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Chapter 10: Stem Cells and the Cardiovascular System

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Which of the following is not true about mechanisms of cell therapy?

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A. Transdifferentiation is when a differentiated cell type commits to becoming a new cell type

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B. Angiogenesis is the formation of new blood vessels

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C. Bone marrow cell therapy is likely to promote ventricular recovery by transdifferentiation into cardiomyocytes

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D. Dedifferentiation likely confers a protective effect for injured cardiomyocytes

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E. Transplanted bone marrow cells are transiently retained in the heart following cardiac injury

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The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 10) Multiple groups have tested the efficacy of bone marrow cell therapy after MI. Bone marrow cells in preclinical models rarely transdifferentiate into cardiomyocytes (options A and C), are transiently retained in the heart (option E), and most likely exert their beneficial effects on cardiac function through a paracrine mechanism that stimulates new blood vessels through angiogenesis (option B).1-4 Lastly, a novel concept in cardiac repair is modulation of dedifferentiation. Dedifferentiation is the process by which cardiomyocytes take on a gene and protein expression profile that is more similar to fetal. This phenotype occurs more often in acute and chronic injury of the heart and seems to confer a potential survival advantage of these cardiomyocytes (option D).

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Which of the following is true of stem cell delivery approaches to the heart?

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A. Intracoronary injection of stem cells results in better engraftment of cells than transendocardial injection

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B. Transendocardial injection does not require adjunctive imaging modalities to target injured myocardium

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C. Intravenous administration of stem cells is a promising approach because stem cell populations evaluated thus far are efficient in their homing to injured myocardium

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D. Transepicardial injection of stem cells requires adjunctive imaging modalities to target injured myocardium

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E. Activation of resident stem cells has been evaluated in human studies after acute myocardial infarction (MI)

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The answer is A. (Hurst’s The Heart, 14th Edition, Chap. 10) While additional work is needed for cell therapy to be considered a treatment modality, the science of stem cell delivery has rapidly developed. Current approaches include intravenous delivery, but this is limited by poor retention of stem cells in the myocardium (option C). Intracoronary injection of stem cells can be done during percutaneous coronary intervention, but stem cell retention is not as good as with transendocardial injection (option A).4,5 Transendocardial injection can also be done in the catheterization laboratory, ...

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