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Cardiology ;—14 DOI To view the fulltext, please log in. To view the pdf, please log in. CHF Subscribe Access to all articles of the subscribed year s guaranteed for 5 years Unlimited re-access via Subscriber Login or MyKarger Unrestricted printing, no saving restrictions for personal use You receive your access authorization within a few days; please copy this article reference into your MySelection. Arias E: United States life tables, J Cardiothorac Vasc Anesth.
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Asian Cardiovasc Thorac Ann. Connexin43 D—F was detectable within transplanted NCMs white arrows and within host myocardium as well as between both small white arrows. Preliminary experiments showed that freshly isolated NCMs survive in culture for up to 7 days after Hoechst staining, without morphological or functional evidence of cellular damage by the staining. APs of these cells Fig. Electrical integration and maturation of transplanted NCMs. B Representative viable slice of a recipient heart containing NCMs in bright field and Hoechst imaging.
Transplanted NCMs could be identified within viable slices of recipient hearts by fluorescence of Hoechst dye applied prior to transplantation. Three days after intramyocardial injection, transplanted NCMs were electrophysiologically integrated into host myocardium following a maximal stimulation frequency of 1. Host CMs followed maximal stimulation frequency of Delay of electrical activation, which quantifies deceleration of excitation spread in transplanted cells and therefore is another parameter to evaluate electrical coupling with surrounding tissue, declined from Measurements of cardiac function 1 week after coronary artery ligation were invasively performed with P-V catheter in 33 rats and noninvasively with echocardiography in 37 rats.
All remaining 30 animals in echocardiographic analyses and 23 animals in P-V analyses showed a homogenously reduced ejection fraction of Cardiac function of infarcted rat hearts. All performed at 1 week after myocardial infarction MI i. Repeated echocardiography showed similar results.
During dobutamine-induced stress, heart rate was significantly increased in all animals, and invasive as well as noninvasive measurements showed a similar contractile reserve in all experimental groups. There was no significant difference between groups in heart weight, heart-to-body weight ratio, lung weight, and lung-to-body weight ratio.
However, a slight trend was seen for lower lung weights in pooled data of all cell-treated animals versus Ctrl 0. Lung weight as well as lung-to-body weight ratio of exemplary healthy rats were almost identical to those of cell-treated groups. Cardiac cell replacement therapy is a promising approach to restore cardiac function in heart failure by replacing lost myocardium with new contractile cells, which ideally should be or become CMs.
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To assess the true potential of this therapy, it is very important to thoroughly investigate the following most crucial issues:. Therefore, we investigated all these crucial issues for the first time in one study using the very reliable model of MI through LAD ligation in rats followed by intramyocardial injection of syngeneic NCMs, which were shown to have a significant persistence over time 9.
Besides the very robust method of quantitative real-time PCR to determine persistence of transplanted cells within recipient hearts, we performed intense electrophysiological analyses of transplanted cells within host myocardium with sharp-electrode measurements in viable slices of recipient hearts as well as histological and immunohistochemical analyses to determine integration and phenotype of transplanted cells. Finally, differentially treated animals underwent detailed functional analyses with repeated invasive and noninvasive measurements of cardiac function.
Number of cells successfully implanted into injured heart and their persistence within the heart is the first essential factor for effective cardiac cell replacement therapy. This finding is consistent with our and other earlier studies 9 , 22 , By increasing applied cell number from 5 to 25 million NCMs, the absolute cell number of detectable cells was increased fivefold, while the percentage of surviving cells did not change.
This suggests that in methods used here, persistence and survival of transplanted cells was not limited due to space and nutrient deficiency, as described by Zhang et al. Importantly for subsequent functional analyses of dose dependence, we could demonstrate that after receiving a fivefold higher number of NCMs at the time of transplantation, hearts in high NCM still contain a significantly and approximately fivefold higher number of persisting and surviving NCMs at the time of second and final functional measurements compared to hearts in low NCM.
Exemplary histological analysis of transplanted NCMs showed some morphological signs of maturation as larger cell volume and incipient longitudinal orientation, in contrast to the phenotype of freshly isolated NCMs. Moreover, connexin43, as an important component of gap junctions and structural basis of electro-physiological coupling, could be shown not only within the graft of transplanted NCMs and within host myocardium but also between graft and host tissue.
Notwithstanding these signs of integration of transplanted NCMs into host myocardium, transplanted NCMs still were significantly smaller than host CMs, indicating that their structural maturation seemed to be incomplete. Consistently, Sato et al. In contrast to the present study and the results of Yao et al. One reason for this different finding may be that in this study, rat FCMs had been transplanted into the infarct scar and therefore lacked direct contact with the host myocardium. Halbach et al. Electrophysiological integration into host myocardium and adoption or preservation of a mature cardiac phenotype are important to enable a functional syncytium of transplanted and host CMs and therefore for a safe and effective cardiac cell replacement therapy.
Rubart et al.
Associate Professor Theodoros Kofidis
Roell et al. However, hearts were dissociated in these studies to enable electrophysiological measurements of transplanted cells, which therefore were isolated from surrounding host tissue. Thus, no information about electrical integration of studied CMs was achieved. Here integration and maturation of transplanted NCMs was examined using sharp-electrode measurements within viable slices of recipient hearts, which allows to sustain nearly in vivo conditions and to elucidate electrophysiological properties of transplanted CMs within the surrounding host tissue 14 , 21 , However, since slicing technique revealed to be impossible for rat hearts after ligation infarction due to severe fibrosis of the tissue, we had to use healthy hearts for these experiments.
For the first time, we were able to show not only a structural 7 but also an electrical integration of transplanted NCMs as early as 3 days after transplantation as indicated by following a stimulation applied to distant host myocardium. This was further improved at 6 days after transplantation, when maximal stimulation frequency without conduction blocks was similar to host CMs, which indicates an optimal electrical integration into the host myocardium.
In contrast to other groups, we observed a marked and rapid electrophysiological maturation of transplanted cells over time. While NCMs possessed quite immature AP properties 3 days after transplantation, already at 6 days NCMs showed almost adult electrophysiological properties.
Sato et al. They suspected that immature cells and their relatively slow maturation may cause arrhythmias and therefore might be a problem and limitation of cell therapy. A reason for this may be the higher maturity at the time of isolation and transplantation. One might speculate that using even more mature CMs in cardiac cell replacement therapy could allow to achieve this optimal state even earlier and may result in improved therapeutic effects. However, persistence and survival of more mature cells, like adult CMs, is dramatically lower and therefore limits this approach.
Certainly, future research is needed to overcome these obstacles. Robust and reliable functional analysis is needed to assess the true therapeutic potential of cardiac cell replacement therapy and is facilitated by repeated measurements, which is therefore mandatory and standard in clinical trials. In our present study with repeated invasive and noninvasive functional analysis, we were able to show a dose-dependent stabilization of systolic left ventricular function and some signs of improvement within 4 weeks after MI and 3 weeks after cell transplantation of NCMs, as well as less left ventricular dilatation and wall thinning in cell-treated versus control hearts.
In contrast, control group showed the natural progress of heart failure with progressive left ventricular remodeling and deterioration. In previous studies with transplanted CMs, Yao et al. Nevertheless, long-term persistence and survival of transplanted stem cell-derived CMs is extremely low and most likely limits their therapeutic effects.
As Etzion et al. Despite improved cardiac function, Kawamura et al.
Repeated functional measurements using echocardiography and P-V catheter after MI before transplantation and after cardiac cell replacement therapy enabled us to follow individual changes of heart function. Nevertheless, our study failed to show a significant improvement of any tested parameter of systolic left ventricular function by cardiac cell replacement therapy in infarcted rat hearts in the course of time, which could have been hoped for regarding efficient engraftment, integration, and maturation of transplanted new CMs.
However, current evidence-based pharmacological treatment like angiotensin-converting enzyme ACE -inhibitor captopril also did not improve cardiac function in small animal infarction models, but it attenuated dramatic deterioration seen in untreated animals Therefore, we believe that dose-dependent stabilization in systolic left ventricular function by cardiac cell replacement therapy seen in our study might still translate into a significant clinical benefit in patients, especially when further optimized and of course combined with all optimal therapies currently recommended.
High lung weight and high lung-to-body weight ratio are strong indicators of congestive heart failure after MI in small animal experiments However, both values were similarly low in cell-treated animals at 4 weeks after MI compared to exemplary healthy controls, which might therefore be taken as a sign of a well-compensated heart failure in cell-treated animals versus placebo controls. In contrast, six cardiac biomarkers tested had similar levels in all groups and therefore seem to be less sensitive systemic indicators of heart failure in our experimental setting.
We performed a detailed placebo-controlled functional study using repeated invasive and noninvasive analyses of cardiac function to investigate the therapeutic effects of cardiac cell replacement therapy with transplantation of different doses of neonatal rat CMs into infarcted syngeneic rat hearts. Furthermore, we quantified persistence and evaluated integration and maturation of transplanted cells. Within 4 weeks after MI and 3 weeks after transplantation, we were able to show that transplanted NCMs:.
Although this exact cell type is not relevant for clinical use, our findings are reassuring that after all cardiac cell replacement therapy is still a promising therapy for ischemic heart disease. However, future investigations need to optimize the use of clinically, more relevant types of CMs in cardiac cell replacement therapy, like derivatives of iPSCs, in order to thoroughly elucidate their true therapeutic potential.
We thank Dr. Alexander Ghanem for his support with echocardiography, Dr. Jan Mauer and Dr. Gunther Rappel for their support with Multiplex analysis, as well as support provided by workshops and the animal facility of Institute of Neurophysiology and Institute of Experimental Medicine of University Hospital of Cologne.
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Aortic Valve Replacement in Patients with Severely Reduced Left Ventricular Function
Published online Jan 1. PMID: Tobias G. Abstract Cardiac cell replacement therapy is a promising therapy to improve cardiac function in heart failure.