c-kitPOS Cardiac Progenitor Cells Research Articles

Abstract 36: Cardiac Progenitor Cell Lineage Tracing During Embryonic Cardiomyogenesis

Introduction: Stem cell therapy represents great promises to myocardium regeneration. Multipotent c-Kit pos cardiac progenitor cells (CPCs) are able to differentiate into endothelial cells, smooth muscle cells, and cardiomyocytes. However, fundamental knowledge of CPC biology remains incomplete. Studies in rodent myocardial infarction model revealed that CPCs have poor long-term survival and engraftment after adoptive transfer, perhaps due to the severely damaged host environment. Therefore, it is critical to understand how CPCs interface with the recipient environment following transfer in order to enhance their true regenerative potentials. Hypothesis: Adoptively transferred stem cells are thought to survive and engraft best in an environment closely resembling their original habitat. Thus, we hypothesized that the embryonic environment provides the optimal spatiotemporal conditions to promote CPCs engraftment and commitment to cardiac fate. Methods: CPCs isolated from adult mouse hearts were expanded, fluorescence-tagged, and injected into blastocysts at E3.75 and in utero at E15.5. Embryos were analyzed following cardiogenesis by immunofluorescence for presence of CPC-derived tissues. Additionally, CPCs were injected intramyocardially at various stages from P0 to P7, to follow long-term adoptive transfer and assess CPCs lineage commitment. Results and Conclusions: At 48 hours post injection, donor CPCs were found anchoring in blastocoel and trophoblasts at E5.5, and were detected within the host myocardium at E17.5 predominantly at perivascular regions (n=4). Interestingly, CPCs also integrated into aminochorionic sac, indicating a novel non-cardiogenic fate of CPCs (n=5). CPCs injected at P3 stably engrafted into left ventricular myocardium by 14 days post injection (n=4), sharing gap junction proteins (ZO-1, Connexin-43) with neighboring cells. In conclusion, this study provides vivid evidence for the first time of CPC engraftment and survival in vivo under homeostasis during cardiogenesis. Future studies will assess the permissive environmental conditions, which may optimize their use in therapeutic applications, and the cardiogenic potential of CPCs in order to provide fundamental insights on CPCs biology.

Myocardial Reparative Properties of Cardiac Mesenchymal Cells Isolated on the Basis of Adherence

BackgroundThe authors previously reported that the c-kit–positive (c-kitPOS) cells isolated from slowly adhering (SA) but not from rapidly adhering (RA) fractions of cardiac mesenchymal cells (CMCs) are effective in preserving left ventricular (LV) function after myocardial infarction (MI). ObjectivesThis study evaluated whether adherence to plastic alone, without c-kit sorting, was sufficient to isolate reparative CMCs. MethodsRA and SA CMCs were isolated from mouse hearts, expanded in vitro, characterized, and evaluated for therapeutic efficacy in mice subjected to MI. ResultsMorphological and phenotypic analysis revealed that murine RA and SA CMCs are indistinguishable; nevertheless, transcriptome analysis showed that they possess fundamentally different gene expression profiles related to factors that regulate post-MI LV remodeling and repair. A similar population of SA CMCs was isolated from porcine endomyocardial biopsy samples. In mice given CMCs 2 days after MI, LV ejection fraction 28 days later was significantly increased in the SA CMC group (31.2 ± 1.0% vs. 24.7 ± 2.2% in vehicle-treated mice; p < 0.05) but not in the RA CMC group (24.1 ± 1.2%). Histological analysis showed reduced collagen deposition in the noninfarcted region in mice given SA CMCs (7.6 ± 1.5% vs. 14.5 ± 2.8% in vehicle-treated mice; p < 0.05) but not RA CMCs (11.7 ± 1.7%), which was associated with reduced infiltration of inflammatory cells (14.1 ± 1.6% vs. 21.3 ± 1.5% of total cells in vehicle and 19.3 ± 1.8% in RA CMCs; p < 0.05). Engraftment of SA CMCs was negligible, which implies a paracrine mechanism of action. ConclusionsWe identified a novel population of c-kit–negative reparative cardiac cells (SA CMCs) that can be isolated with a simple method based on adherence to plastic. SA CMCs exhibited robust reparative properties and offered numerous advantages, appearing to be more suitable than c-kitPOS cardiac progenitor cells for widespread clinical therapeutic application.

Repeated doses of cardiac mesenchymal cells are therapeutically superior to a single dose in mice with old myocardial infarction.

We have recently demonstrated that repeated administrations of c-kitPOS cardiac progenitor cells (CPCs) have cumulative beneficial effects in rats with old myocardial infarction (MI), resulting in markedly greater improvement in left ventricular (LV) function compared with a single administration. To determine whether this paradigm applies to other species and cell types, mice with a 3-week-old MI received one or three doses of cardiac mesenchymal cells (CMCs), a novel cell type that we have recently described. CMCs or vehicle were infused percutaneously into the LV cavity, 14days apart. Compared with vehicle-treated mice, the single-dose group exhibited improved LV ejection fraction (EF) after the 1st infusion (consisting of CMCs) but not after the 2nd and 3rd (vehicle). In contrast, in the multiple-dose group, LV EF improved after each CMC infusion, so that at the end of the study, LV EF averaged 35.5±0.7% vs. 32.7±0.6% in the single-dose group (P<0.05). The multiple-dose group also exhibited less collagen in the non-infarcted region vs. the single-dose group. Engraftment and differentiation of CMCs were negligible in both groups, indicating paracrine effects. These results demonstrate that, in mice with ischemic cardiomyopathy, the beneficial effects of three doses of CMCs are significantly greater than those of one dose, supporting the concept that multiple treatments are necessary to properly evaluate the full therapeutic potential of cell therapy. Thus, the repeated-treatment paradigm is not limited to c-kit POS CPCs or to rats, but applies to other cell types and species. The generalizability of this concept dramatically augments its significance.

Repeated Cell Therapy

Although treatment with stem/progenitor cells is a promising approach to heart disease, enthusiasm for cell therapy has been dampened by the inconsistent, modest, borderline, or undetectable benefits reported in clinical trials (all of which have used 1 dose of cells).1–4 As a result, clinical translation has not occurred (no cell-based therapy is close to being approved for heart disease), and a rising tide of skepticism has bedeviled the field,5,6 leading some critics even to question whether clinical studies should continue. Here, I propose that a major reason for the modest, borderline, or disappointing results is the administration of only 1 dose of cells, which causes the benefits of cell therapy to be underestimated. I argue that just as most pharmacological agents are ineffective when given once but can be highly effective when given repeatedly, so a cell product may be ineffective, or modestly effective, when given as a single treatment, but may turn out to be quite efficacious if given repeatedly. This concept constitutes a major paradigm shift (a “game changer”), with potentially vast implications for the entire field of reparative medicine . The efficacy of cell therapy is limited by the poor engraftment of the cells, which disappear rapidly after transplantation. For example, after administration of c-kitPOS cardiac progenitor cells (CPCs) in mice, rats, and pigs, the number of cells remaining in the heart declines precipitously to very low values1,2,7,8; in the mouse heart, <8% of the CPCs present immediately after transplantation remain 1 week later, and after 35 days this number falls to <3%.8 Despite this, administration of CPCs improves left ventricular (LV) function, and the improvement is long lasting (at least 1 year).1,2,7,8 Rapid disappearance of transplanted cells …

Antiarrhythmic effect of growth factor-supplemented cardiac progenitor cells in chronic infarcted heart.

c-Kit(pos) cardiac progenitor cells (CPCs) represent a successful approach in healing the infarcted heart and rescuing its mechanical function, but electrophysiological consequences are uncertain. CPC mobilization promoted by hepatocyte growth factor (HGF) and IGF-1 improved electrogenesis in myocardial infarction (MI). We hypothesized that locally delivered CPCs supplemented with HGF + IGF-1 (GFs) can concur in ameliorating electrical stability of the regenerated heart. Adult male Wistar rats (139 rats) with 4-wk-old MI or sham conditions were randomized to receive intramyocardial injection of GFs, CPCs, CPCs + GFs, or vehicle (V). Enhanced green fluorescent protein-tagged CPCs were used for cell tracking. Vulnerability to stress-induced arrhythmia was assessed by telemetry-ECG. Basic cardiac electrophysiological properties were examined by epicardial multiple-lead recording. Hemodynamic function was measured invasively. Hearts were subjected to anatomical, morphometric, immunohistochemical, and molecular biology analyses. Compared with V and at variance with individual CPCs, CPCs + GFs approximately halved arrhythmias in all animals, restoring cardiac anisotropy toward sham values. GFs alone reduced arrhythmias by less than CPCs + GFs, prolonging ventricular refractoriness without affecting conduction velocity. Concomitantly, CPCs + GFs reactivated the expression levels of Connexin-43 and Connexin-40 as well as channel proteins of key depolarizing and repolarizing ion currents differently than sole GFs. Mechanical function and anatomical remodeling were equally improved by all regenerative treatments, thus exhibiting a divergent behavior relative to electrical aspects. Conclusively, we provided evidence of distinctive antiarrhythmic action of locally injected GF-supplemented CPCs, likely attributable to retrieval of Connexin-43, Connexin-40, and Cav1.2 expression, favoring intercellular coupling and spread of excitation in mended heart.