A thousand years ago, people lived on average 30 years and even in the last century, people in developed countries were lucky to see their 50s. Today, our life expectancy has grown to an astonishing 80 years.
From the beginning of time, humans have battled their immortality and tried to find ways to stop aging, either by delaying death or by avoiding the other side entirely. Many people spend thousands and thousands on preparations, creams, pills, and whatnot to seem younger, to remain vital, to live longer and to be healthy. But how would you like to be as young as you are now and to postpone aging for, say, the next 200 years? Think of the possibilities!
As impossible as it may sound, scientists have discovered the source of eternal youth that lies in the cells of a small pond creature. This extraordinary source of rejuvenation, discovered by Nobel Prize-winning Australian scientist Elizabeth Blackburn, is also available in the human body. The greatest fears of our times are old age, stress and cancer, and it would seem that these three have something in common - it's an anomalous and mysterious substance that can bring both doom and immortality.
With a better understanding of what keeps us healthy, we’ve managed to raise our life expectancy significantly. But in addition to chronological aging we also experience biological aging. Everyone's biological clock has a different rhythm, reflecting what's going on in our living cells. Professor Leonard Hayflick has studied this type of aging: “For example, if you take inanimate objects such as automobiles of a particular make, model, and year of manufacture, you see that they do not age evenly. Some need repairs early in the beginning, while others last extraordinarily long without intervention. This is due to differences in use, materials and craftsmanship. The same applies to biological indicators, especially in case of humans.”
50 years ago, aging specialist Hayflick examined the human body and discovered that the life cycle of our cells has certain limitations. Our bodies have around 100 trillion cells and most of them are divided by fission. Some are divided in days, others need years. Until 1960, scientists believed that if we could manage to keep our cells healthy, they could live forever or become immortal. But Leonard
Hayflick proved that certain cells only divide 50 times during their life cycle, becoming exhausted and dying after that. When Hayflick tried refrigerating cells, he discovered something amazing – cells have memory. If you take them out of the freezer, they will continue from where their life cycle was halted before refrigeration and divide their given 50 times. This lead Hayflick to the conclusion that cells must have a mechanism that counts divisions. There must be a signal that alerts the cell of final division or the end. But what gives this signal?
Human cells have a nucleus, which contains 23 pairs of chromosomes, that is, long strands of DNA which contain a person’s genetic information. At the ends of chromosomes are DNA elements called telomeres. They have the important task of protecting the ends of DNA. Without these knot-like formations, our DNA would just fall apart. When a cell is divided, it cannot replicate DNA completely. Telomeres become shorter with every division. If a telomere becomes too short, the cell can die. In the words of Elizabeth Blackburn, we indeed used to know everything about DNA, but we just didn’t know anything about the ends of chromosomes.
Blackburn began studying telomeres in 1975. In the 80s, she lived in San Francisco, where she and geneticist Jack Szostak discovered that many species experience lengthening of telomeres. In 1984, postgraduate Carol Greider joined the hunt that had caught the realm of genetics. They knew that in order to balance shortening of telomeres after every cell division, something would have to lengthen telomeres, but their first breakthrough took about 9 months. A great breakthrough was achieved in Christmas-time 1984. A stunning x-ray clearly showed a six strand ladder. They had found an enzyme catalyst that kept telomeres long, while still allowing unlimited cell division. They called it telomerase. It has crucial significance although it is largely unexplained. They had discovered the secret of eternal life, but they weren’t sure whether it would work in the human body.
The discovered enzyme telomerase became very popular. In 1990, cellular biologist Calvin Harley and Carol Greider who linked telomere length to aging, tried to establish how the enzyme worked in people. They discovered that the older a person is, the shorter their telomeres are. Revolutionary knowledge once again – aging can be expressed in DNA. It turned out that if telomeres have been exhausted to a critical limit, genetic instability develops. It’s more or less a genetic bomb. Cells won’t explode but they will die at an explosive rate. As telomeres shrink and cells die, we age. As we lose our cells, we lose our lives.
Cellular biologist Michael West started to study whether aging of cells (and thereby people) could be stopped. 15-20 years ago, when he began his research, people knew that cellular aging is related to our own aging – entirely logical. West believes that our aging is related to cellular aging to the extent of about 80%. But now we have the key to turn this clock back. Is it now possible to talk about immortality? For cell cultures in labs – yes. But when in the human body, some cells will definitely live longer, but there's no guarantee of immortality. Therefore these immortal cells are used to slow down aging processes.
It will be interesting to see how telomeres are used in the future and what part they’ll play in fighting age-related maladies. It would be amazing to postpone aging to live long and as vitally as possible. Elizabeth Blackburn gives us hope, saying that research on telomeres is still on-going: “We haven’t reached the end of our journey.”
(Immortal, USA 2010)