Chemical and mechanical activation of resident cardiac macrophages in the living myocardial slice ex vivo model

Resident cardiac macrophages (rcMACs) are among the most abundant immune cells in the heart. Plasticity and activation are hallmarks of rcMACs in response to changes in the microenvironment, which is essential for in vitro experimentation. The in vivo investigation is confounded by the infiltration of other cells hindering direct studies of rcMACs. As a tool to investigate rcMACs, we applied the ex vivo model of living myocardial slices (LMS). LMS are ultrathin ex vivo multicellular cardiac preparations in which the circulatory network is interrupted. The absence of infiltration in this model enables the investigation of the rcMACs response to immunomodulatory and mechanical stimulations. Such conditions were generated by applying interferon-gamma (IFN-γ) or interleukine-4 (IL-4) and altering the preload of cultured LMS, respectively. The immunomodulatory stimulation of the LMS induced alterations of the gene expression pattern without affecting tissue contractility. Following 24 h culture, low input RNA sequencing of rcMACs isolated from LMS was used for gene ontology analysis. Reducing the tissue stretch (unloading) of LMS altered the gene ontology clusters of isolated rcMACs with intermediate semantic similarity to IFN-γ triggered reaction. Through the overlap of genes affected by IFN-γ and unloading, we identified Allograft inflammatory factor 1 (AIF-1) as a potential marker gene for inflammation of rcMACs as significantly altered in whole immunomodulated LMS. MicroRNAs associated with the transcriptomic changes of rcMACs in unloaded LMS were identified in silico. Here, we demonstrate the approach of LMS to understand load-triggered cardiac inflammation and, thus, identify potential translationally important therapeutic targets.

Effects of controlled ovarian stimulation on vascular barrier and endothelial glycocalyx: a pilot study

Purpose

Controlled ovarian stimulation significantly amplifies the number of maturing and ovulated follicles as well as ovarian steroid production. The ovarian hyperstimulation syndrome (OHSS) increases capillary permeability and fluid extravasation. Vascular integrity intensely is regulated by an endothelial glycocalyx (EGX) and we have shown that ovulatory cycles are associated with shedding of EGX components. This study investigates if controlled ovarian stimulation impacts on the integrity of the endothelial glycocalyx as this might explain key pathomechanisms of the OHSS.

Methods

Serum levels of endothelial glycocalyx components of infertility patients (n=18) undergoing controlled ovarian stimulation were compared to a control group of healthy women with regular ovulatory cycles (n=17).

Results

Patients during luteal phases of controlled ovarian stimulation cycles as compared to normal ovulatory cycles showed significantly increased Syndecan-1 serum concentrations (12.6 ng/ml 6.11^25th–19.13^75th to 13.9 ng/ml 9.6^25th–28.9^75th; p=0.026), indicating shedding and degradation of the EGX.

Conclusion

A shedding of EGX components during ovarian stimulation has not yet been described. Our study suggests that ovarian stimulation may affect the integrity of the endothelial surface layer and increasing vascular permeability. This could explain key features of the OHSS and provide new ways of prevention of this serious condition of assisted reproduction.

A practical guide for investigating cardiac physiology using living myocardial slices

Ex vivo multicellular preparations are essential tools to study tissue physiology. Among them, the recent methodological and technological developments in living myocardial slices (LMS) are attracting increasing interest by the cardiac research field. Despite this, this research model remains poorly perceived and utilized by most research laboratories. Here, we provide a practical guide on how to use LMS to interrogate multiple aspects of cardiac function, structure and biochemistry. We discuss issues that should be considered to conduct successful experiments, including experimental design, sample preparation, data collection and analysis. We describe how laboratory setups can be adapted to accommodate and interrogate this multicellular research model. These adaptations can often be achieved at a reasonable cost with off-the-shelf components and operated reliably using well-established protocols and freely available software, which is essential to broaden the utilization of this method. We will also highlight how current measurements can be improved to further enhance data quality and reliability to ensure inter-laboratory reproducibility. Finally, we summarize the most promising biomedical applications and envision how living myocardial slices can lead to further breakthroughs.

Somatic gene editing ameliorates skeletal and cardiac muscle failure in pig and human models of Duchenne muscular dystrophy

Frameshift mutations in the DMD gene, encoding dystrophin, cause Duchenne muscular dystrophy (DMD), leading to terminal muscle and heart failure in patients. Somatic gene editing by sequence-specific nucleases offers new options for restoring the DMD reading frame, resulting in expression of a shortened but largely functional dystrophin protein. Here, we validated this approach in a pig model of DMD lacking exon 52 of DMD (DMDΔ52), as well as in a corresponding patient-derived induced pluripotent stem cell model. In DMDΔ52 pigs1, intramuscular injection of adeno-associated viral vectors of serotype 9 carrying an intein-split Cas9 (ref. 2) and a pair of guide RNAs targeting sequences flanking exon 51 (AAV9-Cas9-gE51) induced expression of a shortened dystrophin (DMDΔ51-52) and improved skeletal muscle function. Moreover, systemic application of AAV9-Cas9-gE51 led to widespread dystrophin expression in muscle, including diaphragm and heart, prolonging survival and reducing arrhythmogenic vulnerability. Similarly, in induced pluripotent stem cell-derived myoblasts and cardiomyocytes of a patient lacking DMDΔ52, AAV6-Cas9-g51-mediated excision of exon 51 restored dystrophin expression and amelioreate skeletal myotube formation as well as abnormal cardiomyocyte Ca2+ handling and arrhythmogenic susceptibility. The ability of Cas9-mediated exon excision to improve DMD pathology in these translational models paves the way for new treatment approaches in patients with this devastating disease.

Medium-chain fatty acids modulate myocardial function via a cardiac odorant receptor

Several studies have demonstrated the expression of odorant receptors (OR) in various human tissues and their involvement in different physiological and pathophysiological processes. However, the functional role of ORs in the human heart is still unclear. Here, we firstly report the functional characterization of an OR in the human heart. Initial next-generation sequencing analysis revealed the OR expression pattern in the adult and fetal human heart and identified the fatty acid-sensing OR51E1 as the most highly expressed OR in both cardiac development stages. An extensive characterization of the OR51E1 ligand profile by luciferase reporter gene activation assay identified 2-ethylhexanoic acid as a receptor antagonist and various structurally related fatty acids as novel OR51E1 ligands, some of which were detected at receptor-activating concentrations in plasma and epicardial adipose tissue. Functional investigation of the endogenous receptor was carried out by Ca²⁺ imaging of human stem cell-derived cardiomyocytes. Application of OR51E1 ligands induced negative chronotropic effects that depended on activation of the OR. OR51E1 activation also provoked a negative inotropic action in cardiac trabeculae and slice preparations of human explanted ventricles. These findings indicate that OR51E1 may play a role as metabolic regulator of cardiac function.

Intracoronary enalaprilat during angioplasty for acute myocardial infarction: alleviation of postischaemic neurohumoral and inflammatory stress?

AIM

Reperfusion after myocardial ischaemia is associated with a distinct ischaemia/reperfusion injury. Since ACE-inhibition, beyond its influence on cardiac angiotensin II formation and kinin metabolism, has been shown to be cardioprotective by decreasing leucocyte adhesion and endothelin-1 (ET-1) release, we investigated the effects of intracoronary (i.c.) enalaprilat during primary angioplasty in acute myocardial infarction.

METHODS AND RESULTS

Twenty-two patients were randomized to receive i.c. enalaprilat (50 micro g) or placebo immediately after reopening of the infarct-related artery (IRA). Plasma concentrations of soluble L-selectin, P-selectin, intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), ET-1 and nitric oxide metabolite concentrations (NOx) were measured in pulmonary arterial blood. Coronary blood flow was assessed using corrected thrombolysis in myocardial infarction (TIMI) frame counts (CTFC). During reperfusion, there was a significant increase in sL-selectin, sP-selectin and ET-1 in the placebo group, which was greatly diminished by enalaprilat. Levels of sVCAM-1 and sICAM-1 were not affected in either group. CTFC in the placebo group remained higher than normal in both the IRA and nonculprit vessels, whereas myocardial blood flow improved with enalaprilat.

CONCLUSION

Enalaprilat as adjunct to primary angioplasty might be a protective approach to prevent leucocyte adhesion and the release of ET-1, thereby improving coronary blood flow.

Effects of candesartan and enalaprilat on the organ-specific microvascular permeability during haemorrhagic shock in rats

BACKGROUND

To counteract the contribution of angiotensin II to shock-induced ischaemic organ damage pharmacologic blockade of the renin-angiotensin-system (RAS) is currently under investigation. To evaluate potential side-effects of RAS blockade regarding capillary leak, we studied alterations in microvascular permeability in various organs during haemorrhagic shock (HS) in rats pretreated with candesartan (AT(1)-receptor antagonism) or enalaprilat (ACE-inhibition).

METHODS

Thirty-eight instrumented and anaesthetized animals received either candesartan, enalaprilat or placebo. Within each of the three groups 6-7 animals were exposed to HS and 6 animals of each group served as normovolaemic controls. After 30 min of shock, 50 mg kg(-1) Evans blue (EB) was injected i.v. followed by a distribution period of 20 min. Exsanguination was performed with saline, before harvesting organs to quantify albumin-bound EB extravasation.

RESULTS

To reduce cardiac output from 37.5 (1.3) to 20.4 (1.1) ml min(-1) [mean (SEM)] in the shock groups, withdrawal of 4.0 (0.25) ml [mean (SEM)] blood was necessary. Simultaneously mean arterial pressure decreased from 77.5 (3.2) to 36.1 (2) mm Hg. Serum lactate increased significantly from 1.3 (0.1) to 3.5 (0.24) mmol litre(-1). Treatment with candesartan increased EB extravasation in the kidney in normovolaemic controls. Specific AT(1) and ACE-blockade before acute non-resuscitated HS significantly increased EB extravasation in the rat ileum by 53 and 66%, respectively.

CONCLUSION

This observation of increased microvascular albumin extravasation should be borne in mind for any interventional use of candesartan or enalaprilat during circulatory stress.

ACE inhibitors and angiotensin II receptor antagonists

The biological actions of angiotensin II (ANG), the most prominent hormone of the renin-angiotensin-aldosterone system (RAAS), may promote the development of atherosclerosis in many ways. ANG aggravates hypertension, metabolic syndrome, and endothelial dysfunction, and thereby constitutes a major risk factor for cardiovascular disease. The formation of atherosclerotic lesions involves local uptake, synthesis and oxidation of lipids, inflammation, as well as cellular migration and proliferation--mechanisms that may all be enhanced by ANG via its AT1 receptor. ANG may also increase the risk of acute thrombosis by destabilizing atherosclerotic plaques and enhancing the activity of thrombocytes and coagulation. After myocardial infarction, ANG promotes myocardial remodeling and fibrosis, and its many pathological mechanisms deteriorate the prognosis of these high-risk patients in particular. Therapeutically, inhibitors of the angiotensin I-converting enzyme (ACEI) and AT1 receptor blockers (ARB) are available to suppress the generation and cellular signaling of ANG, respectively. Despite major differences in the efficacy of ANG suppression and the modulation of other hormones and receptors, both classes of drugs are generally effective in attenuating numerous pathomechanisms of ANG in vitro, and in diminishing the development of atherosclerotic lesions and restenosis after angioplasty in various animal models. In clinical therapy, ACEI and ACE are well-tolerated antihypertensive drugs that also improve the prognosis of heart failure patients. After myocardial infarction and in stable coronary heart disease, ACEI have been shown to reduce mortality in a manner independent of hemodynamic alterations. However, there is little evidence that inhibitors of the RAAS may be effective against arterial restenosis, and a possible benefit of these substances compared to other antihypertensive drugs in the primary prevention of coronary heart disease in hypertensive patients is still a matter of debate, possibly depending on the specific substance and condition being investigated. As such, the general clinical efficacy of ACEI and ARB may be due to a positive influence on hemodynamic load, vascular function, myocardial remodeling, and neuro-humoral regulation, rather than to a direct attenuation of the atherosclerotic process. Further therapeutic advances may be achieved by identifying optimum drugs, patient populations, and treatment protocols.

A miniature self-inflating bag-mask ventilator for rats

Respiratory depression and apnoea during anaesthesia may lead to hypoxia and myocardial ischaemia. A self-inflating miniature bag-mask device was assembled combining characteristics from the Ambu-bag and the Kuhn-system. This bag-mask device permitted ventilation during anaesthesia-induced apnoea in rats until a safe airway by tracheotomy was achieved.

[Therapy relevant differences in beta blockers and ACE inhibitors. Innovation or plagiarism?]

As exemplified by the two classes of substance beta blockers and ACE inhibitors, the question is considered as to when new developments within a drug family can be termed innovations and when they must be seen purely as plagiarisms ("me-too" preparations). It is noted that in principle no innovations are to be expected from generics, since these substances are are not the subject of specific research. Although large-scale clinical studies in recent years have identified a new indication--cardiac insufficiency--for the beta blockers metoprolol, bisoprolol and carvedilol, this must not be considered an innovation in the sense of a new development. The translatability of the study results to uninvestigated substances is uncertain. In contrast to the beta blockers, the indications for the ACE inhibitors have long been known, but again, the new generic preparations that have come onto the market are not innovations.

Effects of intracoronary low-dose enalaprilat as an adjunct to primary percutaneous transluminal coronary angiography in acute myocardial infarction

Bradykinin accumulation is a potent cardioprotective mechanism underlying angiotensin-converting enzyme (ACE) inhibition in ischemia and/or reperfusion injury. There is, however, concern about treatment with ACE inhibitors in the very early phase of acute myocardial infarction (AMI) due to adverse systemic hemodynamic effects. We tested the hypothesis that cardiac bradykinin metabolism can be influenced by very low doses of intracoronary ACE inhibitors without harmful systemic effects in patients with AMI. Twenty-two patients with AMI in Killip classes II to III who underwent primary percutaneous transluminal coronary angiography (PTCA) were randomized to intracoronary enalaprilat (50 microg) or saline, given immediately after reopening of the infarct-related artery. Hemodynamics and electrocardiograms were monitored continuously and samples for determination of ACE activity, angiotensin II, bradykinin, kininogen, and cardiac marker proteins were collected from pulmonary arterial and central venous blood. Enalaprilat had no adverse effects on systemic hemodynamics, but rather stabilized arterial pressure and cardiac rhythm during reperfusion. Enalaprilat induced a 70% reduction of ACE activity and a significant increase of bradykinin in pulmonary arterial blood. Angiotensin II was not significantly affected by enalaprilat either in pulmonary arterial or in central venous blood. Myoglobin release was lower and the duration of reperfusion arrhythmias was significantly reduced in the enalaprilat group (p <0.05). Thus, in this pilot study, intracoronary enalaprilat infusion in the infarct-related artery is feasible in the setting of primary angioplasty and is safe and well tolerated. Effective cardiac ACE inhibition can be achieved by low-dose intracoronary enalaprilat, which primarily causes a potentiation of bradykinin.