Embryonic stem cells repair sheep hearts

French scientists have used mouse embryonic stem cells (ES cells) to repair damaged heart muscle in sheep. The team, based at the National Center for Scientific Research in Montpellier, successfully transplanted ES cells into nine animals. One month after the procedure, the treated sheep had healthier heart tissue than sheep that had not received the cells, say the scientists, who published their findings in the Lancet. The study suggests that ES cell transplants could one day be used to treat damaged heart muscle in humans.

Many researchers hope that stem cells can be used to develop new treatments for the damage caused by heart attacks. Trials are currently underway to test the ability of adult bone marrow stem cells to regenerate heart tissue. However, it is not known how useful this approach will prove to be, since there is controversy over whether these stem cells can really grow into new heart cells.

Previous research has shown that ES cells can repair heart damage in rodents. To see if ES cells are capable of repairing heart damage in larger mammals, the French team first induced heart attacks in 18 sheep. Two weeks later, they injected about 30 million mouse ES cells into the damaged hearts of nine of the animals. One month after the injections, they found that the hearts of the treated sheep could pump blood 15 per cent more efficiently than the hearts of the untreated sheep.

The team found no evidence that the transplanted mouse cells were being rejected by the sheeps' immune systems - a promising and encouraging sign, according to UK developmental biologist Robin Lovell-Badge. However, he cautioned that the treated animals were only followed up for one month, which might not have been long enough to detect signs of rejection. Team member Michel Puceat says that the group are now testing the ability of human ES cells to repair heart damage in baboons.

Team leader Philippe Menasche says the study shows the potential value of ES cells for repairing damaged hearts. 'These stem cells were able to become heart cells and improve heart function', he said, adding 'it is an additional step, not toward a clinical application, but in favour of the concept that it is probably worthwhile to consider embryonic stem cells for clinical repair'.