WHO WANTS TO LIVE FOREVER?
From the minute we are born we start on the road to death; a harsh fact, but that is the reality at present and likely to be so for a very long time to come. For centuries humanity has been searching for ways to extend our life expectancy. History, myth and legend is full of stories of the search for eternal youth. In the 1500′s Juan Ponce De Leon searched for a Fountain of Youth in the Southern Americas. Before that, around the 1100′s, a Fountain of Youth was reported to exist in the legendary realm of Prester John. Roman, Greek, Norse mythology, all have stories of gods and goddesses with the ability to grant eternal youth or sources of such. Despite the legends and myths humanity has so far failed to unlock the whole secret of staying young. What has been achieved is a longer life expectancy. We have achieved this by improving our knowledge of disease and illness, by eliminating some and finding cures for others. We have a far greater understanding of our bodies, our bodily needs and how to protect ourselves from disease.
Humanity has managed to extend life expectancy greatly. 2000 years ago you could expect to live between 18 and 21 years, by the 1900′s we had increased that to 30 years and by the 1980′s we had reached a world average life expectancy of 62 years at which point it levels out. However, this figure varies hugely across the globe. Economic and political factors have great bearing on life expectancy; the lowest life expectancies are in the African countries of Malawi and Mozambique where you can expect to live around 36 years, whilst the highest are in Japan, Andorra and San Marino, which have life expectancies of around 80 to 83 years. Not satisfied with living longer we also want to stay young, fit and healthy. Some of the most profitable companies are those that produce and market beauty and health pills and potions.
WHY WE AGE
Science doesn’t actually know exactly why we age, though it has made progress in beginning to understand the process. What science does know is, in fact how little it knows. Scientist in a variety of fields have found that a large number of gene sequences play a role in the process of aging. They have identified the SIR2 gene and its relationship to metabolism as possibly one of the major contributors to aging. What this does is turn on some genes within a cell and turn off others. Some of the research has made similar correlations between a cells use of calories and the life span of flies, doubling not only their life span but also their ‘middle age’. Other research has shown that aging happens because cells cease to have the ability to continue to divide. This is known as cellular senescence. Over time cells divide, replicate and repair themselves. However there is a finite number of times that cells can perform this task, further more this number is fixed, slowing down or freezing a cell does not affect the number of times it can divide. What seems to cause this cellular senescence is the breakdown of the telomeres. Telomeres are pieces of DNA that act as a kind of protective end to a chromosome. What seems to happen is that when a cell divides the telomere curls back around to continue to protect the end. However each time the cell divides the telomere gets shorter, eventually it becomes too short to curl back far enough and thus can no longer properly protect the chromosome.
An interesting anomaly seems to occur in cancer cells which appear to be able to produce a enzyme called telomerase that a cell can use to rebuild its telomeres and continue dividing beyond its assumed allotted amount.
HOW CAN WE LIVE LONGER?
We have already touched one way that the human race has found to extend our life span, through the development of better health and social conditions, but what does the future hold? What areas are being researched and developed and which are most likely to produce the next leap in life expectancy?
TELOMERASE, GENETIC ENGINEERING AND GENE THERAPY
The University of Texas Southwestern Medical Center has been researching the use of telomerase in other cells in the hope of extending the ability to divide of other, more useful cells. At the moment they see this research as being useful in helping to keep people healthier for longer rather than extending life expectancy, but eventually it could be developed in that direction. If we can stay healthier for longer then the likelihood is that we can, in fact live longer.
There are three main types of cloning technique, each used for different purposes. They are:
•Recombinant DNA Technology or DNA Cloning:
Used to clone a specific gene, the technique has been in use since the 1970′s and is commonly used in molecular biology labs.
• Reproductive Cloning:
Genetic material is transferred from the nucleus of an adult donor cell to a enucleated egg, the egg is then stimulated to encourage division, once a suitable stage has been achieved the egg is transferred to a uterus and brought to term. This technique was used to produce Dolly the sheep and has since been used to produce many other animals with varying degrees of success.
The most recent, a horse, was reported in April 2005.
• Therapeutic Cloning or embryo cloning:
The basic procedure is the same as that for Reproductive Cloning however the use is different. The embryo is never returned to the uterus and it is not intended to be brought to term, rather it is used as a source for embryonic stem cells which can then be used to produce any kind of organ or tissue which will have a DNA match to the cell donor.
An interesting result of the Dolly experiment was that scientists found that cells where not as specialist as had been previously believed and could be reprogrammed to produce completely different organisms. For example; a cell taken from an udder could produce a liver or heart or, as in the case of Dolly, a whole sheep. It had previously been thought that once a cell had taken on its specialism the redundant genes that had become inactive, could not be reactivated. Dolly showed that this was not so and meant that the cloning of organs for transplant suddenly became much easier. If we can genetically engineer or clone a new organ to replace the one that is faulty, we could ultimately live a very much extended life. Medicine can, already, replace some defective organs by transplanting a donated organ but the donor organ must be a tissue match. If the donor tissue and the recipient’s tissue don’t match then the organ is rejected and therefore useless.
If an organ can be grown using extracted DNA then the tissue will of course match. The idea is this; DNA is extracted from the patient and inserted into a enucleated egg. After the egg containing the patient’s DNA starts to divide, embryonic stem cells that can be transformed into any type of tissue would be harvested. The stem cells would be used to generate an organ or tissue that is a genetic match to the recipient. In 1997 scientists in the USA caused huge controversy when they revealed that they had grown a ‘human ear’ on the back of a mouse and hoped to be able to develop techniques to grow more complex tissues such as livers. In 2000 the scientists who brought us Dolly also brought us cloned pigs. This was useful because pig organs are the mostly likely ones to be able to be used for xenotransplantation; genetically modifying animal organs, tissue and cells for use in human transplantation. Since then both the Dolly team and a team from the University of Missouri in Columbia have progressed the work and produced a series of litters of piglets that have been progressively modified to make them yet more suitable as organ donors.
Whilst not strictly lengthening our life span, whole body cloning is certainly the ultimate in immortality. If we can extract our DNA and transplant or store it we really do have the opportunity to ‘live forever’. There is a separate section on this site about human cloning.
Strategies for Engineered Negligible Senescence
Aubrey de Grey, a scientist working in the Department of Genetics at Cambridge University, believes he has found the cure for aging. He has mapped out a detailed plan that is a strategy for scientists within the various fields of genetic engineering. He believes that, rather than trying to slow down aging by a process of damage limitation, scienctist should be seeking to ‘repair or obviate the accumulating damage and thereby indefinitely postpone the age at which it reaches pathogenic levels.