Benefit of extracorporeal membrane oxygenation in myocardial infarction-induced cardiogenic shock.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is frequently used for emergency support in patients with profound cardiogenic shock (CS) of all etiologies. However, no controlled study investigating ECMO in myocardial infarction (AMI)-induced CS is available. METHODS: Retrospective analysis of patients experiencing AMI induced CS; ECMO therapy vs. non ECMO therapy. A total of 476 patients with AMI-induced CS were investigated. One hundred twenty-seven patients (26.7%) received emergency veno-arterial ECMO support, 349 patients did not receive ECMO support. Patients were propensity score matched based on relevant clinical and laboratory factors and revealed 127 matched pairs. RESULTS: Mean age of patients was 65.0±12.3 years and mean Syntax score was 25.9±7.3 in the full unmatched patient population. Survival at 1, 3 and 5 years after CS was 45.6%, 43.5%, and 41.3% in the ECMO group and 17.4%, 15.8%, and 14.9% in the full unmatched control group (log-rank: P<0.001). After propensity score matching, 1-, 3-, and 5-year survival was 14.4%, 13.5%, and 11.2% in the matched control group (P<0.001). Cox regression analysis identified ECMO support (HR: 2.57; 95% CI: 1.89-3.50; P<0.001) and completeness of revascularization (HR: 1.89; 95% CI: 1.74-2.34, P=0.003) to be independent predictors for long term survival. CONCLUSIONS: Extracorporeal life support by ECMO significantly increased survival in patients with AMI-induced CS. ECMO insertion increased survival probability 2.57-fold and should be considered as first line treatment in patients with profound AMI-induced CS.

Determinants and prognostic relevance of aortic stiffness in patients with recent ST-elevation myocardial infarction.

The association between aortic stiffness, cardiovascular risk factors and prognosis in patients with recent ST-elevation myocardial infarction (STEMI) is poorly understood. We analyzed the relationship between cardiovascular risk factors and arterial stiffening and assessed its prognostic significance in patients with recent STEMI. We prospectively enrolled 408 consecutive patients who sustained a first STEMI and underwent primary percutaneous coronary intervention (PPCI). Aortic pulse wave velocity (PWV), the most widely used measure of aortic stiffness, was determined by the transit-time method using velocity-encoded, phase-contrast cardiac magnetic resonance imaging. Patient characteristics were acquired at baseline and major adverse cardiac and cerebrovascular events (MACCE) were assessed at 13 [interquartile range (IQR) 12-31] months. Cox regression- and logistic regression analysis were performed to explore predictors of aortic stiffness and MACCE. Median aortic PWV was 6.6 m/s (IQR 5.6-8.3 m/s). In multivariable analysis, age [odds ratio (OR) 1.10, 95% confidence interval (CI), 1.08-1.14, p < 0.001] and hypertension (OR 2.45, 95% CI, 1.53-3.91, p < 0.001) were independently associated with increased PWV. Sex, diabetes, smoking status, dyslipidemia, and obesity were not significantly associated with PWV in adjusted analysis (all p > 0.05). High PWV significantly and independently predicted occurrence of MACCE in adjusted analysis [hazard ratio (HR) 2.45, 95% CI 1.19-5.04, p = 0.014]. In patients with recent STEMI, the impact of classical cardiovascular risk factors on aortic stiffness is mainly dependent on age and increased blood pressure. Increased aortic stiffness is associated with adverse clinical outcome post-STEMI, suggesting it as a relevant therapeutic target in this population. Trial (NCT04113356).

Association of plasma interleukin-6 with infarct size, reperfusion injury, and adverse remodelling after ST-elevation myocardial infarction.

AIMS: Little is known about the clinical relevance of interleukin (IL)-6 in patients with acute ST-elevation myocardial infarction (STEMI). This study examined the possible associations of plasma IL-6 concentrations with infarct size (IS), reperfusion injury and adverse left ventricular remodelling (LVR), in STEMI patients treated with primary percutaneous coronary intervention (PCI). METHODS AND RESULTS: We prospectively included 170 consecutive STEMI patients (median age 57 years, 14% women) treated with primary PCI between 2017 and 2019. Blood samples for biomarker analyses including IL-6 were collected on Day 2. Left ventricular ejection fraction (LVEF), IS, and reperfusion injury [microvascular obstruction (MVO) and intramyocardial haemorrhage (IMH)] were determined using cardiac magnetic resonance (CMR) imaging on Day 4. Left ventricular remodelling was defined as ≥10% increase in left ventricular end-diastolic volume from baseline to 4 months CMR follow-up. Patients with IL-6 concentrations ≥median (17 ng/L) showed a significantly lower LVEF (43% vs. 52%, P < 0.001), larger IS (22% vs. 13%, P < 0.001), larger MVO (1.9% vs. 0.0%, P < 0.001), and more frequent IMH (52% vs. 18%, P < 0.001). Left ventricular remodelling was more common in patients with IL-6 ≥ median (24% vs. 9%, P = 0.005). In both linear and binary multivariable regression analyses, IL-6 remained independently associated with lower LVEF [odds ratio (OR): 0.10, 95% confidence interval (CI) 0.02-0.42, P = 0.002], larger IS (OR: 5.29, 95% CI 1.52-18.40, P = 0.009), larger MVO (OR: 5.20, 95% CI 1.30-20.85, P = 0.020), with presence of IMH (OR: 3.73, 95% CI 1.27-10.99, P = 0.017), and adverse LVR (OR: 2.72, 95% 1.06-6.98, P = 0.038). CONCLUSIONS: High concentrations of circulating plasma IL-6 on Day 2 after STEMI were independently associated with worse myocardial function, larger infarct extent, more severe reperfusion injury, and a higher likelihood for LVR, suggesting IL-6 as a useful biomarker of more serious outcome and potential therapeutic target. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT04113356;NCT04113356.

Association of Myocardial Injury With Serum Procalcitonin Levels in Patients With ST-Elevation Myocardial Infarction.

Importance: Myocardial tissue injury due to acute ST-elevation myocardial infarction (STEMI) initiates an inflammatory response that leads to a release of systemic inflammatory biomarkers, including C-reactive protein (CRP) and white blood cells, consequently reducing the usefulness of these routine biomarkers for identifying concomitant infections. The clinical role of procalcitonin (PCT), a promising marker of bacterial infection, to detect concomitant infection in acute STEMI is unknown, mainly because it is unclear whether myocardial injury per se induces systemic PCT release. Objective: To investigate the release of serum PCT in the acute setting of STEMI (24 and 48 hours after primary percutaneous coronary intervention) and to elucidate any associations with myocardial injury markers through a comprehensive assessment by cardiac magnetic resonance (CMR) imaging. Design, Setting, and Participants: This prospective cohort study conducted between 2016 and 2018 included 141 consecutive patients with STEMI treated with primary percutaneous coronary intervention. Concentrations of PCT, high-sensitivity CRP (hs-CRP), and high-sensitivity cardiac troponin T (hs-cTnT) and white blood cell counts were measured serially 24 and 48 hours after infarct. Exposures: Acute STEMI and primary percutaneous coronary intervention. Main Outcomes and Measures: The association of PCT and typical inflammatory marker levels with CMR-determined myocardial damage was assessed. Infarct size, extent of microvascular obstruction, and occurrence of intramyocardial hemorrhage as determined by CMR within the first week following STEMI were also evaluated. Results: In total, 141 patients with STEMI (117 men [83%]) having a median age of 56 years (interquartile range, 50-66 years) were included. The median PCT concentration was 0.07 µg/L (interquartile range, <0.06-0.11 µg/L) 24 hours after intervention and 0.07 µg/L (interquartile range, <0.06-0.09 µg/L) 48 hours after intervention. Whereas hs-CRP and hs-cTnT levels and white blood cell counts were significantly correlated with CMR markers of myocardial damage at both 24 and 48 hours after intervention, the PCT level showed no significant correlation with infarct size (at 24 hours: r = 0.07; P = .40; at 48 hours: r = 0.13; P = .12) or with microvascular obstruction (at 24 hours: r = -0.03; P = .75; at 48 hours: r = 0.09; P = .30). Furthermore, PCT levels at 24 hours (odds ratio, 1.25; 95% CI, 0.63-2.48; P = .52) and 48 hours (odds ratio, 1.56; 95% CI, 0.72-3.41; P = .26) were not significantly associated with the presence of intramyocardial hemorrhage. Conclusions and Relevance: In the acute phase after percutaneous coronary intervention for STEMI, circulating PCT levels remained unassociated with the extent of myocardial and microvascular tissue damage as visualized by CMR imaging.

Extracorporeal Life Support in Myocardial Infarction-Induced Cardiogenic Shock: Weaning Success.

BACKGROUND: Outcome data of patients with acute myocardial infarction (AMI)-induced cardiogenic shock (CS) receiving extracorporeal life support (ECLS) are sparse. METHODS: A consecutive series of 106 patients with AMI-induced CS receiving ECLS was evaluated regarding ECLS weaning success, hospital mortality, and long-term outcome. The Intraaortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) risk score was applied, and multivariable Cox regression analysis was performed. RESULTS: Mean patient age was 58.2 ± 11.2 years, and 78.3% were men. In 34 patients (32.1%), ECLS was implemented during ongoing cardiopulmonary resuscitation. De novo AMI was present in 58 patients (54.7%), and percutaneous coronary intervention complications were causative among 48 patients (45.3%). Multivessel coronary artery disease was diagnosed among 73.6% with mean Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) scores of 30.8 ± 4.8. Actuarial survival was 54.4% at 30 days, 42.2% at 1 year, and 38.0% at 5 years and was significantly higher among patients with low and intermediate IABP-SHOCK II risk scores at ECLS onset (log-rank P = .017). ECLS weaning with curative intention after a mean perfusion time of 6.6 ± 5.1 days was feasible in 51 patients (48.1%) and more likely among patients with complete revascularization (P = .026). Multivariable Cox regression analysis identified complete revascularization (hazard ratio, 2.38; 95% confidence interval, 1.1 to 5.1; P = .028) and absence of relevant mitral regurgitation at ECLS discontinuation (hazard ratio, 2.71; 95% confidence interval, 1.2 to 6.0; P = .014) to be associated with beneficial long-term survival after ECLS discontinuation. CONCLUSIONS: Emergency ECLS is a valuable option among patients with AMI-induced CS with low and intermediate IABP-SHOCK II risk scores. ECLS weaning is manageable, but additional revascularization of all nonculprit lesions is mandatory after ECLS implementation.

Femoral access site closure without prior femoral angiography : A retrospective analysis.

AIMS AND BACKGROUND: Although guideline recommendations have shifted towards a transradial route, femoral puncture is still an established vascular access, especially for complex coronary interventions. The FemoSeal™ vascular closure device (FVCD) helps to reduce femoral compression time and access site complications after removal of the catheter sheath. To ensure safe use, an angiography of the femoral artery prior to FVCD deployment is recommended by the manufacturer. We postulate that omitting this angiography does not relevantly increase the risk for vascular complications. METHODS AND RESULTS: In this retrospective analysis of an all-comers population (n = 1923) including patients receiving a percutaneous coronary intervention (PCI), we could show that combined vascular complication rates without femoral angiography were low (primary endpoint 4.6%) and comparable to a randomized clinical trial that did perform angiography of the vascular access site in a cohort of patients receiving diagnostic coronary angiography only. In addition to this analysis, we could demonstrate that patients with an acute coronary syndrome, receiving periprocedural anticoagulation or anti-platelet therapy had an increased risk for the formation of arterial pseudoaneurysms; however, we did not observe any ischemic vascular event after FVCD deployment. CONCLUSION: Closure of the femoral access site after coronary angiography using the FVCD can be safely performed without femoral angiography; however, due to an increased risk for the formation of pseudoaneurysms we recommend the transradial access in situations with increased bleeding risk.

Reversal of tumor acidosis by systemic buffering reactivates NK cells to express IFN-γ and induces NK cell-dependent lymphoma control without other immunotherapies.

Like other immune cells, natural killer (NK) cells show impaired effector functions in the microenvironment of tumors, but little is known on the underlying mechanisms. Since lactate acidosis, a hallmark of malignant tissue, was shown to contribute to suppression of effective antitumor immune responses, we investigated the impact of tissue pH and lactate concentration on NK-cell functions in an aggressive model of endogenously arising B-cell lymphoma. The progressive loss of IFN-γ production by NK cells observed during development of this disease could be ascribed to decreased pH values and lactate accumulation in the microenvironment of growing tumors. Interestingly, IFN-γ expression by lymphoma-derived NK cells could be restored by transfer of these cells into a normal micromilieu. Likewise, systemic alkalization by oral delivery of bicarbonate to lymphoma-developing mice was capable of enhancing IFN-γ expression in NK cells and increasing the NK-cell numbers in the lymphoid organs where tumors were growing. By contrast, NK-cell cytotoxicity was dampened in vivo by tumor-dependent mechanisms that seemed to be different from lactate acidosis and could not be restored in a normal milieu. Most importantly, alkalization and the concomitant IFN-γ upregulation in NK cells were sufficient to significantly delay tumor growth without any other immunotherapy. This effect was strictly dependent on NK cells.

Gliptins and their target dipeptidyl peptidase 4: implications for the treatment of vascular disease.

Gliptins are accepted as a standard therapy for diabetes mellitus today. By inhibition of the enzyme dipeptidyl peptidase 4 (DPP4), gliptins prolong the GLP1-dependent insulin secretion in the pancreatic ß-cells and thus support physiological blood glucose control. Various studies have now raised hope for an additional protective effect of pharmacological DPP4 inhibition in vascular diseases. Besides GLP1, especially, the inhibition of SDF1 cleavage has been shown to depict a relevant mechanism to enhance endothelial regeneration and reduce atherosclerosis progression via the SDF1-CXCR4 axis. Furthermore, several clinical trials have now shown an excellent safety profile of gliptin therapy in cardiovascular risk patients. In this review, we give a comprehensive overview on DPP4-dependent vascular functions and pathophysiological mechanisms with a detailed discussion of the underlying molecular mechanisms. We further analyse the role of pharmacological DPP4 inhibitors and their potential therapeutic impact on endothelial function and regeneration besides their effect during atherosclerosis development. Finally, we discuss presently available data from in vitro and in vivo studies with respect to the results of the recent clinical trials in diabetic and non-diabetic patients.

FDG-PET reveals improved cardiac regeneration and attenuated adverse remodelling following Sitagliptin + G-CSF therapy after acute myocardial infarction.

AIMS: Dual therapy comprising G-CSF for mobilization of bone marrow-derived progenitor cells (BMPCs), with simultaneous pharmacological inhibition of dipeptidylpeptidase-IV for enhanced myocardial recruitment of circulating BMPC via the SDF-1α/CXCR4-axis, has been shown to improve survival after acute myocardial infarction (AMI). Using an innovative method to provide non-invasive serial in vivo measurements and information on metabolic processes, we aimed to substantiate the possible effects of this therapeutic concept on cardiac remodelling after AMI using 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (FDG-PET). METHODS AND RESULTS: AMI was induced in C57BL/6 mice by performing surgical ligation of the left anterior descending artery in these mice. Animals were then treated with granulocyte-colony stimulating factor + Sitagliptin (GS) or placebo for a duration of 5 days following AMI. From serial PET scans, we verified that the infarct size in GS-treated mice (n = 13) was significantly reduced at Day 30 after AMI when compared with the mice receiving placebo (n = 10). Analyses showed a normalized FDG uptake on Day 6 in GS-treated mice, indicating an attenuation of the cardiac inflammatory response to AMI in treated animals. Furthermore, flow cytometry showed a significant increase in the anti-inflammatory M2-macrophages subpopulation in GS-treated animals. In comparing GS treated with placebo animals, those receiving GS-therapy showed a reduction in myocardial hypertrophy and left ventricular dilatation, which indicates the beneficial effect of GS treatment on cardiac remodelling. Remarkably, flow cytometry and immunohistochemistry showed an increase of myocardial c-kit positive cells in treated mice (n = 12 in both groups). CONCLUSION: Using the innovative method of micro-PET for non-invasive serial in vivo measurements of metabolic myocardial processes in mice, we were able to provide mechanistic evidence that GS therapy improves cardiac regeneration and reduces adverse remodelling after AMI.

Sitagliptin plus granulocyte colony-stimulating factor in patients suffering from acute myocardial infarction: A double-blind, randomized placebo-controlled trial of efficacy and safety (SITAGRAMI trial).

OBJECTIVE: In animal models, G-CSF based progenitor cell mobilization combined with a DPP4 inhibitor leads to increased homing of bone marrow derived progenitor cells to the injured myocardium via the SDF1/CXCR4 axis resulting in improved ejection fraction and survival after acute myocardial infarction (AMI). RESEARCH DESIGN AND METHODS: After successful revascularization in AMI, 174 patients were randomized 1:1 in a multi-centre, prospective, placebo-controlled, parallel group, double blind, phase III efficacy and safety trial to treatment with G-CSF and Sitagliptin (GS) or placebo. Diabetic and non-diabetic patients were included in our trial. The primary efficacy endpoint hierarchically combined global left and right ventricular ejection fraction changes from baseline to 6 months of follow-up (ΔLVEF, ΔRVEF), as determined by cardiac MRI. RESULTS: At follow-up ΔLVEF as well as ΔRVEF did not differ between the GS and placebo group. Patients in the placebo group had a similar risk for a major adverse cardiac event within 12 months of follow-up as compared to patients under GS. CONCLUSION: Progenitor cell therapy comprising the use of G-CSF and Sitagliptin after successfully revascularized acute myocardial infarction fails to show a beneficial effect on cardiac function and clinical events after 12 months. (EudraCT: 2007-003,941-34; ClinicalTrials.gov: NCT00650143, funding: Heinz-Nixdorf foundation).

Critical role of the NKG2D receptor for NK cell-mediated control and immune escape of B-cell lymphoma.

Little is known on the control of lymphomas by NK cells. Here, we study the role of the NK group 2D (NKG2D) receptor for the immunosurveillance of lymphoma. By using transplantable tumors as well as a λ-myc-transgenic model of endogenously arising lymphoma and NKG2D-deficient mice, we show that NK cells eliminate tumor cells in vivo after receiving two signals. One step involved the activation of NK cells giving rise to IFN-γ expression, which was effected by MHCI(low) tumor cells or DCs. However, this was necessary but not sufficient to mediate cytotoxicity. Triggering cytotoxicity additionally required a second step, which could be mediated by engagement of the NKG2D receptor. Thus, NKG2D-deficient NK cells could become activated in vivo, but they were not able to reject transplanted lymphomas or to degranulate in animals bearing autochthonous lymphomas. Tumor growth in NKG2D-deficient λ-myc-transgenic mice was significantly accelerated compared to NKG2D-competent animals. Whereas the latter developed tumors that lost expression of NKG2D ligands (NKG2D-L) in late disease stages, this did not occur in NKG2D-deficient mice. This indicates that NK cells and the NKG2D receptor play a role for control of lymphomas and that selection for NKG2D-L loss mutants provides a mechanism of tumor escape.

Short-term inhibition of DPP-4 enhances endothelial regeneration after acute arterial injury via enhanced recruitment of circulating progenitor cells.

BACKGROUND: Endothelial injuries regularly occur in atherosclerosis and during interventional therapies of the arterial occlusive disease. Disturbances in the endothelial integrity can lead to insufficient blood supply and bear the risk of thrombus formation and acute vascular occlusion. At present, effective therapeutics to restore endothelial integrity are barely available. We analyzed the effect of pharmacological DPP-4-inhibition by Sitagliptin on endogenous progenitor cell-based endothelial regeneration via the SDF-1α/CXCR4-axis after acute endothelial damage in a mouse model of carotid injury. METHODS AND RESULTS: Induction of a defined endothelial injury was performed in the carotid artery of C57Bl/6 mice which led to a local upregulation of SDF-1α expression. Animals were treated with placebo, Sitagliptin or Sitagliptin+AMD3100. Using mass spectrometry we could prove that Sitagliptin prevented cleavage of the chemokine SDF-1α. Accordingly, increased SDF-1α concentrations enhanced recruitment of systemically applied and endogenous circulating CXCR4+ progenitor cells to the site of vascular injury followed by a significantly accelerated reendothelialization as compared to placebo-treated animals. Improved endothelial recovery, as well as recruitment of circulating CXCR4+ progenitor cells (CD133+, Flk1+), was reversed by CXCR4-antagonization through AMD3100. In addition, short-term Sitagliptin treatment did not significantly promote neointimal or medial hyperplasia. CONCLUSION: Sitagliptin can accelerate endothelial regeneration after acute endothelial injury. DPP-4 inhibitors prevent degradation of the chemokine SDF-1α and thus improve the recruitment of regenerative circulating CXCR4+ progenitor cells which mediate local endothelial cell proliferation without adversely affecting vessel wall architecture.

CD40-independent natural killer-cell help promotes dendritic cell vaccine-induced T-cell immunity against endogenous B-cell lymphoma.

It is well established that an interplay between natural killer (NK) cells and dendritic cells (DCs) gives rise to their reciprocal activation and provides a Th1-biased cytokine milieu that fosters antitumor T-cell responses. Ex vivo-differentiated DCs transferred into mice strongly stimulate endogenous NK cells to produce interferon (IFN)-γ and initiate a cascade that eventually leads to cytotoxic T-lymphocyte responses. We show that the ability of exogenous DCs to trigger this pathway obviates CD40 signaling and CD4(+) T-cell help and depends on a preceding maturation step. Importantly, this mechanism was also effective in endogenously arising tumors where IFN-γ production is compromised in contrast to transplantable tumors. In c-myc-transgenic mice developing spontaneous lymphomas, injection of unpulsed DCs caused NK-cell activation and induced CD8(+) T cells capable of recognizing the lymphoma cells. Animals treated with unpulsed DCs showed a survival benefit compared to untreated myc mice. Hence, tumor immunity induced by DC-based vaccines not only depends on specific antigens loaded on the DCs. Rather, DC vaccines generate broader immune responses, because endogenous DCs presenting tumor antigens may also become stimulated by NK cells that were activated by exogenous DCs. Thus, the DC/NK-cell/cytotoxic T lymphocyte axis may commonly have relevance for DC-based vaccination protocols in clinical settings.

Recruitment of natural killer cells in advanced stages of endogenously arising B-cell lymphoma: implications for therapeutic cell transfer.

During inflammation and in transplantable tumor models, natural killer (NK) cells are recruited to pathologic tissues and activated to produce proinflammatory cytokines favoring adaptive immune responses of the T-helper type 1 (Th1) type. Interferon (IFN)-γ is needed to induce chemokines that attract NK cells in transplanted tumors. Nothing, however, is known on NK-cell migration in spontaneous tumors. As effective recruitment is a prerequisite for therapeutic NK-cell transfer, we investigated the cytokine milieu and the mechanisms that are instrumental for NK-cell accumulation in an endogenous tumor model. We make use of λ-myc transgenic mice that harbor the c-myc oncogene and develop spontaneous B-cell lymphoma. In contrast to lymphomas induced by tumor cell injection, virtually no IFN-γ produced by NK or by other cells was present in the tumor environment, particularly in advanced stages. Dendritic cells showed an impaired expression of interleukin-12, which is suggestive of deficient Th1 priming. The IFN-γ-dependent chemokines CXCL9 and CXCL10 were pivotal for NK-cell migration in the endogenous lymphoma model. Although IFN-γ was absent in late tumor stages, there was still expression of CXCL9 and CXCL10 with an ongoing influx of NK cells. The results demonstrate that transplantable tumor models do not reflect the situation as found in endogenously arising neoplasia, because in the latter, effective Th1 and cytotoxic T-lymphocyte responses are presumably not induced because of impaired IFN-γ production. The data also suggest that CXCL9 and CXCL10 production and NK-cell migration become independent of IFN-γ during tumor progression, and therefore support approaches of adoptive NK-cell transfer that hold promise for treatment of cancer.

The use of stem cells for the repair of cardiac tissue in ischemic heart disease.

Ischemic heart diseases are the leading cause of death in the Western world. With increasing numbers of patients surviving their acute myocardial infarction owing to effective heart catheter techniques and intensive care treatment, congestive heart failure has become an increasing health concern. With therapeutic options for the prevention and treatment of ischemic heart disease being limited at present, huge efforts have been made in the field of stem cell research to try to establish new approaches for myocardial tissue regeneration. Owing to their pronounced differentiation potential, pluripotent stem cells seem to represent the most promising cell source for future engineering of myocardial replacement tissue. However, several crucial hurdles regarding cell yield and purity of the cultured cardiovascular progenitor cells have still not been overcome to facilitate a clinical application today. By contrast, plenty of adult stem and progenitor cells have already been well characterized and investigated in human disease. However, all of these heterogeneous cell lines primarily seem to work in a paracrine manner on ischemic myocardial tissue, rather than transdifferentiating into contractile cardiomyocytes. This article will focus on the production, application and present limitations of stem cells potentially applicable for myocardial repair.

Requirements for control of B-cell lymphoma by NK cells.

The role of NK cells in the control of endogenously arising tumors is still unclear. We monitored activation and effector functions of NK cells in a c-myc-transgenic mouse model of spontaneously arising lymphoma. At early stages, tumors demonstrated reduced MHC class I expression and increased expression of natural killer group 2D ligands (NKG2D-L). NK cells in these tumors showed an activated phenotype that correlated with the loss of tumor MHC class I. With increasing tumor load however, NK-cell effector functions became progressively paralyzed or exhausted. In later stages of disease, tumors re-expressed MHC class I and lost NKG2D-L, suggesting a role of these two signals for NK cell-mediated tumor control. Testing a panel of lymphoma cell lines expressing various MHC class I and NKG2D-L levels suggested that NK cell-dependent tumor control required a priming and a triggering signal that were provided by MHC class I down-regulation and by NKG2D-L, respectively. Deleting either of the "two signals" resulted in tumor escape. At early disease stages, immune stimulation through TLR-ligands in vivo efficiently delayed lymphoma growth in a strictly NK cell-dependent manner. Thus, NK-receptor coengagement is crucial for NK-cell functions in vivo and especially for NK cell-mediated tumor surveillance.

Forward programming of pluripotent stem cells towards distinct cardiovascular cell types.

AIMS: The proliferative potential of pluripotent stem cell-derived cardiomyocytes is limited, and reasonable yields for novel therapeutic options have yet to be achieved. In addition, various clinical applications will require the generation of specific cardiac cell types. Whereas early cardiovascular precursors appear to be important for novel approaches such as reseeding decellularized hearts, direct cell transplantation may require ventricular cells. Our recent work demonstrated that MesP1 represents a master regulator sufficient to induce cardiovasculogenesis in pluripotent cells. This led to our hypothesis that 'forward programming' towards specific subtypes may be feasible via overexpression of distinct early cardiovascular transcription factors. METHODS AND RESULTS: Here we demonstrate that forced expression of Nkx2.5 similar to MesP1 is sufficient to enhance cardiogenesis in murine embryonic stem cells (mES). In comparison to control transfected mES cells, a five-fold increased appearance of beating foci was observed as well as upregulated mRNA and protein expression levels. In contrast to MesP1, no increase of the endothelial lineage within the cardiovasculogenic mesoderm was observed. Likewise, Flk-1, the earliest known cardiovascular surface marker, was not induced via Nkx2.5 as opposed to MesP1. Detailed patch clamping analyses showed electrophysiological characteristics corresponding to all subtypes of cardiac ES cell differentiation in Nkx2.5 as well as MesP1 programmed embryoid bodies, but fractions of cardiomyocytes had distinct characteristics: MesP1 forced the appearance of early/intermediate type cardiomyocytes in comparison to control transfected ES cells whereas Nkx2.5 led to preferentially differentiated ventricular cells. CONCLUSION: Our findings show proof of principle for cardiovascular subtype-specific programming of pluripotent stem cells and confirm the molecular hierarchy for cardiovascular specification initiated via MesP1 with differentiation factors such as Nkx2.5 further downstream.