Six cloned calves have cells that appear younger than their biological age, a US biotech firm reported in the current issue of Science. A team working at Advanced Cell Technologies (ACT) found that cells taken from the cows and grown in the laboratory have a lifespan increased by around 50 per cent.
The results surprised the researchers, because the cows were cloned using cultured calf embryo cells that were nearing the end of their lifespan. 'The old cells were not merely returned to a youthful state. They were actually given a longer lifespan than those from normal animals' said Dr Robert Lanza, who carried out the research. The scientists also found that a gene (EPC-1) whose activity normally declines with age was five times more active than normal in the cloned cells.
A cell can usually only multiply a certain number of times before it dies. Each time a cell divides, the ends of its chromosomes, called telomeres, become shorter. The telomeres of the cells from the cloned calves are longer than those of normal cows of the same age. When grown in the laboratory, cells from a normal newborn calf divide up to 60 times, but the cloned cells can divide up to 90 times.
The team thinks its results may be down to the type of cell used to create the clones - a skin cell, or fibroblast. When Dolly the cloned sheep was born, her cells appeared to be the same age as the mammary cell of the six year-old ewe from which she was cloned. Another factor may be the stage in the life cycle of the donor cells. The cells used to create the calves were still growing and multiplying, whereas those used to clone Dolly were in a resting stage.
Although a long cell-life may not mean the animals live longer than normal cows, the company says its work has important implications for human therapeutic cloning - the use of cloned early embryo cells to replace damaged or diseased body tissues. The ability to create a supply of youthful cloned cells may get around the potential problem of growing enough cells in the laboratory before they become too old to use for treating patients. 'It's the first day in a new era in treating age-related disease' claimed Dr Michael West, president of ACT.