Cardiac progenitor cells from adult myocardium: Homing, differentiation, and fusion after infarction

Abstract

Potential repair by cell grafting or mobilizing endogenous cells holds particular attraction in heart disease, where the meager capacity for cardiomyocyte proliferation likely contributes to the irreversibility of heart failure. Whether cardiac progenitors exist in adult myocardium itself is unanswered, as is the question whether undifferentiated cardiac precursor cells merely fuse with preexisting myocytes. Here we report the existence of adult heart-derived cardiac progenitor cells expressing stem cell antigen-1. Initially, the cells express neither cardiac structural genes nor Nkx2.5 but differentiate in vitro in response to 5 -azacytidine, in part depending on Bmpr1a, a receptor for bone morphogenetic proteins. Given intravenously after ischemia͞reperfusion, cardiac stem cell antigen 1 cells home to injured myocardium. By using a Cre͞Lox donor͞ recipient pair (␣MHC-Cre͞R26R), differentiation was shown to occur roughly equally, with and without fusion to host cells. C ardiomyocytes can be formed, at least ex vivo, from diverse adult pluripotent cells (1-5). Apart from therapeutic implications and obviating ethical concerns aroused by embryonic stem cell lines, adult cardiac progenitor cells might provide an explanation distinct from cell cycle reentry, for the reported rare occurrence of cycling ventricular muscle cells (6). However, recent publications suggest the failure of certain stem cells' specification into neurons, skeletal muscle, and myocardium in vivo (7,8) and recommend greater conservatism in evaluating claims of adult stem cell plasticity, for cogent reasons (9-11).The rarity of cardiogenic conversion by endogenous hematopoietic cells (2, 12), requirements for intracardiac injection (3), or mobilization by cytokines (13), uncertain proof for myocytes of host origin in transplanted human hearts (14), and the confounding possibility of cell fusion after grafting in vivo (15, 16) highlight unsettled issues surrounding stem cell plasticity in heart disease. For donor cell types already in clinical studies, the predominant in vivo effect of bone marrow or endothelial progenitor cells may be neoangiogenesis, not cardiac specification (17, 18), and skeletal myoblasts, despite integration and survival, are confounded by arrhythmias, perhaps reflecting lack of transdifferentiation (19). These obstacles underscore the need to seek cardiac progenitor cells beyond the few known sources. Materials and MethodsFlow Cytometry and Magnetic Enrichment. A ''total'' cardiac population was isolated from 6-to 12-wk-old C57BL͞6 mice by coronary perfusion with 0.025% collagenase, as for viable adult mouse cardiomyocytes (20). More typically, a ''myocytedepleted'' population was prepared, incubating minced myocardium in 0.1% collagenase (30 min, 37°C), lethal to most adult mouse cardiomyocytes (20). Cells were then filtered through 70-m mesh. Bone marrow cells (21) were compared, with or without collagenase and filtration. Cells were labeled with stem cell antigen 1 (Sca-1)-phycoerythrin (PE), Sca-1-FITC, c-kit-PE; CD4-...

Research of cardiomyocyte precursors in adult rat heart

“…Moreover, they appeared to have properties of adult cardiac stem cells, able of long-term self-renewal and they could differentiate towards the main specialized cell types of the heart (Messina et al, 2004). Other researchers have isolated from adult myocardium c-Kit − e Sca-1 + cardiac progenitor cells that expressed a number of cardiogenic transcription factors but not cardiac structural genes (Oh et al, 2003). These cells were induced to differentiate in vitro towards the cardiac myogenic lineage in response to 5 -azacytidine.…”

“…These cells were induced to differentiate in vitro towards the cardiac myogenic lineage in response to 5 -azacytidine. When administrated intravenously after ischemia/reperfusion experiments, these cells targeted injured myocardium and differentiated into cardiomyocytes, with and without fusion with the host cells (Oh et al, 2003). In addition, resident stem cells positive to nestin, that has been reported to be expressed during embryonic development of the brain and myoblasts (Kachinsky et al, 1995), have been isolated from normal and damaged rat hearts (El-Helou et al, 2005).…”

“…Other recent studies reported about cardiac stem or progenitor cells from adult mammalian hearts (Oh et al, 2003;Messina et al, 2004), whose purification was based exclusively on the expression of a stem cell-related surface antigen as c-Kit. Indeed, c-Kit + and Lin − cells were found to be self-renewing, clonogenic and multipotent, exhibiting differentiation towards myogenic, smooth muscle, or endothelial cell lineage but failing to contract spontaneously.…”

Stem cells in the heart: What's the buzz all about?—Part 1: Preclinical considerations

“…11 Sca-1 + cells were isolated by antibody targeting and magnetic sorting. Freshly isolated Sca-1 + cells coexpressed CD31 and CD38, lacked c-Kit, CD34, CD45, Flk-1, and Flt-1 and were blood lineage negative.…”

Migration of Resident Cardiac Stem Cells in Myocardial Infarction

“…Thus, repairing or regenerating lost myocardium by stem cell therapies is highly appealing. In recent years various subsets of resident CSCs that are capable of selfrenewal, proliferation, and differentiation into cardiomyocytes, endothelial and smooth muscle cells have been identified (Hierlihy et al, 2002;Beltrami et al, 2003;Oh et al, 2003;Messina et al, 2004;Eisenberg et al, 2004;Di Felice et al, 2009). CSCs have been shown to be able to migrate to the site of injury within the heart and participate in repairing damaged myocardium, leading to improved cardiac function following MI in different experimental MI models (Beltrami et al, 2003;Messina et al, 2004;Oh et al, 2004;Linke et al, 2005).…”