Cardiovascular Research

Accumulation of oxalate in patients with chronic kidney disease (CKD) is associated with CKD progression and increased risk of cardiac death. Whether reducing plasma or urine oxalate slows CKD progression and prevents cardiovascular complications remains unexplored. We colonized the intestines of control and CKD mice with Oxalobacter formigenes (Oxf), an oxalate-degrading microorganism. The mice were fed with the oxalate precursor hydroxyproline for 23 weeks at which time we assessed pathological changes in the kidney and heart. We demonstrate that Oxf reduces plasma oxalate (pOx) and creatinine levels, mitigates inflammation and fibrosis in the kidney, and reduces pathologic cardiac remodeling in the hearts of CKD mice. RNA-seq analysis of ventricular tissue of CKD mice reveals dysregulated expression of metabolic pathways while Oxf colonization reverses these changes. These findings demonstrate that oxalate accumulation plays a role not only in CKD progression but also in associated cardiovascular complications and suggest that strategies to reduce plasma oxalate levels may have therapeutic benefit. Translational statementChronic kidney disease (CKD) is a major health problem that can lead to kidney failure and which increases the risk of cardiovascular disease (CVD) mortality. Oxalate accumulation in advanced kidney disease contributes to further CKD progression and CVD complications. Intestinal colonization with Oxalobacter formigenes (Oxf) in a CKD animal model reduces plasma oxalate level and slows progression of both CKD and CVD. Strategies to reduce plasma oxalate levels may have therapeutic benefit in the setting of CKD.

Chronic systolic heart failure (HF) is a prevalent and morbid disease with marked variability in its progression and response to therapies. The gut microbiome may play a role in pathophysiology and progression of chronic HF, but clinical studies investigating relationships between the two are lacking. We analyzed the gut microbiome in a cohort of adults with chronic systolic HF caused by non-ischemic cardiomyopathy (n=59) using multi-omics profiling and, in some cases, longitudinal sampling. We identified microbiome differences compared to healthy subjects (n=50) and associated these differences with host metabolites, inflammatory markers and physiology. We found depletion of the anti-inflammatory probiotic Bifidobacterium and the associated short chain fatty acid producing and formaldehyde detoxifying pathways in the chronic HF cohort. We also discovered HF-specific microbiome-host immunome interactions. In addition to identifying several taxa and microbial pathways broadly associated with HF disease severity, we found significant links between Bifidobacterium and clinical HF improvement over time. Gut microbiome-host multi-omic data integration revealed a close association between Bifidobacterium and circulating metabolites previously implicated in cardiovascular physiology (e.g., malonic acid), thus pointing to potential mechanisms through which Bifidobacterium may affect chronic HF physiology. Our results suggest that Bifidobacterium may serve as a biomarker for chronic HF trajectory as well as suggest potential novel therapeutic interventions strategies.

The vascular barrier is heavily injured following SARS-CoV-2 infection and contributes enormously to life-threatening complications in COVID-19. This endothelial dysfunction is associated with the phlogistic phenomenon of cytokine storms, thrombotic complications, abnormal coagulation, hypoxemia, and multiple organ failure. The mechanisms surrounding COVID-19 associated endotheliitis have been widely attributed to ACE2-mediated pathways. However, integrins have emerged as possible receptor candidates for SARS-CoV-2, and their complex intracellular signalling events are essential for maintaining endothelial homeostasis. Here, we showed that the spike protein of SARS-CoV-2 depends on its RGD motif to drive barrier dysregulation through hijacking integrin V{beta}3. This triggers the redistribution and internalization of major junction protein VE-Cadherin which leads to the barrier disruption phenotype. Both extracellular and intracellular inhibitors of integrin V{beta}3 prevented these effects, similarly to the RGD-cyclic peptide compound Cilengitide, which suggests that the spike protein - through its RGD motif - binds to V{beta}3 and elicits vascular leakage events. These findings support integrins as an additional receptor for SARS-CoV-2, particularly as integrin engagement can elucidate many of the adverse endothelial dysfunction events that stem from COVID-19.

The superantigen staphylococcal enterotoxin C (SEC) is critical for Staphylococcus aureus infective endocarditis (SAIE) in rabbits. Superantigenicity, its hallmark function, was proposed to be a major underlying mechanism driving SAIE but was not directly tested. With the use of S. aureus MW2 expressing SEC toxoids, we show that superantigenicity does not sufficiently account for vegetation growth, myocardial inflammation, and acute kidney injury in the rabbit model of native valve SAIE. These results highlight the critical contribution of an alternative function of superantigens to SAIE. In support of this, we provide evidence that SEC exerts anti-angiogenic effects by inhibiting branching microvessel formation in an ex vivo rabbit aortic ring model and by inhibiting endothelial cell expression of one of the most potent mediators of angiogenesis, VEGF-A. SECs ability to interfere with tissue re-vascularization and remodeling after injury serves as a mechanism to promote SAIE and its life-threatening systemic pathologies.

Backgroundglobal deletion of Vhl leads to vascular defects and early lethality, precluding the study of VHL/HIF signaling during coronary formation and homeostasis. Hypoxia pathway has been associated with cardiovascular diseases involving inflammation and vascular remodeling like atherosclerosis, but its role in Kawasaki Disease (KD) remains unknown. Coronary dilatation and vessel rupture are the most serious complications of KD, while the molecular mechanisms underlying these cardiac events remain poorly understood. Here we aim to determine the function of VHL/HIF pathway in the development of cardiovascular defects and its role in KD. MethodsWe generated a new mouse model to genetically hyperactivate hypoxia pathway in progenitors contributing to coronary vessels and cardiac fibroblasts (Vhl/Wt1). We characterized the model by means of echocardiography, magnetic resonance imaging, histological analysis and molecular approaches. Human cardiac tissue from KD individuals suffering fatal coronary aneurysm were screened for HIF signaling and inflammatory markers by immunohistochemistry. Resultsconditional Vhl KO do not undergo developmental abnormalities but displays cardiomegaly and epicardial vascular defects, with cardiac hypertrophy and progressive coronary diameter increase, as well as pericardial hemorrhage and systemic inflammation early after birth. Histological characterization reveals inflammation of coronary arteries, vascular remodeling with elastin breaks and dilatation, increased perivascular fibrosis and smooth muscle cells death, together with high incidence of intracoronary thrombus formation. In addition, the mutants display vascular calcification and severe cardiac inflammation and interstitial hemorrhages, dying suddenly between 15-20 weeks of age due to vessel rupture. Simultaneous elimination of HIF2 and VHL prevents the cardiovascular abnormalities displayed by single cVhl KO, highlighting the essential role of HIF2 in coronary instability and vascular inflammation. Histological characterization of human cardiac samples shows positive signal for HIF1 and specially HIF2, in the coronary lesions and its surroundings in regions with high inflammatory infiltration, confirming the activation of hypoxia signaling in KD patients with cardiovascular complications. ConclusionsOur data demonstrate the importance of HIF2 signaling in the development of coronary inflammation and vascular remodeling and provide new evidences connecting low oxygen tensions with cardiovascular lesions occurring during the onset of the most severe cases of KD. Furthermore, the Vhl/Wt1 mouse generated recapitulates cardiac features of KD with critical heart complications, providing a new platform to uncover unknown aspects of KD pathogenesis.

BackgroundObesity is a major risk factor for heart failure (HF), but the molecular mediators linking adiposity to HF remain unclear. The molecular mechanisms by which weight loss reduces the risk of HF are also unknown. Understanding these mechanisms could highlight potential therapeutic targets for all HF patients, including those who are normal weight. We aimed to identify a common metabolic perturbation profile by comparing different weight-loss interventions and to estimate their associations with HF using Mendelian randomisation (MR). MethodsWe first integrated mass spectrometry and nuclear magnetic resonance metabolomic profiling from two weight-loss interventions - a structured diet programme (DiRECT trial) and bariatric surgery (By-Band-Sleeve trial) - with estimates of the effect of life-time body mass index (BMI) exposure on metabolite levels through MR analyses, to identify a consistent BMI-metabolite signature across differing sources of BMI variation. We then assessed the impact of these BMI-metabolites on incident HF within a two sample MR framework. Results1706 metabolites were analysed across three different sources of BMI variation: bariatric surgery, dietary intervention and life-time BMI exposure. 153 (9%) showed strong evidence for association with all three exposures with concordant direction of effect, predominantly comprising lipid fractions, lipoproteins, and amino acid metabolites. Among these metabolites, 44 (29%) had evidence of causal association with at least one HF subtype in MR. Notably, circulating levels of the non-lipid metabolites N-acetylglycine and asparagine were each inversely associated with BMI and with the risk of HF and HF with preserved ejection fraction risk, respectively. Both metabolites have previously been implicated in myocardial function and HF. ConclusionsOur findings suggest that despite differences in the modality of weight loss delivery, there exists a consistent metabolomic profile coincident with weight change. Investigating the association of the identified metabolites with HF provides insights into molecular mediators of the effects of adiposity on HF and potential novel targets for therapeutic intervention.

Right ventricular failure (RVF) is a leading cause of morbidity and mortality in multiple cardiovascular diseases, but there are no approved treatments for RVF as therapeutic targets are not clearly defined. Contemporary transcriptomic/proteomic evaluations of RVF are predominately conducted in small animal studies, and data from large animal models are sparse. Moreover, a comparison of the molecular mediators of RVF across species is lacking. Here, we used transcriptomics and proteomics analyses to define the molecular pathways associated with cardiac MRI-derived values of RV hypertrophy, dilation, and dysfunction in pulmonary artery banded (PAB) piglets. Publicly available data from rat monocrotaline-induced RVF and pulmonary arterial hypertension patients with preserved or impaired RV function were used to compare the three species. Transcriptomic and proteomic analyses identified multiple pathways that were associated with RV dysfunction and remodeling in PAB pigs. Surprisingly, disruptions in fatty acid oxidation (FAO) and electron transport chain (ETC) proteins were different across the three species. FAO and ETC proteins and transcripts were mostly downregulated in rats, but were predominately upregulated in PAB pigs, which more closely matched the human data. Thus, the pig PAB metabolic molecular signature was more similar to human RVF than rodents. These data suggest there may be divergent molecular responses of RVF across species, and that pigs more accurately recapitulate the metabolic aspects of human RVF.

BACKGROUNDDiabetes is an independent risk factor for ischemic stroke. This study was undertaken to determine whether hemodynamic cerebral ischemia (HCI), which increases stroke severity, is more frequent in diabetic patients. METHODSBetween 01/01/1990 and 30/06/2019, we revascularized 4117 carotid bifurcations in 3739 patients (2683 men and 1056 women; mean age: 71 (range: 28-97) years; 940 (25.1%) diabetics and 2799 (74.9%) nondiabetics). HCI was diagnosed clinically, under regional anesthesia, when a shunt needed to be inserted. RESULTSThe HCI rate during carotid-clamping, requiring shunt placement, was 11.0% (114/1034) for diabetics and 7.1% (219/3083) for nondiabetics (odds ratio,1.62 [95% CI, 1.27-2.05]; P<0.0001). CONCLUSIONSDiabetes was associated with increased HCI risk in our patients with carotid stenosis. This HCI-associated excess risk might explain, in part, stroke severity in diabetics and heightened surgical risk. It might be prevented by HCI detection and modification of therapeutic management.

Intermittent hypoxia and hypercapnia (IHC), a hallmark of obstructive sleep apnea (OSA), accelerates atherosclerosis, yet the underlying mechanisms remain unclear. The gut microbiota and metabolites, specifically bile acids, change with IHC and thus the bile acid receptor farnesoid X receptor (FXR) might mediate IHC-induced atherosclerosis. In this study, ApoE-/- and ApoE-/- FXR-/- mice were exposed to IHC or room air and fed with a high-fat, high-cholesterol diet for 10 weeks. Markers of atherosclerosis, fecal microbiome, and metabolome were then examined via Sudan IV staining, absolute abundance shotgun metagenomics, and untargeted liquid chromatography tandem mass spectrometry (LC-MS/MS). IHC markedly increased aortic atherosclerosis in ApoE-/-mice, an increase that was abolished by FXR deficiency. In addition, IHC reshaped gut microbial composition, promoting enrichment of bile acid-modifying taxa and increasing levels of microbial hydroxysteroid dehydrogenase (hsdh). The bile acid pool was also remodeled and associated with aortic atherosclerosis via FXR-dependent metabolic signals in ApoE-/- mice. Knockout of FXR disrupted microbiome shift under IHC and uncoupled microbial bile acid metabolism from vascular lesion development, thereby protecting against aortic atherosclerosis. These findings show that FXR has a central role in linking IHC, microbial bile acid metabolism, and cardiovascular pathology.

Aortic distensibility refers to the ability of arteries to expand in response to pulse pressure generated by the cardiac cycle, and this often decreases with age. Genome-wide association studies have identified genetic variants associated with distensibility; however, the mechanisms leading to changes in distensibility re-main unclear. In this study we examined aortic distensibility through the lens of genomics, considering both cellular composition and cell type specific gene expression, inferred from bulk gene expression data, to investigate how these factors contribute to the observed changes in distensibility associated with age and genotype. We found age-related decreases in the proportions of Pericytes and Fibroblast I cells, while the proportion of vascular smooth muscle cells type II (VSMC II) increased. Notably, most of the gene expression changes asso-ciated with age were identified in VSMC I, VSMC II and Fibroblast I cells. Furthermore, we observed that the cell type-specific expression of most genes associated with distensibility correlated with age, specifically VSMC I, VSMC II, Fibroblast I, and Pericyte cells. We also tested for genetic associations with the extent of increased distensibility with age in the UK Biobank and found two independent loci, both of which showed a marginally significant associa-tion with the increased distensibility with age. None of the identified GWAS SNPs were significantly associated with the inferred cellular proportions. Inter-estingly, we found two independent SNPs that had a genome-wide significant association with distensibility were also associated with cell type specific ex-pression of nearby genes (SRR in VSMC I, VSMC II and Fibroblast I, as well as CDH13 in VSMC I) that have been implicated in aortic distensibility. Over-all, our results identify cell type specific changes in gene expression that may help to explain genetic and age-related variation in this important physiological phenotype.

Vascular cognitive impairment (VCI) shares major risk factors with heart failure with preserved ejection fraction (HFpEF), including obesity, diabetes and hypertension. Yet VCI research often relies on single-stimulus models, whereas patients experience combined risk factors. We therefore assessed cerebrovascular and cognitive phenotypes in an HFpEF model and investigated underlying mechanisms. Male Lean and Obese ZSF1 rats underwent longitudinal assessments of blood pressure, glucose, cardiac function, and behavioural performance. Cerebral blood flow and neurovascular coupling were assessed by laser speckle contrast imaging. White matter integrity, blood-brain barrier (BBB) permeability, and vascular density were analysed by (immuno)histochemistry. Cortical microvessels were isolated for transcriptomic profiling, and selected targets were validated using multiplex in-situ hybridization. Obese rats exhibited neurovascular uncoupling and impaired short- and long-term memory and spatial learning, accompanied by brain atrophy and reduced myelin. BBB permeability increased at 22-23 weeks and vascular density at 34-35 weeks in Obese vs Lean rats. Transcriptomic analysis of brain microvessels revealed altered processes related to angiogenesis, vasoreactivity, immune mechanisms and vascular remodelling, with consistent downregulation of Trpv4 and Klf2. Obese ZSF1 rats develop progressive neurovascular dysfunction associated with HFpEF onset and reduced Trpv4 and Klf2 expression in cerebral microvessels, two key vasoprotective genes.

We address a paradox, that AMPK may facilitate hypoxic pulmonary vasoconstriction and its deficiency precipitate pulmonary hypertension. Here we show that AMPK-1/2 deficiency in smooth muscles promotes persistent pulmonary hypertension of the newborn. Accordingly, dual AMPK-1/2 deletion in smooth muscles causes premature death of mice after birth, associated with increased muscularization and remodeling throughout the pulmonary arterial tree, reduced alveolar numbers and alveolar membrane thickening, but with no edema. Spectral Doppler ultrasound indicates pulmonary hypertension and attenuated hypoxic pulmonary vasoconstriction. Age-dependent right ventricular pressure elevation, dilation and reduced cardiac output was also evident. KV1.5 potassium currents of pulmonary arterial myocytes are markedly smaller under normoxia, which is known to facilitate pulmonary hypertension. Mitochondrial fragmentation and reactive oxygen species accumulation is also evident. Importantly, there is no evidence of systemic vasculopathy or hypertension in these mice. Moreover, hypoxic pulmonary vasoconstriction is attenuated by AMPK-1 or AMPK-2 deletion without triggering pulmonary hypertension.

Hypoxia is associated with the onset of cardiovascular diseases including cardiac hypertrophy and pulmonary arterial hypertension (PAH). Endothelial HIF2 signaling mediates pulmonary arterial remodeling and subsequent right ventricular systolic pressure (RVSP) elevation during chronic hypoxia, encouraging novel therapeutic opportunities for PAH based on specific HIF2 inhibitors. Nevertheless, HIF2 relevance beyond the pulmonary endothelium or in the cardiac adaptation to hypoxia remains elusive. Wilms tumor 1 lineage contributes to heart and lung vascular compartments including pericytes, endothelial and smooth muscle cells. Here we describe the response to chronic hypoxia of a novel HIF2 mutant mouse model in the Wt1 lineage (Hif2/Wt1 cKO). Hif2/Wt1 cKO is protected against pulmonary remodeling and increased RVSP induced by hypoxia, but displays alveolar congestion, inflammation and hemorrhages associated with microvascular instability. Furthermore, lack of HIF2 in the Wt1 lineage leads to cardiomegaly, capillary remodeling, right and left ventricular hypertrophy, systolic dysfunction and left ventricular dilation, suggesting pulmonary-independent cardiac direct roles of HIF2 in hypoxia. These structural defects are partially restored upon reoxygenation, while functional parameters remain altered. Our results suggest that cardiopulmonary HIF2 signaling prevents excessive vascular proliferation during chronic hypoxia and define novel protective roles of HIF2 to warrant stable microvasculature and organ function.

Vascular properties of the retina are indicative not only of ocular but also of systemic cardio- and cere-brovascular health. However, the specific relationships between retinal vascular phenotypes and those in other organs have not been systematically investigated in large samples. Here, we compared vascular image-derived phenotypes from the brain, carotid artery, aorta, and retina from the UK Biobank, with sample sizes ranging from 18,808 to 68,740 participants per phenotype. We examined the cross-organ phenotypic and genetic correlations, as well as common associated genes and pathways. White matter hyperintensities were positively correlated with carotid intima-media thickness (r=0.03), lumen diameter (r=0.14), and aortic cross-sectional areas (r=0.09), but negatively correlated with aortic distensibilities (r[&le;]-0.05). Arterial retinal vascular density showed negative correlations with white matter hyperintensities (r=-0.04), intima-media thickness (r=-0.04), lumen diameter (r=-0.06), and aortic areas (r=-0.05), while positively correlated with aortic distensibilities (r=0.04). Significant correlations were also observed between other retinal phenotypes and white matter hyperintensities, as well as aortic phenotypes. Correcting for hypertension reduced the magnitude of these correlations, though the overall correlation structure persisted. Genetic correlations and gene enrichment analyses identified potential modulators of these phenotypes, with some shared genetic influence between retinal and non-retinal phenotypes. Our study sheds light on the complex interplay between vascular morphology in different organs, revealing shared and distinct genetic underpinnings, and suggesting that retinal vascular features may reflect broader vascular morphology.

Cardiac complications are among the most common and severe extrapulmonary manifestations of influenza virus infection, yet they are rarely recapitulated in mouse models without immunodeficiency. We found that influenza virus A/California/04/2009 (H1N1) carrying a mouse-adaptive amino acid substitution in the PB2 protein (E158A) disseminates to the heart in WT C57BL/6 mice, where it induces inflammation, electrical dysfunction, and fibrotic remodeling. Influenza virus-infected heart tissue was significantly altered in mitochondrial metabolism, extracellular matrix, circadian rhythm, and immunity pathways. Particularly striking was activation of gene expression downstream of the mitochondrial biogenesis-promoting AMPK/PGC-1 axis, which occurred late in infection but failed to reverse the repression of mitochondria-associated genes, suggesting an insufficient or delayed compensatory response. Accordingly, we administered AMPK activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) early in infection and observed restoration of mitochondria-associated gene levels, amelioration of cardiac electrical dysfunction and fibrosis, and improvement in survival without overt effects on lung function. Overall, the advent of an immunocompetent model for severe influenza-associated cardiac dysfunction revealed activation of AMPK signaling as a host-targeted metabolic intervention for mitigating virus-induced heart pathologies

BackgroundPulmonary arterial hypertension (PAH) is a progressive disease characterized by pulmonary microvascular loss and obliterative remodeling, driven by metabolic reprogramming, oxidative stress, and endothelial dysfunction. While BMPR2 mutations contribute to metabolic shifts in pulmonary microvascular endothelial cells (PMVECs), their low penetrance suggests additional genetic modifiers play a role. A genetic screen of PAH PMVECs identified carboxylesterase 1 (CES1)--an endoplasmic reticulum (ER) enzyme involved in lipid metabolism and detoxification--as a candidate regulator of endothelial metabolism and angiogenesis. We hypothesize that CES1 loss promotes endothelial dysfunction via metabolic reprogramming, lipotoxicity, and oxidative stress. MethodsPAH and healthy PMVECs and lung tissues were obtained from transplant donors and commercial sources. CES1 expression was modulated in PMVECs using siRNA knockdown and plasmid overexpression. Mitochondrial and ER function were assessed via confocal microscopy and proteomics. CES1 heterozygous knockout (HET KO) and endothelial-specific knockout (ECKO) mice were exposed to normoxia or hypoxia, with lung tissues analyzed by single-cell RNA sequencing (scRNA-seq) and histopathology. ResultsCES1 expression was significantly reduced in PAH PMVECs and vascular lesions. CES1-deficient PMVECs exhibited increased apoptosis, reactive oxygen species (ROS) production, mitochondrial fragmentation, ER stress, and impaired angiogenesis. Confocal imaging and metabolic studies revealed lipid droplet accumulation, reduced fatty acid oxidation, and a glycolytic shift-- phenotypes reversed by CES1 restoration. Mechanistically, CES1 transcription was induced by BMPR2 via NRF2 activation, a key regulator of redox and metabolic homeostasis. In vivo, CES1-deficient mice developed severe pulmonary hypertension (PH) under hypoxia, with extensive vascular remodeling, right ventricular dysfunction, and dysregulated angiogenesis and lipid metabolism pathways, as confirmed by lung scRNA-seq. ConclusionsCES1 is essential for pulmonary endothelial homeostasis and serves as a critical modifier of BMPR2 signaling. Given the limited efficacy of current PAH therapies in reversing endothelial dysfunction and small-vessel loss, restoring CES1 expression represents a promising therapeutic strategy.

Fibrillin-1 assembles into microfibrils that not only define the structural integrity and biomechanics of the aorta but also target and sequester growth factors within the extracellular microenvironment of aortic resident cells. To better understand how dominant negative effects on fibrillin microfibril stability manifest in growth factor driven aortic disease, we analyzed early events of aortic aneurysm formation within the first two weeks of postnatal life in the dominant negative Fbn1 GT8 Marfan mouse model. Echocardiography analysis of homozygous GT8 Fbn1 mice showed significant aortic root enlargement within the second week of postnatal life which correlated with the onset of fibrillin-1 fiber degradation, aberrantly increased BMP activity and upregulated transcript levels of the collagenase MMP-13. We also found the aortic collagen network structurally disturbed where the mutant GT8-fibrillin-1 was detected. Genetic ablation or pharmacological inhibition of MMP-13 in Fbn1 GT8 Marfan mice prevents aortic root dilatation implicating the relevance of this mechanism in aortic aneurysm formation in Marfan syndrome.

OPA1 is an inner mitochondrial membrane protein that mediates diverse signaling processes. OPA1 is important for cardiac function and protects against cardiac insults such as ischemia reperfusion injury. We sought to further assess OPA1 in human and mouse cardiac pathologies, hypothesizing that OPA1 may also function in a protective manner in chronic heart failure. Bioinformatic analyses of histological and transcript data from the GTEx database indicated that OPA1 expression levels vary in the human heart, where elevated OPA1 transcript levels were correlated with fatty acid, branch chain amino acid and contractile gene signatures. To experimentally assess these correlations, mice with a 1.5-fold whole body OPA1 overexpression (OPA1-OE) were subjected to transverse aortic constriction surgery and displayed improved 2D and 4D cardiac functional parameters compared to WT mice. OPA1-OE mice had no induction of fibrotic transcript markers and displayed sustained transcript levels of fatty acid, branch chain amino acid and contractile markers. Maximal oxidative capacity was sustained in both WT and OPA1-OE cardiac myofibers post-TAC. These results further demonstrate the important role of OPA1 in mediating cardiac function and highlight protective signaling pathways.

BackgroundVein graft failure (VGF) following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. While previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on VGF. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury. MethodsEmploying a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing (snRNA-seq) and spatial transcriptomics (ST) analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-cartoid vein bypass implantation in a canine model (n=4). ResultsSpatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P < 0.05) involved in the activation of endothelial cells (ECs), fibroblasts (FBs), and vascular smooth muscle cells (VSMCs), namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and extracellular matrix (ECM) remodeling throughout the vein wall. Subsequent snRNA-seq analysis supported these findings and further unveiled distinct EC and FB subpopulations with significant upregulation (P < 0.00001) of markers related to endothelial injury response and cellular activation of ECs, FBs, and VSMCs. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury-response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN (versican), FBN1 (fibrillin-1), and VEGFC (vascular endothelial growth factor C), in addition to novel genes of interest such as GLIS3 (GLIS family zinc finger 3) and EPHA3 (ephrin-A3). These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the ST and snRNA-seq datasets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and FBs were notably enriched in the intima and media of distended veins. Lastly, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal transitioning ECs, protomyofibroblasts, and VSMCs in upregulating signaling pathways associated with cellular proliferation (MDK, PDGF, VEGF), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension. ConclusionsVein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

BackgroundRecent advances have revealed the importance of epigenetic modifications to gene regulation and transcriptional activity. DNA methylation, a determinant of genetic imprinting and de novo silencing of genes genome-wide, is known to be controlled by DNA methyltransferases (DNMT) and demethylases (TET) under disease conditions. However, the mechanism(s)/factor(s) influencing the expression and activity of DNMTs and TETs, and thus DNA methylation, in healthy vascular tissue is incompletely understood. Based on our recent studies, we hypothesized that glucose-6-phosphate dehydrogenase (G6PD) is a modifier of DNMT and TET expression and activity and an enabler of gene expression. MethodsIn aorta of CRISPR-edited rats with the Mediterranean G6PD variant we determined DNA methylation by whole-genome bisulfite sequencing, gene expression by RNA sequencing, and large artery stiffness by echocardiography. ResultsHere, we documented higher expression of Dnmt3a, Tet2, and Tet3 in aortas from Mediterranean G6PDS188F variant (a loss-of-function single nucleotide polymorphism) rats than their wild-type littermates. Concomitantly, we identified 17,618 differentially methylated loci genome-wide (5,787 hypermethylated loci, including down-regulated genes encoding inflammation- and vasoconstriction-causing proteins, and 11,827 hypomethylated loci, including up-regulated genes encoding smooth muscle cell differentiation- and fatty acid metabolism-promoting proteins) in aorta from G6PDS188F as compared to wild-type rats. Further, we observed less large artery (aorta) stiffness in G6PDS188F as compared to wild-type rats. ConclusionsThese results establish a noncanonical function of the wild-type G6PD and G6PDS188F variant in the regulation of DNA methylation and gene expression in healthy vascular tissue and reveals G6PDS188F variant contributes to reduce large artery stiffness. HighlightsO_LIThe wild-type G6PD and G6PDS188F variant regulates the expression and activity of nuclear DNMT and TET and selectively evokes hyper/hypo-methylation of loci/promoter regions genome-wide. C_LIO_LIG6PDS188F variant represses and activates genes detrimental and beneficial to vascular cell phenotype and function, respectively. C_LIO_LIG6PDS188F variant reduces large artery stiffness. C_LI