CARDIAC REGENERATION
Process of regeneration restores tissue architecture through events including cellular proliferation, differentiation and dedifferentiation, and coordinated morphogenic rearrangements. In response to cardiac injury, adult mammals, including humans, fail to regenerate the majority of the lost cardiomyocytes and instead replace necrotic muscle with scar tissue. The loss of cardiomyocytes eventually compromises contractility of the remaining myocardium, leading to heart failure and death when the extent of injury is severe. However, recent data indicate that mammalian cardiogenesis occurs during adult life, including in humans. In addition, the neonatal mouse heart has a regenerative response immediately after birth. Thus, regeneration of myocardial tissue is an exciting therapeutic goal. We are far from a complete understanding of how heart tissue can regenerate, but we are now defining molecular mechanisms that could open the door to stimulating adult mammalian heart regeneration.[29]
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Stem cells from the BM circulate throughout the body. The early mesoderm can induce blood cells and cardiac cells. The stem cells isolated as c-Kit positive cells from the BM were shown to differentiate into cardiomyocytes in an ischemic heart to regenerate a damaged heart. Therefore, BMCs can contribute to the supply of stem cells for organ regeneration. BMCs have been tested for clinical use, and positive effects have been demonstrated. These positive effects are due to direct cardiomyocyte differentiation or paracrine effects on angiogenesis. The paracrine effects of angiogenesis thicken the infarcted area supplying energy and oxygen through new blood, brought from the cytokines released from the stem cells. Indeed, c-Kit positive stem cells were reported to induce angiogenesis and research commenced to describe the mechanism of the recovery from infarcts using BM c-Kit positive