Doctors freeze eggs of girls, 5
Doctors have managed to extract eggs from 5 -year-old girls and freeze them for use when they are old enough to have children.
The scientific advance, which was thought to be impossible, will enable girls suffering childhood cancers such as leukemia to become parents later in life. Thousands are left infertile each year after undergoing chemotherapy.
It also opens the possibility of storing girls’ eggs to protect them against any form of infertility in later life.
Previously it was believed the eggs of prepubescent girls were too immature to be extracted. It was thought they became viable only at puberty by reacting to hormonal changes in the body.
Israeli doctors have, however, managed to extract the eggs and then culture them in test-tubes to make them viable. The resulting eggs are no different to those of a 20-year-old girl, say the doctors.
Breakthrough as eggs from young cancer patients frozen
Eggs from girls as young as five have been successfully removed, matured and stored in deep freeze by fertility scientists, it was revealed yesterday.
The breakthrough offers hope to children with cancer whose fertility is damaged by chemotherapy treatment. Scientists believe the frozen eggs stand a good chance of producing a pregnancy after being artificially fertilised.
It is hoped the technique might offer an effective way to preserve the eggs and fertility of young girls undergoing aggressive treatments, who typically end up sterile or experience the menopause a decade or more early.
The technique involved surgically removing ovarian tissue containing the egg-producing follicles. A laboratory procedure was then used to "suck out" the eggs, which were matured with stimulating hormones and frozen in liquid nitrogen.
A total of 18 girls and young women took part in the trial, including a five, eight and 10-year-old as well as older patients up to the age of 20.
In the case of the five-year-old, who is still receiving therapy for kidney cancer, a total of seven eggs were obtained - one of which was successfully matured.
Both the eight and 10-year-old were suffering from bone cancer. Two out of eight extracted eggs were matured for the eight-year-old and five out of 17 for the 10-year-old.
Eggs were obtained from all but one patient. In total, 167 were collected and 41 matured and frozen.
Dr Ariel Revel led the research team from Hadassah University Hospital in Jerusalem and presented the results at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Lyon, France.
He said: "We were surprised to obtain oocytes eggs from the follicles of such young girls. We didn't expect to get eggs at all, or that we could mature them.
"No eggs have yet been thawed, so we do not know whether pregnancies will result, but we are encouraged by our results so far - particularly the young ages of the patients from which we were able to collect eggs.
"We believe no younger patients have ever undergone egg collection, in-vitro laboratory maturation and egg freezing."
An alternative approach would be to freeze lumps of ovarian tissue, complete with follicles and eggs, for future transplantation, said Dr Revel.
However, this strategy had so far proved disappointing in adults since the tissue was often damaged by freezing. To date, only two pregnancies were known to have resulted using this method. Dr Revel described the ovary as a "one-time endowment of eggs".
Before birth, the developing female foetus has between five and six million eggs which gradually die off without being replaced, he added. By birth, 80% were already lost. In the course of 40 years of reproductive life only 500 eggs might be available for fertilisation.
Scientists are working on ovary-protecting drugs to be given at the same time as chemotherapy, but mouse studies have shown they suffer from the fatal flaw of helping cancer survive.
At present, only egg preservation had a chance of preventing infertility in young cancer patients, said Dr Revel.
Gillian Lockwood, head of Midlands Fertility Services, the only British clinic to have achieved live births from frozen eggs, said: "If it works it's good news because the big block has always been that we thought you had to wait until they reached puberty before getting the eggs.
"But this raises significant ethical issues. The parents will be making the decision in these cases and it may be that they are keen to have grandchildren, and I don't know if a very young girl will fully appreciate all of the arguments."
作者:admin@医学,生命科学 2011-03-05 17:23