Identification of cardiovascular high-risk groups from dynamic retinal vessel signals using untargeted machine learning.

AIMS: Dynamic retinal vessel analysis (DVA) provides a non-invasive way to assess microvascular function in patients and potentially to improve predictions of individual cardiovascular (CV) risk. The aim of our study was to use untargeted machine learning on DVA in order to improve CV mortality prediction and identify corresponding response alterations. METHODS AND RESULTS: We adopted a workflow consisting of noise reduction and extraction of independent components within DVA signals. Predictor performance was assessed in survival random forest models. Applying our technique to the prediction of all-cause mortality in a cohort of 214 haemodialysis patients resulted in the selection of a component which was highly correlated to maximal venous dilation following flicker stimulation (vMax), a previously identified predictor, confirming the validity of our approach. When fitting for CV mortality as the outcome of interest, a combination of three components derived from the arterial signal resulted in a marked improvement in predictive performance. Clustering analysis suggested that these independent components identified groups of patients with substantially higher CV mortality. CONCLUSION: Our results provide a machine learning workflow to improve the predictive performance of DVA and identify groups of haemodialysis patients at high risk of CV mortality. Our approach may also prove to be promising for DVA signal analysis in other CV disease states.

Electrocardiographic parameters of left ventricular hypertrophy and prediction of mortality in hemodialysis patients.

BACKGROUND: In hemodialysis patients, left ventricular hypertrophy (LVH) contributes to high cardiovascular mortality. We examined cardiovascular mortality prediction by the recently proposed Peguero-Lo Presti voltage since it identifies more patients with electrocardiographic (ECG) LVH than Cornell or Sokolow-Lyon voltages. METHODS: A total of 308 patients on hemodialysis underwent 24 h ECG recordings. LVH parameters were measured before and after dialysis. The primary endpoint of cardiovascular mortality was recorded during a median 3-year follow up. Risk prediction was assessed by Cox regression, both unadjusted and adjusted for the Charlson Comorbidity Index and the Cardiovascular Mortality Risk Score. RESULTS: The Peguero-Lo Presti voltage identified with 21% the most patients with positive LVH criteria. All voltages significantly increased during dialysis. Factors such as ultrafiltration rate, Kt/V, body mass index, sex, and phosphate were the most relevant for these changes. During follow-up, 26 cardiovascular deaths occurred. Post-dialysis Peguero-Lo Presti cut-off as well as the Peguero-Lo Presti and Cornell voltages were independently associated with cardiovascular mortality in unadjusted and adjusted analysis. The Sokolow-Lyon voltage was not significantly associated with mortality. An optimal cut-off for the prediction of cardiovascular mortality was estimated at 1.38 mV for the Peguero-Lo Presti. CONCLUSIONS: The post-dialysis Peguero-Lo Presti cut-off as well as the Peguero-Lo Presti and Cornell voltages allowed independent risk prediction of cardiovascular mortality in hemodialysis patients. Measuring the ECG LVH parameters after dialysis might allow a standardized interpretation as dialysis-specific factors influence the voltages.

A Telemedicine-Guided Self-Collection Approach for PCR-Based SARS-CoV-2 Testing: Comparative Study.

BACKGROUND: Large-scale, polymerase chain reaction (PCR)-based SARS-CoV-2 testing is expensive, resource intensive, and time consuming. A self-collection approach is a probable alternative; however, its feasibility, cost, and ability to prevent infections need to be evaluated. OBJECTIVE: This study aims to compare an innovative self-collection approach with a regular SARS-CoV-2 testing strategy in a large European industrial manufacturing site. METHODS: The feasibility of a telemedicine-guided PCR-based self-collection approach was assessed for 150 employees (intervention group) and compared with a regular SARS-CoV-2 testing approach used for 143 employees (control group). Acceptance, ergonomics, and efficacy were evaluated using a software application. A simulation model was implemented to evaluate the effectiveness. An interactive R shiny app was created to enable customized simulations. RESULTS: The test results were successfully communicated to and interpreted without uncertainty by 76% (114/150) and 76.9% (110/143) of the participants in the intervention and control groups, respectively (P=.96). The ratings for acceptability, ergonomics, and efficacy among intervention group participants were noninferior when compared to those among control group participants (acceptability: 71.6% vs 37.6%; ergonomics: 88.1% vs 74.5%; efficacy: 86.4% vs 77.5%). The self-collection approach was found to be less time consuming (23 min vs 38 min; P<.001). The simulation model indicated that both testing approaches reduce the risk of infection, and the self-collection approach tends to be slightly less effective owing to its lower sensitivity. CONCLUSIONS: The self-collection approach for SARS-CoV-2 diagnosis was found to be technically feasible and well rated in terms of acceptance, ergonomics, and efficacy. The simulation model facilitates the evaluation of test effectiveness; nonetheless, considering context specificity, appropriate adaptation by companies is required.

U-Shaped Association of the Heart Rate Variability Triangular Index and Mortality in Hemodialysis Patients With Atrial Fibrillation.

Background: Atrial fibrillation (AF) is common in hemodialysis patients and contributes to increased mortality. We aimed to examine heart rate variability triangular index (HRVI) in hemodialysis patients with AF as it has recently been reported to predict mortality in AF patients without kidney disease. Methods: A total of 88 patients on hemodialysis with a medical history of AF or newly diagnosed AF underwent 24-h electrocardiography recordings. The primary endpoint of cardiovascular mortality was recorded during a median follow up of 3.0 years. Risk prediction was assessed by Cox regression, both unadjusted and adjusted for the Charlson Comorbidity Index and the Cardiovascular Mortality Risk Score. Results: Median age was 76 years, median dialysis vintage was 27 months. Altogether, 22 and 44 patients died due to cardiovascular and non-cardiovascular causes. In 55% of patients AF was present during the recording. Kaplan-Meier plots of HRVI quartiles suggested a non-linear association between HRVI, cardiovascular, and all-cause mortality which was confirmed in non-linear Cox regression analysis. Adjusted linear Cox regression revealed a hazard ratio of 6.2 (95% CI: 2.1-17.7, p = 0.001) and 2.2 (95% CI: 1.3-3.8, p = 0.002) for the outer quartiles (combined first and fourth quartile) for cardiovascular and all-cause mortality, respectively. Patients in the first quartile were more likely to have sinus rhythm whereas patients in the fourth quartile were more likely to have AF. Conclusions: We found a U-shaped association between HRVI and mortality in hemodialysis AF patients. The results might contribute to risk stratification independent of known risk scores in hemodialysis AF patients.

Development and validation of a simplified risk score for the prediction of critical COVID-19 illness in newly diagnosed patients.

Scores to identify patients at high risk of progression of coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), may become instrumental for clinical decision-making and patient management. We used patient data from the multicentre Lean European Open Survey on SARS-CoV-2-Infected Patients (LEOSS) and applied variable selection to develop a simplified scoring system to identify patients at increased risk of critical illness or death. A total of 1946 patients who tested positive for SARS-CoV-2 were included in the initial analysis and assigned to derivation and validation cohorts (n = 1297 and n = 649, respectively). Stability selection from over 100 baseline predictors for the combined endpoint of progression to the critical phase or COVID-19-related death enabled the development of a simplified score consisting of five predictors: C-reactive protein (CRP), age, clinical disease phase (uncomplicated vs. complicated), serum urea, and D-dimer (abbreviated as CAPS-D score). This score yielded an area under the curve (AUC) of 0.81 (95% confidence interval [CI]: 0.77-0.85) in the validation cohort for predicting the combined endpoint within 7 days of diagnosis and 0.81 (95% CI: 0.77-0.85) during full follow-up. We used an additional prospective cohort of 682 patients, diagnosed largely after the "first wave" of the pandemic to validate the predictive accuracy of the score and observed similar results (AUC for the event within 7 days: 0.83 [95% CI: 0.78-0.87]; for full follow-up: 0.82 [95% CI: 0.78-0.86]). An easily applicable score to calculate the risk of COVID-19 progression to critical illness or death was thus established and validated.

Application of regularized regression to identify novel predictors of mortality in a cohort of hemodialysis patients.

Cohort studies often provide a large array of data on study participants. The techniques of statistical learning can allow an efficient way to analyze large datasets in order to uncover previously unknown, clinically relevant predictors of morbidity or mortality. We applied a combination of elastic net penalized Cox regression and stability selection with the aim of identifying novel predictors of mortality in a cohort of prevalent hemodialysis patients. In our analysis we included 475 patients from the "rISk strAtification in end-stage Renal disease" (ISAR) study, who we split into derivation and confirmation cohorts. A wide array of examinations was available for study participants, resulting in over a hundred potential predictors. In the selection approach many of the well established predictors were retrieved in the derivation cohort. Additionally, the serum levels of IL-12p70 and AST were selected as mortality predictors and confirmed in the withheld subgroup. High IL-12p70 levels were specifically prognostic of infection-related mortality. In summary, we demonstrate an approach how statistical learning can be applied to a cohort study to derive novel hypotheses in a data-driven way. Our results suggest a novel role of IL-12p70 in infection-related mortality, while AST is a promising additional biomarker in patients undergoing hemodialysis.

Aging-regulated anti-apoptotic long non-coding RNA Sarrah augments recovery from acute myocardial infarction.

Long non-coding RNAs (lncRNAs) contribute to cardiac (patho)physiology. Aging is the major risk factor for cardiovascular disease with cardiomyocyte apoptosis as one underlying cause. Here, we report the identification of the aging-regulated lncRNA Sarrah (ENSMUST00000140003) that is anti-apoptotic in cardiomyocytes. Importantly, loss of SARRAH (OXCT1-AS1) in human engineered heart tissue results in impaired contractile force development. SARRAH directly binds to the promoters of genes downregulated after SARRAH silencing via RNA-DNA triple helix formation and cardiomyocytes lacking the triple helix forming domain of Sarrah show an increase in apoptosis. One of the direct SARRAH targets is NRF2, and restoration of NRF2 levels after SARRAH silencing partially rescues the reduction in cell viability. Overexpression of Sarrah in mice shows better recovery of cardiac contractile function after AMI compared to control mice. In summary, we identified the anti-apoptotic evolutionary conserved lncRNA Sarrah, which is downregulated by aging, as a regulator of cardiomyocyte survival.

Cardiac myocyte miR-29 promotes pathological remodeling of the heart by activating Wnt signaling.

Chronic cardiac stress induces pathologic hypertrophy and fibrosis of the myocardium. The microRNA-29 (miR-29) family has been found to prevent excess collagen expression in various organs, particularly through its function in fibroblasts. Here, we show that miR-29 promotes pathologic hypertrophy of cardiac myocytes and overall cardiac dysfunction. In a mouse model of cardiac pressure overload, global genetic deletion of miR-29 or antimiR-29 infusion prevents cardiac hypertrophy and fibrosis and improves cardiac function. Targeted deletion of miR-29 in cardiac myocytes in vivo also prevents cardiac hypertrophy and fibrosis, indicating that the function of miR-29 in cardiac myocytes dominates over that in non-myocyte cell types. Mechanistically, we found cardiac myocyte miR-29 to de-repress Wnt signaling by directly targeting four pathway factors. Our data suggests that, cell- or tissue-specific antimiR-29 delivery may have therapeutic value for pathological cardiac remodeling and fibrosis.

Preferential microRNA targeting revealed by in vivo competitive binding and differential Argonaute immunoprecipitation.

MicroRNAs (miRNAs) have been described to simultaneously inhibit hundreds of targets, albeit to a modest extent. It was recently proposed that there could exist more specific, exceptionally strong binding to a subgroup of targets. However, it is unknown, whether this is the case and how such targets can be identified. Using Argonaute2-ribonucleoprotein immunoprecipitation and in vivo competitive binding assays, we demonstrate for miRNAs-21, -199-3p and let-7 exceptional regulation of a subset of targets, which are characterized by preferential miRNA binding. We confirm this finding by analysis of independent quantitative proteome and transcriptome datasets obtained after miRNA silencing. Our data suggest that mammalian miRNA activity is guided by preferential binding of a small set of 3'-untranslated regions, thereby shaping a steep gradient of regulation between potential targets. Our approach can be applied for transcriptome-wide identification of such targets independently of the presence of seed complementary sequences or other predictors.

Circular RNAs in heart failure.

Cardiovascular disease, and particularly heart failure, is still a serious health care issue for which novel treatments and biomarkers are needed. The RNA family comprises different subgroups, among which the small-sized microRNAs and the larger long non-coding RNAs have shown some potential to aid in moving personalized health care of heart failure patients a step forward. Here, members of the Cardiolinc network review the recent findings suggesting that the less well-known circular RNAs may constitute a novel reservoir of therapeutic targets and biomarkers of heart failure. The knowledge of the mode of biogenesis of circular RNAs will first be reported, followed by a description of different features that make these RNA molecules of interest for the heart failure community. The functions of circular RNAs in the heart will be described, with some emphasis given to their regulation in the failing heart. Circulating in the bloodstream, circular RNAs have appeared as potential biomarkers and recent findings associated with the use of circular RNAs as heart failure biomarkers will be discussed. Finally, some directions for future research will be provided.

Characterization of circular RNAs in human, mouse and rat hearts.

Deep sequencing techniques and advanced data analysis methods recently enabled the characterization of thousands of circular RNA isoforms (circRNAs) from a number of tissues and organisms. There is emerging evidence that some circRNAs may have important biological functions or serve as diagnostic biomarkers in disease conditions. In order to analyze circRNA expression in the heart and its changes in different conditions we performed RNA-Seq analysis of ribosome-depleted libraries from rats (neonatal and adult), mice (sham or after transverse aortic constriction, TAC) and humans (failing, non-failing). All samples were sequenced after treatment with exonuclease RNase R or a mock treatment and >9000 candidate circRNAs were detected for each species. Additionally, we performed separate isolation of nuclear and cytoplasmic RNA and co-immunoprecipitated RNA interacting with endogenous argonaute 2 (Ago2) in primary cardiac myocytes. We found circRNAs to be significantly enriched in the cytoplasm compared to linear transcripts and to have a similar level of association with Ago2. Notably in all three species we observed dozens of circRNAs arising from the titin (Ttn) gene, which is known to undergo highly complex alternative splicing during heart maturation. Correspondingly we observed extensive differential regulation of Ttn circRNAs between neonatal and adult rat hearts, suggesting that circRNA formation could be involved in the regulation of titin splicing. We expect that our inventory of cardiac circRNAs, as well as the information on their conservation and differential expression will provide an important basis for further studies addressing their function and suitability as biomarkers.

Development of an intein-mediated split-Cas9 system for gene therapy.

Using CRISPR/Cas9, it is possible to target virtually any gene in any organism. A major limitation to its application in gene therapy is the size of Cas9 (>4 kb), impeding its efficient delivery via recombinant adeno-associated virus (rAAV). Therefore, we developed a split-Cas9 system, bypassing the packaging limit using split-inteins. Each Cas9 half was fused to the corresponding split-intein moiety and, only upon co-expression, the intein-mediated trans-splicing occurs and the full Cas9 protein is reconstituted. We demonstrated that the nuclease activity of our split-intein system is comparable to wild-type Cas9, shown by a genome-integrated surrogate reporter and by targeting three different endogenous genes. An analogously designed split-Cas9D10A nickase version showed similar activity as Cas9D10A. Moreover, we showed that the double nick strategy increased the homologous directed recombination (HDR). In addition, we explored the possibility of delivering the repair template accommodated on the same dual-plasmid system, by transient transfection, showing an efficient HDR. Most importantly, we revealed for the first time that intein-mediated split-Cas9 can be packaged, delivered and its nuclease activity reconstituted efficiently, in cells via rAAV.

Rapid and highly efficient inducible cardiac gene knockout in adult mice using AAV-mediated expression of Cre recombinase.

AIMS: Inducible gene targeting in mice using the Cre/LoxP system has become a valuable tool to analyse the roles of specific genes in the adult heart. However, the commonly used Myh6-MerCreMer system requires time-consuming breeding schedules and is potentially associated with cardiac side effects, which may result in transient cardiac dysfunction. The aim of our study was to establish a rapid and simple system for cardiac gene inactivation in conditional knockout mice by gene transfer of a Cre recombinase gene using adeno-associated viral vectors of serotype 9 (AAV9). METHODS AND RESULTS: AAV9 vectors expressing Cre under the control of a human cardiac troponin T promoter (AAV-TnT-Cre) enabled a highly efficient Cre/LoxP switching in cardiomyocytes 2 weeks after injection into 5- to 6-week-old ROSA26-LacZ reporter mice. Recombination efficiency was at least as high as observed with the Myh6-MerCreMer system. No adverse side effects were detected upon application of AAV-TnT-Cre. As proof of principle, we studied AAV-TnT-Cre in a conditional knockout model (Srf-flex1 mice) to deplete the myocardium of the transcription factor serum response factor (SRF). Four weeks after AAV-TnT-Cre injection, a strong decrease in the cardiac expression of SRF mRNA and protein was observed. Furthermore, mice developed a severe cardiac dysfunction with increased interstitial fibrosis in accordance with the central role of SRF for the expression of contractile and calcium trafficking proteins in the heart. CONCLUSIONS: AAV9-mediated expression of Cre is a promising approach for rapid and efficient conditional cardiac gene knockout in adult mice.

MiR-378 controls cardiac hypertrophy by combined repression of mitogen-activated protein kinase pathway factors.

BACKGROUND: Several microRNAs (miRs) have been shown to regulate gene expression in the heart, and dysregulation of their expression has been linked to cardiac disease. miR-378 is strongly expressed in the mammalian heart but so far has been studied predominantly in cancer, in which it regulates cell survival and tumor growth. METHODS AND RESULTS: Here, we report tight control of cardiomyocyte hypertrophy through miR-378. In isolated primary cardiomyocytes, miR-378 was found to be both necessary and sufficient to repress cardiomyocyte hypertrophy. Bioinformatic prediction suggested that factors of the mitogen-activated protein kinase (MAPK) pathway are enriched among miR-378 targets. Using mRNA and protein expression analysis along with luciferase assays, we validated 4 key components of the MAPK pathway as targets of miR-378: MAPK1 itself, insulin-like growth factor receptor 1, growth factor receptor-bound protein 2, and kinase suppressor of ras 1. RNA interference with these targets prevented the prohypertrophic effect of antimiR-378, suggesting their functional relation with miR-378. Because miR-378 significantly decreases in cardiac disease, we sought to compensate for its loss through adeno-associated virus-mediated, cardiomyocyte-targeted expression of miR-378 in an in vivo model of cardiac hypertrophy (pressure overload by thoracic aortic constriction). Restoration of miR-378 levels significantly attenuated thoracic aortic constriction-induced cardiac hypertrophy and improved cardiac function. CONCLUSIONS: Our data identify miR-378 as a regulator of cardiomyocyte hypertrophy, which exerts its activity by suppressing the MAPK signaling pathway on several distinct levels. Restoration of disease-associated loss of miR-378 through cardiomyocyte-targeted adeno-associated virus-miR-378 may prove to be an effective therapeutic strategy in myocardial disease.

Comparison of IL-10 and MCP-1-7ND gene transfer with AAV9 vectors for protection from murine autoimmune myocarditis.

AIMS: Overexpression of therapeutic genes with potential disease-limiting effects, specifically at the site of inflammation, remains a major clinical challenge. In this study, we investigate the potential of adeno-associated virus (AAV)-9-mediated cardiac expression of the anti-inflammatory mediators interleukin (IL)-10 and a dominant-negative inhibitor of monocyte chemoattractant protein-1 (MCP1-7ND) on prevention of autoimmune myocarditis. METHODS AND RESULTS: Autoimmune myocarditis was induced by immunizing A/J mice with subcutaneous injection of 120 µg cardiac troponin I (cTnI) on Days 0, 7, and 14. Two weeks prior to initial immunization, each mouse received a single systemic dose of 10(12) AAV9 vectors carrying the coding sequence of IL-10 or MCP1-7ND transcriptionally targeted to the heart. Mice were sacrificed 28 days after initial immunization for further analysis. Only expression of IL-10 resulted in a highly significant decrease in myocardial inflammation and fibrosis, as well as an increased ejection fraction compared with controls. Further analyses of cytokine profiles of cTnI-stimulated splenocytes from IL-10 and MCP1-7ND-treated mice revealed significant alterations compared with controls. In addition, transcript levels of chemokine receptor CCR4 and T-cell activation gene were significantly reduced in hearts of IL-10-treated mice as determined by quantitative real-time PCR. CONCLUSION: Our study suggests that cardiac expression of IL-10 with AAV9 vectors is a promising therapeutic approach for autoimmune myocarditis.