What’s New in Stem Cells? Expert Discusses Hematopoietic Status and Newer Mesenchymal Approaches

Stem cells are attractive for MS treatment because they are capable of undergoing self-renewal and differentiating into multiple different cell families, potentially allowing for correction of aberrant processes in the immune system, said Mark Freedman, MSc, MD, a recognized expert in stem cell therapeutics.Stem cell treatments (SCT) have been described as a promising and powerful therapeutic strategy for severe multiple sclerosis (MS), a highly experimental approach, or a dubious sham treatment preying on unwary patients. So, which is correct? This depends upon which type of SCT one is discussing. Mark S. Freedman, MSc, MD, Professor of Neurology at the University of Ottawa in Ontario, Canada, provided listeners with a status update on SCT at the Consortium of Multiple Sclerosis Centers (CMSC) Virtual Annual Meeting on Thursday, May 28.

The first description, promising and powerful, applies to autologous hematopoietic SCT (aHSCT), the most advanced procedures to date in terms of research for MS. The rationale for this approach, also called bone marrow transplant, is: complete removal of the diseased immune system to halt ongoing MS immune-mediated damage to the central nervous system; purified bone marrow stem cells may be capable of fully restoring a functional immune system; the reconstituted immune system will not likely result in re-development of the previous aberrant immune response; and transplanted stem cells may also be capable of inducing repair.

aHSCT must be done in combination with chemotherapy in order to fully ablate the existing immune system. In fact, this is the efficacious part of the treatment, while the infused stem cells are what keeps the patient alive to allow the immune system to reboot. The efficacy and safety equation for different aHSCT techniques depends in part upon what type of chemoablative conditioning regimen is used prior to infusing the stem cells. A more extreme myeloablative regimen is the most effective but also the most risky. This approach involves complete ablation of all elements of the hematopoietic system using total body radiation and chemotherapy. The lymphoablative approach, meanwhile, is a less-toxic, neutrophil-sparing regimen involving removal of cells outside of the bone marrow. This involves chemotherapy prior to infusion of the stem cells, but sacrifices some efficacy.

Another variable is whether the procedure involves purifying for CD34+ cells. In this technique, done only in specialized facilities, CD34-reactive cells are separated from non-reactive cells via a magnetic process. This selects out stem cells that are better for grafting and believed to have a better chance of eliminating immune cells that may lead to disease recurrence.

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