Prognostic impact of resting full-cycle ratio and diastolic non-hyperemic pressure ratios in patients with deferred revascularization.

BACKGROUND: Non-hyperemic pressure ratios (NHPRs) like resting full-cycle ratio (RFR), diastolic pressure ratio during entire diastole (dPR[entire]) and diastolic pressure ratio during wave-free period (dPR[WFP]) are increasingly used to guide revascularization. The effect of NHPRs on mid-term prognosis has not been well established. OBJECTIVE: We investigated the prognostic implications of NHRPs in patients whose revascularization was deferred based on fractional flow reserve (FFR) in a single-centre population. METHODS: NHPRs and FFR were calculated offline from pressure tracings by an independent core laboratory. Follow-up data were acquired through records of hospital visits or telephone interviews. The primary outcome was a vessel-oriented composite outcome (VOCO) (a composite of cardiac death, vessel-related myocardial infarction, and ischemia-driven revascularization) in deferred vessels at 2 years. RESULTS: 316 patients with 377 deferred lesions were analysed. Discordance of NHPRs and FFR was found in 13.0-18.3% of lesions. The correlation coefficient between NHPRs was 0.99 (95% confidence interval 0.99-1.00). At 2 years, VOCO occurred in 19 lesions (5.0%). Estimated glomerular filtration rate < 30 mL/min/1.73 m2 [hazard ratio (HR) 5.7, p = 0.002], previous myocardial infarction (HR 3.3, p = 0.018), diabetes (HR 2.7, p = 0.042), RFR ≤ 0.89 (HR 2.7, p = 0.041) and dPR[WFP] ≤ 0.89 (HR 2.7, p = 0.049) were associated with higher incidence of VOCO at 2 years in the univariable analysis. A non-significant trend was found for dPR[entire] (HR 1.9, p = 0.26). CONCLUSION: A positive RFR or dPR[WFP] were associated with a worse prognosis in deferred lesions, suggesting that the use of NHPRs in addition to FFR may improve risk estimation.

Contemporary treatment of mitral valve disease with transcatheter mitral valve implantation.

BACKGROUND: Transcatheter mitral valve implantation (TMVI) with self-expanding (SAV) or balloon-expandable (BAV) valves are rising as promising treatment options for high-risk patients with symptomatic mitral valve (MVD) disease unsuitable for alternative treatment options. AIMS: The aim of this study was to examine the clinical, procedural and outcome parameters of patients undergoing SAV or BAV for MVD. METHODS: In this observational and single-center case series, fifteen consecutive patients treated with the Tendyne Mitral Valve System (SAV) and thirty-one patients treated with SAPIEN prosthesis (BAV) were included. RESULTS: The patients (aged 78 years [interquartile range (IQR): 65.5 to 83.1 years], 41% women, EuroSCORE II 10.3% [IQR: 5.5 to 17.0%] were similar regarding baseline characteristics, despite a higher rate of prior heart valve surgery and prevalence of MV stenosis in the SAV-group. At discharge, the SAV-group had a mean transvalvular gradient of 4.2 mmHg, whereas the BAV-group had a mean transvalvular gradient of 6.2 mmHg. None or trace paravalvular leakage (PVL) was assessed in 85% in SAV-group and 80% in the BAV-group. 320 day all-cause and cardiac mortality rates were comparable in both groups (SAV: 26.7% vs BAV: 20%, p = 0.60). Four deaths occurred early in the SAV-group until 32 days of follow-up. CONCLUSIONS: In high-risk patients with MVD, TMVI presents a promising treatment option with encouraging mid-term outcomes and good valve durability. TMVI either with BAV or SAV may be developed to an established treatment option.

Diagnostic performance of quantitative flow ratio versus fractional flow reserve and resting full-cycle ratio in intermediate coronary lesions.

BACKGROUND: Quantitative flow ratio (QFR) is a novel angiography-derived index aimed to assess the functional relevance of coronary stenoses without pressure wires and adenosine. Good diagnostic yield with the hyperemic fractional flow reserve (FFR) have been reported, while data on the comparison of QFR to non-hyperemic pressure ratios (NHPR) are scarce. METHODS: In this retrospective, observational and single-center study with a large population representative of the real practice, we assessed and compared the diagnostic performance of contrast flow (cQFR) and fixed flow (fQFR) QFR against the NHPR resting full-cyle ratio (RFR) using FFR as reference standard. RESULTS: A total of 626 lesions from 544 patients were investigated. Mean diameter stenosis, FFR, cQFR, fQFR and RFR were 44.8%, 0.842, 0.847, 0.857 and 0.912, respectively. The correlation between cQFR and FFR was stronger (r = 0.830, P < 0.001) compared to that between FFR and RFR (r = 0.777, P < 0.001) and between cQFR and RFR (r = 0.687, P < 0.001). Using FFR ≤0.80 as reference, the sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy for cQFR were 82%, 95%, 87%, 92%, and 91%, respectively. cQFR displayed a higher area under the curve (AUC) than fQFR and RFR (0.938 vs. 0.891 vs. 0.869, P < 0.01). The good diagnostic yield of cQFR appeared to be maintained in different clinical subsets including female gender, aortic valve stenosis and atrial fibrillation, and in different anatomical subsets including focal and non-focal lesions. CONCLUSION: cQFR has a high and better diagnostic performance than the NHPR RFR in predicting FFR-based functional significance of coronary stenoses.

Persistence of intramyocardially transplanted murine induced pluripotent stem cell-derived cardiomyocytes from different developmental stages.

BACKGROUND: Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) are regarded as promising cell type for cardiac cell replacement therapy, but it is not known whether the developmental stage influences their persistence and functional integration in the host tissue, which are crucial for a long-term therapeutic benefit. To investigate this, we first tested the cell adhesion capability of murine iPSC-CM in vitro at three different time points during the differentiation process and then examined cell persistence and quality of electrical integration in the infarcted myocardium in vivo. METHODS: To test cell adhesion capabilities in vitro, iPSC-CM were seeded on fibronectin-coated cell culture dishes and decellularized ventricular extracellular matrix (ECM) scaffolds. After fixed periods of time, stably attached cells were quantified. For in vivo experiments, murine iPSC-CM expressing enhanced green fluorescent protein was injected into infarcted hearts of adult mice. After 6-7 days, viable ventricular tissue slices were prepared to enable action potential (AP) recordings in transplanted iPSC-CM and surrounding host cardiomyocytes. Afterwards, slices were lysed, and genomic DNA was prepared, which was then used for quantitative real-time PCR to evaluate grafted iPSC-CM count. RESULTS: The in vitro results indicated differences in cell adhesion capabilities between day 14, day 16, and day 18 iPSC-CM with day 14 iPSC-CM showing the largest number of attached cells on ECM scaffolds. After intramyocardial injection, day 14 iPSC-CM showed a significant higher cell count compared to day 16 iPSC-CM. AP measurements revealed no significant difference in the quality of electrical integration and only minor differences in AP properties between d14 and d16 iPSC-CM. CONCLUSION: The results of the present study demonstrate that the developmental stage at the time of transplantation is crucial for the persistence of transplanted iPSC-CM. iPSC-CM at day 14 of differentiation showed the highest persistence after transplantation in vivo, which may be explained by a higher capability to adhere to the extracellular matrix.

In Vitro Grown Micro-Tissues for Cardiac Cell Replacement Therapy in Vivo.

BACKGROUND/AIMS: Different approaches have been considered to improve heart reconstructive medicine and direct delivery of pluripotent stem cell-derived cardiomyocytes (PSC-CMs) appears to be highly promising in this context. However, low cell persistence post-transplantation remains a bottleneck hindering the approach. Here, we present a novel strategy to overcome the low engraftment of PSC-CMs during the early post-transplantation phase into the myocardium of both healthy and cryoinjured syngeneic mice. METHODS: Adult murine bone marrow mesenchymal stem cells (MSCs) and PSC-CMs were co-cultured on thermo-responsive polymers and later detached through temperature reduction, resulting in the protease-free generation of cell clusters (micro-tissues) composed of both cells types. Micro-tissues were transplanted into healthy and cryo-injured murine hearts. Short term cell retention was quantified by real-time-PCR. Longitudinal cell tracking was performed by bioluminescence imaging for four weeks. Transplanted cells were further detected by immunofluorescence staining of tissue sections. RESULTS: We demonstrated that in vitro grown micro-tissues consisting of PSC-CMs and MSCs can increase cardiomyocyte retention by >10fold one day post-transplantation, but could not fully rescue a further cell loss between day 1 and day 2. Neutrophil infiltration into the transplanted area was detected in healthy hearts and could be attributed to the cellular implantation rather than tissue damage exerted by the transplantation cannula. Injected PSC-CMs were tracked and successfully detected for up to four weeks by bioluminescence imaging. CONCLUSION: This approach demonstrated that in vitro grown micro-tissues might contribute to the development of cardiac cell replacement therapies.

An exploratory propensity score matched comparison of second-generation and first-generation baroreflex activation therapy systems.

Baroreflex activation therapy (BAT) is a device-based therapy for patients with treatment-resistant hypertension. In a randomized, controlled trial, the first-generation system significantly reduced blood pressure (BP) versus sham. Although an open-label validation study of the second-generation system demonstrated similar BP reductions, controlled data are not presently available. Therefore, this investigation compares results of first- and second-generation BAT systems. Two cohorts of first-generation BAT system patients were generated with propensity matching to compare against the validation group of 30 second-generation subjects. The first cohort was drawn from the first-generation randomized trial sham group and the second cohort from the active therapy group. Safety and efficacy were compared for the second-generation group relative to the first generation. At 6 months, second-generation BAT outperformed first-generation sham systolic BP reduction by 20 ± 28 mm Hg (mean ± standard deviation, P = .008), while BP reduction in first- and second-generation active groups was similar. At 12 months, efficacy was comparable between all three groups after the sham group had received 6 months of therapy; 47% of second-generation patients achieved goal systolic BP of 140 mm Hg or less after 12 months, comparable to 50% of patients at goal in the first-generation group (P > .999). Implant procedure time, system/procedural safety, and pulse generator longevity improved with the second-generation system. Propensity-matched cohort analysis of the first- and second-generation BAT systems suggests similar therapeutic benefit and superior BP reduction of the second-generation system relative to sham control. Implantation procedure duration and perioperative safety were improved with the second-generation device. These findings should be validated in a prospective randomized trial.

Baroreflex activation therapy in patients with prior renal denervation.

BACKGROUND: Both baroreflex activation therapy (BAT) and renal denervation modulate sympathetic activity. The aim of this study was to systematically investigate whether additive modulation of autonomic nervous system by BAT lowers blood pressure (BP) in patients who still suffer from uncontrolled resistant hypertension despite prior renal denervation. METHODS: From 2012 to January 2015, patients treated with BAT for uncontrolled resistant hypertension, who prior received renal denervation were consecutively analyzed in four German centers for hypertension. Analyses of office BP, 24-h ambulatory BP, central hemodynamics, parameters of renal function were performed. RESULTS: A total of 28 patients, who underwent renal denervation at least 5 months before and still suffer from uncontrolled BP, were subsequently treated with BAT. The office SBP decreased from 182 ±â€Š28 to 163 ±â€Š27 mmHg (P < 0.01) with a responder rate of 68% (office SBP reduction ≥10 mmHg) at month 6, whereas the number of prescribed antihypertensive drug classes remained unchanged (6.2 ±â€Š1.5 vs. 6.0 ±â€Š1.7, P = 0.30). Serum creatinine, estimated glomerular filtration rate and cystatin C remained stable (P = 1.00, P = 0.41 and P = 0.22, respectively), whereas albuminuria was significantly reduced by a median of -29% (P = 0.02). Central SBP (-15 ±â€Š24 mmHg, P = 0.047) and end systolic pressure (-14 ±â€Š20 mmHg, P = 0.03) were significantly reduced. CONCLUSION: The present data demonstrate that BAT may exert BP-lowering as well as antiproteinuric effects in patients with prior renal denervation. However, precise evaluation of BAT effects in patients with prior renal denervation will need randomized controlled trials using sham procedures.

The Interaction between Adult Cardiac Fibroblasts and Embryonic Stem Cell-Derived Cardiomyocytes Leads to Proarrhythmic Changes in In Vitro Cocultures.

Transplantation of stem cell-derived cardiomyocytes is one of the most promising therapeutic approaches after myocardial infarction, as loss of cardiomyocytes is virtually irreversible by endogenous repair mechanisms. In myocardial scars, transplanted cardiomyocytes will be in immediate contact with cardiac fibroblasts. While it is well documented how the electrophysiology of neonatal cardiomyocytes is modulated by cardiac fibroblasts of the same developmental stage, it is unknown how adult cardiac fibroblasts (aCFs) affect the function of embryonic stem cell-derived cardiomyocytes (ESC-CMs). To investigate the effects of aCFs on ESC-CM electrophysiology, we performed extra- and intracellular recordings of murine aCF-ESC-CM cocultures. We observed that spontaneous beating behaviour was highly irregular in aCF-ESC-CM cocultures compared to cocultures with mesenchymal stem cells (coefficient of variation of the interspike interval: 40.5 ± 15.2% versus 9.3 ± 2.0%, p = 0.008) and that action potential amplitude and maximal upstroke velocity (V max) were reduced (amplitude: 52.3 ± 1.7 mV versus 65.1 ± 1.5 mV, V max: 7.0 ± 1.0 V/s versus 36.5 ± 5.3 V/s), while action potential duration (APD) was prolonged (APD50: 25.6 ± 1.0 ms versus 16.8 ± 1.9 ms, p < 0.001; APD90: 52.2 ± 1.5 ms versus 43.3 ± 3.3 ms, p < 0.01) compared to controls. Similar changes could be induced by aCF-conditioned medium. We conclude that the presence of aCFs changes automaticity and induces potentially proarrhythmic changes of ESC-CM electrophysiology.

Surgical Experience and Long-term Results of Baroreflex Activation Therapy for Heart Failure With Reduced Ejection Fraction.

The purpose of this publication is to describe the intraoperative experience along with long-term safety and efficacy of the second-generation baroreflex activation therapy (BAT) system in patients with heart failure (HF) and reduced ejection fraction HF (HFrEF). In a randomized trial of New York Heart Association Class III HFrEF, 140 patients were assigned 1:1 to receive BAT plus medical therapy or medical therapy alone. Procedural information along with safety and efficacy data were collected and analyzed over 12 months. Within the cohort of 71 patients randomized to BAT, implant procedure time decreased with experience, from 106 ± 37 minutes on the first case to 83 ± 32 minutes on the third case. The rate of freedom from system- and procedure-related complications was 86% through 12 months, with the percentage of days alive without a complication related to system, procedure, or underlying cardiovascular condition identical to the control group. The complications that did occur were generally mild and short-lived. Overall, 12 months therapeutic benefit from BAT was consistent with previously reported efficacy through 6 months: there was a significant and sustained beneficial treatment effect on New York Heart Association functional Class, quality of life, 6-minute hall walk distance, plasma N-terminal pro-brain natriuretic peptide, and systolic blood pressure. This was true for the full trial cohort and a predefined subset not receiving cardiac resynchronization therapy. There is a rapid learning curve for the specialized procedures entailed in a BAT system implant. BAT system implantation is safe with the therapeutic benefits of BAT in patients with HFrEF being substantial and maintained for at least 1 year.

[Indications for surgery for valvular heart disease]. / Indikationen zur Operation bei kardialen Vitien.

Due to the demographic change, chronic valvular heart disease becomes increasingly important - especially age-related primary diseases of the aortic and mitral valve as well as secondary diseases of the mitral and tricuspid valve caused by other age-related cardiac disorders. Medical treatment is limited to symptom relief by use of diuretics. Specific drugs or drugs with a prognostic benefit are not available. Thus, valve repair or replacement are the key options for treatment of relevant valvular heart disease. While open heart surgery was the only approach for a long time, interventional, catheter-based therapies have evolved in the last decade. This article describes up-to-date recommendations on indications for surgery for the most prevalent valvular heart diseases in adults - aortic stenosis, and aortic, mitral and tricuspid regurgitation).

Neuregulin-1ß induces mature ventricular cardiac differentiation from induced pluripotent stem cells contributing to cardiac tissue repair.

Stem cell-derived cardiomyocytes (CMs) are often electrophysiologically immature and heterogeneous, which represents a major barrier to their in vitro and in vivo application. Therefore, the purpose of this study was to examine whether Neuregulin-1ß (NRG-1ß) treatment could enhance in vitro generation of mature "working-type" CMs from induced pluripotent stem (iPS) cells and assess the regenerative effects of these CMs on cardiac tissue after acute myocardial infarction (AMI). With that purpose, adult mouse fibroblast-derived iPS from α-MHC-GFP mice were derived and differentiated into CMs through NRG-1ß and/or dimethyl sulfoxide (DMSO) treatment. Cardiac specification and maturation of the iPS was analyzed by gene expression array, quantitative real-time polymerase chain reaction, immunofluorescence, electron microscopy, and patch-clamp techniques. In vivo, the iPS-derived CMs or culture medium control were injected into the peri-infarct region of hearts after coronary artery ligation, and functional and histology changes were assessed from 1 to 8 weeks post-transplantation. On differentiation, the iPS displayed early and robust in vitro cardiogenesis, expressing cardiac-specific genes and proteins. More importantly, electrophysiological studies demonstrated that a more mature ventricular-like cardiac phenotype was achieved when cells were treated with NRG-1ß and DMSO compared with DMSO alone. Furthermore, in vivo studies demonstrated that iPS-derived CMs were able to engraft and electromechanically couple to heart tissue, ultimately preserving cardiac function and inducing adequate heart tissue remodeling. In conclusion, we have demonstrated that combined treatment with NRG-1ß and DMSO leads to efficient differentiation of iPS into ventricular-like cardiac cells with a higher degree of maturation, which are capable of preserving cardiac function and tissue viability when transplanted into a mouse model of AMI.

Preconditioning of skeletal myoblast-based engineered tissue constructs enables functional coupling to myocardium in vivo.

OBJECTIVE: Skeletal myoblasts fuse to form functional syncytial myotubes as an integral part of the skeletal muscle. During this differentiation process, expression of proteins for mechanical and electrical integration is seized, which is a major drawback for the application of skeletal myoblasts in cardiac regenerative cell therapy, because global heart function depends on intercellular communication. METHODS: Mechanically preconditioned engineered tissue constructs containing neonatal mouse skeletal myoblasts were transplanted epicardially. A Y-chromosomal specific polymerase chain reaction (PCR) was undertaken up to 10 weeks after transplantation to confirm the presence of grafted cells. Histologic and electrophysiologic analyses were carried out 1 week after transplantation. RESULTS: Cells within the grafted construct expressed connexin 43 at the interface to the host myocardium, indicating electrical coupling, confirmed by sharp electrode recordings. Analyses of the maximum stimulation frequency (5.65 ± 0.37 Hz), conduction velocity (0.087 ± 0.011 m/s) and sensitivity for pharmacologic conduction block (0.736 ± 0.080 mM 1-heptanol) revealed effective electrophysiologic coupling between graft and host cells, although significantly less robust than in native myocardial tissue (maximum stimulation frequency, 11.616 ± 0.238 Hz, P < .001; conduction velocity, 0.300 ± 0.057 m/s, P < .01; conduction block, 1.983 ± 0.077 mM 1-heptanol, P < .001). CONCLUSIONS: Although untreated skeletal myoblasts cannot couple to cardiomyocytes, we confirm that mechanical preconditioning enables transplanted skeletal myoblasts to functionally interact with cardiomyocytes in vivo and, thus, reinvigorate the concept of skeletal myoblast-based cardiac cell therapy.

Electrophysiological integration and action potential properties of transplanted cardiomyocytes derived from induced pluripotent stem cells.

AIMS: Induced pluripotent stem cell-derived cardiomyocytes (iPSCM) are regarded as promising cell type for cardiac cell replacement therapy. We investigated long-term electrophysiological integration and maturation of transplanted iPSCM, which are essential for therapeutic benefit. METHODS AND RESULTS: Murine iPSCM expressing enhanced green fluorescent protein and a puromycin resistance under control of the α-myosin heavy chain promoter were purified by antibiotic selection and injected into adult mouse hearts. After 6-12 days, 3-6 weeks, or 6-8 months, viable slices of recipient hearts were prepared. Slices were focally stimulated by a unipolar electrode placed in host tissue, and intracellular action potentials (APs) were recorded with glass microelectrodes in transplanted cells and neighbouring host tissue within the slices. Persistence and electrical integration of transplanted iPSCM into recipient hearts could be demonstrated at all time points. Quality of coupling improved, as indicated by a maximal stimulation frequency without conduction blocks of 5.77 ± 0.54 Hz at 6-12 days, 8.98 ± 0.38 Hz at 3-6 weeks and 10.82 ± 1.07 Hz at 6-8 months after transplantation. AP properties of iPSCM became more mature from 6-12 days to 6-8 months after transplantation, but still differed significantly from those of host APs. CONCLUSION: Transplanted iPSCM can persist in the long term and integrate electrically into host tissue, supporting their potential for cell replacement therapy. Quality of electrical integration improves between 6-12 days and 6-8 months after transplantation, and there are signs of an electrophysiological maturation. However, even after 6-8 months, AP properties of transplanted iPSCM differ from those of recipient cardiomyocytes.

Hyperaldosteronism is associated with a decrease in number and altered growth factor expression of endothelial progenitor cells in rats.

BACKGROUND: Aldosterone plays a role in hypertension, the pathogenesis of heart failure and vascular injury. However, little information exists about the possible influence of aldosterone on bone marrow derived endothelial progenitor cells (EPC), which are involved in the repair of damaged endothelium. This study was designed to determine the long- term in vivo influence of aldosterone on the number of EPC. METHODS: Male Wistar rats were equipped with a subcutaneous pump which released aldosterone (n=20) or placebo (n=20) over 28 days. The animals were either fed with or without the aldosterone antagonist spironolactone (each n=10). EPC were identified by the uptake of ac-LDL and BS-1. The expression of VEGF-2 receptor, VEGF, HGF, SDF1 and the mineralocorticoid receptor (MR) in EPC was assessed by quantitative PCR. Finally, VEGF concentration was measured in the serum of all animals by ELISA. RESULTS: The total number of EPC was significantly lowered by chronic aldosterone treatment. Spironolactone compensated the effect and lead to a 2-fold increase. While the SDF1 mRNA was not affected by aldosterone, HGF, MR2 and VEGF receptor mRNA were significantly downregulated in EPC. Strikingly spironolactone not only leads to increases in the mRNA expression in hyper-aldosteronemic animals but also exhibited significant increases above the control levels. CONCLUSION: The present data indicate that high levels of aldosterone impair the function and reduce the numbers of EPC and lead to a downregulation of VEGF and the VEGF receptor in vivo. Spironolactone antagonized these effects. MR blockade by spironolactone may therefore represent a future tool to enhance the response to cell based therapy.

Influence of cell treatment with PDGF-BB and reperfusion on cardiac persistence of mononuclear and mesenchymal bone marrow cells after transplantation into acute myocardial infarction in rats.

Bone marrow cells are used for cell therapy after myocardial infarction (MI) with promising results. However, cardiac persistence of transplanted cells is rather low. Here, we investigated strategies to increase the survival and cardiac persistence of mononuclear (MNC) and mesenchymal (MSC) bone marrow cells transplanted into infarcted rat hearts. MNC and MSC (male Fischer 344 rats) were treated with different doses of PDGF-BB prior to intramyocardial injection into border zone of MI (syngeneic females, permanent LAD ligation) and hearts were harvested after 5 days and 3 weeks. In additional experiments, untreated MNC and MSC were injected immediately after permanent or temporary LAD ligation and hearts were harvested after 48 h, 5 days, 3 weeks, and 6 weeks. DNA of the hearts was isolated and the number of donor cells was determined by quantitative real-time PCR with Y chromosome-specific primers. There was a remarkable though not statistically significant (p = 0.08) cell loss of approximately 46% between 5 days and 3 weeks in the control group, which was completely inhibited by treatment with high dose of PDGF-BB. Forty-eight hours after reperfusion only 10% of injected MSC or 1% for MNC were found in the heart, decreasing to 1% for MSC and 0.5% for MNC after 6 weeks. These numbers were lower than after permanent LAD ligation for both MNC and MSC at all time points studied. Treatment with PDGF-BB seems to prevent loss of transplanted bone marrow cells at later times presumably by inhibition of apoptosis, while reperfusion of the occluded artery enhances cell loss at early times putatively due to enhanced early wash-out. Further investigations are needed to substantially improve the persistence and survival of grafted bone marrow cells in infarcted rat hearts, in order to fully explore the therapeutic potential of this novel treatment modality for myocardial repair.

Physiological differences between transplanted and host tissue cause functional decoupling after in vitro transplantation of human embryonic stem cell-derived cardiomyocytes.

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) might provide cells to repopulate injured myocardium. Electrical coupling of these cells to the host myocardium is a prerequisite for improved functionality. The aim of this study was to investigate electrical interaction of hESC-CMs with myocardial tissue and to identify factors challenging functional integration. Beating clusters containing hESC-CMs were cocultured in vitro with viable slices of late-stage embryonic murine ventricles. Field potentials recorded with micro-electrode arrays and video data were analyzed. The effects of heptanol, electrical pacing, beta-adrenergic, and muscarinic stimulation on coupling were studied. Beating clusters integrated morphologically and functionally resulting in a synchronized beating pattern after two to four days of coculture. Heptanol-induced conduction block between transplanted cells and host tissue and immunoreactivity for connexin43 suggested electrical coupling via gap junctions. Beta-adrenergic or muscarinic stimulation induced uncoupling and arrhythmias probably due to genetically determined differences of hormonal modulation of spontaneous beating rates of transplanted cells and host tissue. HESC-CMs can integrate functionally and develop synchronized beating. Interventions unraveling the different electrophysiological properties of transplanted and host tissue induce functional disintegration. Successful cellular replacement has to improve coupling but should also aim to transplant cardiomyocytes with similar electrophysiological properties as the host tissue.

Entrapment of embryonic stem cells-derived cardiomyocytes in macroporous biodegradable microspheres: preparation and characterization.

Embryonic Stem (ES) cells-derived cardiomyocytes can possibly be applied for cell therapy of diseases such as heart failure. Biodegradable scaffolds will significantly improve the expansion of sufficient functional ES cell-derived cardiomyocytes and may also increase the survival rate of cardiomyocytes after their transplantation. In the present study, we cultivated cardiomyocytes isolated from a transgenic a-myosin heavy chain (alpha-MHC) ES cell lineage expressing both puromycin resistance and enhanced green fluorescent protein (EGFP) under the control of the alpha-MHC promoter in macroporous gelatine microspheres using small-scale bioreactors and proved that cardiomyocytes function after their cultivation in micropsperes. The average number of cultivated cells per microsphere was optimised once the most suitable agitation conditions and the optimal timeframe of cultivation were identified. Our study shows that 72% of CultiSpher-S beads were colonised by cardiomyocytes under optimal conditions. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that colonization of the beads was not limited to the surface, but that cells also invaded the inner surfaces of the microspheres. Electrophysiological experiments demonstrated that the action potentials (APs) of alpha-MHC(+) cardiomyocytes entrapped in microspheres were identical to action potentials of control cells. This attractive approach for cultivation and expansion of functional cardiomyocytes in biodegradable macroporous may offer a perspective for higher transplantation efficiencies of ES cell-derived cardiomyocytes.

Role of balloon occlusion for mononuclear bone marrow cell deposition after intracoronary injection in pigs with reperfused myocardial infarction.

AIMS: In clinical studies on cell therapy for acute myocardial infarction (MI), cells are usually applied by intracoronary infusion with balloon (IC/B). To test the utility of balloon occlusion, mononuclear bone marrow cell (MNC) retention after intracoronary infusion without balloon (IC/noB) was compared with IC/B and intramyocardial (IM) injection. METHODS AND RESULTS: Four hours after LAD ligation in male pigs, reperfusion was allowed (confirmed by coronary angiography). Five days later, 1 x 10(8) autologous (111)Indium-labelled MNC were injected IC/noB (n = 4), IC/B (n = 4), or IM (n = 4). At 1 h the fraction of injected MNC that was detected in the heart was 4.1 +/- 1.1% after IC/noB injection, 6.1 +/- 2.5% after IC/B injection (P = 0.19), and 20.7 +/- 2.3% after IM injection (P < 0.001 vs. IC/noB and IC/B). At 24 h it was 3.0 +/- 0.6% (IC/noB), 3.3 +/- 0.5% (IC/B, P = 0.43), and 15.0 +/- 3.1% (IM, P < 0.001 vs. IC/noB and IC/B). Dynamic scintigrammes during each of four consecutive IC/B injections showed a rapid 19.6 +/- 8.0% cell loss during balloon inflation (no-flow period, phase 1) and a rapid 36.6 +/- 17.8% cell loss after balloon deflation (re-flow period, phase 2). After each of four consecutive IC/noB injections the peak cell deposit was lower, followed by one phase of rapid cell loss (30.9 +/- 11.0% after 6 min). After IM injection only a slow linear cell loss was observed (9.7% per h). In histology, PKH-67 labelled cells only rarely had passed the endothelial barrier after 24 h after IC injection, while they were exclusively found in the interstitium after IM injection. CONCLUSION: The observation of a similar cell persistence after IC injections with and without balloon occlusion suggests that the balloon procedures currently applied in clinical studies are not necessary for cell deposit. If longer term persistence of cells plays a role for the clinical benefit of cardiac cell therapy, IM injection may be superior to IC applications.