learn anything from the people in those regions?

Good diets and lifestyles definitely play a role in healthy aging. The olive oil often used in Mediterranean countries and the consumption of fish in Japan can have a positive effect on life expectancy. We also know that stress and obesity accelerate biological aging, while sports and exercise have a positive effect. It’s important to understand that although we can’t do much about our genetic makeup, we can change our habits in order to live healthier lives.

Some say that those who go hungry live longer. Is that true?

Lower food intake lengthens the lifespan and improves the health of various organisms. This was first demonstrated with flies and worms, but these days we also know it to be true about mice and monkeys. It’s not just the metabolism decrease that slows the aging process here, as a large number of protective mechanisms— such as autophagy—are also triggered when caloric intake declines. Autophagy launches a process in which cells detect damaged proteins and disassemble them. This type of detoxification has a positive effect. However, lower food intake also inhibits the formation of immune cells. That increases an organism’s susceptibility to infection.

Japanese stem cell researcher Shinya Yamanaka has demonstrated in the laboratory that it is possible to reset the life clock of every cell in the body back to zero—the embryonic stage. In 2012 Yamanaka was awarded the Nobel Prize in Medicine for this reprogramming feat. Doesn’t his research point the way toward defeating the aging process?

Research conducted on mice has shown that it is in fact possible to rejuvenate tissue with cell reprogramming. The danger here is that you might end up not only reprogramming the cells you want to affect but also activating other cells that never come to rest—and can therefore turn cancerous.

»We’re searching not for the secret of immortality but rather for moreeffective treatments for age-related illnesses«

In your research you have attempted to lengthen the period in which adult stem cells are able to divide and thus improve the regeneration potential of the body’s organs. Have you succeeded in doing this?

Studies with animals have shown that it is possible to keep organs functioning properly for a longer period of time, strengthen the immune system, and improve muscle power and blood formation in old age. This can delay the onset of certain age-related dysfunctions and diseases, or even eliminate them. I definitely believe that there are certain ways to improve the health of the elderly, but I don’t see any way to stop the aging process throughout the entire body. The organism that is our body, with all of its different cell types and organs, is simply not programmed for that.

So science will never be able to cheat death?

An unlimited lifespan is not possible; evolution has seen to that through certain provisions—such as the telomeres that are located at the ends of every chromosome and get shorter with each cell division. We can block certain signals and shut down control points, and in this manner lengthen the cell division process. However, there is a limit. When the telomeres get too short, the body descends into genetic chaos and its cells die.

If you link the circulation systems of an old and a young mouse in a lab, the old mouse gets stronger, cleverer, and healthier without the younger mouse being negatively affected in any way. Can young blood lengthen the life of a human being?

Cell aging is evidently caused not only by processes in the cells themselves but also by external factors in their surroundings. Messenger substances and proteins in the blood help ensure that cells function properly. This is a very important insight, but we still don’t know enough about what exactly occurs during parabiosis—in other words, a linkage between two organisms— and which proteins or messenger substances cause the deterioration of cell functioning in an individual’s old age.

Still, some US companies in are making a lot of money selling young blood…

You can’t assume that the results achieved with mice in a lab are directly reproducible in humans. Research here is very much in its infancy.

Scientists at the Max Planck Institute for Biology of Ageing in Cologne have shown that older killifish live longer when they are fed the feces of younger killifish. Can feces transplantations lengthen the human lifespan?

The bacteria that live in and on us have a major influence on our physiology and on the aging process. They interact with our bodies and also send out messenger substances that enter our bodies. We know that the composition of the bacteria in human intestines changes throughout the course of a person’s life—and this is probably the reason why some organs lose their ability to regenerate. We are currently putting together a research group that will try to identify which bacteria have a negative influence on aging and which ones have a positive effect.

Google’s chief developer, Ray Kurzweil, believes that in 30 years it will be possible to download a human brain and digitalize the intelligence of each and every human being and his or her way of thinking. Would that be a form of immortality?

I can imagine that learning-enabled computers can make an important contribution to the development of humanity, and that they will also be used for aging research. They could definitely come up with possible solutions that we as humans have perhaps overlooked. However, I cannot imagine that a human brain can be recreated on a computer. Humans are spontaneous; they have spontaneous ideas and inspirations that are strongly linked to interaction with their environment. Artificial intelligence will not make anyone immortal.

Will it someday be possible to reanimate people who are now having their bodies cryopreserved—that is, frozen—after they die?

I don’t think it will be possible to revitalize these bodies. It is possible today to freeze and thaw individual cells and small tissue segments without damaging them, but a lot of damage would definitely occur if this were done to highly complex organisms. In my opinion, the purpose of aging research is not to search for the secret to immortality but instead to search for knowledge that will enable more effective treatment of age-related illnesses and keep the elderly healthy longer. If average life expectancy then increases to 100 because people stay healthy for longer periods of time, then so much the better.

The research group headed by Karl Lenhard Rudolph examines the causes, processes, and effects of stem cell aging. The stem cells of an adult organism are indispensable to the lifelong maintenance and regeneration of the body’s tissues and organs. The molecular mechanisms that cause the loss of functionality of stem cells are still largely unknown

Find out more about the research group

Andrzej Rybak

used his sister-inlaw as a research source for this interview: She is the director of The Laboratory of Molecular Bases of Aging at the Institute for Experimental Biology in Warsaw