'Tissue Typing' Used on Embryos Ready for In Vitro Fertilization
Technique helps select embryos that could be donor for a child in need of stem cells
TUESDAY, May 4, 2004 (HealthDayNews) -- For the past 10 years or so, parents have been able to use a test called "pre-implantation genetic diagnosis" to check fertilized embryos ready for assisted reproduction for certain genetic disorders.
By testing the embryos before implantation in a woman, parents confronting the presence of an unwelcome mutation do not need to make the agonizing decision to abort.
At the same time, Human Leukocyte Antigen testing, also known as "tissue typing," has been used to see if an embryo could be a donor for a child in need of stem cell transplantation.
So far, Human Leukocyte Antigen testing (HLA) has only been done in tandem with pre-implantation genetic diagnosis (PGD), to make sure an embryo would be healthy while also providing a tissue-type match for a sibling-to-be. For instance, the two tests have been used to avoid giving birth to a child with Fanconi anemia, a bone marrow disorder, as well as to provide a tissue-compatible sibling to give bone marrow or cord blood transplantation to the ill sibling.
Now an article in the May 5 issue of the Journal of the American Medical Association reports the first instances of HLA being used alone.
The parents who underwent the procedure had an existing child who needed stem cell transplantation for a disorder that could not be traced to a genetic mutation.
"It's not really a technology breakthrough," said Dr. Owen Davis, president of the Society for Assisted Reproductive Technology and associate director of in vitro fertilization at Weill Cornell Medical College in New York City. It is a different use for an existing technology, he explained.
The study authors looked at HLA tissue-matching procedures conducted on nine couples at the Reproductive Genetics Institute in Chicago, which funded the study. The parents had children with various disorders, including acute lymphoid leukemia, acute myeloid leukemia, or Diamond-Blackfan anemia, when the bone marrow produces little or no red blood cells. All the children required stem cell transplantation.
None of the disorders in question had any detectable mutation that caused the problems, and all of the couples wanted to have another child anyway, according to the study authors.
"The parents always thought that they would like to have another child," said lead investigator Dr. Anver Kuliev, director of research of the Reproductive Genetics Institute. "One of the primary achievements is just to have a child."
The study authors first did in vitro fertilization, using sperm and eggs from each couple, then conducted genetic testing of the embryos. Embryos that matched were transferred to the mother's uterus.
In all, 199 embryos were tested and 45 (23 percent) were matches; of these, 28 were transferred resulting in five pregnancies and the birth of five babies. According to the study, the five children are now all about 1 year old and healthy.
One older sibling with Diamond-Blackfan anemia had a stem cell transplantation and no longer needs red blood cell transfusions, the study reported. The rest of the ill siblings are getting ready for a transplantation or are in remission.
In these situations, the stem cell procedure is not an invasive one requiring the destruction of an embryo to harvest the cells. "If you have an HLA-matched sibling who's a newborn, you can use the umbilical cord [for stem cells] at the time of delivery," Davis said.
The research will undoubtedly raise some concerns about heading down the proverbial "slippery slope" of genetic selection.
Kuliev, however, said this report will not open the door for other types of genetic selection, such as eye color. "It is putting people at a lot of inconvenience," he said. "It's not a natural way of having children. You have to go through IVF. The authors, however, pointed out that."
The couples who come in for HLA testing, Kuliev added, tend to have exhausted all over options.
The procedure is also expensive -- about $3,000 for the HLA typing and another $10,000 for in vitro fertilization, the study stated.
"The whole ethical question is, is there an issue with doing PGD where you're basically selecting a characteristic that isn't of benefit to the child being born," Davis added. "In the past, PGD was of benefit to the child being born. This child is going to be loved and selected for a trait that's not going to be harmful. It doesn't sound like that crazy an idea."
The American Society for Reproductive Medicine has more on pre-implantation genetic diagnosis.