A man and woman who are both carriers of the sickle cell anemia mutation can have a healthy child by fertilizing eggs in a lab, then deciding which of multiple embryos that develop from the eggs will become the baby, a case study indicates.
It also showed that umbilical cord blood stem cells from a healthy baby born this way could be used to treat a brother or sister with sickle cell anemia.
The study, published in the journal JBRA Assisted Reproduction, is titled “The first South American case of pre-implantation genetic diagnosis to select compatible embryo for cord blood transplantation as treatment for sickle cell anemia.”
Sickle cell anemia is an autosomal recessive disease, meaning that a child has to inherit two mutated copies of the hemoglobin gene to develop it — one from each parent. If a child inherits one mutated copy and one normal copy, they will have sickle cell trait, a condition that generally shows no symptoms.
If both parents have sickle cell trait, there is a 25 percent chance the child will have sickle cell anemia and a 50 percent chance it will have sickle cell trait.
Couples with sickle cell trait can have a child without sickle cell anemia by fertilizing the woman’s eggs in a lab, then deciding which one to implant in her womb. The terms for these procedures are in vitro fertilizatin and pre-implantation genetics diagnosis.
South American doctors did a case study of a couple who had a normal child using these techniques.
The parents, both with sickle cell trait, had already had a daughter with sickle cell anemia. Before having their next child, they opted for genetic testing.
Then they underwent six cycles of in vitro fertilization that resulted in 53 embryos. Each was analyzed for a hemoglobin gene mutation.
Fifteen of the 53 embryos had a normal hemoglobin gene, 12 had two copies of the sickle cell anemia mutation, 20 had one copy of the sickle cell anemia mutation, and the results for 6 embryos were inconclusive.
One treatment for sickle cell anemia is a hematopoietic stem cell transplant — a type that gives rise to blood cells. But for a patient to receive the bone marrow transplant, a compatible donor is necessary.
On the other hand, umbilical cord blood tends to be rich in hematopoietic stem cells. So cord blood stem cells from a healthy child can be used to restore the hematopoietic bone marrow of a compatible sickle cell anemia patient.
In the case study, doctors knew that if the new baby was compatible with the sister who had sickle cell anemia, then the baby’s umbilical cord blood stem cells could be used to treat the sister.
So the researchers analyzed the 53 embryos for compatibility with the sister. Only 9 with either a normal hemoglobin gene, or a gene with one copy of the mutation, were compatible.
Doctors implanted one of the 9 into the mother, who delivered a healthy boy. The baby’s umbilical cord blood stem cells were then collected and stored.
Physicians used the umbilical cord blood to successfully treat the sister.
“Embryo selection using PGD [pre-implantation genetic diagnosis] technologies represent the most effective treatment plan for parents who want to have a healthy child, and it could cure another child already affected by inherited hemoglobinopathy [hemoglobin disease],” the researchers concluded.