Tests on Molly Nash, the 6 year old in the United States who received an umbilical cord blood transplant from her newborn brother, Adam, have shown that she does now carry bone marrow cells.
The results of the bone marrow aspiration test came 21 days after specialists at the University of Minnesota carried out the transplant to treat Molly's Fanconi's anaemia.
"Molly's blood counts have steadily increased over the past week, indicating bone marrow recovery," said Dr John Wagner. "The test over the last few days shows that there is donor cell engraftment and that the cellularity of the bone marrow is phenomenal. What we know for sure is that for the first time in years, Molly is making neutrophils . . . and platelets."
It is anticipated that Molly will be discharged within a week. Dr Wagner will follow her closely over the next two months, and if all goes well, she will be back home in Colorado for Christmas.
"Obviously, we will continue to evaluate the durability of the engraftment as well as Molly's progress toward freedom from the underlying disease," said Dr Wagner.
The transplant triggered controversy because it is the first time preimplantation genetic diagnosis has been used for the express purpose of ensuring a perfect stem cell donor (14 October,
The embryo that became Adam was selected from other available embryos (that had developed through in vitro fertilisation) because not only was it was free of disease but it was also a tissue match with Molly.
"The medical community needs to elevate a public dialogue around this issue," says Dr Wagner, clinical director at the stem cell centre at the university.
He continued: "Clearly there are a number of ethical issues, and one of the goals in telling this story has been to make people aware that embryo research can be very positive and that our motivation is pure. We are doing this to improve the treatment outcome for children like Molly.
"When we started out we said we would use this technology principally for the purpose of offering families the opportunity of having a child that was disease negative. Then we said that since we were already there, we might as well do the test for tissue matching as well.
"We tried to be thoughtful about it. My biggest fear is that people will think we went ahead without thinking it through. Even if people disagree with what we are doing, I hope they will appreciate that we have been very thoughtful about it."
The technique offers hope that people affected by a number of other genetic disorders, including sickle cell anaemia, leukaemia, thalassaemia, Hurler's syndrome, and severe combined immune efficiency, could be similarly treated.