Adult Stem Cell Technologies in Heart Disease
Adult stem cells are stem cells in your body that are undifferentiated--they haven't yet specialized to perform a specific function--and can divide to replace worn-out or dead cells. While adult stem cells are not as versatile as embryonic stem cells (ESCs), they have other advantages that make them a promising area of research. Among the treatments some researchers hope adult stem cells will eventually yield is a new approach to treating heart disease.
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Heart disease
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According to the Centers for Disease Control, heart disease is the leading cause of death in the United States, accounting for roughly a quarter of all deaths each year. One of the chief culprits is a condition called coronary artery disease in which plaque accumulates on the interior walls of the arteries that supply blood to the heart muscle. The excess plaque buildup may cause a clot to form, leading to a heart attack that typically causes irreparable damage to the heart muscle tissue. If doctors could replace damaged heart tissue with new heart muscle cells (cardiomyocytes) they might be able to reverse this damage and save more lives.
Stem cells
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Most of the cells in your body are specialized to perform specific functions. Stem cells, by contrast, remain undifferentiated--they haven't yet committed to a particular function. When they divide, they do so asymmetrically, in that one of the two daughter cells is a stem cell while the other is a more specialized (differentiated) cell. In principle, stem cells can divide without limit to replace other cells or generate various tissue types during growth and development.
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Embryonic and adult stem cells
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Embryonic stem cells (ESCs) are derived from the inner cell mass of a blastocyst (an early-stage embryo) and can develop into any cell type in the body, an ability called pluripotence. This remarkable versatility could make ESCs an especially powerful way to replace or repair damaged tissues in patients with conditions like spinal cord injuries. This research has sparked controversy because human embryos have been used to obtain the cells. The immune system might reject and attack transplanted ESCs in very much the same way it rejects some organ transplants. Adult stem cells, on the other hand, are derived from adult tissues, where they are comparatively rare but perform a vital function by replacing dead or worn-out cells. Adult stem cells are less likely to provoke an immune system response since the patient's own stem cells, rather than a donor's, are used to replace damaged tissue. Adult stem cells are less versatile than ESCs, however, since it seems they can only generate a limited number of cell types and may thus have fewer applications.
Adult stem cells & heart disease
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If scientists could find ways to culture a patient's adult stem cells to produce more stem cells and reintroduce them into the patient's heart muscle, doctors would gain a powerful technique to repair damage following a heart attack. A study by published in the journal Nature in 2001 demonstrated that it's possible to do so in rats, and a number of subsequent studies have explored this possibility further both in animal models and in humans as part of various clinical trials.
Current status and future prospects
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Unfortunately, despite adult stem cells' tremendous potential, progress to date has been modest and many challenges remain. A study published in the Journal of Clinical Investigation in 2010 noted that "treatment of heart disease with bone marrow cells and skeletal muscle progenitors has had only marginal positive benefits in clinical trials, perhaps because adult stem cells have limited plasticity." Researchers are pursuing different approaches, using stem cells from different sources and working to understand more about the factors that determine when stem cells divide and differentiate in hopes this research will identify better treatments for heart disease, America's leading cause of death.
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References
- NIH Stem Cell Page - "Can Stem Cells Repair a Damaged Heart?"
- "A purified population of multipotent cardiovascular progenitors derived from primate pluripotent stem cells engrafts in postmyocardial infarcted nonhuman primates." "Journal of Clinical Investigation." Blin, Nury, Stefanovic et al. 2010.
- "Bone marrow cells regenerate infarcted myocardium." "Nature." Orlic, Kajstura, Chimenti et al. 2001.
Resources
- Photo Credit Blue Heart image by netzfrisch.de from Fotolia.com
