Stem cell therapy may have helped patients with a form of multiple sclerosis, according to a preliminary study.

Patients with relapsing-remitting multiple sclerosis showed signs of improvement after being treated with their own, or autologous "nonmyeloablative hematopoietic stem cells," a class of blood-forming stem cells, the study found. It was published Tuesday in the Journal of the American Medical Association.

Half, or 41 patients, tested two years after treatment experienced significant improvement on the Expanded Disability Status Scale, a measure of disability. And of patients tested at 4 years, 23, or 64 percent, showed significant improvement. Four-year relapse-free survival was 80 percent and progression-free survival was 87 percent.

"To our knowledge, this is the first report of significant and sustained improvement in the EDSS score following any treatment for MS," stated the study. It was led by Dr. Richard K. Burt of Northwestern University in Chicago.

However, only limited conclusions can be drawn from the uncontrolled study, according to scientists who examined the results. While the therapy was associated with improvement, the stem cell transplant may not have been key. A conditioning regimen that partially depleted the stem cells before transplantation may have been responsible, said Dr. Stephen L. Hauser in a JAMA article accompanying the study.

"According to Carl Sagan, 'extraordinary claims require extraordinary evidence,' a standard that is not always met in this report, and not claimed by the authors. Even though the authors appropriately acknowledge many of the limitations associated with their case series, their statement that 'to our knowledge, this is the first report of significant and sustained improvement in the EDSS score following any treatment for MS' could be challenged," Hauser wrote.

Jeanne Loring, a stem cell researcher who studies multiple sclerosis and other neurodegenerative diseases, agreed that the results are far from conclusive.

"Multiple sclerosis is an autoimmune disease, meaning that the patients' own immune cells attack their own nervous systems," Loring said by email after examining the study. "The authors of the JAMA article treated MS patients with their own blood stem cells in the hope that these cells would replace some of the self-destructive immune cells."

However, the uneven course of MS makes it hard to draw conclusions, wrote Loring, who heads the Center for Regenerative Medicine at The Scripps Research Institute in La Jolla.

"Most patients with MS have attacks, followed by recovery, followed by another attack. In a few of these patients, the blood stem cell treatment seemed to extend their time between attacks. It's important to understand that other treatments, including drugs, have shown similar modest improvements, so it's too soon to celebrate a stem cell therapy."

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MS patients given stem cells improve