Monday, 18 March 2013

Umbilical cord stem cells may be a better candidate for Hurler's syndrome

A recent study on children with Hurler's syndrome (HS), shows that stem cells derived from umbilical cords may be an effective and safe treatment the condition. At present, the only available treatment for Hurler's is hematopoietic stem cell transplantation, with matching donors being very rare.

Hurler's syndrome (HS), also known as mucopolysaccharidosis type I and gargoylism,  is a rare debilitating disorder resulting from the deficiency of alpha-L iduronidase. HS occurs in about 1 in every 100,000 babies born. Some common symptoms include:
  • Breathing problems
  • Broad forehead and heavy eyebrows 
  • Deformed bones and stiff joints
  • Hearing problems and frequent ear infections 
  • Heart problems
  • Large head size
  • Mental retardation
  • Short size 

Children with HS usually have a very poor prognosis, many times dieing before the age 10 .

Lately doctors have been experimenting with  hematopoietic stem cell transplants (HSCs) as the transplanted HSCs can start producing new blood cells with the capacity to produce the missing enzymes, thus halting the progression of the disease.

In this study the researchers,led by Jaap Jan Boelens, analyzed the final outcome of 258 children following a stem cell transplant. The age varied from  from 2 months to 18 years whereas the transplant operations had been carried out from 1995 and 2007.  Median age at transplant was 16.7 months and median follow-up was 57 months.The study examined two groups:
  • Children that had received cord blood stem cells (45%)
  • Children that had received bone marrow stem cells (55 %)

Image of a bone marrow transplant
A bone marrow transplant

Prior to the transplantation all patients had received  high-dose chemotherapy and 19 % of them underwent
enzyme replacement therapy with alpha-L iduronidase. The researchers examined the following factors:
  • Overall survival
  • Graft success ratio
  • Death incidences
  • Event-free survival 

The researchers reported promising results for both groups, with the overall survival period exceeding the 5 year mark. The majority of the patients (91%) showed clear signs of donor cell recovery two months after the transplantation and only 12 % of the participants presented with secondary graft failure (when the graft is initially accepted, but rejected later on)

The findings strongly indicate that stem cells from umbilical cord blood are probably a better candidate compared to bone marrow stem cells, as they had both a higher rate of engraftment (complete replacement of the original bone marrow by the donated cells) and better enzyme levels than those who had received bone marrow transplants from matched sibling donors or matched/unmatched unrelated donors.

"These results are important to the transplant community because they provide strong evidence that umbilical cord blood can be a useful and effective source of stem cells for a transplant when a well-matched source of cells is not available," "Further, our ongoing research, which is currently in the analysis phase, may help refine how we treat young patients with Hurler's syndrome by providing additional evidence on the link between cord blood enzyme levels and long-term outcomes. International networks are of utmost importance to improve the outcomes of treatments in rare diseases like HS." said Boelens.

The children were also examined for graft-versus-host disease (GVHD), which occurs when the transplanted cells regard the recipient's body as foreign and attack the its cells. At 100 days post op, around 25 % of the children experienced moderate to severe acute GVHD, and 16 % percent presented with chronic GVHD (lasting 5 years+ post op).

Hurler syndrome has an autosomal recessive pattern of inheritance.

Boelens, J., Aldenhoven, M., Purtill, D., Ruggeri, A., DeFor, T., Wynn, R., Wraith, E., Cavazzana-Calvo, M., Rovelli, A., Fischer, A., Tolar, J., Prasad, V., Escolar, M., Gluckman, E., O'Meara, A., Orchard, P., Veys, P., Eapen, M., Kurtzberg, J., & Rocha, V. (2013). Outcomes of transplantation using various hematopoietic cell sources in children with Hurler's syndrome after myeloablative conditioning Blood DOI: 10.1182/blood-2012-09-455238

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