P. A. Doevendans

Cardiac tissue engineering using tissue printing technology and human cardiac progenitor cells.

Tissue engineering is emerging as a potential therapeutic approach to overcome limitations of cell therapy, like cell retention and survival, as well as to mechanically support the ventricular wall and thereby prevent dilation. Tissue printing technology (TP) offers the possibility to deliver, in a defined and organized manner, scaffolding materials and living cells. The aim of our study was to evaluate the combination of TP, human cardiac-derived cardiomyocyte progenitor cells (hCMPCs) and biomaterials to obtain a construct with cardiogenic potential for in vitro use or in vivo application. With this approach, we were able to generate an in vitro tissue with homogenous distribution of cells in the scaffold. Cell viability was determined after printing and showed that 92% and 89% of cells were viable at 1 and 7 days of culturing, respectively. Moreover, we demonstrated that printed hCMPCs retained their commitment for the cardiac lineage. In particular, we showed that 3D culture enhanced gene expression of the early cardiac transcription factors Nkx2.5, Gata-4 and Mef-2c as well as the sarcomeric protein TroponinT. Printed cells were also able to migrate from the alginate matrix and colonize a matrigel layer, thereby forming tubular-like structures. This indicated that printing can be used for defined cell delivery, while retaining functional properties.

A prospective validation of the HEART score for chest pain patients at the emergency department

BACKGROUND The focus of the diagnostic process in chest pain patients at the emergency department is to identify both low and high risk patients for an acute coronary syndrome (ACS). The HEART score was designed to facilitate this process. This study is a prospective validation of the HEART score. METHODS A total of 2440 unselected patients presented with chest pain at the cardiac emergency department of ten participating hospitals in The Netherlands. The HEART score was assessed as soon as the first lab results and ECG were obtained. Primary endpoint was the occurrence of major adverse cardiac events (MACE) within 6 weeks. Secondary endpoints were (i) the occurrence of AMI and death, (ii) ACS and (iii) the performance of a coronary angiogram. The performance of the HEART score was compared with the TIMI and GRACE scores. RESULTS Low HEART scores (values 0-3) were calculated in 36.4% of the patients. MACE occurred in 1.7%. In patients with HEART scores 4-6, MACE was diagnosed in 16.6%. In patients with high HEART scores (values 7-10), MACE occurred in 50.1%. The c-statistic of the HEART score (0.83) is significantly higher than the c-statistic of TIMI (0.75)and GRACE (0.70) respectively (p<0.0001). CONCLUSION The HEART score provides the clinician with a quick and reliable predictor of outcome, without computer-required calculating. Low HEART scores (0-3), exclude short-term MACE with >98% certainty. In these patients one might consider reserved policies. In patients with high HEART scores (7-10) the high risk of MACE may indicate more aggressive policies.

Cardiomyocyte progenitor cell-derived exosomes stimulate migration of endothelial cells

•  Cell therapy •  The paracrine hypothesis •  Exosomes •  Collection CMPC secreted exosomes •  Conditioned medium and exosomes in in vitro scratch wound assay •  Exosomal signalling via MMP and EMMPRIN •  Discussion

Preservation of Left Ventricular Function and Attenuation of Remodeling After Transplantation of Human Epicardium-Derived Cells Into the Infarcted Mouse Heart

Background— Proper development of compact myocardium, coronary vessels, and Purkinje fibers depends on the presence of epicardium-derived cells (EPDCs) in embryonic myocardium. We hypothesized that adult human EPDCs might partly reactivate their embryonic program when transplanted into ischemic myocardium and improve cardiac performance after myocardial infarction. Methods and Results— EPDCs were isolated from human adult atrial tissue. Myocardial infarction was created in immunodeficient mice, followed by intramyocardial injection of 4×105 enhanced green fluorescent protein–labeled EPDCs (2-week survival, n=22; 6-week survival, n=15) or culture medium (n=24 and n=18, respectively). Left ventricular function was assessed with a 9.4T animal MRI unit. Ejection fraction was similar between groups on day 2 but was significantly higher in the EPDC-injected group at 2 weeks (short term), as well as after long-term survival at 6 weeks. End-systolic and end-diastolic volumes were significantly smaller in the EPDC-injected group than in the medium-injected group at all ages evaluated. At 2 weeks, vascularization was significantly increased in the EPDC-treated group, as was wall thickness, a development that might be explained by augmented DNA-damage repair activity in the infarcted area. Immunohistochemical analysis showed massive engraftment of injected EPDCs at 2 weeks, with expression of α-smooth muscle actin, von Willebrand factor, sarcoplasmic reticulum Ca2+-ATPase, and voltage-gated sodium channel (α-subunit; SCN5a). EPDCs were negative for cardiomyocyte markers. At 6-weeks survival, wall thickness was still increased, but only a few EPDCs could be detected. Conclusions— After transplantation into ischemic myocardium, adult human EPDCs preserve cardiac function and attenuate ventricular remodeling. Autologous human EPDCs are promising candidates for clinical application in infarcted hearts.

Progenitor cells isolated from the human heart: a potential cell source for regenerative therapy

Background. In recent years, resident cardiac progenitor cells have been identified in, and isolated from the rodent heart. These cells show the potential to form cardiomyocytes, smooth muscle cells, and endothelial cells in vitro and in vivo and could potentially be used as a source for cardiac repair. However, previously described cardiac progenitor cell populations show immature development and need co-culture with neonatal rat cardiomyocytes in order to differentiate in vitro. Here we describe the localisation, isolation, characterisation, and differentiation of cardiomyocyte progenitor cells (CMPCs) isolated from the human heart.Methods. hCMPCs were identified in human hearts based on Sca-1 expression. These cells were isolated, and FACS, RT-PCR and immunocytochemistry were used to determine their baseline characteristics. Cardiomyogenic differentiation was induced by stimulation with 5-azacytidine.Results. hCMPCs were localised within the atria, atrioventricular region, and epicardial layer of the foetal and adult human heart. In vitro, hCMPCs could be induced to differentiate into cardiomyocytes and formed spontaneously beating aggregates, without the need for co-culture with neonatal cardiomyocytes.Conclusion. The human heart harbours a pool of resident cardiomyocyte progenitor cells, which can be expanded and differentiated in vitro. These cells may provide a suitable source for cardiac regeneration cell therapy. (Neth Heart J 2008;16: 163-9.)

Renal denervation: a new treatment option in resistant arterial hypertension.

Hypertension is one of the most prevalent cardiovascular risk factors. Despite this high prevalence and a broad availability of effective pharmaceutical agents, a significant proportion of patients do not reach treatment goals. Partly this can be explained by secondary causes of hypertension or non-compliance of patients. Nevertheless, a subgroup of patients can be diagnosed with ‘resistant hypertension’. Activation of the sympathetic nervous system is known to be an important factor in the development and progression of systemic hypertension. In this context, a percutaneous, catheter–based approach has been developed using radiofrequency energy to disrupt renal sympathetic nerves. The first studies have shown this technique to be safe, illustrated by a lack of vascular or renal injury. More importantly, catheter-based renal nerve ablation resulted in a significant reduction in blood pressure on top of traditional medical therapy. Additional to the encouraging effects shown on hypertension, a positive influence of this intervention in other conditions, characterised by sympathetic overactivation, may be expected. Though this technique seems promising, further studies are needed to address long-term safety and efficacy of renal denervation in hypertension and other disease states.

Cardiac stem cell therapy to modulate inflammation upon myocardial infarction

BACKGROUND After myocardial infarction (MI) a local inflammatory reaction clears the damaged myocardium from dead cells and matrix debris at the onset of scar formation. The intensity and duration of this inflammatory reaction are intimately linked to post-infarct remodeling and cardiac dysfunction. Strikingly, treatment with standard anti-inflammatory drugs worsens clinical outcome, suggesting a dual role of inflammation in the cardiac response to injury. Cardiac stem cell therapy with different stem or progenitor cells, e.g. mesenchymal stem cells (MSC), was recently found to have beneficial effects, mostly related to paracrine actions. One of the suggested paracrine effects of cell therapy is modulation of the immune system. SCOPE OF REVIEW MSC are reported to interact with several cells of the immune system and could therefore be an excellent means to reduce detrimental inflammatory reactions and promote the switch to the healing phase upon cardiac injury. This review focuses on the potential use of MSC therapy for post-MI inflammation. To understand the effects MSC might have on the post-MI heart the cellular and molecular changes in the myocardium after MI need to be understood. MAJOR CONCLUSIONS By studying the general pathways involved in immunomodulation, and examining the interactions with cell types important for post-MI inflammation, it becomes clear that MSC treatment might provide a new therapeutic opportunity to improve cardiac outcome after acute injury. GENERAL SIGNIFICANCE Using stem cells to target the post-MI inflammation is a novel therapy which could have considerable clinical implications. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

Human versus porcine mesenchymal stromal cells: phenotype, differentiation potential, immunomodulation and cardiac improvement after transplantation

Although mesenchymal stromal cells (MSCs) have been applied clinically to treat cardiac diseases, it is unclear how and to which extent transplanted MSCs exert their beneficial effects. To address these questions, pre‐clinical MSC administrations are needed for which pigs appear to be the species of choice. This requires the use of porcine cells to prevent immune rejection. However, it is currently unknown to what extent porcine MSCs (pMSCs) resemble human MSCs (hMSCs). Aim of this study was to compare MSC from porcine bone marrow (BM) with human cells for phenotype, multi‐lineage differentiation potential, immune‐modulatory capacity and the effect on cardiac function after transplantation in a mouse model of myocardial infarction. Flow cytometric analysis revealed that pMSC expressed surface antigens also found on hMSC, including CD90, MSCA‐1 (TNAP/W8B2 antigen), CD44, CD29 and SLA class I. Clonogenic outgrowth was significantly enriched following selection of CD271+ cells from BM of human and pig (129 ± 29 and 1961 ± 485 fold, respectively). hMSC and pMSC differentiated comparably into the adipogenic, osteogenic or chondrogenic lineages, although pMSC formed fat much faster than hMSC. Immuno‐modulation, an important feature of hMSC, was clearly demonstrated for pMSC when co‐cultured with porcine peripheral blood cells stimulated with PMA and pIL‐2. Finally, pMSC transplantation after myocardial infarction attenuated adverse remodelling to a similar extent as hMSC when compared to control saline injection. These findings demonstrate that pMSCs have comparable characteristics and functionality with hMSCs, making reliable extrapolation of pre‐clinical pMSC studies into a clinical setting very well possible.

Bone marrow cell therapy after acute myocardial infarction: the HEBE trial in perspective, first results.

AbstractDuring the last decennium, the role of bone marrow mononuclear cells (BMMC) has been underscored in the healing process after acute myocardial infarction (AMI). Although these cells improve left ventricular recovery after AMI in experimental studies, results from large-scale randomised trials investigating BMMC therapy in patients with AMI have shown contradictory results. To address this issue the HEBE study was designed, a multicentre, randomised trial, evaluating the effects of intracoronary infusion of BMMCs and the effects of intracoronary infusion of peripheral blood mononuclear cells after primary percutaneous coronary intervention. The primary endpoint of the HEBE trial is the change in regional myocardial function in dysfunctional segments at four months relative to baseline, based on segmental analysis as measured by magnetic resonance imaging. The results from the HEBE trial will provide detailed information about the effects of intracoronary BMMC therapy on post-infarct left ventricular recovery. In addition, further analysis of the data and material obtained may provide important mechanistic insights into the contribution of BMMCs to natural recovery from AMI as well as the response to cell therapy. This may significantly contribute to the development of improved cell-based therapies, aiming at optimising post-infarct recovery and preventing heart failure. (Neth Heart J 2008;16:436-9.)

Left ventricular pressure–volume measurements in mice: Comparison of closed–chest versus open–chest approach

AbstractObjectiveWe investigated whether in vivo closed–chest left ventricular pressure–volume measurements would yield similar values for LV hemodynamics compared with open–chest PV measurements under several anesthetics.MethodsThe right common carotid of C57Bl/6 mice was cannulated with a combined pressure–conductance catheter and inserted retrogradely into the left ventricle in the closed–chest model. The open–chest model consisted of an abdominal approach involving the opening of the thoracic cavity by transverse opening of the diaphragm and ventricular catheterization by apical stab. Measurements were performed under urethane or pentobarbital intraperitoneal injection anesthesia.ResultsCardiac function in the open–chest model was characterized by larger ejection fraction and stroke volume with a leftward shift in ventricular volume compared to the closed–chest model. Further observed characteristics include low endsystolic pressure and arterial–ventricular coupling mismatch in the openchest model. Arrhythmias were not detected in either model.ConclusionMurine cardiac function determination via open–chest or closed–chest protocols is sensitive, reproducible and comparable. The choice for open– or closed–chest pressure–volume measurements in mice depends on the aims of the study.