INJECTING tiny loops of DNA into cells could give them a new lease of life. The finding could spawn new techniques for growing organs for transplant and novel treatments for age-related diseases.
The DNA loops were designed to lengthen stretches of DNA called telomeres, which are found at the ends of every chromosome. Telomeres normally become shorter each time a cell divides. When they become too short, the cell stops dividing. This has led researchers to implicate telomeres in ageing and some ageing-related diseases.
Eric Kool and his team of chemists at Stanford University in California built each DNA loop from a string of 54 nucleotide bases. The loops were constructed so that when they were added to a solution of three types of base, adenine (A), guanine (G) and thymine (T), they would act as a template producing strands of DNA that repeated the sequence TTAGGG. This is the repeating sequence of bases that makes up a telomere.
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In tests, Kool found that the DNA loops not only produced long strands of DNA identical to telomeres, the strands also attached themselves to the ends of chromosomes in the solution.
Kool says his team is now trying to insert the DNA loops into living cells to see if they extend their telomeres. If they succeed, he says, the method could be useful for extending the lives of cells used in lab experiments. Eventually, the technique could give researchers a new way to grow organs for transplantation, because tissue taken from the body could be encouraged to grow for much longer than normal.
Extending telomeres inside cells has its problems, though. One characteristic of cancer cells is that their telomeres don鈥檛 shorten as they divide, so the cells can divide indefinitely. Any technique to grow telomeres in humans would need to be designed to prevent them becoming cancerous.
David Corey, a biochemist at the University of Texas Southwestern Medical Center in Dallas, says Kool鈥檚 method could be more practical than other attempts to use gene therapy to lengthen telomeres for medical treatments. 鈥淧erhaps it would be a more short-term approach to therapeutic applications,鈥� he says. 鈥淭hat鈥檚 why this is exciting.鈥�