Flat worms may hold key to immortality

By Dr. Ananya Mandal, MDMar 1 2012

British researchers have found that that the worms, which live in ponds and lakes, could live forever after examining their ability to repeatedly regenerate.

Experts from Nottingham University created a colony of more than 20,000 flatworms from one original by chopping it into pieces and observing each section grow into a new complete worm. They believe that it could help scientists develop new methods to allow humans to stay younger for longer.

“We’ve been studying two types of planarian worms; those that reproduce sexually, like us, and those that reproduce asexually, simply dividing in two,” said Dr. Aziz Aboobaker from the University’s School of Biology who led the study. “Both appear to regenerate indefinitely by growing new muscles, skin, guts and even entire brains over and over again. “Usually when stem cells divide - to heal wounds, or during reproduction or for growth - they start to show signs of aging. This means that the stem cells are no longer able to divide and so become less able to replace exhausted specialized cells in the tissues of our bodies. Our aging skin is perhaps the most visible example of this effect. Planarian worms and their stem cells are somehow able to avoid the aging process and to keep their cells dividing.”

“Our data satisfy one of the predictions about what it would take for an animal to be potentially immortal,” Aziz Aboobaker. “The next goals for us are to understand the mechanisms in more detail and to understand more about how you evolve an immortal animal.”

Flatworms, known as planarian worms, have long fascinated scientists because they have an extraordinary ability to regenerate. A planarian worm split lengthways or crossways will regenerate into two separate living worms. The researchers found that flatworms can continuously maintain the length of a crucial part of their DNA, known as telomeres, during regeneration.

Scientists know that one of the key factors associated with ageing cells is telomere length. Telomeres are sections of DNA that cap the ends of chromosomes, protecting them from damage and the loss of cell functions linked to ageing. Shorter telomeres are thought to be an indicator of faster ageing. An enzyme called telomerase regenerates the telomores, however in most sexually reproductive organisms it is only active during the organism’s development. Once it reaches maturity, the enzyme stops functioning, and the telomeres become shorter and shorter until cell replication is made impossible, otherwise the DNA would become too severely damaged.

An immortal animal is able to maintain telomere length indefinitely so that they can continue to replicate, and Dr. Aboobaker and colleagues were able to demonstrate that the flatworms actively maintain the ends of their chromosomes in adult stem cells, leading to theoretical immortality.