British scientists at the University of Nottingham say they have discovered how a species of flatworm are able to overcome ageing processs and achieve potential immortality. The scientists say their study may shed light on ageing process in humans.
The British scientists, in a study published in the Proceedings of the National Academy of Sciences journal on Monday, said that flatworms known as planarias have the ability to maintain a constant length of a part of their DNA known as telomeres which previous studies have shown is related to the life span of animals.
Dr. Aziz Aboobaker of the University of Nottingham's School of Biology, said: "We've been studying two types of planarian worms; those that reproduce sexually, like us, and those that reproduce asexually, simply dividing in two. Both appear to regenerate indefinitely by growing new muscles, skin, guts and even entire brains over and over again." The biologist explained further: "Usually when stem cells divide — to heal wounds, or during reproduction or for growth — they start to show signs of ageing. This means that the stem cells are no longer able to divide and so become less able to replace exhausted specialised cells in the tissues of our bodies. Our ageing skin is perhaps the most visible example of this effect. Planarian worms and their stem cells are somehow able to avoid the ageing process and to keep their cells dividing."
Biologists have long been interested in planarian worms because of their unusual ability to regenerate. According to Aboobaker who has been studying the planarian worms for years, when an individual worm is split lengthwise or crosswise it will regenerate into two seperate living worms.
Previous scientific research has shown that an important factor in life span of animals is telomere length. According to God Discussion:
"Telomeres consist of a chain of pairs of sequences which form what has been describe as a protective cap at the tip of the DNA molecule...The telomere sequences themselves do not code for any important enzymes or proteins in the organism's development. They are...blank leaders....which help to align the DNA molecule during replication process so that vital information in the inner sections is not copied out of synch."God Discussion explains why the length of the telomeres are important in determining an animal's life span:
"The telomere sequences...[provide] a protective buffer zone where replication or copying errors may accumulate without threat to the vital information contained in other essential coding sequences of the DNA strand. Unfortunately, however, repeated copying or replication of a DNA molecule leads to wear and tear [ and shortening of telomere length]...Over time, shortening...may become so pronounced that the entire DNA molecule is deprived of its vital buffer zone for absorbing replication errors. Copying errors begin accumulating rapidly in the DNA molecule at every round of replication...The replication inefficiencies resulting are associated with our aging or senescence...."
Scientists have shown that the activity of an enzyme called telomerase helps to maintain telomere length. Aboobaker and his colleagues identified the planarian version of the gene coding for the enzyme telomerase and turned down its activity. This resulted in reduced telomere length. Measurements found that the asexual worms dramatically increased the activity of the telomerase gene when they regenerate.
Dr Aboobaker, according to Physorg.com, concluded: "Asexual planarian worms demonstrate the potential to maintain telomere length during regeneration. Our data satisfy one of the predictions about what it would take for an animal to be potentially immortal and that it is possible for this scenario to evolve. The next goals for us are to understand the mechanisms in more detail and to understand more about how you evolve an immortal animal."
Reuters reports that Douglas Kell, chief executive of the Biotechnology and Biological Sciences Research Council which part-funded the study, said the findings about telomerase activity in planarians was "exciting" and "contributes significantly to our fundamental understanding of some of the processes involved in ageing."
According to Kell, the work "builds strong foundations for improving health and potentially longevity in other organisms, including humans."