The world's first live births from a transplanted uterus have been achieved, say Swedish researchers. The procedure, conducted in mice, would be easier to repeat in humans, they predict.
A mouse uterus is V-shaped. The team led by Mats Brännström at Göteborg University, Sweden, grafted one arm of the V from a donor mouse into another's abdomen, alongside its existing uterus. In a woman, the procedure would involve removing the existing organ and replacing the whole donor uterus.
The implanted partial uterus was connected to the mouse's blood supply. Several days later, tests demonstrated that blood flow in both organs was similar, the team says. Three fertilised embryos were then transplanted into each of the uteruses.
Their report, published in the Journal of Endocrinology, reveals that one of the three in the donor organ, and all three in the mouse's native uterus, developed into healthy fetuses. The experiment was terminated after 13 days, two-thirds of the way through the pregnancies, due to ethical restrictions placed on the research.
"This experiment demonstrates that uteruses can be transplanted and pregnancy is possible. Foetal weight and size is similar for those in native and implanted uteruses," Brännström says. And, he adds: "We have since carried out similar experiments that are unpublished using mice which have gone full-term and led to live births."
John Mills, chairman of the British Fertility Society, says the research gives hope to surgeons who want to carry out similar operations in humans, but he cautions that more research is needed.
Clotting blood
"We obviously have to consider the problem of rejection and, in particular, the problem of rejection and pregnancy," Mills says.
So far attempts at uterine transplants in humans have been unsuccessful. The most promising, performed in April 2000 in Saudi Arabia, lasted just 99 days before clotting in the blood vessels stopped the new organ's blood supply. But Brännström believes the first human pregnancy in a transplanted uterus could occur within two years.
"The uterus is basically a big tissue of muscle so it is not complicated to transplant. The reason our experiment worked is because we connected the vascular system of the implanted uterus directly to the existing blood supplies, rather than using stents which have caused other transplants to fail, Brännström told New Scientist.
Outside the body
"Mice have an extremely complicated vascular system with the diameter of the vessels measuring less than one millimetre - humans would be much easier because of their larger size," he says.
The group avoided the problem of rejection by using transgenic mice. But Brännström says that successful pregnancies in women with other transplanted organs have shown immunosuppressant drugs can be used during pregnancy.
"We have begun in-vitro research using human tissue to learn more about rejection and other factors, such as how long a donated uterus can survive outside the body before implantation," he says.
Journal reference: Journal of Endocrinology (vol 174, p157)