Thalji, Nassir M

Myxomatous mitral valve disease (MMVD), if untreated, progresses to valve prolapse, mitral regurgitation, and heart failure. Molecular mechanisms contributing to MMVD are poorly understood, and surgery remains the primary treatment for this disease. In the current study, we used whole‐genome expression microarrays in normal (n = 12) and myxomatous (n = 11) mitral valves as a nonbiased approach to identify novel pathways contributing to MMVD. In addition to identifying known contributors to fibrosis in MMVD (e.g. TGFβ signaling), we found robust evidence of immune cell infiltration and activation in myxomatous valves. Specifically, toll‐like receptors (TLRs) 3 and 7, which play a key role in antigen recognition, alongside cell surface receptors CD14 and CD83, characteristic of antigen presenting cells of monocytic lineage, were overexpressed in myxomatous tissue. Interleukin‐7 and the chemokine receptor CX3CR1, implicated in monocyte activation and recruitment, were also upregulated. Interestingly, immune localization appeared independent of “classic” inflammatory cytokines such as IL‐6. Differential expression of a subset of genes was confirmed with qRT‐PCR and immunohistochemistry. In conclusion, these data are the first to demonstrate infiltration of immune cells in MMVD, which may represent a critical process in the initiation and/or progression of this disease. NHLBI

In angiotensin II‐induced hypertension, activation of NADPH oxidase is a major contributor to reactive oxygen species generation and endothelial dysfunction. As exercise has been associated with the augmentation of antioxidant enzyme expression in endothelial cells, we hypothesized that exercise would improve endothelial function in mice angiotensin II‐induced hypertension. Three‐month old received either saline or a pressor dose of angiotensin II (1000 ng/kg/min) using subcutaneous osmotic minipumps, and were housed in cages with or without a running wheel. Endothelium‐dependent relaxation in response to acetylcholine was studied in carotid arteries using isolated organ chamber baths. Gene expression was examined using qRT‐PCR. In angiotensin II‐infused sedentary mice, endothelium‐dependent relaxation was significantly impaired, and was partially improved when NADPH oxidase was inhibited by apocynin. mRNA levels of SOD1, SOD2, SOD3, and NOX2 were increased in aorta, and mRNA levels of NOX4 and NOS3 were substantially decreased. In contrast to our hypothesis, endothelium‐dependent relaxation was not improved in angiotensin II‐infused exercised mice housed with running wheels, despite marked increases in physical activity over the two week time period. We conclude that angiotensin II‐induced hypertension results in profound endothelial dysfunction that is not attenuated by voluntary wheel running exercise. Ongoing work is examining molecular mechanisms underlying these observations, as well as evaluation of the protective effects of regimented exercise of varying intensities.

Reduced antioxidant enzyme activity and subsequent impairments in endothelial function are major contributors to progression of atherosclerosis. We previously reported that endothelium‐dependent relaxation is well‐preserved in manganese superoxide dismutase‐deficient mice (MnSOD +/‐ ) due to production of a compensatory, H 2 O 2 ‐derived endothelial hyperpolarizing factor (EDHF). It is unclear, however, whether similar phenomena occur in hypercholesterolemic mice, and whether reconstitution of mitochondrial antioxidant capacity with mitochondria‐targeted antioxidants (mito‐Tempo) can reverse this phenomena. We used Ldlr ‐/‐ ApoB 100/100 (LA) mice that were either wild‐type (LA‐MnSOD +/+ ) or heterozygous (LA‐MnSOD +/‐ ) for MnSOD. After 6 months of Western diet, mice were treated with either saline (SAL) or MT (0.7mg/kg/day) using osmotic minipumps for 2 weeks. Endothelial function in aorta was assessed using isolated organ chamber baths in the presence or absence of apocynin (an NAD(P)H oxidase inhibitor, APO) . Osmotic minipump implantation significantly worsened baseline endothelial function compared to non‐implanted mice. Overall, relaxation to acetylcholine (MR ACH ) was unchanged between LA‐MnSOD +/+ and LA‐MnSOD +/‐ treated with SAL (3.8±4.5% and 13.6±14.5%, respectively). Treatment with MT significant improved endothelial function in LA‐MnSOD +/+ mice (21.6±7.1%), and MR ACH was further improved after acute incubation with APO (25±6.7%). In LA‐MnSOD +/‐ , MT greatly improved MR ACH (38.6±3.4%). In contrast to LA‐MnSOD +/+ , however, acute incubation of vessels with APO impaired MR ACH (27.3±10%). Collectively, our data suggest that increasing mitochondrial antioxidant capacity substantially improves endothelial function in hypercholesterolemic mice, but does not completely reverse compensatory molecular mechanisms that preserve endothelial function during prolonged mitochondrial antioxidant deficiency. NHLBI Grant Funding Source : Supported by NHLBI

Background and Aims Reliance on exception points to prioritize children for liver transplantation (LT) stems from concerns that the Pediatric End‐Stage Liver Disease (PELD) score underestimates mortality. Renal dysfunction and serum sodium disturbances are negative prognosticators in adult LT candidates and various pediatric populations, but are not accounted for in PELD. We retrospectively evaluated the effect of these parameters in predicting 90‐day wait‐list death/deterioration among pediatric patients (<12 years) listed for isolated LT in the United States between February 2002 and June 2018. Approach and Results Among 4,765 patients, 2,303 (49.3%) were transplanted, and 231 (4.8%) died or deteriorated beyond transplantability within 90 days of listing. Estimated glomerular filtration rate (eGFR) (hazard ratio [HR] 1.09 per 5‐unit decrease, 95% confidence interval [CI] 1.06‐1.10) and dialysis (HR 7.24, 95% CI 3.57‐14.66) were univariate predictors of 90‐day death/deterioration (P < 0.001). The long‐term benefit of LT persisted in patients with renal dysfunction, with LT as a time‐dependent covariate conferring a 2.4‐fold and 17‐fold improvement in late survival among those with mild and moderate‐to‐severe dysfunction, respectively. Adjusting for PELD, sodium was a significant nonlinear predictor of outcome, with 90‐day death/deterioration risk increased at both extremes of sodium (HR 1.20 per 1‐unit decrease below 137 mmol/L, 95% CI 1.16‐1.23; HR per 1‐unit increase above 137 mmol/L 1.13, 95% CI 1.10‐1.17, P < 0.001). A multivariable model incorporating PELD, eGFR, dialysis, and sodium demonstrated improved performance and superior calibration in predicting wait‐list outcomes relative to the PELD score. Conclusions Listing eGFR, dialysis, and serum sodium are potent, independent predictors of 90‐day death/deterioration in pediatric LT candidates, capturing risk not accounted for by PELD. Incorporation of these variables into organ allocation systems may highlight patient subsets with previously underappreciated risk, augment ability of PELD to prioritize patients for transplantation, and ultimately mitigate reliance on nonstandard exceptions.

Background— Pathological processes underlying myxomatous mitral valve degeneration (MMVD) remain poorly understood. We sought to identify novel mechanisms contributing to the development of this condition. Methods and Results— Microarrays were used to measure gene expression in 11 myxomatous and 11 nonmyxomatous human mitral valves. Differential gene expression (thresholds P <0.05; fold-change >1.5) and pathway activation (Ingenuity) were confirmed using quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. Contributions of bone morphogenetic protein 4 and transforming growth factor (TGF)-β2 to differential gene expression were evaluated in vitro. Contributions of angiotensin II to differential pathway activation were examined in mice in vivo. A total of 2602 genes were differentially expressed between myxomatous and nonmyxomatous valves. Canonical TGF-β signaling was increased in MMVD because of increased ligand expression and derepression of SMA mothers against decapentaplegic 2/3 signaling and was confirmed with quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. Myxomatous valves demonstrated activation of canonical bone morphogenetic protein and Wnt/β-catenin signaling and upregulation of their common target runt-related transcription factor 2. Our data set provided transcriptional and immunohistochemical evidence for activated immune cell infiltration. In vitro treatment of mitral valve interstitial cells with TGF-β2 increased β-catenin signaling at mRNA and protein levels, suggesting interactions between TGF-β2 and Wnt signaling. In vivo infusion of mice with angiotensin II recaptured several changes in signaling pathways characteristic of human MMVD. Conclusions— These data support a new disease framework whereby activation of TGF-β2, bone morphogenetic protein 4, Wnt/β-catenin, or immune signaling plays major roles in the pathogenesis of MMVD. We propose these pathways act in a context-dependent manner to drive phenotypic changes that fundamentally differ from those observed in aortic valve disease and open novel avenues guiding future research into the pathogenesis of MMVD.

AbstractTranslational stories range from straightforward to complex. In this commentary, the story of the rapid and successful translation of rituximab therapy for the treatment of non‐Hodgkin's lymphoma (NHL) is examined. Development of this monoclonal antibody therapy began in the late 1980s. In 1994, rituximab received its first approval for the treatment of NHL by the United States Food and Drug Administration (FDA). Rituximab has since been approved for additional indications and has transformed medical practice. However, the social and political implications of these rapid successes are only beginning to become clear. In this commentary, key events in the rapid translation of rituximab from the bench to bedside are highlighted and placed into this historical framework. To accomplish this, the story of rituximab is divided into the following six topics, which we believe to be widely applicable to case studies of translation: (1) underlying disease, (2) key basic science, (3) key clinical studies in translation, (4) FDA approval process, (5) changes to medical practice, and (6) the social and political influences on translation.