“Latest Stem Cells News”

Bond strengthened: Eight-year-old Thamirabharuni, holding her brother who donated the stem cells, did not suffer from rejection or graft versus host disease as the tissue match was perfect - Photo: V. Ganesan

Eight-year-old Thamirabharuni and her one-year-old brother Pugazhendhi share a special kind of bond not commonly seen among siblings. Thanks to her brother, Thamirabharuni no longer suffers from thalassemia disease.

The stem cells transplanted in March helped her get rid of thalassemia. And hundred days after the procedure, one can safely say that her disease has been cured.
The stem cells that were transplanted came from two different sources — her brother’s cord blood, which was harvested during the time of his birth, and his bone marrow. Stem cells from the bone marrow had to be transplanted as there was insufficient number of stem cells in Pugazhendhi’s cord blood.

In the absence of cord blood stem cells, about 200 ml of bone marrow would have been required. It is difficult to get this quantity of bone marrow from a nine-month-old baby.
The cord blood was collected by and stored at Chennai based LifeCell International Pvt. Ltd., a private cord blood bank.

Risk of infection

So is it all over? “One has to be still careful. There is a risk of infection till the end of the first year [after transplantation],” said Dr. Revathy Raj, Consultant Paediatric Haemato Oncologist, Apollo Speciality Hospital, Chennai. Dr. Raj had done the transplantation for Thamirabharuni and two other cord blood transplantations for thalassemia before this.
The fact that patients are on immuno suppressing drugs for one year makes them vulnerable to infections. The risk of rejection of the transplanted stem cells, and the graft versus host disease (GVHD) reduce with time.

Thalassemia arises when red blood corpuscles (RBC) production is defective. A person suffers from the disease only when he inherits a defective gene from both parents. He becomes a carrier when he inherits a defective gene from only one parent. The diseased person has to undergo blood transfusion once every month for the rest of his life.

Gold standard

Though stem cells separated from bone marrow have been used for more than 30 years to treat thalassemia, and is a gold standard in treating the disease, cord blood stem cells are slowly becoming an attractive alternative.
Contrary to what is projected by some cord blood banks, doctors are very reluctant to use cord blood stem cells to treat thalassemia in the absence of a full tissue match.

Perfect match

“We need a 6/6 [perfect match] for thalassemia. Even a 5/6 match is not sufficient,” asserted Dr. Raj. And doctors refrain from using stem cells from unrelated donors, even if there is a perfect match.

Apart from infections, there are two major challenges from transplantation — graft versus host disease (GVHD) and rejection of the donated stem cells. “There is a 30 per cent chance of having graft versus host disease even when it is from a fully matched related (sibling) donor.” This risk increases to 50 per cent when it is from an unrelated donor, even if there is 6/6 tissue match.

Rejection rate becomes an issue even when there is a perfect tissue match. According to her, in the case of thalassemia, the rejection rate can be up to 20 per cent even with related donors, and up to 40 per cent in the case of unrelated donors.
But why should rejection and GVHD be an issue at all when there is a perfect 6/6 tissue match, and why should it be so high when stem cells are from unrelated donors?

Minor HLAs not tested

“There are several minor HLA antigens that are not tested. So if we use stem cells from people belonging to some other ethnic background, there are greater chances of [minor] HLA differences,” Dr. Raj stressed. “And this causes rejection and GVHD.”
In general, greater the tissue match and higher the stem cell count in cord blood, lesser are the chances of rejection and GVHD.

“So why undertake procedures that are risky when thalassemia can be treated through monthly transfusions,” she noted.
Private banking of cord blood for use by the family therefore becomes important when one of the siblings is suffering from a disease that can be cured using it.

Case for public banking

Despite the risk of rejection and GVHD, a less than perfect sample can be used to treat children suffering from life threatening diseases such as leukaemia and aplastic anaemia. This is where public cord blood banking gains significance.
There is a strong case for promoting public banks as depending solely on bone marrow samples will not be wise.

Even if a perfectly matched bone marrow donor is found, chances are that the person may no longer be interested in donating.
Collecting cord blood samples is easy, the number of samples that can be banked is limited only by resources, and samples can be made available at very short notice.

from  The Hindu

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