About Stem Cells In a Nut Shell: What are Stem Cells?

Simply put, in your body there are many different kinds of cells, each specialized for its own distinct task. Just as a banker works in a bank and a teacher works in a school, we have cardiac myocytes which are heart muscle cells, and retinal cells that work in eyes and allow us to see. Stem cells are immature cells which have the capability of becoming these more specialized cells. By purifying and amplifying these cells, we have developed an exciting new method to repair organs that are irreversibly damaged by the ravages of disease.

Importantly, adult stem cells can be obtained from adult human bone marrow. When extracted and grown under laboratory conditions, bone marrow stem cells can grow into many different kinds of cells, depending on the laboratory conditions under which they are grown.

Consider this scenario: you have a heart attack. You go to hospital. The doctors treat you and stabilize your condition, but they are unable to actually repair the damage your heart has sustained. Because of this you are at risk for other medical problems.

Doctors at the University of Miami Miller School of Medicines Interdisciplinary Stem Cell Institute are working on new therapies to address this specific problem. Using adult stem cells from the bone marrow, early tests have shown that cell-based therapies can reverse the damage your heart has sustained. Because of this, cell-based therapy may in the future improve the quality of life of patients who have had heart attacks. The mission of the Interdisciplinary Stem Cell Institute at the University of Miami is to make this happen as soon as possible and to conduct basic research to help understand exactly how this works.

This scenario, with further research and careful clinical trials, has the potential to be applicable to the repair of damaged liver, lung, spinal cord, and even improve treatments for diabetes.

These stem cells have never been anywhere near an embryo. They were made and live in adult bone marrow.

Stem Cells are undifferentiated cells that have the potential to differentiate into a variety of different cell types. Most in the news are embryonic stem cells, derived from terminated embryos, but our researchers use stem cells that are isolated from adult bone marrow, with no risk to the donor. In particular, for heart repair, we use mesenchymal stem cells (MSCs) which are found in bone marrow, in muscle, skin and adipose tissue. They are able to differentiate into a number mesenchymal tissues, such as muscle, fibroblasts, bone, tendon, ligament and adipose tissue. They express signature markers that are unique, and easily distinguished from those of hematopoeitic and other types of stem cells.

Following myocardial infarction, heart tissue looses cardiac myocytes, which are irreplaceable nonrenewable cells. To compensate, it undergoes remodeling which results in hypertrophy and scar formation through accumulation of collagen and fibrosis. The heart thus enlarges and this leads to congestive heart failure. The ultimate goal of mesenchymal stem cell therapy is to stimulate repopulation of the damaged region with new heart tissue, and thus delay or prevent the progression from myocardial infarction to total heart failure.

Preliminary experimental and clinical trials have yielded promising results. MSCs, injected into heart tissue using a specialized catheter, were able to differentiate into cardiomyocytes and endothelial cells. In addition, these new cells were able to perform the same function as the cells that were lost due to cardiac infarction. The results thus imply that MSCs are actually differentiating into functional, integrated cardiomyocytes.

The paradigm thus begins to shift , with the emphasis being placed on regenerative medicine. For heart attack, all existing therapies restore blood flow or aim to minimize damage to the heart. Now we can conceive for the first time of reversing the damage caused by the heart attack. Many challenges lie ahead. We need to find the optimal cell, and the best way to deliver it. We must make sure the therapies are safe, and we must fully understand all of the different ways in which cell therapy works. And finally, we need to do the formal and rigorous testing to make sure that the therapies are safe and effective. All of our testing in humans is performed with the approval of the United States Food and Drug Administration.

This strategy is applicable to a wide range of tissue types and diseases. Researchers at the Interdisciplinary Stem Cell Institute are working together not only on finding treatments for heart failure, but also for cancer, diabetes, bone and neurodegenerative diseases.

Boyle A.J., Schulman S.P. and Hare J.M. (2006) Stem cell therapy for cardiac repair: ready for the next step. Circulation 114: 339-352.

Laflamme M.A. and Murry C.E. (2005) Regenerating the heart. Nat Biotech 23: 845-856.

Zimmet J.M. and Hare J.M. (2005) Emerging role for bone marrow derived mesenchymal stem cells in myocardial regenerative therapy. Basic Res Cardiol 100: 471 481.

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