It lives in the Mediterranean, bears the name Turritopsis nutricula, and is not much more than a floating watery jelly disk. But it has an amazing property: it is immortal (as long as it is not eaten). For this particular jellyfish has a cell program, which reverses the usual translation of young cells into differentiated […]
It lives in the Mediterranean, bears the name Turritopsis nutricula, and is not much more than a floating watery jelly disk. But it has an amazing property: it is immortal (as long as it is not eaten). For this particular jellyfish has a cell program, which reverses the usual translation of young cells into differentiated cells. It thus permanently “rejuvenates” its cells.
Even some forms of unicellular life like the paramecium have the chance to live billions of years, as they continue to divide into new cells. Many creatures are thus potentially immortal. Man, however, ages until he finally dies, latest at an age of little more than 120 years. But is there a chance that in the future we become immortal like the jellyfish or the paramecium?
The life expectancy of humans can never exceed 64 years and 9 months, so calculated the US-American demographer and statistician of the insurance company Metropolitan Life, Louis Dublin, in the late 1920s. However, contrary to Dublin’s prediction, the average human life span in the most highly developed countries has increased to more than 80 years. And it continues to grow with an average of 2.5 years per decade. Its doubling over the past 150 years is almost entirely due to advances in the medical and natural sciences, including better hygiene standards, more adequate nutrition, and more comprehensive medical emergency care. But how far can the human life be prolonged?
But why are we even getting older and irrevocably die at some point? Surprisingly, science cannot yet provide an exact answer to this question. None of the different theories of aging is generally accepted. In simple terms: Our cells and organs simply lose their capacity to function. Some of today’s geneticists assume that this process can be stopped or even reversed.
They believe that the possibilities in genetic manipulation might make a human primordial dream come true: the fountain of eternal life. Already one of the oldest narrations of human history deals with this hope: the Gilgamesh epic from the 3rd millennium BC. Therein, the Sumerian king Gilgamesh in his search for eternal life finally finds the secret of immortality in the form of a plant. But when he rests at a well, a snake steal the plant from him. Does man 4500 years later once again gets to lay his hands on this plant?
Many medical experts and biologists believe that there is no insurmountable biological limit for human age. For aging is ultimately nothing more than the succession of defects in cell division and repair – caused by increasingly frequent genetic copying errors. If the damaged genes can be “healed” through genetic editing techniques such as CRISPR / Cas9, we could witness the decisive breakthrough in man’s fight against aging or even death. The internet giant Google has invested more than a third of its investment budget for biotechnology in various companies dedicated to the extension of the human life span.
How would that work in detail? The most popular theory of aging is that us growing older has to do with the ends of each DNA strand. Geneticists call these gene regions “telomeres”. Telomeres can be compared with the plastic sleeves at the end of shoelaces, which are supposed to protect those from unraveling. Biologists have observed that the telomeres shorten each time the cell divides. This continues until chromosome and thus cell division is no longer possible. As a result, the cell dies. However, if the cell has a specific enzyme, the telomeres are no longer shortens. For gerontologists (scientists who deal with the process of biological aging), CRISPR / Cas9 and the possibility to edit genes like texts in a Word document constitutes an amazing opportunity. These could enable the cells to produce this particular enzyme and thus continue to divide further indefinitely.
Also research in the field of gerontogenes (genes, which control the aging processes) has the goal of extending our life span. The geneticists have already identified some genes that control the aging process in lower organisms, such as the “age-1”, the “2daf-2”, the “bcat-1”, and the “clk-1” gene. Also the “FoxO3” gene broadly referred to as the Methuselian gene is a member of this group. By deliberately inserting, changing or blocking these genes, genetic researcher have already massively increased the lifespan of animals in the laboratory.
Parallel to research on the level of cells, biologists and doctors also work to breed entire substitute organs. As soon as existing organs loses its function in our body, respective replacement organs could be implanted. Thus, the cultivation of organs in animals has long been on the agenda of the researchers. Already over a hundred years ago, the zoologist Ross Harrison was able get nerve cells he had cultivated outside the body to divide. In 1972, Richard Knazek and his team were able to grow liver cells from mice on hollow fibers. And just ten years later, burn victims were transplanted skin which had previously been bred from body-borne cells. A last example: In 1999, biologists were for the first time able to breed nerve cells from embryonic stem cells of mice. When these were injected into other mice which were infected with a kind of multiple sclerosis, the animals recovered.
We can further simply print organs. This is already done on the basis of a small tissue sample and a 3D image of the corresponding organ. The organ is then built up layer-by-layer with body-specific “ink cells”, which are produced from stem cell cultures (in the terminology of 3D printing this technique is referred to as the “rapid prototyping method”). Already today, hip bone and foot bone transplants are printed in 3D printers with an accuracy unimaginable just a few years ago.
With this type of “tissue engineering” another powerful method can be made available to doctors. In the past, one way of therapy has been to take differentiated cells from a donor’s organism and multiply those in the laboratory with the goal replacing diseased tissue in another patient. The persistent problem with this methods however has so far been the rejections by the receiver’s body. Here the stem cells come into play. Their advantage: the tissues bred with them are not classified as foreign bodies by the patient’s immune system and are thus not rejected. Adult stem cells are multipotent. For example, an adult stem cell from the skin can generate all cell types, a simple liver cell or blood cell is not able to do that.
The combination of genetic engineering, stem cell research and nanotechnology (3D-printing) could increase our physical and mental well-being and, last but not least, our life expectancy into yet unimaginable dimensions. If we specifically edit and re-program those genes that control the aging of our cells, breed substitute organs in the laboratory (or in animals), or use stem cells to heal our ill cells and organs, the dream of a further prolongation of our lives or even reaching human immortality no longer seems so utopian. Even though human immortality is unlikely to be realized very soon, this project will certainly remain on the radar screen of our scientific efforts.
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