The Dutch list of essential drugs for undergraduate medical education: A modified Delphi study.

AIMS: Prescribing errors among junior doctors are common in clinical practice because many lack prescribing competence after graduation. This is in part due to inadequate education in clinical pharmacology and therapeutics (CP&T) in the undergraduate medical curriculum. To support CP&T education, it is important to determine which drugs medical undergraduates should be able to prescribe safely and effectively without direct supervision by the time they graduate. Currently, there is no such list with broad-based consensus. Therefore, the aim was to reach consensus on a list of essential drugs for undergraduate medical education in the Netherlands. METHODS: A two-round modified Delphi study was conducted among pharmacists, medical specialists, junior doctors and pharmacotherapy teachers from all eight Dutch academic hospitals. Participants were asked to indicate whether it was essential that medical graduates could prescribe specific drugs included on a preliminary list. Drugs for which ≥80% of all respondents agreed or strongly agreed were included in the final list. RESULTS: In all, 42 (65%) participants completed the two Delphi rounds. A total of 132 drugs (39%) from the preliminary list and two (3%) newly proposed drugs were included. CONCLUSIONS: This is the first Delphi consensus study to identify the drugs that Dutch junior doctors should be able to prescribe safely and effectively without direct supervision. This list can be used to harmonize and support the teaching and assessment of CP&T. Moreover, this study shows that a Delphi method is suitable to reach consensus on such a list, and could be used for a European list.

Exogenous and endogenous angiotensin-II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow.

KEY POINTS: Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary. We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats. This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation. Exogenous angiotensin-II reduced renal cortical tissue PO2 more than equi-pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine. Activation of the endogenous renin-angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin-II receptor type 1 antagonist. Angiotensin-II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease. ABSTRACT: We hypothesised that both exogenous and endogenous angiotensin-II (AngII) can decrease the partial pressure of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn contribute to the progression of chronic kidney disease. Rats were instrumented with telemeters equipped with a carbon paste electrode for continuous measurement of renal cortical tissue PO2. The method reproducibly detected acute changes in cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious rats, renal cortical PO2 was dose-dependently reduced by intravenous AngII. Reductions in PO2 were significantly greater than those induced by equi-pressor doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not affected, and filtration fraction was increased only in the AngII infused animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood flow (RBF) fell by 3.3 ml min-1 . Equi-pressor infusion of phenylephrine did not significantly reduce RBF or renal oxygen delivery. Activation of the endogenous renin-angiotensin system in Cyp1a1Ren2 transgenic rats reduced cortical tissue PO2. This could be reversed within minutes by pharmacological angiotensin-II receptor type 1 (AT1 R) blockade. Thus AngII is an important modulator of renal cortical oxygenation via AT1 receptors. AngII had a greater influence on cortical oxygenation than did phenylephrine. This phenomenon appears to be attributable to the profound impact of AngII on renal oxygen delivery. We conclude that the ability of AngII to promote renal cortical hypoxia may contribute to its influence on initiation and progression of chronic kidney disease.

Reversal of hypoxia in murine atherosclerosis prevents necrotic core expansion by enhancing efferocytosis.

OBJECTIVE: Advanced murine and human plaques are hypoxic, but it remains unclear whether plaque hypoxia is causally related to atherogenesis. Here, we test the hypothesis that reversal of hypoxia in atherosclerotic plaques by breathing hyperoxic carbogen gas will prevent atherosclerosis. APPROACH AND RESULTS: Low-density lipoprotein receptor-deficient mice (LDLR(-/-)) were fed a Western-type diet, exposed to carbogen (95% O2, 5% CO2) or air, and the effect on plaque hypoxia, size, and phenotype was studied. First, the hypoxic marker pimonidazole was detected in murine LDLR(-/-) plaque macrophages from plaque initiation onwards. Second, the efficacy of breathing carbogen (90 minutes, single exposure) was studied. Compared with air, carbogen increased arterial blood pO2 5-fold in LDLR(-/-) mice and reduced plaque hypoxia in advanced plaques of the aortic root (-32%) and arch (-84%). Finally, the effect of repeated carbogen exposure on progression of atherosclerosis was studied in LDLR(-/-) mice fed a Western-type diet for an initial 4 weeks, followed by 4 weeks of diet and carbogen or air (both 90 min/d). Carbogen reduced plaque hypoxia (-40%), necrotic core size (-37%), and TUNEL(+) (terminal uridine nick-end labeling positive) apoptotic cell content (-50%) and increased efferocytosis of apoptotic cells by cluster of differentiation 107b(+) (CD107b, MAC3) macrophages (+36%) in advanced plaques of the aortic root. Plaque size, plasma cholesterol, hematopoiesis, and systemic inflammation were unchanged. In vitro, hypoxia hampered efferocytosis by bone marrow-derived macrophages, which was dependent on the receptor Mer tyrosine kinase. CONCLUSIONS: Carbogen restored murine plaque oxygenation and prevented necrotic core expansion by enhancing efferocytosis, likely via Mer tyrosine kinase. Thus, plaque hypoxia is causally related to necrotic core expansion.

Echogenic perfluorohexane-loaded macrophages adhere in vivo to activated vascular endothelium in mice, an explorative study.

BACKGROUND: Macrophages may concentrate ultrasound contrast agents and exhibit selective adhesion to activated endothelium. The present study investigates in mice the potential of perfluorohexane (PFH) loaded macrophages to act as ultrasound contrast agent with high reflectivity and specifically targeted at (atherosclerotic) vascular lesions. METHODS: Lung passage was evaluated with a mouse echo scanner after injection, at a slow pace or as a bolus, of varying doses of PFH-loaded and unloaded bone marrow macrophages (BMM) into the jugular vein. The interaction of PFH-loaded and unloaded BMM with TNF-α stimulated carotid artery endothelium after tail vein injection was assessed by means of intravital microscopy. RESULTS: High doses of jugular vein injected PFH-loaded BMM were visible with ultrasound in the pulmonary artery and detectable in the carotid artery. At intravital microscopy, tail vein injected BMM exhibited rolling and adhesion behavior at the TNF-α stimulated carotid endothelium, similar to that of native blood leukocytes. Rolling behavior was not different between PFH-loaded and unloaded BMM (p = 0.38). CONCLUSION: In vivo, perfluorohexane loaded macrophages pass the pulmonary circulation and appear on the arterial side. Moreover, they roll and adhere selectively to activated endothelium under physiological flow conditions. These findings indicate that perfluorohexane loaded BMM could be used to study processes in vivo where endothelial activation plays a role, such as atherosclerosis.

Protein kinase-D1 overexpression prevents lipid-induced cardiac insulin resistance.

In the insulin resistant heart, energy fuel selection shifts away from glucose utilization towards almost complete dependence on long-chain fatty acids (LCFA). This shift results in excessive cardiac lipid accumulation and eventually heart failure. Lipid-induced cardiomyopathy may be averted by strategies that increase glucose uptake without elevating LCFA uptake. Protein kinase-D1 (PKD1) is involved in contraction-induced glucose, but not LCFA, uptake allowing to hypothesize that this kinase is an attractive target to treat lipid-induced cardiomyopathy. For this, cardiospecific constitutively active PKD1 overexpression (caPKD1)-mice were subjected to an insulin resistance-inducing high fat-diet for 20-weeks. Substrate utilization was assessed by microPET and cardiac function by echocardiography. Cardiomyocytes were isolated for measurement of substrate uptake, lipid accumulation and insulin sensitivity. Wild-type mice on a high fat-diet displayed increased basal myocellular LCFA uptake, increased lipid deposition, greatly impaired insulin signaling, and loss of insulin-stimulated glucose and LCFA uptake, which was associated with concentric hypertrophic remodeling. The caPKD1 mice on high-fat diet showed none of these characteristics, whereas on low-fat diet a shift towards cardiac glucose utilization in combination with hypertrophy and ventricular dilation was observed. In conclusion, these data suggest that PKD pathway activation may be an attractive therapeutic strategy to mitigate lipid accumulation, insulin resistance and maladaptive remodeling in the lipid-overloaded heart, but this requires further investigation.

Glyoxalase-1 overexpression reduces endothelial dysfunction and attenuates early renal impairment in a rat model of diabetes.

AIMS/HYPOTHESIS: In diabetes, advanced glycation end-products (AGEs) and the AGE precursor methylglyoxal (MGO) are associated with endothelial dysfunction and the development of microvascular complications. In this study we used a rat model of diabetes, in which rats transgenically overexpressed the MGO-detoxifying enzyme glyoxalase-I (GLO-I), to determine the impact of intracellular glycation on vascular function and the development of early renal changes in diabetes. METHODS: Wild-type and Glo1-overexpressing rats were rendered diabetic for a period of 24 weeks by intravenous injection of streptozotocin. Mesenteric arteries were isolated to study ex vivo vascular reactivity with a wire myograph and kidneys were processed for histological examination. Glycation was determined by mass spectrometry and immunohistochemistry. Markers for inflammation, endothelium dysfunction and renal dysfunction were measured with ELISA-based techniques. RESULTS: Diabetes-induced formation of AGEs in mesenteric arteries and endothelial dysfunction were reduced by Glo1 overexpression. Despite the absence of advanced nephrotic lesions, early markers of renal dysfunction (i.e. increased glomerular volume, decreased podocyte number and diabetes-induced elevation of urinary markers albumin, osteopontin, kidney-inflammation-molecule-1 and nephrin) were attenuated by Glo1 overexpression. In line with this, downregulation of Glo1 in cultured endothelial cells resulted in increased expression of inflammation and endothelium dysfunction markers. In fully differentiated cultured podocytes incubation with MGO resulted in apoptosis. CONCLUSIONS/INTERPRETATION: This study shows that effective regulation of the GLO-I enzyme is important in the prevention of vascular intracellular glycation, endothelial dysfunction and early renal impairment in experimental diabetes. Modulating the GLO-I pathway therefore may provide a novel approach to prevent vascular complications in diabetes.

Macrophage microRNA-155 promotes cardiac hypertrophy and failure.

BACKGROUND: Cardiac hypertrophy and subsequent heart failure triggered by chronic hypertension represent major challenges for cardiovascular research. Beyond neurohormonal and myocyte signaling pathways, growing evidence suggests inflammatory signaling pathways as therapeutically targetable contributors to this process. We recently reported that microRNA-155 is a key mediator of cardiac inflammation and injury in infectious myocarditis. Here, we investigated the impact of microRNA-155 manipulation in hypertensive heart disease. METHODS AND RESULTS: Genetic loss or pharmacological inhibition of the leukocyte-expressed microRNA-155 in mice markedly reduced cardiac inflammation, hypertrophy, and dysfunction on pressure overload. These alterations were macrophage dependent because in vivo cardiomyocyte-specific microRNA-155 manipulation did not affect cardiac hypertrophy or dysfunction, whereas bone marrow transplantation from wild-type mice into microRNA-155 knockout animals rescued the hypertrophic response of the cardiomyocytes and vice versa. In vitro, media from microRNA-155 knockout macrophages blocked the hypertrophic growth of stimulated cardiomyocytes, confirming that macrophages influence myocyte growth in a microRNA-155-dependent paracrine manner. These effects were at least partly mediated by the direct microRNA-155 target suppressor of cytokine signaling 1 (Socs1) because Socs1 knockdown in microRNA-155 knockout macrophages largely restored their hypertrophy-stimulating potency. CONCLUSIONS: Our findings reveal that microRNA-155 expression in macrophages promotes cardiac inflammation, hypertrophy, and failure in response to pressure overload. These data support the causative significance of inflammatory signaling in hypertrophic heart disease and demonstrate the feasibility of therapeutic microRNA targeting of inflammation in heart failure.

Improving membrane based multiplex immunoassays for semi-quantitative detection of multiple cytokines in a single sample.

BACKGROUND: Inflammatory mediators can serve as biomarkers for the monitoring of the disease progression or prognosis in many conditions. In the present study we introduce an adaptation of a membrane-based technique in which the level of up to 40 cytokines and chemokines can be determined in both human and rodent blood in a semi-quantitative way. The planar assay was modified using the LI-COR (R) detection system (fluorescence based) rather than chemiluminescence and semi-quantitative outcomes were achieved by normalizing the outcomes using the automated exposure settings of the Odyssey readout device. The results were compared to the gold standard assay, namely ELISA. RESULTS: The improved planar assay allowed the detection of a considerably higher number of analytes (n = 30 and n = 5 for fluorescent and chemiluminescent detection, respectively). The improved planar method showed high sensitivity up to 17 pg/ml and a linear correlation of the normalized fluorescence intensity with the results from the ELISA (r = 0.91). CONCLUSIONS: The results show that the membrane-based technique is a semi-quantitative assay that correlates satisfactorily to the gold standard when enhanced by the use of fluorescence and subsequent semi-quantitative analysis. This promising technique can be used to investigate inflammatory profiles in multiple conditions, particularly in studies with constraints in sample sizes and/or budget.

Lysosomal integral membrane protein 2 is a novel component of the cardiac intercalated disc and vital for load-induced cardiac myocyte hypertrophy.

The intercalated disc (ID) of cardiac myocytes is emerging as a crucial structure in the heart. Loss of ID proteins like N-cadherin causes lethal cardiac abnormalities, and mutations in ID proteins cause human cardiomyopathy. A comprehensive screen for novel mechanisms in failing hearts demonstrated that expression of the lysosomal integral membrane protein 2 (LIMP-2) is increased in cardiac hypertrophy and heart failure in both rat and human myocardium. Complete loss of LIMP-2 in genetically engineered mice did not affect cardiac development; however, these LIMP-2 null mice failed to mount a hypertrophic response to increased blood pressure but developed cardiomyopathy. Disturbed cadherin localization in these hearts suggested that LIMP-2 has important functions outside lysosomes. Indeed, we also find LIMP-2 in the ID, where it associates with cadherin. RNAi-mediated knockdown of LIMP-2 decreases the binding of phosphorylated beta-catenin to cadherin, whereas overexpression of LIMP-2 has the opposite effect. Collectively, our data show that LIMP-2 is crucial to mount the adaptive hypertrophic response to cardiac loading. We demonstrate a novel role for LIMP-2 as an important mediator of the ID.

Mild oxidative damage in the diabetic rat heart is attenuated by glyoxalase-1 overexpression.

Diabetes significantly increases the risk of heart failure. The increase in advanced glycation endproducts (AGEs) and oxidative stress have been associated with diabetic cardiomyopathy. We recently demonstrated that there is a direct link between AGEs and oxidative stress. Therefore, the aim of the current study was to investigate if a reduction of AGEs by overexpression of the glycation precursor detoxifying enzyme glyoxalase-I (GLO-I) can prevent diabetes-induced oxidative damage, inflammation and fibrosis in the heart. Diabetes was induced in wild-type and GLO-I transgenic rats by streptozotocin. After 24-weeks of diabetes, cardiac function was monitored with ultrasound under isoflurane anesthesia. Blood was drawn and heart tissue was collected for further analysis. Analysis with UPLC-MSMS showed that the AGE Nε-(1-carboxymethyl)lysine and its precursor 3-deoxyglucosone were significantly elevated in the diabetic hearts. Markers of oxidative damage, inflammation, and fibrosis were mildly up-regulated in the heart of the diabetic rats and were attenuated by GLO-I overexpression. In this model of diabetes, these processes were not accompanied by significant changes in systolic heart function, i.e., stroke volume, fractional shortening and ejection fraction. This study shows that 24-weeks of diabetes in rats induce early signs of mild cardiac alterations as indicated by an increase of oxidative stress, inflammation and fibrosis which are mediated, at least partially, by glycation.

Blocking of frizzled signaling with a homologous peptide fragment of wnt3a/wnt5a reduces infarct expansion and prevents the development of heart failure after myocardial infarction.

BACKGROUND: The molecular pathways that control the wound healing after myocardial infarction (MI) are not completely elucidated. One of these pathways is the Wnt/Frizzled pathway. In this study, we evaluated Frizzled as a novel therapeutic target for MI. These Frizzled proteins act as receptors for Wnt proteins and were previously shown to be expressed in the healing infarct. METHODS AND RESULTS: Wnt/Frizzled signaling has been studied for decades, but synthetic ligands that interfere with the interaction between Wnts and Frizzled have not been described to date. Here we report the selection of 3 peptides derived from regions of high homology between Wnt3a and Wnt5a that act as antagonists for Frizzled proteins. UM206, the peptide with the highest affinity, antagonized the effect of Wnt3a and Wnt5a in different in vitro assays. Administration of UM206 to mice for 5 weeks, starting immediately after the induction of MI, reduced infarct expansion and increased the numbers of capillaries and myofibroblasts in the infarct area. Moreover, heart failure development was inhibited by this therapy. CONCLUSIONS: Blocking of Frizzled signaling reduces infarct expansion and preserves cardiac function after MI. Our findings underscore the potential of Frizzled receptors as a target for pharmacotherapy of cardiac remodeling after MI.

Myofibroblasts in the infarct area: concepts and challenges.

Myofibroblasts are differentiated fibroblasts that hold a key role in wound healing and remodeling following myocardial infarction (MI). A large repertoire of stimuli, such as mechanical stretch, growth factors, cytokines, and vasoactive peptides, induces myofibroblast differentiation. Myofibroblasts are responsible for the production and deposition of collagen, leading to the establishment of a dense extracellular matrix that strengthens the infarcted tissue and minimizes dilatation of the infarct area. In addition, cells contributing to fibrosis act on sites distal from the infarct area and promote collagen deposition in noninfarcted tissue, thus contributing to adverse remodeling and consequently to the development of congestive heart failure (CHF). Current drugs that are used to treat post-MI CHF do influence fibroblasts and myofibroblasts; however, their therapeutic efficacy is far from being regarded as ideal. Novel therapeutic agents targeting (myo)fibroblasts are being developed to successfully prevent the cardiac remodeling of sites remote from the infarct area and therefore hinder the establishment of CHF. The purpose of this review article is to discuss the basic concepts of the myofibroblasts' actions in cardiac wound healing processes, factors that influence them, currently available pharmacological agents, and future challenges in this area.

The CD40-TRAF6 axis is the key regulator of the CD40/CD40L system in neointima formation and arterial remodeling.

We investigated the role of CD40 and CD40L in neointima formation and identified the downstream CD40-signaling intermediates (tumor necrosis factor [TNF]-receptor associated factors [TRAF]) involved. Neointima formation was induced in wild-type, CD40(-/-), CD40L(-/-), and in CD40(-/-) mice that contained a CD40 transgene with or without mutations at the CD40-TRAF2,3&5, TRAF6, or TRAF2,3,5&6 binding sites. Compared with wild-type mice, CD40(-/-) mice showed a significant decrease in neointima formation with increased collagen deposition and decreased inflammatory cell infiltration. Neointima formation was also impaired in wild-type mice reconstituted with CD40(-/-) bone marrow. In vitro, the capacity of CD40(-/-) leukocytes to adhere to the endothelium was reduced. Ligated carotid arteries of CD40(-/-) mice showed a smaller total vessel volume and an impaired remodeling capacity, reflected by decreased gelatinolytic/collagenolytic activity. Comparable results were found in mice with defects in CD40-TRAF6 and CD40-TRAF 2/3/5&6 binding, but not in mice with defects in CD40-TRAF2/3&5 binding. Neointima formation and vascular remodeling in CD40-receptor-deficient mice is impaired, due to a decreased inflammatory cell infiltration and matrix-degrading protease activity, with CD40-TRAF6 signaling as the key regulator. This identifies the CD40-TRAF6 axis as a potential therapeutic target in vascular disease.

Haemodynamic effects of the flavonoid quercetin in rats revisited.

BACKGROUND AND PURPOSE: The flavonoid quercetin increased the in vitro potency of the α1 -antagonist tamsulosin to reduce phenylephrine-dependent arterial contractions by 10-fold. To examine if this supplement-drug interaction luxates hypotensive and orthostatic events in vivo, several set of studies were conducted in spontaneously hypertensive (SHR) and normotensive (Wistar Kyoto [WKY]) rats. EXPERIMENTAL APPROACH: First, in rats pretreated with quercetin or its vehicle, responses to phenylephrine and tamsulosin were examined. Second, tamsulosin-induced changes in renal, mesenteric, hindquarter and carotid conductance were compared in quercetin- and vehicle-treated rats instrumented with Doppler flow probes. Animals were also placed on a tilt table to record regional haemodynamic changes to orthostatic challenges. Third, adult SHR were instrumented with telemeters to measure 24-hr patterns of BP. Recordings were made before and during a 5-week oral treatment of quercetin. Finally, pre-hypertensive SHR were treated with quercetin from 4 to 8 weeks of age and arterial pressure was measured at 8 and 12 weeks. KEY RESULTS: Pretreatment with quercetin did not influence the responses to phenylephrine and tamsulosin, in neither WKY nor SHR. While tamsulosin treatment and tilting lowered BP and increased conductance in all vascular beds, effect size was not influenced by pretreatment with quercetin. Prolonged treatment with quercetin, in either prehypertensive SHR or adult SHR with established hypertension did not lower BP. CONCLUSIONS AND IMPLICATIONS: Cumulatively, these data demonstrate that quercetin does not amplify haemodynamic effects of tamsulosin or tilting in vivo in rats and has no effect on BP development in SHR.

Smoothelin-B deficiency results in reduced arterial contractility, hypertension, and cardiac hypertrophy in mice.

BACKGROUND: Smoothelins are actin-binding proteins that are abundantly expressed in healthy visceral (smoothelin-A) and vascular (smoothelin-B) smooth muscle. Their expression is strongly associated with the contractile phenotype of smooth muscle cells. Analysis of mice lacking both smoothelins (Smtn-A/B(-/-) mice) previously revealed a critical role for smoothelin-A in intestinal smooth muscle contraction. Here, we report on the generation and cardiovascular phenotype of mice lacking only smoothelin-B (Smtn-B(-/-)). METHODS AND RESULTS: Myograph studies revealed that the contractile capacity of the saphenous and femoral arteries was strongly reduced in Smtn-B(-/-) mice, regardless of the contractile agonist used to trigger contraction. Arteries from Smtn-A/B(-/-) compound mutant mice exhibited a similar contractile deficit. Smtn-B(-/-) arteries had a normal architecture and expressed normal levels of other smooth muscle cell-specific genes, including smooth muscle myosin heavy chain, alpha-smooth muscle actin, and smooth muscle-calponin. Decreased contractility of Smtn-B(-/-) arteries was paradoxically accompanied by increased mean arterial pressure (20 mm Hg) and concomitant cardiac hypertrophy despite normal parasympathetic and sympathetic tone in Smtn-B(-/-) mice. Magnetic resonance imaging experiments revealed that cardiac function was not changed, whereas distension of the proximal aorta during the cardiac cycle was increased in Smtn-B(-/-) mice. However, isobaric pulse wave velocity and pulse pressure measurements indicated normal aortic distensibility. CONCLUSIONS: Collectively, our results identify smoothelins as key determinants of arterial smooth muscle contractility and cardiovascular performance. Studies on mutations in the Smtn gene or alterations in smoothelin levels in connection to hypertension in humans are warranted.

Cardiac hypertrophy is enhanced in PPAR alpha-/- mice in response to chronic pressure overload.

AIMS: Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a nuclear receptor regulating cardiac metabolism that also has anti-inflammatory properties. Since the activation of inflammatory signalling pathways is considered to be important in cardiac hypertrophy and fibrosis, it is anticipated that PPARalpha modulates cardiac remodelling. Accordingly, in this study the hypothesis was tested that the absence of PPARalpha aggravates the cardiac hypertrophic response to pressure overload. METHODS AND RESULTS: Male PPARalpha-/- and wild-type mice were subjected to transverse aortic constriction (TAC) for 28 days. TAC resulted in a more pronounced increase in ventricular weight and left ventricular (LV) wall thickness in PPARalpha-/- than in wild-type mice. Compared with sham-operated mice, TAC did not affect cardiac function in wild-type mice, but significantly depressed LV ejection fraction and LV contractility in PPARalpha-/- mice. Moreover, after TAC mRNA levels of hypertrophic (atrial natriuretic factor, alpha-skeletal actin), fibrotic (collagen 1, matrix metalloproteinase-2), and inflammatory (interleukin-6, tumour necrosis factor-alpha, cyclo-oxygenase-2) marker genes were higher in PPARalpha-/- than in wild-type mice. The mRNA levels of genes involved in fatty acid metabolism (long-chain acyl-CoA synthetase, hydroxyacyl-CoA dehydrogenase) were decreased in PPARalpha-/- mice, but were not further compromised by TAC. CONCLUSION: The present findings show that the absence of PPARalpha results in a more pronounced hypertrophic growth response and cardiac dysfunction that are associated with an enhanced expression of markers of inflammation and extracellular matrix remodelling. These findings indicate that PPARalpha exerts salutary effects during cardiac hypertrophy.

The Beneficial Effects of UM206 on Wound Healing After Myocardial Infarction in Mice Are Lost in Follow-Up Experiments.

Introduction: An inadequate wound healing following myocardial infarction (MI) is one of the main etiologies of heart failure (HF) development. Interventions aiming at improving this process may contribute to preserving cardiac function after MI. Our group, as well as others, have demonstrated the crucial role of Wnt/frizzled signaling in post-MI remodeling. In this overview, we provide the results of different studies aimed at confirming an initial study from our group, in which we observed beneficial effects of administration of a peptide fragment of Wnt5a, UM206, on infarct healing in a mouse MI model. Methods: Mice were subjected to permanent left coronary artery ligation, and treated with saline (control) or UM206, administered via osmotic minipumps. Cardiac function was assessed by echocardiography and hemodynamic measurements, while infarct size and myofibroblast content were characterized by (immuno)histochemistry. Results: In total, we performed seven follow-up studies, but we were unable to reproduce the beneficial effects of UM206 on infarct healing in most of them. Variations in dose and timing of UM206 administration, its manufacturer and the genetic background of the mice could not restore the phenotype. An in-depth analysis of the datasets revealed that the absence of effect of UM206 coincided with a lack of adverse cardiac remodeling and HF development in all experimental groups, irrespective of the treatment. Discussion: Irreproducibility of experimental observations is a major issue in biomedical sciences. It can arise from a relatively low number of experimental observations in the original study, a faulty hypothesis or a variation in the experimental model that cannot be controlled. In this case, the lack of adverse cardiac remodeling and lung weight increases in the follow-up studies point out to altered experimental conditions as the most likely explanation.

Endogenous hedgehog expression contributes to myocardial ischemia-reperfusion-induced injury.

The developmentally important hedgehog (Hh) pathway is activated in ischemic tissue, and exogenously administered Sonic hedgehog (Shh) supports tissue repair after cardiac ischemia. Hence, it is currently assumed that the endogenous increase in Shh during ischemia serves a beneficial role in limiting cardiac tissue damage. To prove or refute this hypothesis, we treated mice with the smoothened (Smo) inhibitor cyclopamine to block the Hh pathway during myocardial ischemia and reperfusion. The experimental induction of myocardial ischemia resulted in activation of the Hh pathway and hallmark features of myocardial damage, such as left ventricular dilatation and reduced cardiac output. Unexpectedly, cyclopamine treatment ameliorated left ventricular dilatation and cardiac output. As the beneficial effect of exogenous Shh was suggested to depend on reduced apoptosis, increased vascularization, and reduced fibrosis, we subsequently assessed the effect of cyclopamine on these processes. Vascularization was similar in cyclopamine-treated and control-treated animals, but increased apoptosis and reduced fibrosis were observed in the cyclopamine-treated animals. Thus, Hh seems to exert a dualistic action in cardiac ischemia in which high exogenous levels are able to foster tissue repair and endogenous Hh seems to be deleterious.