Stem cells harvested from adult blood or bone marrow may provide benefits when treating select patients with certain autoimmune diseases and cardiovascular disorders, according to a clinical review in the February 27, 008 issue of JAMA.
There are two basic types of stem cells: embryonic stem cells and adult stem cells. Human embryonic stem cells are collected from a four to five day old blastocyst, an early stage in the development of an embryo. These cells theoretically have the potential to become any type of cell in the body. Adult stem cells, in contrast, are located in several types of tissue in different parts of the body, including bone marrow, brain, mammary glands, testicles, and liver. They usually function as a reserve to help replace damaged and aging cells, and are generally limited in the cell types into which they can differentiate.
The field of stem cell therapy is developing quickly and has great potential. However, according to the authors, “but clinical application has lagged due to ethical concerns or difficulties in harvesting or safely and efficiently expanding sufficient quantities. In contrast, clinical indications for blood-derived (from peripheral or umbilical cord blood) and bone marrow-derived stem cells, which can be easily and safely harvested, are rapidly increasing.”
A review of previous studies related to clinical indications and outcomes for use of blood and bone marrow derived cells between January 1997 and December 2007 was performed by Richard K. Burt, M.D., of the Northwestern University Feinberg School of Medicine, Chicago, and colleagues. They combed databases to yield 323 reports that were analyzed for feasibility and toxicity of treatment. 69 studies were evaluated based on outcomes.
In preparation for the transplantation of stem cells, a myoablation regimen is often applied in varying degrees to weaken the immune system and improve integration of the new cells. When this team examined studies related to autoimmune diseases, 26 reports representing 854 patients reported: nonmyeloablative transplants with a treatment-related mortality rate of less than one percent (2/220 patients); dose-reduced myeloablative transplants with a treatment-related mortality rate of less than two percent (3/197 patients); and intense myeloablative regiments (including total body irradiation or high-dose bulsulfan, which is often used in some types of chronic leukemia) with a mortality rate of 18 percent.
The researchers believe that this is still inconclusive evidence for this type of study. “While all trials performed during the inflammatory stage of autoimmune disease suggested that transplantation of hematopoietic [formation of blood or blood cells] stem cells (HSCs) may have a potent disease-remitting effect, remission duration remains unclear, and no randomized trials have been published,” they write.
When reporting on cardiovascular diseases, the researchers examined 17 reports about 1,002 heart attack patients, 16 reports about 493 patients with chronic coronary artery disease, and three meta-analysis. The data seemed to suggest that stem cell transplantation in patientswith coronary artery disease could contribute to some improvement in cardiac function.
The authors conclude with some cautiously hopeful words. “Stem cells harvested from blood or marrow, whether administered as purified HSCs or mesenchymal [cells that develop into connective tissue, blood vessels and lymphatic tissue] stem cells or as an unmanipulated or unpurified product can, under appropriate conditions in select patients, provide disease-ameliorating effects in some autoimmune diseases and cardiovascular disorders. Clinical trials are needed to determine the most appropriate cell type, dose, method, timing of delivery, and adverse effects of adult HSCs for these and other nonmalignant disorders.”
Clinical Applications of Blood-Derived and Marrow-Derived Stem Cells for Nonmalignant Diseases
Richard K. Burt, MD; Yvonne Loh, MD; William Pearce, MD; Nirat Beohar, MD; Walter G. Barr, MD; Robert Craig, MD; Yanting Wen, MD; Jonathan A. Rapp, MD; John Kessler, MD
JAMA. 2008;299(8):925-936.
Written by Anna Sophia McKenney