Pathological Interplay and Clinical Complications between COVID-19 and Cardiovascular Diseases: An Overview in 2023.

BACKGROUND: The coronavirus disease 2019 (COVID-19) involves all organs of the body, of which the interaction with cardiovascular diseases is the most important. SUMMARY: Numerous studies have reported that COVID-19 patients complicated with cardiovascular comorbidities (hypertension, coronary heart disease, chronic heart failure (HF), cerebrovascular disease) are more likely to develop into critical illness and have higher mortality. Conversely, COVID-19 may also cause myocardial injury in patients through various pathological mechanisms such as direct virus attack on cardiomyocytes, overactivation of immune response, microthrombus formation, which may lead to fatal acute ST-segment elevation myocardial infarction, arrhythmia, acute worsening of chronic HF, etc. In addition, the symptoms of the so-called long-COVID may remain in some patients who survived the acute viral infection. Positional tachycardia has been widely reported, and cardiovascular autonomic disorders are thought to play a pathogenic role. KEY MESSAGE: The review summarizes the interaction between COVID-19 and cardiovascular disease in terms of pathological mechanism, clinical features, and sequelae. Therapeutic and rehabilitation programs after COVID-19 infection are compiled and need to be further standardized in the future.

Polo-like kinase 1 promotes pulmonary hypertension.

BACKGROUND: Pulmonary hypertension (PH) is a lethal vascular disease with limited therapeutic options. The mechanistic connections between alveolar hypoxia and PH are not well understood. The aim of this study was to investigate the role of mitotic regulator Polo-like kinase 1 (PLK1) in PH development. METHODS: Mouse lungs along with human pulmonary arterial smooth muscle cells and endothelial cells were used to investigate the effects of hypoxia on PLK1. Hypoxia- or Sugen5416/hypoxia was applied to induce PH in mice. Plk1 heterozygous knockout mice and PLK1 inhibitors (BI 2536 and BI 6727)-treated mice were checked for the significance of PLK1 in the development of PH. RESULTS: Hypoxia stimulated PLK1 expression through induction of HIF1α and RELA. Mice with heterozygous deletion of Plk1 were partially resistant to hypoxia-induced PH. PLK1 inhibitors ameliorated PH in mice. CONCLUSIONS: Augmented PLK1 is essential for the development of PH and is a druggable target for PH.

Nomogram for Postoperative Headache in Adult Patients Undergoing Elective Cardiac Surgery.

Background Postoperative headache (POH) is frequent after cardiac surgery; however, few studies on risk factors for POH exist. The aims of the current study were to explore risk factors related to POH after elective cardiac surgery and to establish a predictive system. Methods and Results Adult patients undergoing elective open-heart surgery under cardiopulmonary bypass from 2016 to 2020 in 4 cardiac centers were retrospectively included. Two thirds of the patients were randomly allocated to a training set and one third to a validation set. Predictors for POH were selected by univariate and multivariate analysis. POH developed in 3154 of the 13 440 included patients (23.5%) and the overall mortality rate was 2.3%. Eight independent risk factors for POH after elective cardiac surgery were identified, including female sex, younger age, smoking history, chronic headache history, hypertension, lower left ventricular ejection fraction, longer cardiopulmonary bypass time, and more intraoperative transfusion of red blood cells. A nomogram based on the multivariate model was constructed, with reasonable calibration and discrimination, and was well validated. Decision curve analysis revealed good clinical utility. Finally, 3 risk intervals were divided to better facilitate clinical application. Conclusions A nomogram model for POH after elective cardiac surgery was developed and validated using 8 predictors, which may have potential application value in clinical risk assessment, decision-making, and individualized treatment associated with POH.

Predictors and outcomes of postoperative tracheostomy in patients undergoing acute type A aortic dissection surgery.

BACKGROUND: Despite surgical advances, acute type A aortic dissection remains a life-threatening disease with high mortality and morbidity. Tracheostomy is usually used for patients who need prolonged mechanical ventilation in the intensive care unit (ICU). However, data on the risk factors for requiring tracheostomy and the impact of tracheostomy on outcomes in patients after Stanford type A acute aortic dissection surgery (AADS) are limited. METHODS: A retrospective single-institutional study including consecutive patients who underwent AADS between January 2016 and December 2019 was conducted. Patients who died intraoperatively were excluded. Univariate analysis and multivariate logistic regression analysis were used to identify independent risk factors for postoperative tracheostomy (POT). A nomogram to predict the probability of POT was constructed based on independent predictors and their beta-coefficients. The area under the receiver operating characteristic curve (AUC) was performed to assess the discrimination of the model. Calibration plots and the Hosmer-Lemeshow test were used to evaluate calibration. Clinical usefulness of the nomogram was assessed by decision curve analysis. Propensity score matching analysis was used to analyze the correlation between requiring tracheostomy and clinical prognosis. RESULTS: There were 492 patients included in this study for analysis, including 55 patients (11.2%) requiring tracheostomy after AADS. Compared with patients without POT, patients with POT experienced longer ICU and hospital stay and higher mortality. Age, cerebrovascular disease history, preoperative white blood cell (WBC) count and renal insufficiency, intraoperative amount of red blood cell (RBC) transfusion and platelet transfusion were identified as independent risk factors for POT. Our constructed nomogram had good discrimination with an AUC = 0.793 (0.729-0.856). Good calibration and clinical utility were observed through the calibration and decision curves, respectively. For better clinical application, we defined four intervals that stratified patients from very low to high risk for occurrence of POT. CONCLUSIONS: Our study identified preoperative and intraoperative risk factors for POT and found that requiring tracheostomy was related to the poor outcomes in patients undergoing AADS. The established prediction model was validated with well predictive performance and clinical utility, and it may be useful for individual risk assessment and early clinical decision-making to reduce the incidence of tracheostomy.

Cytosporone B (Csn-B), an NR4A1 agonist, attenuates acute cardiac allograft rejection by inducing differential apoptosis of CD4+T cells.

CD4+T cell-mediated acute rejection remains a major factor that affects the early survival of transplanted organs post-transplantation. Here, we reveal that nuclear receptor subfamily 4 Group A member 1 (Nr4A1) was upregulated during cardiac allograft rejection and that the increased Nr4A1 was primarily localized in intragraft-infiltrating CD4+T cells. Nr4A1 acts as a transcription factor with an important role in CD4+T cell apoptosis, differentiation and T cell dysfunction, which indicates that Nr4A1 may play a critical role in transplant rejection. Cytosporone B (Csn-B) is a naturally occurring agonist of Nr4A1, and the role of Csn-B in the physiological process of cardiac rejection is poorly defined. This study constructed an acute rejection model of abdominal heterotopic cardiac transplantation in mice and investigated whether Csn-B could attenuate acute transplant rejection by modulating the CD4+T lymphocyte response. The results showed that Csn-B prolonged murine cardiac allograft survival and reduced inflammation in allografts. Subsequently, it was confirmed that Csn-B functions by inducing non-Treg apoptosis and promoting Treg cell differentiation. Finally, we also confirmed that Csn-B attenuates acute rejection by directly targeting Nr4A1 in CD4+T cells. Our data suggest that Csn-B is a promising novel therapeutic approach for acute cardiac allograft rejection.

Nomogram Models to Predict Postoperative Hyperlactatemia in Patients Undergoing Elective Cardiac Surgery.

Objectives: Postoperative hyperlactatemia (POHL) is common in patients undergoing cardiac surgery and is associated with poor outcomes. The purpose of this study was to develop and validate two predictive models for POHL in patients undergoing elective cardiac surgery (ECS). Methods: We conducted a multicenter retrospective study enrolling 13,454 adult patients who underwent ECS. All patients involved in the analysis were randomly assigned to a training set and a validation set. Univariate and multivariate analyses were performed to identify risk factors for POHL in the training cohort. Based on these independent predictors, the nomograms were constructed to predict the probability of POHL and were validated in the validation cohort. Results: A total of 1,430 patients (10.6%) developed POHL after ECS. Age, preoperative left ventricular ejection fraction, renal insufficiency, cardiac surgery history, intraoperative red blood cell transfusion, and cardiopulmonary bypass time were independent predictors and were used to construct a full nomogram. The second nomogram was constructed comprising only the preoperative factors. Both models showed good predictive ability, calibration, and clinical utility. According to the predicted probabilities, four risk groups were defined as very low risk (<0.05), low risk (0.05-0.1), medium risk (0.1-0.3), and high risk groups (>0.3), corresponding to scores of ≤ 180 points, 181-202 points, 203-239 points, and >239 points on the full nomogram, respectively. Conclusions: We developed and validated two nomogram models to predict POHL in patients undergoing ECS. The nomograms may have clinical utility in risk estimation, risk stratification, and targeted interventions.

Development and Validation of Nomogram Models for Postoperative Pneumonia in Adult Patients Undergoing Elective Cardiac Surgery.

Background: Postoperative pneumonia (POP) is a frequent complication following cardiac surgery, related to increased morbidity, mortality and healthcare costs. The objectives of this study were to investigate the risk factors associated with POP in adults undergoing elective cardiac surgery and to develop and validate nomogram models. Methods: We conducted a multicenter retrospective study in four cardiac centers in China. Adults operated with elective open-heart surgery from 2016 to 2020 were included. Patients were randomly allocated to training and validation sets by 7:3 ratio. Demographics, comorbidities, laboratory data, surgical factors, and postoperative outcomes were collected and analyzed. Risk factors for POP were identified by univariate and multivariate analysis. Nomograms were constructed based on the multivariate logistic regression models and were evaluated with calibration, discrimination and decision curve analysis. Results: A total of 13,380 patients meeting the criteria were included and POP developed in 882 patients (6.6%). The mortality was 2.0%, but it increased significantly in patients with POP (25.1 vs. 0.4%, P < 0.001). Using preoperative and intraoperative variables, we constructed a full nomogram model based on ten independent risk factors and a preoperative nomogram model based on eight preoperative factors. Both nomograms demonstrated good calibration, discrimination, and were well validated. The decision curves indicated significant clinical usefulness. Finally, four risk intervals were defined for better clinical application. Conclusions: We developed and validated two nomogram models for POP following elective cardiac surgery using preoperative and intraoperative factors, which may be helpful for individualized risk evaluation and prevention decisions.

Incidence, Risk Factors and Outcomes of Postoperative Headache After Stanford Type a Acute Aortic Dissection Surgery.

Background: Postoperative headache (POH) is common in clinical practice, however, no studies about POH after Stanford type A acute aortic dissection surgery (AADS) exist. This study aims to describe the incidence, risk factors and outcomes of POH after AADS, and to construct two prediction models. Methods: Adults who underwent AADS from 2016 to 2020 in four tertiary hospitals were enrolled. Training and validation sets were randomly assigned according to a 7:3 ratio. Risk factors were identified by univariate and multivariate logistic regression analysis. Nomograms were constructed and validated on the basis of independent predictors. Results: POH developed in 380 of the 1,476 included patients (25.7%). Poorer outcomes were observed in patients with POH. Eight independent predictors for POH after AADS were identified when both preoperative and intraoperative variables were analyzed, including younger age, female sex, smoking history, chronic headache history, cerebrovascular disease, use of deep hypothermic circulatory arrest, more blood transfusion, and longer cardiopulmonary bypass time. White blood cell and platelet count were also identified as significant predictors when intraoperative variables were excluded from the multivariate analysis. A full nomogram and a preoperative nomogram were constructed based on these independent predictors, both demonstrating good discrimination, calibration, clinical usefulness, and were well validated. Risk stratification was performed and three risk intervals were defined based on the full nomogram and clinical practice. Conclusions: POH was common after AADS, portending poorer outcomes. Two nomograms predicting POH were developed and validated, which may have clinical utility in risk evaluation, early prevention, and doctor-patient communication.

A Predictive Scoring Model for Postoperative Tracheostomy in Patients Who Underwent Cardiac Surgery.

BACKGROUND: A subset of patients require a tracheostomy as respiratory support in a severe state after cardiac surgery. There are limited data to assess the predictors for requiring postoperative tracheostomy (POT) in cardiac surgical patients. METHODS: The records of adult patients who underwent cardiac surgery from 2016 to 2019 at our institution were reviewed. Univariable analysis was used to assess the possible risk factors for POT. Then multivariable logistic regression analysis was performed to identify independent predictors. A predictive scoring model was established with predictor assigned scores derived from each regression coefficient divided by the smallest one. The area under the receiver operating characteristic curve and the Hosmer-Lemeshow goodness-of-fit test were used to evaluate the discrimination and calibration of the risk score, respectively. RESULTS: A total of 5,323 cardiac surgical patients were included, with 128 (2.4%) patients treated with tracheostomy after cardiac surgery. Patients with POT had a higher frequency of readmission to the intensive care unit (ICU), longer stay, and higher mortality (p < 0.001). Mixed valve surgery and coronary artery bypass grafting (CABG), aortic surgery, renal insufficiency, diabetes mellitus, chronic obstructive pulmonary disease (COPD), pulmonary edema, age >60 years, and emergent surgery were independent predictors. A 9-point risk score was generated based on the multivariable model, showing good discrimination [the concordance index (c-index): 0.837] and was well-calibrated. CONCLUSIONS: We established and verified a predictive scoring model for POT in patients who underwent cardiac surgery. The scoring model was conducive to risk stratification and may provide meaningful information for clinical decision-making.

BCL6 inhibitor FX1 attenuates inflammatory responses in murine sepsis through strengthening BCL6 binding affinity to downstream target gene promoters.

BACKGROUND: Sepsis occurs when an infection triggers deranged inflammatory responses. There exists no efficacious treatment for this condition. The transcriptional repressor B-cell Lymphoma 6 (BCL6) is known to act as an inhibitor of macrophage-mediated inflammatory responses. FX1, a novel specific BCL6 BTB inhibitor, is able to attenuate activity of B cell-like diffuse large B cell lymphoma (ABC-DLBCL). Nevertheless, the effect of FX1 in inflammatory responses and sepsis remains unknown. OBJECTIVES: Here, we explored the effect and potential mechanisms of FX1 on the regulation of LPS-induced inflammatory responses in murine sepsis. METHOD: Mice models of LPS-induced sepsis were monitored for survival rate following FX1 administration. ELISA was used to assess how FX1 administration affected pro-inflammatory cytokines present in macrophages exposed to LPS and in the serum of mice sepsis models. Flow cytometric analysis, Western blot and qRT-PCR were performed to evaluate differences in macrophages immune responses after FX1 pre-treatment. Finally, the affinity of BCL6 binding to downstream target genes was checked by ChIP. RESULTS: The survival rate of mice models of LPS-induced sepsis was improved in following FX1 administration. FX1 decreased the production of inflammatory cytokines, attenuated macrophage infiltration activities and reduced monocytes chemotaxis activities, all of which suggest that FX1 exert anti-inflammatory effects. Mechanistically, FX1 may enhance the affinity of BCL6 binding to downstream target pro-inflammatory genes. CONCLUSIONS: These findings illustrated the anti-inflammatory properties and potential mechanisms of FX1 in sepsis caused by LPS. FX1 could potentially become a new immunosuppressive and anti-inflammatory drug candidate in sepsis therapy.

Nucleotide-Binding Oligomerization Domain-Like Receptor Protein 3 Deficiency in Vascular Smooth Muscle Cells Prevents Arteriovenous Fistula Failure Despite Chronic Kidney Disease.

Background The arteriovenous fistula ( AVF ) is the preferred hemodialysis access for patients with chronic kidney disease. Chronic kidney disease can increase neointima formation, which greatly contributes to AVF failure by an unknown mechanism. Our study aimed to determine the role of nucleotide-binding oligomerization domain-like receptor protein 3 ( NLRP 3) in neointima formation induced by experimental AVF s in the presence of chronic kidney disease. Methods and Results From our findings, NLRP 3 was upregulated in the intimal lesions of AVF s in both uremic mice and patients. Smooth muscle-specific knockout NLRP 3 mice exhibited markedly decreased neointima formation in the outflow vein of AVF s. Compared with primary vascular smooth muscle cells isolated from control mice, those isolated from smooth muscle-specific knockout NLRP 3 mice showed compromised proliferation, migration, phenotypic switching, and a weakened ability to activate mononuclear macrophages. To identify how NLRP 3 functions, several small-molecule inhibitors were used. The results showed that NLRP 3 regulates smooth muscle cell proliferation and migration through Smad2/3 phosphorylation rather than through caspase-1/interleukin-1 signaling. Unexpectedly, the selective NLRP 3-inflammasome inhibitor MCC 950 also repressed Smad2/3 phosphorylation and relieved chronic kidney disease-promoted AVF failure independent of macrophages. Conclusions Our findings suggest that NLRP 3 in vascular smooth muscle cells may play a crucial role in uremia-associated AVF failure and may be a promising therapeutic target for the treatment of AVF failure.

MicroRNA-21 Knockout Exacerbates Angiotensin II-Induced Thoracic Aortic Aneurysm and Dissection in Mice With Abnormal Transforming Growth Factor-ß-SMAD3 Signaling.

OBJECTIVE: Thoracic aortic aneurysm and dissection (TAAD) are severe vascular conditions. Dysfunctional transforming growth factor-ß (TGF-ß) signaling in vascular smooth muscle cells and elevated angiotensin II (AngII) levels are implicated in the development of TAAD. In this study, we investigated whether these 2 factors lead to TAAD in a mouse model and explored the possibility of using microRNA-21 (miR-21) for the treatment of TAAD. APPROACH AND RESULTS: TAAD was developed in Smad3 (mothers against decapentaplegic homolog 3) heterozygous (S3+/-) mice infused with AngII. We found that p-ERK (phosphorylated extracellular regulated protein kinases)- and p-JNK (phosphorylated c-Jun N-terminal kinase)-associated miR-21 was higher in TAAD lesions. We hypothesize that downregulation of miR-21 mitigate TAAD formation. However, Smad3+/-:miR-21-/- (S3+/-21-/-) mice exhibited conspicuous TAAD formation after AngII infusion. The vascular wall was dilated, and aortic rupture occurred within 23 days during AngII infusion. We then examined canonical and noncanonical TGF-ß signaling and found that miR-21 knockout in S3+/- mice increased SMAD7 and suppressed canonical TGF-ß signaling. Vascular smooth muscle cells lacking TGF-ß signals tended to switch from a contractile to a synthetic phenotype. The silencing of Smad7 with lentivirus prevented AngII-induced TAAD formation in S3+/-21-/- mice. CONCLUSIONS: Our study demonstrated that miR-21 knockout exacerbated AngII-induced TAAD formation in mice, which was associated with TGF-ß signaling dysfunction. Therapeutic strategies targeting TAAD should consider unexpected side effects associated with alterations in TGF-ß signaling.

MicroRNA-155 promotes neointimal hyperplasia through smooth muscle-like cell-derived RANTES in arteriovenous fistulas.

OBJECTIVE: Arteriovenous fistula (AVF) suffers from a high number of failures caused by insufficient outward remodeling and venous neointimal hyperplasia formation. The aim was to investigate the exact mechanism by which microRNA-155 (miR-155) in the outflow vein of AVF is regulated. METHODS: AVFs between the branch of the jugular vein and carotid artery in an end-to-end manner were created in C57BL/6 and miR-155-/- mice with a C57BL/6 background. The venous segments were harvested at day 7, 14, 21, and 28, and the AVFs were analyzed histologically and at a messenger RNA level using real-time quantitative polymerase chain reactions. The outflow vein of AVF and the normal great saphenous vein, collected from patients with chronic kidney disease and coronary artery bypass surgery, were analyzed by histologic and molecular biologic approaches. RESULTS: Venous neointimal hyperplasia is significantly alleviated in miR-155-/- mice, and the expression of several chemokines and cytokines in the vessel wall, including regulated on activation, normal T-cell expressed and secreted factor (RANTES), monocyte chemoattractant protein 1, and vascular endothelial growth factor, was inhibited. miR-155 promoted the RANTES expression of smooth muscle-like cells, which in turn facilitated cell proliferation and extracellular matrix production. CONCLUSIONS: miR-155 enhances venous neointima formation through the autocrine and paracrine effects of smooth muscle-like cell-derived RANTES in a nuclear factor κB-dependent manner during the entire AVF process, especially at the advanced stage.

A Disintegrin and Metalloprotease-22 Attenuates Hypertrophic Remodeling in Mice Through Inhibition of the Protein Kinase B Signaling Pathway.

BACKGROUND: Severe cardiac hypertrophy can lead to cardiac remodeling and even heart failure in the end, which is a leading cause of cardiovascular disease-related mortality worldwide. A disintegrin and metalloprotease-22 (ADAM22), a member of the transmembrane and secreted metalloendopeptidase family, participates in many biological processes, including those in the cardiovascular system. However, there is no explicit information on whether ADAM22 can regulate the process of cardiac hypertrophy; the effects that ADAM22 exerts in cardiac hypertrophy remain elusive. METHODS AND RESULTS: We observed significantly increased ADAM22 expression in failing hearts from patients with dilated cardiomyopathy and hypertrophic cardiomyopathy; the same trend was observed in mice induced by transaortic constriction and in neonatal rat cardiomyocytes treated by angiotensin II. Therefore, we constructed both cardiac-specific ADAM22 overexpression and knockout mice. At 4 weeks after transaortic constriction, cardiac-specific ADAM22 knockout, by the CRISPR/Cas9 (clustered regularly interspaced palindromic repeat (CRISPR)-Cas9) system, deteriorated the severity of cardiac hypertrophy in mice, whereas cardiac-specific ADAM22 overexpression mitigated the degrees of cardiac hypertrophy in mice. Similarly, altered ADAM22 expression modulated the angiotensin II-mediated cardiomyocyte hypertrophy in neonatal rat cardiomyocytes. After screening several signaling pathways, we found ADAM22 played a role in inhibition of protein kinase B (AKT) activation. Under the cardiac-specific ADAM22 knockout background, AKT activation was enhanced in transaortic constriction-induced mice and angiotensin II-stimulated neonatal rat cardiomyocytes, with a severe degree of cardiac hypertrophy. Treatment of a specific AKT inhibitor attenuated the transaortic constriction-enhanced AKT activation and cardiac hypertrophy in mice. CONCLUSIONS: The findings demonstrated that ADAM22 negatively regulates the AKT activation and the process of cardiac hypertrophy and may provide new insights into the pathobiological features of cardiac hypertrophy.

Inhibition of intimal hyperplasia in murine aortic allografts by administration of a small-molecule TLR4 inhibitor TAK-242.

Graft arteriosclerosis (GA) is the leading cause of late cardiac allograft dysfunction. The innate immune system plays a major role in GA, paprticularly Toll-like receptor 4 (TLR4) signaling. Here we characterized the role of TLR4 and its antagonist TAK-242 in a mouse model of GA. BALB/c (H-2d) donor aortas were transplanted into C57BL/6 (H-2b) recipients, and the mice received intraperitoneal injection of 3 or 10 mg/kg of TAK-242 or vehicle every other day for 1, 2, 4, 6, 8 and 12 weeks. With TAK-242 administration, intimal hyperplasia initially appeared at 2 weeks after transplantation, and TAK-242 postponed the progression of neointimal formation in allogeneic aortic grafts. TAK-242 treatment reduced CD68+ macrophage accumulation in the allografts, reduced the levels of ly-6Chi monocytes in peripheral blood, bone marrow and spleen, and downregulated proinflammatory cytokine and chemokine levels. Ex vivo we observed that TAK-242 could improve the graft microenvironment by interfering the Tck/Mφ IL12p70 and IFNγ axis, reducing CCL2-mediated migration of vascular smooth cells.

Knockout of microRNA-155 ameliorates the Th1/Th17 immune response and tissue injury in chronic rejection.

BACKGROUND: MicroRNAs (miRNAs) are integral for maintaining immune homeostasis and self-tolerance. The influence of miRNAs on T-cell differentiation and plasticity are critical in the development of chronic rejection of transplanted hearts. In this study, we sought to determine whether the knockout of miR-155 affects the development of cardiac allograft vasculopathy (CAV) in a murine model. METHODS: miRNA microarray and quantitative polymerase chain reaction (qPCR) analyses were performed for allograft neointimal lesion samples in chronic rejection. A model of heterotopic murine heart transplantation (bm12 to miR-155+/+ or miR-155-/- mice) was then used to analyze allograft survival, histology, mRNA expression and T-cell sub-populations in spleens. The accelerated experiments were performed by intraperitoneal injection of either recombinant interleukin-17A or phosphate-buffered saline (PBS) after heart transplantation. For the competitive transfer experiments, CD4+ splenocytes from wild-type (WT) or miR-155-/- mice were mixed and injected into Rag1-/- mice, and cardiac transplantation was performed after 24 hours. The differentiation of T-helper subsets (Th1/Th17/iTreg) was investigated in vitro. RESULTS: miR-155-/- mice showed resistance to cardiac rejection along with weakened T-cell-mediated inflammation, especially for Th17 cells. Recombinant IL-17A could restore this relieved injury. The competitive experiments implied that miR-155 plays a vital role in the stability of the Th17 phenotype. In vitro, we also demonstrated that miR-155-/- mice exhibit a defect in Th17 differentiation. CONCLUSIONS: miR-155 regulates Th1/Th17-related inflammation in chronic cardiac rejection and may be a potential therapeutic target to attenuate cardiac allograft rejection. Despite advancements in immunosuppressive therapy, the immunologic mechanisms responsible for allograft rejection remain an important issue for both clinicians and researchers. Allograft rejection is a T-cell-dependent phenomenon and is critically dependent on inflammation mediated by CD4+ Th subsets, including Th1, Th2, Th17, Th9 and regulatory T (Treg) cells.

A novel mouse model of high flow-induced pulmonary hypertension-surgically induced by right pulmonary artery ligation.

BACKGROUND: This study sought to establish a new model of high-flow pulmonary hypertension (PH) in mice. This model may be useful for studies seeking to reduce the pulmonary vascular resistance and delay the development of PH caused by congenital heart disease. MATERIALS AND METHODS: The right pulmonary artery was ligated via a right posterolateral thoracotomy. Pulmonary hemodynamics was evaluated by right heart catheterization immediately after ligation and at 2, 4, 8, and 12 wk postoperatively. The right ventricle (RV) and the left ventricle (LV) with septum (S) were weighed to calculate the RV/(LV + S) ratio as an index of right ventricular hypertrophy. Morphologic changes in the left lungs were analyzed, and percentages of muscularized pulmonary vessels were assessed by hematoxylin and eosin, elastica van Gieson and alpha-smooth muscle actin staining. All the study data were compared with data from a model of PH generated by hypoxic stimulation. RESULTS: A pulmonary hypertensive state was successfully induced by 2 wk after surgery. However, the morphologic analysis demonstrated that pulmonary vascular muscularization, as evaluated using right ventricular systolic pressure and RV/(LV + S), was not significantly increased until 4 wk postoperatively. When mice from the new model and the hypoxic model were compared, no significant differences were observed in any of the evaluated indices. CONCLUSIONS: High-flow PH can be induced within 4 wk after ligation of the right pulmonary artery, which is easily performed in mice. Such mice can be used as a model of high-flow PH.

MicroRNA-150 Inhibits the Activation of Cardiac Fibroblasts by Regulating c-Myb.

BACKGROUND/AIMS: Cardiac fibrosis is the primary cause of deteriorated cardiac function in various cardiovascular diseases. Numerous studies have demonstrated that microRNAs (miRNAs) are critical regulators of myocardial fibrosis. Specifically, many studies have reported that miR-150 is downregulated in cardiovascular diseases, such as acute myocardial infarction (AMI), myocardial hypertrophy and myocardial fibrosis. However, the exact role of miR-150 in these pathological processes remains unknown. METHODS: We used the transverse aortic constriction (TAC) mouse model to study the role of miR-150 in cardiac fibrosis induced by pressure overload. After the TAC operation, qRT-PCR was used to measure the expression profiles of miR-150 in left ventricle tissues and populations of primary heart cell types. Then, we used both miR-150 knockout mice and wild type (WT) mice in the TAC model. Changes in cardiac function and pathology were measured using transthoracic echocardiography and pathological analysis, respectively. Furthermore, we predicted the target of miR-150 in cardiac fibroblasts (CFs) and completed in vitro CF transfection experiments using miR-150 analogs and siRNA corresponding to the predicted target. RESULTS: We observed decreased expression levels of miR-150 in hearts suffering pressure overload, and these levels decreased more sharply in CFs than in cardiomyocytes. In addition, the degrees of cardiac function deterioration and cardiac fibrosis in miR-150-/- mice were more severe than were those in WT mice. By transfecting CFs with an miR-150 analog in vitro, we observed that miR-150 inhibited cardiac fibroblast activation. We predicted that the transcription factor c-Myb was the target of miR-150 in CFs. Transfecting CFs with c-Myb siRNA eliminated the effects of an miR-150 inhibitor, which promoted CF activation. CONCLUSION: These findings reveal that miR-150 acts as a pivotal regulator of pressure overload-induced cardiac fibrosis by regulating c-Myb.

MicroRNA-155 Promotes the Directional Migration of Resident Smooth Muscle Progenitor Cells by Regulating Monocyte Chemoattractant Protein 1 in Transplant Arteriosclerosis.

OBJECTIVE: Smooth muscle-like cells are major cell components of transplant arteriosclerosis lesions. This study investigated the origin of the smooth muscle-like cells, the mechanisms responsible for their accumulation in the neointima, and the factors that drive these processes. APPROACH AND RESULTS: A murine aortic transplantation model was established by transplanting miR-155(-/-) bone marrow cells into miR-155(+/+) mice. MicroRNA-155 was found to play a functional role in the transplant arteriosclerosis. Moreover, we found that the nonbone marrow-derived progenitor cells with markers of both early differentiated smooth muscles and stem cells in the allograft adventitia were smooth muscle progenitor cells. Purified smooth muscle progenitor cells expressed a mature smooth muscle cell marker when induced by platelet-derived growth factor-BB in vitro. In vivo, these cells could migrate into the intima from the adventitia and could contribute to the neointimal hyperplasia. The loss of microRNA-155 in bone marrow-derived cells decreased the concentration gradient of monocyte chemoattractant protein 1 between the intima and the adventitia of the allografts, which reduced the migration of smooth muscle progenitor cells from the adventitia into the neointima. CONCLUSIONS: This study demonstrated that microRNA-155 promoted the directional migration of smooth muscle progenitor cells from the adventitia by regulating the monocyte chemoattractant protein 1 concentration gradient, which aggravated transplant arteriosclerosis.

MicroRNA-150 protects the heart from injury by inhibiting monocyte accumulation in a mouse model of acute myocardial infarction.

BACKGROUND: MicroRNAs (miRs) and inflammatory monocytes participate in many cardiac pathophysiological processes including acute myocardial infarction (AMI). Recently, we observed that miR-150 is downregulated in injured mouse plasma after AMI as well as in human infarcted monocytes. However, the precise functional role of miR-150 in response to AMI remains unknown. METHODS AND RESULTS: In a mouse model of AMI and in human subjects with AMI, we found that miR-150 expression was reduced in monocytes. In vitro studies showed that ectopic expression of miR-150 markedly reduced monocyte migration and proinflammatory cytokine production, whereas blockade of miR-150 had opposing effects. In vivo studies showed that overexpression of miR-150 in mice resulted in improved cardiac function, reduced myocardial infarction size, inhibition of apoptosis, and reduced inflammatory Ly-6C(high) monocyte invasion levels after AMI. Wild-type mice transplanted with miR-150 null (-/-) bone marrow cells could reverse this protective effect. Mechanistic studies demonstrated that miR-150 inhibited the expression of chemokine receptor 4 (CXCR4), thereby promoting monocyte migration. CONCLUSIONS: Our findings indicate that miR-150 acts as a critical regulator of monocyte cell migration and production of proinflammatory cytokines, leading to cardioprotective effects against AMI-induced injury. Thus, miR-150 may be a suitable target for therapeutic intervention in the setting of ischemic heart disease.