The central role of natural killer cells in mediating acute myocarditis after mRNA COVID-19 vaccination

BACKGROUND

Vaccine-related acute myocarditis is recognized as a rare and specific vaccine complication following mRNA-based COVID-19 vaccinations. The precise mechanisms remain unclear. We hypothesized that natural killer (NK) cells play a central role in its pathogenesis.

METHODS

Samples from 60 adolescents with vaccine-related myocarditis were analyzed, including pro-inflammatory cytokines, cardiac troponin T, genotyping, and immunophenotyping of the corresponding activation subsets of NK cells, monocytes, and T cells. Results were compared with samples from 10 vaccinated individuals without myocarditis and 10 healthy controls.

FINDINGS

Phenotypically, high levels of serum cytokines pivotal for NK cells, including interleukin-1β (IL-1β), interferon α2 (IFN-α2), IL-12, and IFN-γ, were observed in post-vaccination patients with myocarditis, who also had high percentage of CD57+ NK cells in blood, which in turn correlated positively with elevated levels of cardiac troponin T. Abundance of the CD57+ NK subset was particularly prominent in males and in those after the second dose of vaccination. Genotypically, killer cell immunoglobulin-like receptor (KIR) KIR2DL5B(-)/KIR2DS3(+)/KIR2DS5(-)/KIR2DS4del(+) was a risk haplotype, in addition to single-nucleotide polymorphisms related to the NK cell-specific expression quantitative trait loci DNAM-1 and FuT11, which also correlated with cardiac troponin T levels in post-vaccination patients with myocarditis.

CONCLUSION

Collectively, these data suggest that NK cell activation by mRNA COVID-19 vaccine contributed to the pathogenesis of acute myocarditis in genetically and epidemiologically vulnerable subjects.

FUNDING

This work was funded by the Hong Kong Collaborative Research Fund (CRF) 2020/21 and the CRF Coronavirus and Novel Infectious Diseases Research Exercises (reference no. C7149-20G).

Troponin T1 silencing inhibits paclitaxel resistance and the development of breast cancer via suppressing rat sarcoma virus/rapidly accelerated fibrosarcoma 1 pathway

OBJECTIVE

We aimed to determine the role of Troponin T1 (TNNT1) in paclitaxel (PTX) resistance and tumor progression in breast cancer (BC).

METHODS

Differentially expressed genes were obtained from the GSE4298 and GSE90564 datasets. Hub genes were isolated from protein-protein interaction networks and further validated by real-time quantitative polymerase chain reaction. The effect of TNNT1 on PTX resistance was determined using cell counting kit-8, 5-ethynyl-2'-deoxyuridine, wound healing, transwell, flow cytometry assays, and subcutaneous xenografted tumor model. Western blotting was used to detect proteins associated with PTX resistance, apoptosis, migration, invasion, and other key pathways. Hematoxylin-eosin and immunohistochemical staining were used to evaluate the role of TNNT1 in tumors.

RESULTS

After comprehensive bioinformatic analysis, we identified CCND1, IGF1, SFN, INHBA, TNNT1, and TNFSF11 as hub genes for PTX resistance in BC. TNNT1 plays a key role in BC and is upregulated in PTX-resistant BC cells. TNNT1 silencing inhibited PTX resistance, proliferation, migration, and invasion while promoting apoptosis of PTX-resistant BC cells. Tumor xenograft experiments revealed that TNNT1 silencing suppresses PTX resistance and tumor development in vivo. In addition, TNNT1 silencing inhibited the expression of proteins in the rat sarcoma virus (RAS)/rapidly accelerated fibrosarcoma1 (RAF1) pathway in vivo. Treatment with a RAS/RAF1 pathway activator reversed the inhibitory effect of TNNT1 silencing on proliferation, migration, and invasion while promoting apoptosis of PTX resistance BC cells.

CONCLUSION

Silencing of TNNT1 suppresses PTX resistance and BC progression by inhibiting the RAS/RAF1 pathway, which is a promising biomarker and therapeutic target for drug resistance in BC.

Redox differences between rat neonatal and adult cardiomyocytes under hypoxia

It is generally accepted that oxidative stress plays a key role in the development of ischemia-reperfusion injury in ischemic heart disease. However, the mechanisms how reactive oxygen species trigger cellular damage are not fully understood. Our study investigates redox state and highly reactive substances within neonatal and adult cardiomyocytes under hypoxia conditions. We have found that hypoxia induced an increase in H2O2 production in adult cardiomyocytes, while neonatal cardiomyocytes experienced a decrease in H2O2 levels. This finding correlates with our observation of the difference between the electron transport chain (ETC) properties and mitochondria amount in adult and neonatal cells. We demonstrated that in adult cardiomyocytes hypoxia caused the significant increase in the ETC loading with electrons compared to normoxia. On the contrary, in neonatal cardiomyocytes ETC loading with electrons was similar under both normoxic and hypoxic conditions that could be due to ETC non-functional state and the absence of the electrons transfer to O2 under normoxia. In addition to the variations in H2O2 production, we also noted consistent pH dynamics under hypoxic conditions. Notably, the pH levels exhibited a similar decrease in both cell types, thus, acidosis is a more universal cellular response to hypoxia. We also demonstrated that the amount of mitochondria and the levels of cardiac isoforms of troponin I, troponin T, myoglobin and GAPDH were significantly higher in adult cardiomyocytes compared to neonatal ones. Remarkably, we found out that under hypoxia, the levels of cardiac isoforms of troponin T, myoglobin, and GAPDH were elevated in adult cardiomyocytes, while their level in neonatal cells remained unchanged. Obtained data contribute to the understanding of the mechanisms of neonatal cardiomyocytes' resistance to hypoxia and the ability to maintain the metabolic homeostasis in contrast to adult ones.

Cardiac Troponin T and NT-proBNP for Prediction of 30-Day Readmission or Death in Patients with Acute Dyspnea: Data from the Akershus Cardiac Examination 2 Study

INTRODUCTION

N-terminal pro-B-type natriuretic peptide (NT-proBNP) and cardiac troponin T (cTnT) measurements are recommended in patients with acute dyspnea. We aimed to assess the prognostic merit of cTnT compared to NT-proBNP for 30-day readmission or death in patients hospitalized with acute dyspnea.

METHODS

We measured cTnT and NT-proBNP within 24 h in 314 patients hospitalized with acute dyspnea and adjudicated the cause of the index admission. Time to first event of readmission or death ≤30 days after hospital discharge was recorded, and cTnT and NT-proBNP measurements were compared head-to-head.

RESULTS

Patients who died (12/314) or were readmitted (71/314) within 30 days had higher cTnT concentrations (median: 32.6, Q1-Q3: 18.4-74.2 ng/L vs. median: 19.4, Q1-Q3: 8.4-36.1 ng/L; p for comparison <0.001) and NT-proBNP concentrations (median: 1,753.6, Q1-Q3: 464.2-6,862.0 ng/L vs. median 984, Q1-Q3 201-3,600 ng/L; for comparison p = 0.027) compared to patients who survived and were not readmitted. cTnT concentrations were associated with readmission or death within 30 days after discharge both in the total cohort (adjusted hazard ratio [aHR]: 1.64, 95% confidence interval [CI]: 1.30-2.05) and in patients with heart failure (HF) (aHR: 1.58, 95% CI: 1.14-2.18). In contrast, NT-proBNP concentrations were not associated with short-term events, neither in the total cohort (aHR: 1.10, 95% CI: 0.94-1.30) nor in patients with adjudicated HF (aHR: 1.06, 95% CI: 0.80-1.40).

CONCLUSION

cTnT concentrations are associated with 30-day readmission or death in patients hospitalized with acute dyspnea, as well as in patients adjudicated HF.

Endothelial-derived extracellular vesicles from obese/hypertensive adults increase factors associated with hypertrophy and fibrosis in cardiomyocytes

Obesity and hypertension, independently and combined, are associated with increased risk of heart failure and heart failure-related morbidity and mortality. Interest in circulating endothelial cell-derived microvesicles (EMVs) has intensified because of their involvement in the development and progression of endothelial dysfunction, atherosclerosis, and cardiomyopathy. The experimental aim of this study was to determine, in vitro, the effects of EMVs isolated from obese/hypertensive adults on key proteins regulating cardiomyocyte hypertrophy [cardiac troponin T (cTnT), α-actinin, nuclear factor-kB (NF-kB)] and fibrosis [transforming growth factor (TGF)-β, collagen1-α1], as well as endothelial nitric oxide synthase (eNOS) expression and nitric oxide (NO) production. EMVs (CD144+ microvesicles) were isolated from plasma by flow cytometry in 12 normal weight/normotensive [8 males/4 females; age: 56 ± 5 yr; body mass index (BMI): 23.3 ± 2.0 kg/m2; blood pressure (BP): 117/74 ± 4/5 mmHg] and 12 obese/hypertensive (8 males/4 females; 57 ± 5 yr; 31.7 ± 1.8 kg/m2; 138/83 ± 8/7 mmHg) adults. Human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were cultured and treated with EMVs from either normal weight/normotensive or obese/hypertensive adults for 24 h. Expression of cTnT (64.1 ± 13.9 vs. 29.5 ± 7.8 AU), α-actinin (66.0 ± 14.7 vs. 36.2 ± 10.3 AU), NF-kB (166.3 ± 13.3 vs. 149.5 ± 8.8 AU), phosphorylated-NF-kB (226.1 ± 25.2 vs. 179.1 ± 25.5 AU), and TGF-β (62.1 ± 13.3 vs. 23.5 ± 8.8 AU) were significantly higher and eNOS activation (16.4 ± 4.3 vs. 24.8 ± 3.7 AU) and nitric oxide production (6.8 ± 1.2 vs. 9.6 ± 1.3 µmol/L) were significantly lower in iPSC-CMs treated with EMVs from obese/hypertensive compared with normal weight/normotensive adults. These data indicate that EMVs from obese/hypertensive adults induce a cardiomyocyte phenotype prone to hypertrophy, fibrosis, and reduced nitric oxide production, central factors associated with heart failure risk and development.NEW & NOTEWORTHY In the present study we determined the effect of endothelial microvesicles (EMVs) isolated from obese/hypertensive adults on mediators of cardiomyocyte hypertrophy [cardiac troponin T (cTnT), α-actinin, nuclear factor-kB (NF-kB)] and fibrosis [transforming growth factor (TGF-β), collagen1-α1] as well as endothelial nitric oxide synthase (eNOS) expression and NO production. EMVs from obese/hypertensive induced significantly higher expression of hypertrophic (cTnT, α-actinin, NF-kB) and fibrotic (TGF-β) proteins as well as significantly lower eNOS activation and NO production in cardiomyocytes than EMVs from normal weight/normotensive adults. EMVs are a potential mediating factor in the increased risk of cardiomyopathy and heart failure with obesity/hypertension.

Myofilaments promote wing expansion and maintain genitalia morphology in the American cockroach, Periplaneta americana

Insects are the most widely distributed and successful animals on the planet. A large number of insects are capable of flight with functional wings. Wing expansion is an important process for insects to achieve functional wings after eclosion and healthy genital morphology is crucial for adult reproduction. Myofilaments are functional units that constitute sarcomeres and trigger muscle contraction. Here, we identified four myofilament proteins, including Myosin, Paramyosin, Tropomyosin and Troponin T, from the wing pads of nymphs in the American cockroach, Periplaneta americana. RNAi-mediated knockdown of Myosin, Paramyosin, Tropomyosin and Troponin T in the early stage of final instar nymphs caused a severely curly wing phenotype in the imaginal moult, especially in the Paramyosin and Troponin T knockdown groups, indicating that these myofilament proteins are involved in controlling wing expansion behaviours during the nymph-adult transition. In addition, the knockdown resulted in abnormal external genitalia, caused ovulation failure, and affected male accessory gland development. Interestingly, the expression of myofilament genes was induced by methoprene, a juvenile hormone (JH) analogue, and decreased by the depletion of the JH receptor gene Met. Altogether, we have determined that myofilament genes play an important role in promoting wing expansion and maintaining adult genitalia morphology, and their expression is induced by JH signalling. Our data reveal a novel mechanism by which wing expansion is regulated by myofilaments and the functions of myofilaments are involved in maintaining genitalia morphology.

Impact of Troponin in Cardiomyopathy Development Caused by Mutations in Tropomyosin

Tropomyosin (Tpm) mutations cause inherited cardiac diseases such as hypertrophic and dilated cardiomyopathies. We applied various approaches to investigate the role of cardiac troponin (Tn) and especially the troponin T (TnT) in the pathogenic effects of Tpm cardiomyopathy-associated mutations M8R, K15N, A277V, M281T, and I284V located in the overlap junction of neighboring Tpm dimers. Using co-sedimentation assay and viscosity measurements, we showed that TnT1 (fragment of TnT) stabilizes the overlap junction of Tpm WT and all Tpm mutants studied except Tpm M8R. However, isothermal titration calorimetry (ITC) indicated that TnT1 binds Tpm WT and all Tpm mutants similarly. By using ITC, we measured the direct K_D of the Tpm overlap region, N-end, and C-end binding to TnT1. The ITC data revealed that the Tpm C-end binds to TnT1 independently from the N-end, while N-end does not bind. Therefore, we suppose that Tpm M8R binds to TnT1 without forming the overlap junction. We also demonstrated the possible role of Tn isoform composition in the cardiomyopathy development caused by M8R mutation. TnT1 dose-dependently reduced the velocity of F-actin-Tpm filaments containing Tpm WT, Tpm A277V, and Tpm M281T mutants in an in vitro motility assay. All mutations impaired the calcium regulation of the actin-myosin interaction. The M281T and I284V mutations increased the calcium sensitivity, while the K15N and A277V mutations reduced it. The Tpm M8R, M281T, and I284V mutations under-inhibited the velocity at low calcium concentrations. Our results demonstrate that Tpm mutations likely implement their pathogenic effects through Tpm interaction with Tn, cardiac myosin, or other protein partners.

Breast milk mesenchymal stem cells abate cisplatin-induced cardiotoxicity in adult male albino rats via modulating the AMPK pathway

Myocardial injury influenced by cisplatin (Cis) is a compelling reason to hunt out a treatment modality to overcome such a threat in cisplatin-treated patients. Breast Milk mesenchymal stem cells (Br-MSCs) are a non-invasive, highly reproducible source of stem cells. Herein, we investigate Br-MSCs' role in cardiotoxicity induced by cisplatin. Rats were divided into; control, Cis-treated (received 12 mg/kg single intraperitoneal injection), BrMSCs-treated (received single intraperitoneal injection of 0.5 ml sterilized phosphate-buffered saline containing 2 × 107 cells of Br-MSCs); metformin-treated (received 250 mg/kg/day orally) and BrMSCs + metformin + Cis treated groups. At the experiment end, serum creatine kinase (CK-MB) and cardiac troponin T (cTnT) activates were estimated, cardiac malondialdehyde (MDA), superoxide dismutase (SOD), interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) levels were measured, cardiac expression of Bax and Bcl-2 and AMP-activated protein kinase (AMPK), as well as heart histopathology, were evaluated. Study results showed that Cis explored acute cardiotoxicity evidenced by deteriorated cardiac indices, induction of oxidative stress, and inflammation with myocardium histological alterations. Treatment with Br-MSCs restored heart function and structure deteriorated by Cis injection. The antioxidant/anti-inflammatory/anti-apoptotic results of Br-MSCs were supported by AMPK activation denoting their protective role against cisplatin-induced cardiac injury. These results were superior when metformin was added to the treatment protocol.

Serine biosynthesis as a novel therapeutic target for dilated cardiomyopathy

AIMS

Genetic dilated cardiomyopathy (DCM) is a leading cause of heart failure. Despite significant progress in understanding the genetic aetiologies of DCM, the molecular mechanisms underlying the pathogenesis of familial DCM remain unknown, translating to a lack of disease-specific therapies. The discovery of novel targets for the treatment of DCM was sought using phenotypic sceening assays in induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) that recapitulate the disease phenotypes in vitro.

METHODS AND RESULTS

Using patient-specific iPSCs carrying a pathogenic TNNT2 gene mutation (p.R183W) and CRISPR-based genome editing, a faithful DCM model in vitro was developed. An unbiased phenotypic screening in TNNT2 mutant iPSC-derived cardiomyocytes (iPSC-CMs) with small molecule kinase inhibitors (SMKIs) was performed to identify novel therapeutic targets. Two SMKIs, Gö 6976 and SB 203580, were discovered whose combinatorial treatment rescued contractile dysfunction in DCM iPSC-CMs carrying gene mutations of various ontologies (TNNT2, TTN, LMNA, PLN, TPM1, LAMA2). The combinatorial SMKI treatment upregulated the expression of genes that encode serine, glycine, and one-carbon metabolism enzymes and significantly increased the intracellular levels of glucose-derived serine and glycine in DCM iPSC-CMs. Furthermore, the treatment rescued the mitochondrial respiration defects and increased the levels of the tricarboxylic acid cycle metabolites and ATP in DCM iPSC-CMs. Finally, the rescue of the DCM phenotypes was mediated by the activating transcription factor 4 (ATF4) and its downstream effector genes, phosphoglycerate dehydrogenase (PHGDH), which encodes a critical enzyme of the serine biosynthesis pathway, and Tribbles 3 (TRIB3), a pseudokinase with pleiotropic cellular functions.

CONCLUSIONS

A phenotypic screening platform using DCM iPSC-CMs was established for therapeutic target discovery. A combination of SMKIs ameliorated contractile and metabolic dysfunction in DCM iPSC-CMs mediated via the ATF4-dependent serine biosynthesis pathway. Together, these findings suggest that modulation of serine biosynthesis signalling may represent a novel genotype-agnostic therapeutic strategy for genetic DCM.

Proteasomal Degradation of TRAF2 Mediates Mitochondrial Dysfunction in Doxorubicin-Cardiomyopathy

BACKGROUND

Cytokines such as tumor necrosis factor-α (TNFα) have been implicated in cardiac dysfunction and toxicity associated with doxorubicin (DOX). Although TNFα can elicit different cellular responses, including survival or death, the mechanisms underlying these divergent outcomes in the heart remain cryptic. The E3 ubiquitin ligase TRAF2 (TNF receptor associated factor 2) provides a critical signaling platform for K63-linked polyubiquitination of RIPK1 (receptor interacting protein 1), crucial for nuclear factor-κB (NF-κB) activation by TNFα and survival. Here, we investigate alterations in TNFα-TRAF2-NF-κB signaling in the pathogenesis of DOX cardiotoxicity.

METHODS

Using a combination of in vivo (4 weekly injections of DOX 5 mg·kg-1·wk-1) in C57/BL6J mice and in vitro approaches (rat, mouse, and human inducible pluripotent stem cell-derived cardiac myocytes), we monitored TNFα levels, lactate dehydrogenase, cardiac ultrastructure and function, mitochondrial bioenergetics, and cardiac cell viability.

RESULTS

In contrast to vehicle-treated mice, ultrastructural defects, including cytoplasmic swelling, mitochondrial perturbations, and elevated TNFα levels, were observed in the hearts of mice treated with DOX. While investigating the involvement of TNFα in DOX cardiotoxicity, we discovered that NF-κB was readily activated by TNFα. However, TNFα-mediated NF-κB activation was impaired in cardiac myocytes treated with DOX. This coincided with loss of K63- linked polyubiquitination of RIPK1 from the proteasomal degradation of TRAF2. Furthermore, TRAF2 protein abundance was markedly reduced in hearts of patients with cancer treated with DOX. We further established that the reciprocal actions of the ubiquitinating and deubiquitinating enzymes cellular inhibitors of apoptosis 1 and USP19 (ubiquitin-specific peptidase 19), respectively, regulated the proteasomal degradation of TRAF2 in DOX-treated cardiac myocytes. An E3-ligase mutant of cellular inhibitors of apoptosis 1 (H588A) or gain of function of USP19 prevented proteasomal degradation of TRAF2 and DOX-induced cell death. Furthermore, wild-type TRAF2, but not a RING finger mutant defective for K63-linked polyubiquitination of RIPK1, restored NF-κB signaling and suppressed DOX-induced cardiac cell death. Last, cardiomyocyte-restricted expression of TRAF2 (cardiac troponin T-adeno-associated virus 9-TRAF2) in vivo protected against mitochondrial defects and cardiac dysfunction induced by DOX.

CONCLUSIONS

Our findings reveal a novel signaling axis that functionally connects the cardiotoxic effects of DOX to proteasomal degradation of TRAF2. Disruption of the critical TRAF2 survival pathway by DOX sensitizes cardiac myocytes to TNFα-mediated necrotic cell death and DOX cardiotoxicity.

miR-15b-5p REGULATES THE NLRP3 INFLAMMASOME SIGNAL THROUGH TARGETING SIRT3 TO REGULATE HYPOXIA/REOXYGENATION-INDUCED CARDIOMYOCYTE PYROPTOSIS PROCESS

ABSTRACT

Hypoxia/reoxygenation (H/R) induces pyroptosis in the setting of acute myocardial infarction (AMI). Previous studies have shown that the expression of the miR-15 family is stimulated in myocardial ischemia-reperfusion injury or H/R-induced cardiomyocyte injury, and miR-15 is a promoter of cardiac ischemia-reperfusion or H/R injury. However, whether miR-15b-5p regulates H/R injury and cardiomyocyte pyroptosis and its mechanism still need to be further clarified. Bioinformatics analysis elicited that SIRT3 was the downstream regulatory target gene of miR-15b-5p. SIRT3 has been shown to participate in the regulation of pyroptosis by negatively regulating the NLRP3 inflammasome pathway. Therefore, we hypothesized that miR-15b-5p targets SIRT3 and activated the NLRP3 inflammasome pathway to promote H/R-induced cardiomyocyte pyroptosis. We first show that H/R increases miR-15b-5p in rat cardiomyocytes H9C2. Next, we tested the effects of inhibition of miR-15b-5p or overexpression of SIRT3. We found that miR-15b-5p downregulation or SIRT3 overexpression could reverse the H/R-induced pyroptosis. Furthermore, silencing SIRT3 antagonized the protective effect of miR-15b-5p downregulation on H9C2 cells. NLRP3 inhibitor MCC950 annulled the previously mentioned antagonistic effect of silencing SIRT3 on the protection of miR-15b-5p downregulation against pyroptosis. We then used a rat AMI model to analyze myocardial infarction area by triphenyl tetrazolium chloride staining and assess serum cardiac troponin T level by ELISA and found that miR-15b-5p silencing reduced AMI injury in rats. Collectively, these results suggest that miR-15b-5p increase H/R-induced pyroptosis in cardiomyocytes by targeting SIRT3 and activating the NLRP3 inflammasome.

Key role of Extracellular RNA in hypoxic stress induced myocardial injury

Myocardial infarction (MI), atherosclerosis and other inflammatory and ischemic cardiovascular diseases (CVDs) have a very high mortality rate and limited therapeutic options. Although the diagnosis is based on markers such as cardiac Troponin-T (cTrop-T), the mechanism of cTrop-T upregulation and release is relatively obscure. In the present study, we have investigated the mechanism of cTrop-T release during acute hypoxia (AH) in a mice model by ELISA & immunohistochemistry. Our study showed that AH exposure significantly induces the expression and release of sterile inflammatory as well as MI markers in a time-dependent manner. We further demonstrated that activation of TLR3 (mediated by eRNA) by AH exposure in mice induced cTrop-T release and Poly I:C (TLR3 agonist) also induced cTrop-T release, but the pre-treatment of TLR3 immuno-neutralizing antibody or silencing of Tlr3 gene or RNaseA treatment two hrs before AH exposure, significantly abrogated AH-induced Caspase 3 activity as well as cTrop-T release. Our immunohistochemistry and Masson Trichrome (MT) staining studies further established the progression of myocardial injury by collagen accumulation, endothelial cell and leukocyte activation and adhesion in myocardial tissue which was abrogated significantly by pre-treatment of RNaseA 2 hrs before AH exposure. These data indicate that AH induced cTrop-T release is mediated via the eRNA-TLR3-Caspase 3 pathway.

Identification of myocardial injury using perioperative troponin surveillance in major noncardiac surgery and net benefit over the Revised Cardiac Risk Index

BACKGROUND

Patients with perioperative myocardial injury are at risk of death and major adverse cardiovascular and cerebrovascular events (MACCE). The primary aim of this study was to determine optimal thresholds of preoperative and perioperative changes in high-sensitivity cardiac troponin T (hs-cTnT) to predict MACCE and mortality.

METHODS

Prospective, observational, cohort study in patients ≥50 yr of age undergoing elective major noncardiac surgery at seven hospitals in Sweden. The exposures were hs-cTnT measured before and days 0-3 after surgery. Two previously published thresholds for myocardial injury and two thresholds identified using receiver operating characteristic analyses were evaluated using multivariable logistic regression models and externally validated. The weighted comparison net benefit method was applied to determine the additional value of hs-cTnT thresholds when compared with the Revised Cardiac Risk Index (RCRI). The primary outcome was a composite of 30-day all-cause mortality and MACCE.

RESULTS

We included 1291 patients between April 2017 and December 2020. The primary outcome occurred in 124 patients (9.6%). Perioperative increase in hs-cTnT ≥14 ng L^-1 above preoperative values provided statistically optimal model performance and was associated with the highest risk for the primary outcome (adjusted odds ratio 2.9, 95% confidence interval 1.8-4.7). Validation in an independent, external cohort confirmed these findings. A net benefit over RCRI was demonstrated across a range of clinical thresholds.

CONCLUSIONS

Perioperative increases in hsTnT ≥14 ng L^-1 above baseline values identifies acute perioperative myocardial injury and provides a net prognostic benefit when added to RCRI for the identification of patients at high risk of death and MACCE.

CLINICAL TRIAL REGISTRATION

NCT03436238.

Generation, selection and modification of anti-cardiac troponin I antibodies with high specificity and affinity

Current diagnosis of acute myocardial infarction involves quantification of circulating cTn levels. This work endeavoured to generate and enhance recombinant antibody fragments targeting various epitopes on the N- and C-terminals of the cTnI molecule, thereby facilitating highly sensitive detection of the troponin molecule. From this approach, two anti-cTnI scFv antibodies were successfully selected using either phage display or structural reformatting of full length anti-cTnI IgG. Their antibody binding affinity was further optimised via chain shuffling and/or site directed mutagenesis, resulting in scFv with heightened sensitivity when compared to the wild-type scFv. If used in conjunction with existing anti-mid fragment cTnI antibodies, these N- and C- terminal-targeting scFvs show high potential for the enhancement of current cTnI detection assays by limiting the effects from cTnI degradation or troponin complex formation.

Incidence and outcomes of perioperative myocardial infarction/injury diagnosed by high-sensitivity cardiac troponin I

BACKGROUND

 Perioperative myocardial infarction/injury (PMI) diagnosed by high-sensitivity troponin (hs-cTn) T is frequent and a prognostically important complication of non-cardiac surgery. We aimed to evaluate the incidence and outcome of PMI diagnosed using hs-cTnI, and compare it to PMI diagnosed using hs-cTnT.

METHODS

We prospectively included 2455 patients at high cardiovascular risk undergoing 3111 non-cardiac surgeries, for whom hs-cTnI and hs-cTnT concentrations were measured before surgery and on postoperative days 1 and 2. PMI was defined as a composite of perioperative myocardial infarction (PMIInfarct) and perioperative myocardial injury (PMIInjury), according to the Fourth Universal Definition of Myocardial Infarction. All-cause mortality was the primary endpoint.

RESULTS

Using hs-cTnI, the incidence of overall PMI was 9% (95% confidence interval [CI] 8-10%), including PMIInfarct 2.6% (95% CI 2.0-3.2) and PMIInjury 6.1% (95% CI 5.3-6.9%), which was lower versus using hs-cTnT: overall PMI 15% (95% CI 14-16%), PMIInfarct 3.7% (95% CI 3.0-4.4) and PMIInjury 11.3% (95% CI 10.2-12.4%). All-cause mortality occurred in 52 (2%) patients within 30 days and 217 (9%) within 1 year. Using hs-cTnI, both PMIInfarct and PMIInjury were independent predictors of 30-day all-cause mortality (adjusted hazard ratio [aHR] 2.5 [95% CI 1.1-6.0], and aHR 2.8 [95% CI 1.4-5.5], respectively) and, 1-year all-cause mortality (aHR 2.0 [95% CI 1.2-3.3], and aHR 1.8 [95% CI 1.2-2.7], respectively). Overall, the prognostic impact of PMI diagnosed by hs-cTnI was comparable to the prognostic impact of PMI using hs-cTnT.

CONCLUSIONS

Using hs-cTnI, PMI is less common versus using hs-cTnT. Using hs-cTnI, both PMIInfarct and PMIInjury remain independent predictors of 30-day and 1-year mortality.

H3K9me2 regulates early transcription factors to promote mesenchymal stem‑cell differentiation into cardiomyocytes

Studies have shown that histone H3 at lysine 9 (H3K9me2) is an important epigenetic modifier of embryonic development, cell reprogramming and cell differentiation, but its specific role in cardiomyocyte formation remains to be elucidated. The present study established a model of 5‑Azacytidine‑induced differentiation of rat bone mesenchymal stem cells (MSCs) into cardiomyocytes and, on this basis, investigated the dimethylation of H3K9me2 and its effect on cardiomyocyte formation by knockdown of H3K9me2 methylase, euchromatic histone‑lysine N‑methyltransferase 2 (G9a) and H3K9me2 lysine demethylase 3A (KDM3A). The results demonstrated that, in comparison with the normal induction process, the knockdown of G9a could significantly reduce the H3K9me2 level of the MSCs in the induced model. Reverse transcription‑quantitative (RT‑q) PCR demonstrated that the expression of cardiac troponin T(cTnT) was significantly increased. In addition, flow cytometry demonstrated that the proportion of cTnT‑positive cells was significantly increased on day 21. With the knockdown of KDM3A, the opposite occurred. In order to explore the specific way of H3K9me2 regulating cardiomyocyte formation, western blotting and RT‑qPCR were used to detect the expression of key transcription factors including GATA binding protein 4 (GATA‑4), NK2 Homeobox 5 (Nkx2.5) and myocyte enhancer factor 2c (MEF2c) during cardiomyocyte formation. The decrease of H3K9me2 increased the expression of transcription factors GATA‑4, Nkx2.5 and MEF2c in the early stage of myocardial development while the increase of H3K9me2 inhibited the expression of those transcription factors. Accordingly, it was concluded that H3K9me2 is a negative regulator of cardiomyocyte formation and can participate in cardiomyocyte formation by activating or inhibiting key transcription factors of cardiomyocytes, which will lay the foundation for the optimized induction efficiency of cardiomyocytes in in vitro and clinical applications.

Cardiac Troponin Composition Characterization after Non ST-Elevation Myocardial Infarction: Relation with Culprit Artery, Ischemic Time Window, and Severity of Injury

BACKGROUND

Troponin composition characterization has been implicated as a next step to differentiate among non-ST elevation myocardial infarction (NSTEMI) patients and improve distinction from other conditions with troponin release. We therefore studied coronary and peripheral troponin compositions in relation to clinical variables of NSTEMI patients.

METHODS

Samples were obtained from the great cardiac vein (GCV), coronary sinus (CS), and peripheral circulation of 45 patients with NSTEMI. We measured total cTnI concentrations, and assessed both complex cTnI (binary cTnIC + all ternary cTnTIC forms), and large-size cTnTIC (full-size and partially truncated cTnTIC). Troponin compositions were studied in relation to culprit vessel localization (left anterior descending artery [LAD] or non-LAD), ischemic time window, and peak CK-MB value.

RESULTS

Sampling occurred at a median of 25 hours after symptom onset. Of total peripheral cTnI, a median of 87[78-100]% consisted of complex cTnI; and 9[6-15]% was large-size cTnTIC. All concentrations (total, complex cTnI, and large-size cTnTIC) were significantly higher in the CS than in peripheral samples (P < 0.001). For LAD culprit patients, GCV concentrations were all significantly higher; in non-LAD culprit patients, CS concentrations were higher. Proportionally, more large-size cTnTIC was present in the earliest sampled patients and in those with the highest CK-MB peaks.

CONCLUSIONS

In coronary veins draining the infarct area, concentrations of both full-size and degraded troponin were higher than in the peripheral circulation. This finding, and the observed associations of troponin composition with the ischemic time window and the extent of sustained injury may contribute to future characterization of different disease states among NSTEMI patients.

Myocardial Injury and the Release of Troponins I and T in the Blood of Patients

BACKGROUND

Cardiac troponin I (cTnI) and cTnT are the established biomarkers of cardiomyocyte damage and the recommended biomarkers for the diagnosis of acute myocardial infarction (MI). High-sensitivity immunochemical diagnostic systems are able to measure the cTn concentrations in the blood of a majority of healthy people. At the same time, the concentration of cTn may be increased not only after MI but also because of other pathologies that might affect myocardium. This effect reduces the clinical specificity of cTn for MI and may complicate the diagnosis.

CONTENT

This review summarizes the existing information regarding the causes and mechanisms that lead to the increase of cTn concentration in blood and the forms of cTn that are present in circulation after MI or other types of myocardial injury.

SUMMARY

Different etiologies of disease associated with increases of cTn above the 99th percentile and various mechanisms of troponin release from myocardium could result in the appearance of different forms of cTn in blood and provide the first clinical evidence of injury. Additional research is needed for the careful characterization of cTn forms that are present in the blood in different clinical settings. That knowledge may lead to the development of immunochemical systems that would differentiate certain forms of troponins and possibly certain types of cardiac disease.

Late Outcomes of the RAPID-TnT Randomized Controlled Trial: 0/1-Hour High-Sensitivity Troponin T Protocol in Suspected ACS

BACKGROUND

High-sensitivity troponin assays are increasingly being adopted to expedite evaluation of patients with suspected acute coronary syndromes. Few direct comparisons have examined whether the enhanced performance of these assays at low concentrations leads to changes in care that improves longer-term outcomes. This study evaluated late outcomes of participants managed under an unmasked 0/1-hour high-sensitivity cardiac troponin T (hs-cTnT) protocol compared with a 0/3-hour masked hs-cTnT protocol.

METHODS

We conducted a multicenter prospective patient-level randomized comparison of care informed by unmasked 0/1-hour hs-cTnT protocol (reported to <5 ng/L) versus standard practice masked hs-cTnT testing (reported to ≤29 ng/L) assessed at 0/3 hours and followed participants for 12 months. Participants included were those presenting to metropolitan emergency departments with suspected acute coronary syndromes, without ECG evidence of coronary ischemia. The primary end point was time to all-cause death or myocardial infarction using Cox proportional hazards models adjusted for clustering within hospitals.

RESULTS

Between August 2015 and April 2019, we randomized 3378 participants, of whom 108 withdrew, resulting in 12-month follow-up for 3270 participants (masked: 1632; unmasked: 1638). Among these, 2993 (91.5%) had an initial troponin concentration of ≤29 ng/L. Deployment of the 0/1-hour hs-cTnT protocol was associated with reductions in functional testing. Over 12-month follow-up, there was no difference in invasive coronary angiography (0/1-hour unmasked: 232/1638 [14.2%]; 0/3-hour masked: 202/1632 [12.4%]; P=0.13), although an increase was seen among patients with hs-cTnT levels within the masked range (0/1-hour unmasked arm: 168/1507 [11.2%]; 0/3-hour masked arm: 124/1486 [8.3%]; P=0.010). By 12 months, all-cause death and myocardial infarction did not differ between study arms overall (0/1-hour: 82/1638 [5.0%] versus 0/3-hour: 62/1632 [3.8%]; hazard ratio, 1.32 [95% CI, 0.95-1.83]; P=0.10). Among participants with initial troponin T concentrations ≤29 ng/L, unmasked hs-cTnT reporting was associated with an increase in death or myocardial infarction (0/1-hour: 55/1507 [3.7%] versus 0/3-hour: 34/1486 [2.3%]; hazard ratio, 1.60 [95% CI, 1.05-2.46]; P=0.030).

CONCLUSIONS

Unmasked hs-cTnT reporting deployed within a 0/1-hour protocol did not reduce ischemic events over 12-month follow-up. Changes in practice associated with the implementation of this protocol may be associated with an increase in death and myocardial infarction among those with newly identified troponin elevations. Registration: URL: https://www.anzctr.org.au; Unique identifier: ACTRN12615001379505.

Cardiac Troponin T: The Impact of Posttranslational Modifications on Analytical Immunoreactivity in Blood up to the Excretion in Urine

Cardiac troponin T (cTnT) is a sensitive and specific biomarker for detecting cardiac muscle injury. Its concentration in blood can be significantly elevated outside the normal reference range under several pathophysiological conditions. The classical analytical method in routine clinical analysis to detect cTnT in serum or plasma is a single commercial immunoassay, which is designed to quantify the intact cTnT molecule. The targeted epitopes are located in the central region of the cTnT molecule. However, in blood cTnT exists in different biomolecular complexes and proteoforms: bound (to cardiac troponin subunits or to immunoglobulins) or unbound (as intact protein or as proteolytic proteoforms). While proteolysis is a principal posttranslational modification (PTM), other confirmed PTMs of the proteoforms include N-terminal initiator methionine removal, N-acetylation, O-phosphorylation, O-(N-acetyl)-glucosaminylation, N(ɛ)-(carboxymethyl)lysine modification and citrullination. The immunoassay probably detects several of those cTnT biomolecular complexes and proteoforms, as long as they have the centrally targeted epitopes in common. While analytical cTnT immunoreactivity has been studied predominantly in blood, it can also be detected in urine, although it is unclear in which proteoform cTnT immunoreactivity is present in urine. This review presents an overview of the current knowledge on the pathophysiological lifecycle of cTnT. It provides insight into the impact of PTMs, not only on the analytical immunoreactivity, but also on the excretion of cTnT in urine as one of the waste routes in that lifecycle. Accordingly, and after isolating the proteoforms from urine of patients suffering from proteinuria and acute myocardial infarction, the structures of some possible cTnT proteoforms are reconstructed using mass spectrometry and presented.

A Proposed Mechanism for the Initial Myosin Binding Event on the Cardiac Thin Filament: A Metadynamics Study

The movement of tropomyosin over filamentous actin regulates the cross-bridge cycle of the thick with thin filament of cardiac muscle by blocking and revealing myosin binding sites. Tropomyosin exists in three, distinct equilibrium states with one state blocking myosin-actin interactions (blocked position) and the remaining two allowing for weak (closed position) and strong myosin binding (open position). However, experimental information illuminating how myosin binds to the thin filament and influences tropomyosin's transition across the actin surface is lacking. Using metadynamics, we mimic the effect of a single myosin head binding by determining the work required to pull small segments of tropomyosin toward the open position in several distinct regions of the thin filament. We find differences in required work due to the influence of cardiac troponin T lead to preferential binding sites and determine the mechanism of further myosin head recruitment.

Role of Endogenous Cathepsin L in Muscle Protein Degradation in Olive Flounder (Paralichthys olivaceus) Surimi Gel

We investigated the effect of endogenous cathepsin L on surimi gel produced from olive flounder (Paralichthys olivaceus). The amino acid sequences of six proteins predicted or identified as cathepsin L were obtained from the olive flounder genome database, and a phylogenetic analysis was conducted. Next, cathepsin L activity toward N-α-benzyloxycarbonyl-l-phenylalanyl-l-arginine-(7-amino-4-methylcoumarin) (Z-F-R-AMC) was detected in crude olive flounder extract and a crude enzyme preparation. A considerable decrease in the level of myosin heavy chain (MHC) in surimi occurred during autolysis at 60 °C. In contrast, the levels of actin, troponin-T, and tropomyosin decreased only slightly. To prevent protein degradation by cathepsin L, a protease inhibitor was added to surimi. In the presence of 1.0% protease inhibitor, the autolysis of olive flounder surimi at 60 °C was inhibited by 12.2%; the degree of inhibition increased to 44.2% as the inhibitor concentration increased to 3.0%. In addition, the deformation and hardness of modori gel increased as the inhibitor concentration increased to 2.0%. Therefore, cathepsin L plays an important role in protein degradation in surimi, and the quality of surimi gel could be enhanced by inhibiting its activity.

Defining Kawasaki disease and pediatric inflammatory multisystem syndrome-temporally associated to SARS-CoV-2 infection during SARS-CoV-2 epidemic in Italy: results from a national, multicenter survey

BACKGROUND

There is mounting evidence on the existence of a Pediatric Inflammatory Multisystem Syndrome-temporally associated to SARS-CoV-2 infection (PIMS-TS), sharing similarities with Kawasaki Disease (KD). The main outcome of the study were to better characterize the clinical features and the treatment response of PIMS-TS and to explore its relationship with KD determining whether KD and PIMS are two distinct entities.

METHODS

The Rheumatology Study Group of the Italian Pediatric Society launched a survey to enroll patients diagnosed with KD (Kawasaki Disease Group - KDG) or KD-like (Kawacovid Group - KCG) disease between February 1st 2020, and May 31st 2020. Demographic, clinical, laboratory data, treatment information, and patients' outcome were collected in an online anonymized database (RedCAP®). Relationship between clinical presentation and SARS-CoV-2 infection was also taken into account. Moreover, clinical characteristics of KDG during SARS-CoV-2 epidemic (KDG-CoV2) were compared to Kawasaki Disease patients (KDG-Historical) seen in three different Italian tertiary pediatric hospitals (Institute for Maternal and Child Health, IRCCS "Burlo Garofolo", Trieste; AOU Meyer, Florence; IRCCS Istituto Giannina Gaslini, Genoa) from January 1st 2000 to December 31st 2019. Chi square test or exact Fisher test and non-parametric Wilcoxon Mann-Whitney test were used to study differences between two groups.

RESULTS

One-hundred-forty-nine cases were enrolled, (96 KDG and 53 KCG). KCG children were significantly older and presented more frequently from gastrointestinal and respiratory involvement. Cardiac involvement was more common in KCG, with 60,4% of patients with myocarditis. 37,8% of patients among KCG presented hypotension/non-cardiogenic shock. Coronary artery abnormalities (CAA) were more common in the KDG. The risk of ICU admission were higher in KCG. Lymphopenia, higher CRP levels, elevated ferritin and troponin-T characterized KCG. KDG received more frequently immunoglobulins (IVIG) and acetylsalicylic acid (ASA) (81,3% vs 66%; p = 0.04 and 71,9% vs 43,4%; p = 0.001 respectively) as KCG more often received glucocorticoids (56,6% vs 14,6%; p < 0.0001). SARS-CoV-2 assay more often resulted positive in KCG than in KDG (75,5% vs 20%; p < 0.0001). Short-term follow data showed minor complications. Comparing KDG with a KD-Historical Italian cohort (598 patients), no statistical difference was found in terms of clinical manifestations and laboratory data.

CONCLUSION

Our study suggests that SARS-CoV-2 infection might determine two distinct inflammatory diseases in children: KD and PIMS-TS. Older age at onset and clinical peculiarities like the occurrence of myocarditis characterize this multi-inflammatory syndrome. Our patients had an optimal response to treatments and a good outcome, with few complications and no deaths.

Defining Kawasaki disease and pediatric inflammatory multisystem syndrome-temporally associated to SARS-CoV-2 infection during SARS-CoV-2 epidemic in Italy: results from a national, multicenter survey

BACKGROUND

There is mounting evidence on the existence of a Pediatric Inflammatory Multisystem Syndrome-temporally associated to SARS-CoV-2 infection (PIMS-TS), sharing similarities with Kawasaki Disease (KD). The main outcome of the study were to better characterize the clinical features and the treatment response of PIMS-TS and to explore its relationship with KD determining whether KD and PIMS are two distinct entities.

METHODS

The Rheumatology Study Group of the Italian Pediatric Society launched a survey to enroll patients diagnosed with KD (Kawasaki Disease Group - KDG) or KD-like (Kawacovid Group - KCG) disease between February 1st 2020, and May 31st 2020. Demographic, clinical, laboratory data, treatment information, and patients' outcome were collected in an online anonymized database (RedCAP®). Relationship between clinical presentation and SARS-CoV-2 infection was also taken into account. Moreover, clinical characteristics of KDG during SARS-CoV-2 epidemic (KDG-CoV2) were compared to Kawasaki Disease patients (KDG-Historical) seen in three different Italian tertiary pediatric hospitals (Institute for Maternal and Child Health, IRCCS "Burlo Garofolo", Trieste; AOU Meyer, Florence; IRCCS Istituto Giannina Gaslini, Genoa) from January 1st 2000 to December 31st 2019. Chi square test or exact Fisher test and non-parametric Wilcoxon Mann-Whitney test were used to study differences between two groups.

RESULTS

One-hundred-forty-nine cases were enrolled, (96 KDG and 53 KCG). KCG children were significantly older and presented more frequently from gastrointestinal and respiratory involvement. Cardiac involvement was more common in KCG, with 60,4% of patients with myocarditis. 37,8% of patients among KCG presented hypotension/non-cardiogenic shock. Coronary artery abnormalities (CAA) were more common in the KDG. The risk of ICU admission were higher in KCG. Lymphopenia, higher CRP levels, elevated ferritin and troponin-T characterized KCG. KDG received more frequently immunoglobulins (IVIG) and acetylsalicylic acid (ASA) (81,3% vs 66%; p = 0.04 and 71,9% vs 43,4%; p = 0.001 respectively) as KCG more often received glucocorticoids (56,6% vs 14,6%; p < 0.0001). SARS-CoV-2 assay more often resulted positive in KCG than in KDG (75,5% vs 20%; p < 0.0001). Short-term follow data showed minor complications. Comparing KDG with a KD-Historical Italian cohort (598 patients), no statistical difference was found in terms of clinical manifestations and laboratory data.

CONCLUSION

Our study suggests that SARS-CoV-2 infection might determine two distinct inflammatory diseases in children: KD and PIMS-TS. Older age at onset and clinical peculiarities like the occurrence of myocarditis characterize this multi-inflammatory syndrome. Our patients had an optimal response to treatments and a good outcome, with few complications and no deaths.

SARS-CoV-2 infection in an infant with severe dilated cardiomyopathy

A four- and a half-month-old girl with severe dilated cardiomyopathy due to neonatal enterovirus myocarditis, treated with diuretics and milrinone for the past 4 months, was infected with SARS-CoV-2. The disease course was characterised by high fever and gastrointestinal symptoms. Cardiac function, as measured by echocardiography, remained stable. The treatment focused on maintaining a normal heart rate and a stable fluid balance. In children with severe underlying cardiac disease, even a mild SARS-CoV-2 infection can require close monitoring and compound treatment.

Ameliorative effect of ferruginol on isoprenaline hydrochloride-induced myocardial infarction in rats

Cardiovascular-related diseases continue to be a leading cause of death globally. Among ischemic-induced cardiac diseases, myocardial infarction (MI) is reported to be of an alarming value. Despite numerous improvements in the medical intrusions, still this armamentarium fails to be effective in managing the illness without setbacks. Ferruginol (FGL) is a major polyphenols and terpenoids with numerous pharmacological activities including antioxidant and anti-inflammatory. Following, this work was aimed to explore the cardio protective effect of FGL (50 mg/kg) in isoprenaline hydrochloride (ISO)-induced MI in experimental rats. After treatment with FGL in ISO-induced MI in rats, noticeable changes were observed in the experimental rats. Injection of ISO to rats resulted in the augmented cardiac weight, serum cardiac markers (creatine kinase, creatine kinase-MB, cardiac troponin T, and Cardiac troponin I), lipid peroxidation end products (thiobarbituric acid-reactive substance and lipid hydroperoxides), reduced endogenous antioxidants (superoxide dismutase, catalase, glutathione peroxidase, and glutathione), reduced ATPase activity, and escalated pro-inflammatory cytokines (interleukin-6, tumor necrosis factor-α, and nuclear factor-κB) levels. Interestingly, the FGL supplementation to the ISO-treated rats revealed the diminished heart weight, reduced cardiac markers, and lipid peroxidation. FGL also possessed the improved antioxidants status and diminished pro-inflammatory mediator levels. The outcomes of histological analysis also evidenced the cardio protective role of FGL. Treatment with FGL reduced the cardiac damage biomarkers maintained to near normal levels in ISO-induced rats. These study findings disclose the prospective capability of FGL in the treatment of MI in the future.

Diagnostic Performance of High-Sensitivity Cardiac Troponin T Strategies and Clinical Variables in a Multisite US Cohort

BACKGROUND

European data support the use of low high-sensitivity troponin (hs-cTn) measurements or a 0/1-hour (0/1-h) algorithm for myocardial infarction to exclude major adverse cardiac events (MACEs) among patients in the emergency department with possible acute coronary syndrome. However, modest US data exist to validate these strategies. This study evaluated the diagnostic performance of an initial hs-cTnT measure below the limit of quantification (LOQ: 6 ng/L), a 0/1-h algorithm, and their combination with history, ECG, age, risk factors, and initial troponin (HEART) scores for excluding MACE in a multisite US cohort.

METHODS

A prospective cohort study was conducted at 8 US sites, enrolling adult patients in the emergency department with symptoms suggestive of acute coronary syndrome and without ST-elevation on ECG. Baseline and 1-hour blood samples were collected, and hs-cTnT (Roche; Basel, Switzerland) was measured. Treating providers blinded to hs-cTnT results prospectively calculated HEART scores. MACE (cardiac death, myocardial infarction, and coronary revascularization) at 30 days was adjudicated. The proportion of patients with initial hs-cTnT measures below the LOQ and risk according to a 0/1-h algorithm was determined. The negative predictive value (NPV) was calculated for both strategies when used alone or with a HEART score.

RESULTS

Among 1462 participants with initial hs-cTnT measures, 46.4% (678 of 1462) were women and 37.1% (542 of 1462) were Black with an age of 57.6±12.9 (mean±SD) years. MACEs at 30 days occurred in 14.4% (210 of 1462) of participants. Initial hs-cTnT measures below the LOQ occurred in 32.8% (479 of 1462), yielding an NPV of 98.3% (95% CI, 96.7-99.3) for 30-day MACEs. A low-risk HEART score with an initial hs-cTnT below the LOQ occurred in 20.1% (294 of 1462), yielding an NPV of 99.0% (95% CI, 97.0-99.8) for 30-day MACEs. A 0/1-h algorithm was complete in 1430 patients, ruling out 57.8% (826 of 1430) with an NPV of 97.2% (95% CI, 95.9-98.2) for 30-day MACEs. Adding a low HEART score to the 0/1-h algorithm ruled out 30.8% (441 of 1430) with an NPV of 98.4% (95% CI, 96.8-99.4) for 30-day MACEs.

CONCLUSIONS

In a prospective multisite US cohort, an initial hs-cTnT below the LOQ combined with a low-risk HEART score has a 99% NPV for 30-day MACEs. The 0/1-h hs-cTnT algorithm did not achieve an NPV >99% for 30-day MACEs when used alone or with a HEART score. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02984436.

Cardioprotective effect of boswellic acids against doxorubicin induced myocardial infarction in rats

The aim of the present study was to evaluate the cardioprotective activity of boswellic acids in doxorubicin (DOX) induced cardiotoxicity. DOX (2.5mg/kg) was used intraperitoneally in rats to induce cardiotoxicity in six divided doses every alternate day over a period of two weeks. Dexrazoxane (10:1) was used as a standard drug. Boswellic acids (250, 500 and 750 mg/kg) were orally administered to rats for 14 days. After 14 days, rats were sacrificed, and blood was withdrawn through cardiac puncture. The blood lipid profile and cardiac biomarkers including LDH, CK-MB, CPK, SGOT and troponin T were measured. The heart of rats was isolated for histopathological studies. Graphpad Prism was used for statistical analysis. There was a significant increase in the level of cardiac enzymes and complete lipid profile parameters in diseased group as compared to control group. Pre-treatment with boswellic acids decreased level of all the measured parameters and decreased the severity of myocardial damage as supported by histopathological studies. It was concluded that boswellic acids possess cardioprotective potential by lowering cardiac biomarkers and blood lipid profile. Thus, boswellic acids might act as cardioprotective agent against doxorubicin induced cardiotoxicity.

Generation of transgenic mice that conditionally express microRNA miR-145

MicroRNAs are modulators of cellular phenotypes and their functions contribute to development, homeostasis, and disease. miR-145 is a conserved microRNA that has been implicated in regulating an array of phenotypes. These include supporting smooth muscle differentiation, repression of stem cell pluripotency, and inhibition of tumor growth and metastasis. Previously, our lab demonstrated that miR-145 acts to suppress cardiac fibrosis through inhibition of the TGF-β signaling pathway. The range of effects that miR-145 has on different cell types makes it an attractive microRNA for further study. Here we describe the generation of transgenic mice that conditionally express miR-145 through Cre recombinase-mediated activation. Characterization of individual founder lines indicates that overexpression of miR-145 in the developing cardiovascular system has detrimental effects, with three independent miR-145 transgenic lines exhibiting Cre-dependent lethality. Expression analysis demonstrates that the transgene is robustly expressed and our analysis reveals a novel downstream target of miR-145, Tnnt2. The miR-145 transgenic mice represent a valuable tool to understand the role of miR-145 in diverse cell types and to address its potential as a therapeutic mediator for the treatment of disease.

TNNT2 mutations in the tropomyosin binding region of TNT1 disrupt its role in contractile inhibition and stimulate cardiac dysfunction

Muscle contraction is regulated by the movement of end-to-end-linked troponin-tropomyosin complexes over the thin filament surface, which uncovers or blocks myosin binding sites along F-actin. The N-terminal half of troponin T (TnT), TNT1, independently promotes tropomyosin-based, steric inhibition of acto-myosin associations, in vitro. Recent structural models additionally suggest TNT1 may restrain the uniform, regulatory translocation of tropomyosin. Therefore, TnT potentially contributes to striated muscle relaxation; however, the in vivo functional relevance and molecular basis of this noncanonical role remain unclear. Impaired relaxation is a hallmark of hypertrophic and restrictive cardiomyopathies (HCM and RCM). Investigating the effects of cardiomyopathy-causing mutations could help clarify TNT1's enigmatic inhibitory property. We tested the hypothesis that coupling of TNT1 with tropomyosin's end-to-end overlap region helps anchor tropomyosin to an inhibitory position on F-actin, where it deters myosin binding at rest, and that, correspondingly, cross-bridge cycling is defectively suppressed under diastolic/low Ca2+ conditions in the presence of HCM/RCM lesions. The impact of TNT1 mutations on Drosophila cardiac performance, rat myofibrillar and cardiomyocyte properties, and human TNT1's propensity to inhibit myosin-driven, F-actin-tropomyosin motility were evaluated. Our data collectively demonstrate that removing conserved, charged residues in TNT1's tropomyosin-binding domain impairs TnT's contribution to inhibitory tropomyosin positioning and relaxation. Thus, TNT1 may modulate acto-myosin activity by optimizing F-actin-tropomyosin interfacial contacts and by binding to actin, which restrict tropomyosin's movement to activating configurations. HCM/RCM mutations, therefore, highlight TNT1's essential role in contractile regulation by diminishing its tropomyosin-anchoring effects, potentially serving as the initial trigger of pathology in our animal models and humans.

A comparison of intraoperative goal-directed intravenous administration of crystalloid versus colloid solutions on the postoperative maximum N-terminal pro brain natriuretic peptide in patients undergoing moderate- to high-risk noncardiac surgery

BACKGROUND

N-terminal pro brain natriuretic peptide (NT-proBNP) and troponin T are released during myocardial wall stress and/or ischemia and are strong predictors for postoperative cardiovascular complications. However, the relative effects of goal-directed, intravenous administration of crystalloid compared to colloid solutions on NT-proBNP and troponin T, especially in relatively healthy patients undergoing moderate- to high-risk noncardiac surgery, remains unclear. Thus, we evaluated in this sub-study the effect of a goal-directed crystalloid versus a goal-directed colloid fluid regimen on postoperative maximum NT-proBNP concentration. We further evaluated the incidence of myocardial injury after noncardiac surgery (MINS) between both study groups.

METHODS

Thirty patients were randomly assigned to receive additional intravenous fluid boluses of 6% hydroxyethyl starch 130/0.4 and 30 patients to receive lactated Ringer's solution. Intraoperative fluid management was guided by oesophageal Doppler-according to a previously published algorithm. The primary outcome were differences in postoperative maximum NT-proBNP (maxNT-proBNP) between both groups. As our secondary outcome we evaluated the incidence of MINS between both study groups. We defined maxNT-proBNP as the maximum value measured within 2 h after surgery and on the first and second postoperative day.

RESULTS

In total 56 patients were analysed. There was no significant difference in postoperative maximum NT-proBNP between the colloid group (258.7 ng/L (IQR 199.4 to 782.1)) and the crystalloid group (440.3 ng/L (IQR 177.9 to 691.2)) during the first 2 postoperative days (P = 0.29). Five patients in the colloid group and 7 patients in the crystalloid group developed MINS (P = 0.75).

CONCLUSIONS

Based on this relatively small study goal-directed colloid administration did not decrease postoperative maxNT-proBNP concentration as compared to goal-directed crystalloid administration.

TRIAL REGISTRATION

ClinicalTrials.gov ( NCT01195883 ) Registered on 6th September 2010.

Dilated cardiomyopathy mutations in thin-filament regulatory proteins reduce contractility, suppress systolic Ca2+, and activate NFAT and Akt signaling

Dilated cardiomyopathy (DCM) is clinically characterized by dilated ventricular cavities and reduced ejection fraction, leading to heart failure and increased thromboembolic risk. Mutations in thin-filament regulatory proteins can cause DCM and have been shown in vitro to reduce contractility and myofilament Ca²⁺-affinity. In this work we have studied the functional consequences of mutations in cardiac troponin T (R131W), cardiac troponin I (K36Q) and α-tropomyosin (E40K) using adenovirally transduced isolated guinea pig left ventricular cardiomyocytes. We find significantly reduced fractional shortening with reduced systolic Ca²⁺. Contraction and Ca²⁺ reuptake times were slowed, which contrast with some findings in murine models of myofilament Ca²⁺ desensitization. We also observe increased sarcoplasmic reticulum (SR) Ca²⁺ load and smaller fractional SR Ca²⁺ release. This corresponds to a reduction in SR Ca²⁺-ATPase activity and increase in sodium-calcium exchanger activity. We also observe dephosphorylation and nuclear translocation of the nuclear factor of activated T cells (NFAT), with concordant RAC-α-serine/threonine protein kinase (Akt) phosphorylation but no change to extracellular signal-regulated kinase activation in chronically paced cardiomyocytes expressing DCM mutations. These changes in Ca²⁺ handling and signaling are common to all three mutations, indicating an analogous pathway of disease pathogenesis in thin-filament sarcomeric DCM. Previous work has shown that changes to myofilament Ca²⁺ sensitivity caused by DCM mutations are qualitatively opposite from hypertrophic cardiomyopathy (HCM) mutations in the same genes. However, we find several common pathways such as increased relaxation times and NFAT activation that are also hallmarks of HCM. This suggests more complex intracellular signaling underpinning DCM, driven by the primary mutation.NEW & NOTEWORTHY Dilated cardiomyopathy (DCM) is a frequently occurring cardiac disorder with a degree of genetic inheritance. We have found that DCM mutations in proteins that regulate the contractile machinery cause alterations to contraction, calcium-handling, and some new signaling pathways that provide stimuli for disease development. We have used guinea pig cells that recapitulate human calcium-handling and introduced the mutations using adenovirus gene transduction to look at the initial triggers of disease before remodeling.

Injectable collagen scaffold promotes swine myocardial infarction recovery by long-term local retention of transplanted human umbilical cord mesenchymal stem cells

Stem cell therapy is an attractive approach for recovery from myocardial infarction (MI) but faces the challenges of rapid diffusion and poor survival after transplantation. Here we developed an injectable collagen scaffold to promote the long-term retention of transplanted cells in chronic MI. Forty-five minipigs underwent left anterior descending artery (LAD) ligation and were equally divided into three groups 2 months later (collagen scaffold loading with human umbilical mesenchymal stem cell (hUMSC) group, hUMSC group, and placebo group (only phosphate-buffered saline (PBS) injection)). Immunofluorescence staining indicated that the retention of transplanted cells was promoted by the collagen scaffold. Echocardiography and cardiac magnetic resonance imaging (CMR) showed much higher left ventricular ejection fraction (LVEF) and lower infarct size percentage in the collagen/hUMSC group than in the hUMSC and placebo groups at 12 months after treatment. There were also higher densities of vWf-, α-sma-, and cTnT-positive cells in the infarct border zone in the collagen/cell group, as revealed by immunohistochemical analysis, suggesting better angiogenesis and more cardiomyocyte survival after MI. Thus, the injectable collagen scaffold was safe and effective on a large animal myocardial model, which is beneficial for constructing a favorable microenvironment for applying stem cells in clinical MI.

Cardiac function modulates endocardial cell dynamics to shape the cardiac outflow tract

Physical forces are important participants in the cellular dynamics that shape developing organs. During heart formation, for example, contractility and blood flow generate biomechanical cues that influence patterns of cell behavior. Here, we address the interplay between function and form during the assembly of the cardiac outflow tract (OFT), a crucial connection between the heart and vasculature that develops while circulation is under way. In zebrafish, we find that the OFT expands via accrual of both endocardial and myocardial cells. However, when cardiac function is disrupted, OFT endocardial growth ceases, accompanied by reduced proliferation and reduced addition of cells from adjacent vessels. The flow-responsive TGFβ receptor Acvrl1 is required for addition of endocardial cells, but not for their proliferation, indicating distinct modes of function-dependent regulation for each of these essential cell behaviors. Together, our results indicate that cardiac function modulates OFT morphogenesis by triggering endocardial cell accumulation that induces OFT lumen expansion and shapes OFT dimensions. Moreover, these morphogenetic mechanisms provide new perspectives regarding the potential causes of cardiac birth defects.

The evaluation of a tissue-engineered cardiac patch seeded with hips derived cardiac progenitor cells in a rat left ventricular model

BACKGROUND

Ventricular septal perforation and left ventricular aneurysm are examples of potentially fatal complications of myocardial infarction. While various artificial materials are used in the repair of these issues, the possibility of associated infection and calcification is non-negligible. Cell-seeded biodegradable tissue-engineered patches may be a potential solution. This study evaluated the feasibility of a new left ventricular patch rat model to study neotissue formation in biodegradable cardiac patches.

METHODS

Human induced pluripotent stem cell-derived cardiac progenitor cells (hiPS-CPCs) were cultured onto biodegradable patches composed of polyglycolic acid and a 50:50 poly (l-lactide-co-ε-caprolactone) copolymer for one week. After culturing, patches were implanted into left ventricular walls of male athymic rats. Unseeded controls were also used (n = 10/group). Heart conditions were followed by echocardiography and patches were subsequently explanted at 1, 2, 6, and 9 months post-implantation for histological evaluation.

RESULT

Throughout the study, no patches ruptured demonstrating the ability to withstand the high pressure left ventricular system. One month after transplantation, the seeded patch did not stain positive for human nuclei. However, many new blood vessels formed within patches with significantly greater vessels in the seeded group at the 6 month time point. Echocardiography showed no significant difference in left ventricular contraction rate between the two groups. Calcification was found inside patches after 6 months, but there was no significant difference between groups.

CONCLUSION

We have developed a surgical method to implant a bioabsorbable scaffold into the left ventricular environment of rats with a high survival rate. Seeded hiPS-CPCs did not differentiate into cardiomyocytes, but the greater number of new blood vessels in seeded patches suggests the presence of cell seeding early in the remodeling process might provide a prolonged effect on neotissue formation. This experiment will contribute to the development of a treatment model for left ventricular failure using iPS cells in the future.

Establishing a model for predicting the outcome of COVID-19 based on combination of laboratory tests

Introduction

There are currently no satisfactory methods for predicting the outcome of Coronavirus Disease-2019 (COVID-19). The aim of this study is to establish a model for predicting the prognosis of the disease.

Methods

The laboratory results were collected from 54 deceased COVID-19 patients on admission and before death. Another 54 recovered COVID-19 patients were enrolled as control cases.

Results

Many laboratory indicators, such as neutrophils, AST, γ-GT, ALP, LDH, NT-proBNP, Hs-cTnT, PT, APTT, D-dimer, IL-2R, IL-6, IL-8, IL-10, TNF-α, CRP, ferritin and procalcitonin, were all significantly increased in deceased patients compared with recovered patients on admission. In contrast, other indicators such as lymphocytes, platelets, total protein and albumin were significantly decreased in deceased patients on admission. Some indicators such as neutrophils and procalcitonin, others such as lymphocytes and platelets, continuously increased or decreased from admission to death in deceased patients respectively. Using these indicators alone had moderate performance in differentiating between recovered and deceased COVID-19 patients. A model based on combination of four indicators (P = 1/[1 + e^{−(−2.658+0.587×neutrophils – 2.087×lymphocytes – 0.01×platelets+0.004×IL−2R)}]) showed good performance in predicting the death of COVID-19 patients. When cutoff value of 0.572 was used, the sensitivity and specificity of the prediction model were 90.74% and 94.44%, respectively.

Conclusions

Using the current indicators alone is of modest value in differentiating between recovered and deceased COVID-19 patients. A prediction model based on combination of neutrophils, lymphocytes, platelets and IL-2R shows good performance in predicting the outcome of COVID-19.

The effect of supplemental oxygen on perioperative brain natriuretic peptide concentration in cardiac risk patients - a protocol for a prosprective randomized clinical trial

BACKGROUND

Elevated postoperative N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations are predictive for cardiac adverse events in noncardiac surgery. Studies indicate that supplemental oxygen decreases sympathetic nerve activity and might, therefore, improve cardiovascular function. Thus, we will test the effect of perioperative supplemental oxygen administration on NT-proBNP release after surgery.

METHODS/DESIGN

We will conduct a single-center, double-blinded, randomized trial at the Medical University of Vienna, including 260 patients with increased cardiac risk factors undergoing moderate- to high-risk noncardiac surgery. Patients will be randomly assigned to receive 80% versus 30% oxygen during surgery and for 2 h postoperatively. The primary outcome will be the difference in maximum NT-proBNP release after surgery. As secondary outcomes we will assess the effect of supplemental oxygen on postoperative maximum troponin T concentration, oxidation-reduction potential, von Willebrand factor concentration and perioperative fluid requirements. We will perform outcome measurements 2 h after surgery, on postoperative day 1 and on postoperative day 3. The NT-proBNP concentration and the oxidation-reduction potential will also be measured within 72 h before discharge.

DISCUSSION

Our trial should determine whether perioperative supplemental oxygen administration will reduce the postoperative release of NT-proBNP in patients with preoperative increased cardiovascular risk factors undergoing noncardiac surgery.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT03366857. Registered on 8th December 2017.

The glutamic acid-rich-long C-terminal extension of troponin T has a critical role in insect muscle functions

The troponin complex regulates the Ca2+ activation of myofilaments during striated muscle contraction and relaxation. Troponin genes emerged 500-700 million years ago during early animal evolution. Troponin T (TnT) is the thin-filament-anchoring subunit of troponin. Vertebrate and invertebrate TnTs have conserved core structures, reflecting conserved functions in regulating muscle contraction, and they also contain significantly diverged structures, reflecting muscle type- and species-specific adaptations. TnT in insects contains a highly-diverged structure consisting of a long glutamic acid-rich C-terminal extension of ∼70 residues with unknown function. We found here that C-terminally truncated Drosophila TnT (TpnT-CD70) retains binding of tropomyosin, troponin I, and troponin C, indicating a preserved core structure of TnT. However, the mutant TpnTCD70 gene residing on the X chromosome resulted in lethality in male flies. We demonstrate that this X-linked mutation produces dominant-negative phenotypes, including decreased flying and climbing abilities, in heterozygous female flies. Immunoblot quantification with a TpnT-specific mAb indicated expression of TpnT-CD70 in vivo and normal stoichiometry of total TnT in myofilaments of heterozygous female flies. Light and EM examinations revealed primarily normal sarcomere structures in female heterozygous animals, whereas Z-band streaming could be observed in the jump muscle of these flies. Although TpnT-CD70-expressing flies exhibited lower resistance to cardiac stress, their hearts were significantly more tolerant to Ca2+ overloading induced by high-frequency electrical pacing. Our findings suggest that the Glu-rich long C-terminal extension of insect TnT functions as a myofilament Ca2+ buffer/reservoir and is potentially critical to the high-frequency asynchronous contraction of flight muscles.

Clinical outcomes for chest pain patients discharged home from emergency departments using high-sensitivity versus conventional cardiac troponin assays

BACKGROUND

High-sensitivity cardiac troponin (hs-cTn) assays enhance detection of lower circulating troponin concentrations, but the impact on outcomes in clinical practice is unclear. Our objective was to compare outcomes of chest pain patients discharged from emergency departments (EDs) using hs-cTn and conventional troponin (cTn) assays.

METHODS

We conducted an observational study of chest pain patients aged 40-105 years who presented to an ED from April 1, 2013, to March 31, 2017, and were discharged home. We compared 30-day and 1-year outcomes of EDs that used hs-cTn versus cTn assays. The primary outcome was a composite of all-cause death, myocardial infarction or unstable angina. Comparisons were conducted with (1) no adjustment; (2) adjustment for demographic, socioeconomic, and hospital characteristics; and (3) full clinical adjustment.

RESULTS

Among the 394,910 patients, 62,138 (15.7%) were evaluated at hs-cTn EDs and 332,772 (84.3%) were evaluated at cTn EDs. Patients discharged from hs-cTn EDs were less likely to have diabetes, hypertension, or prior heart disease. At 30 days, the unadjusted primary outcome rate was lower in hs-cTn EDs (0.9% vs 1.0%, P < .001). The 30-day hazard ratios for the primary outcome were 0.84 (95% CI 0.77-0.92) for no adjustment and 0.98 (95% CI 0.88-1.08) for full adjustment. Over 1 year, patients discharged from hs-cTn EDs had significantly fewer primary outcomes (3.7% vs 4.1%, P < .001) and lower hazard ratio (0.93; 95% CI 0.89-0.98) even after full adjustment.

CONCLUSIONS

Hs-cTn testing was associated with a significantly lower adjusted hazard of myocardial infarction, angina, and all-cause hospitalization at 1 year but not 30 days.

Cardiac Troponin T Release after Football 7 in Healthy Children and Adults

The objective of this study was to compare the release of cardiac troponin T (cTnT) after a football 7 match between two cohorts of children and adult players. Thirty-six male football players (children = 24, adult = 12) played a football 7 match, and cTnT was measured before, and 3 h after exercise. Concentrations of cTnT were compared between groups and time, and correlated with participants' characteristics, as well as internal and external exercise load. Cardiac troponin T was elevated in all participants (p < 0.001), and exceeded the upper reference limit for myocardial infarction in 25 (~70%) of them. Baseline concentrations were higher in adults (p < 0.001), but the elevation of cTnT was comparable between the groups (p = 0.37). Age (p < 0.001), body mass (p = 0.001) and height (p < 0.001), and training experience (p = 0.001) were associated to baseline cTnT values, while distance (p < 0.001), mean speed (p < 0.001), and peak (p = 0.013) and mean (p = 0.016) heart rate were associated to the elevation of cTnT. The present study suggests that a football 7 match evoked elevations of cTnT during the subsequent hours in healthy players regardless of their age. However, adults might present higher resting values of cTnT than children. In addition, results suggest that the exercise-induced elevations of cTnT might be mediated by exercise load but not participant characteristics.

The intrinsically disordered C terminus of troponin T binds to troponin C to modulate myocardial force generation

Aberrant regulation of myocardial force production represents an early biomechanical defect associated with sarcomeric cardiomyopathies, but the molecular mechanisms remain poorly defined. Here, we evaluated the pathogenicity of a previously unreported sarcomeric gene variant identified in a pediatric patient with sporadic dilated cardiomyopathy, and we determined a molecular mechanism. Trio whole-exome sequencing revealed a de novo missense variant in TNNC1 that encodes a p.I4M substitution in the N-terminal helix of cardiac troponin C (cTnC). Reconstitution of this human cTnC variant into permeabilized porcine cardiac muscle preparations significantly decreases the magnitude and rate of isometric force generation at physiological Ca2+-activation levels. Computational modeling suggests that this inhibitory effect can be explained by a decrease in the rates of cross-bridge attachment and detachment. For the first time, we show that cardiac troponin T (cTnT), in part through its intrinsically disordered C terminus, directly binds to WT cTnC, and we find that this cardiomyopathic variant displays tighter binding to cTnT. Steady-state fluorescence and NMR spectroscopy studies suggest that this variant propagates perturbations in cTnC structural dynamics to distal regions of the molecule. We propose that the intrinsically disordered C terminus of cTnT directly interacts with the regulatory N-domain of cTnC to allosterically modulate Ca2+ activation of force, perhaps by controlling the troponin I switching mechanism of striated muscle contraction. Alterations in cTnC-cTnT binding may compromise contractile performance and trigger pathological remodeling of the myocardium.

Comparative analysis of the DYRK1A-SRSF6-TNNT2 pathway in myocardial tissue from individuals with and without Down syndrome

Down syndrome (trisomy 21) is characterized by genome-wide imbalances that result in a range of phenotypic manifestations. Altered expression of DYRK1A in the trisomic context has been linked to some Down syndrome phenotypes. DYRK1A regulates the splicing of cardiac troponin (TNNT2) through a pathway mediated by the master splicing factor SRSF6. Here, we documented the expression of the DYRK1A-SRSF6-TNNT2 pathway in a collection of myocardial samples from persons with and without Down syndrome. Results suggest that "gene dosage effect" may drive the expression of DYRK1A mRNA but has no effect on DYRK1A protein levels in trisomic myocardium. The levels of phosphorylated DYRK1A-Tyr321 tended to be higher (~35%) in myocardial samples from donors with Down syndrome. The levels of phosphorylated SRSF6 were 2.6-fold higher in trisomic myocardium. In line, the expression of fetal TNNT2 variants was higher in myocardial tissue with trisomy 21. These data provide a representative picture on the extent of inter-individual variation in myocardial DYRK1A-SRSF6-TNNT2 expression in the context of Down syndrome.

Generation of human induced pluripotent stem cell-derived cardiomyocytes in 2D monolayer and scalable 3D suspension bioreactor cultures with reduced batch-to-batch variations

Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are promising candidates to treat myocardial infarction and other cardiac diseases. Such treatments require pure cardiomyocytes (CMs) in large quantities. Methods: In the present study we describe an improved protocol for production of hiPSC-CMs in which hiPSCs are first converted into mesodermal cells by stimulation of wingless (Wnt) signaling using CHIR99021, which are then further differentiated into CM progenitors by simultaneous inhibition of porcupine and tankyrase pathways using IWP2 and XAV939 under continuous supplementation of ascorbate during the entire differentiation procedure. Results: The protocol resulted in reproducible generation of >90% cardiac troponin T (TNNT2)-positive cells containing highly organized sarcomeres. In 2D monolayer cultures CM yields amounted to 0.5 million cells per cm2 growth area, and on average 72 million cells per 100 mL bioreactor suspension culture without continuous perfusion. The differentiation efficiency was hardly affected by the initial seeding density of undifferentiated hiPSCs. Furthermore, batch-to-batch variations were reduced by combinatorial use of ascorbate, IWP2, and XAV939. Conclusion: Combined inhibition of porcupine and tankyrase sub-pathways of Wnt signaling and continuous ascorbate supplementation, enable robust and efficient production of hiPSC-CMs.

Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy

Familial dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death and a major indicator for heart transplant. The disease is frequently caused by mutations of sarcomeric proteins; however, it is not well understood how these molecular mutations lead to alterations in cellular organization and contractility. To address this critical gap in our knowledge, we studied the molecular and cellular consequences of a DCM mutation in troponin-T, ΔK210. We determined the molecular mechanism of ΔK210 and used computational modeling to predict that the mutation should reduce the force per sarcomere. In mutant cardiomyocytes, we found that ΔK210 not only reduces contractility but also causes cellular hypertrophy and impairs cardiomyocytes' ability to adapt to changes in substrate stiffness (e.g., heart tissue fibrosis that occurs with aging and disease). These results help link the molecular and cellular phenotypes and implicate alterations in mechanosensing as an important factor in the development of DCM.

Multi-Site Coronary Vein Sampling Study on Cardiac Troponin T Degradation in Non-ST-Segment-Elevation Myocardial Infarction: Toward a More Specific Cardiac Troponin T Assay

Background Cardiac troponin T ( cTnT ) is seen in many other conditions besides myocardial infarction, and recent studies demonstrated distinct forms of cTnT . At present, the in vivo formation of these different cTnT forms is incompletely understood. We therefore performed a study on the composition of cTnT during the course of myocardial infarction, including coronary venous system sampling, close to its site of release. Methods and Results Baseline samples were obtained from multiple coronary venous system locations, and a peripheral artery and vein in 71 non- ST -segment-elevation myocardial infarction patients. Additionally, peripheral blood was drawn at 6- and 12-hours postcatheterization. cTnT concentrations were measured using the high-sensitivity- cTnT immunoassay. The cTnT composition was determined via gel filtration chromatography and Western blotting in an early and late presenting patient. High-sensitivity - cTnT concentrations were 28% higher in the coronary venous system than peripherally (n=71, P<0.001). Coronary venous system samples demonstrated cT n T-I-C complex, free intact cTnT , and 29 kD a and 15 to 18 kD a cTnT fragments, all in higher concentrations than in simultaneously obtained peripheral samples. While cT n T-I-C complex proportionally decreased, and disappeared over time, 15 to 18 kD a cTnT fragments increased. Moreover, cT n T-I-C complex was more prominent in the early than in the late presenting patient. Conclusions This explorative study in non- ST -segment-elevation myocardial infarction shows that cTnT is released from cardiomyocytes as a combination of cT n T-I-C complex, free intact cTnT , and multiple cTnT fragments indicating intracellular cTnT degradation. Over time, the cT n T-I-C complex disappeared because of in vivo degradation. These insights might serve as a stepping stone toward a high-sensitivity- cTnT immunoassay more specific for myocardial infarction.

Alpha-1 Adrenergic Receptor Agonist Phenylephrine Inhibits Sepsis-Induced Cardiomyocyte Apoptosis and Cardiac Dysfunction via Activating ERK1/2 Signal Pathway

It was demonstrated that α1 adrenergic receptor (α1-AR) activation by phenylephrine (PE) attenuated cardiac dysfunction in lipopolysaccharide (LPS)-challenged mice. However, it is unclear whether PE suppresses sepsis-induced cardiomyocyte apoptosis. Here, we investigated the effects of PE on cardiomyocyte apoptosis in LPS-treated adult rat ventricular myocytes (ARVMs) and septic rats induced by cecal ligation and puncture. Cardiomyocyte apoptosis and caspase activity were detected by TUNEL and spectrophotometrical assay, respectively. Bax, Bcl-2 and cytochrome c (Cyt c) levels as well as IκBα, ERK1/2, p38 MAPK, JNK and cardiac troponin I (cTnI) phosphorylation were analyzed by Western blotting, and TNF-α concentration was analyzed by ELISA. PE inhibited LPS-induced caspase-3 activation in ARVMs, which was reversed by prazosin (a membrane permeable α1-AR antagonist), but not by CGP12177A (a membrane impermeable α1-AR antagonist). PE upregulated phosphorylated ERK1/2 and Bcl-2 contents, decreased TNF-α and Bax levels, Cyt c release, caspase-8/-9 activities as well as IκBα, p38MAPK and JNK phosphorylation in LPS-treated ARVMs, all of which were abolished by prazosin. Treatment with U0126 (a specific ERK1/2 inhibitor) reversed the effects of PE on IκBα, p38MAPK and JNK phosphorylation as well as caspase-3/-8/-9 activation in LPS-treated ARVMs. In septic rats, PE not only inhibited myocardial apoptosis as well as IκBα, p38MAPK, and JNK phosphorylation, but also upregulated myocardial phosphorylated ERK1/2. Furthermore, PE inhibited myocardial cTnI phosphorylation and improved cardiac function in septic rats. Taken together, our data suggest that α1-AR activation by PE inhibits sepsis-induced cardiomyocyte apoptosis and cardiac dysfunction via activating ERK1/2 signal pathway.

Chronic Calmodulin-Kinase II Activation Drives Disease Progression in Mutation-Specific Hypertrophic Cardiomyopathy

BACKGROUND

Although the genetic causes of hypertrophic cardiomyopathy (HCM) are widely recognized, considerable lag in the development of targeted therapeutics has limited interventions to symptom palliation. This is in part attributable to an incomplete understanding of how point mutations trigger pathogenic remodeling. As a further complication, similar mutations within sarcomeric genes can result in differential disease severity, highlighting the need to understand the mechanism of progression at the molecular level. One pathway commonly linked to HCM progression is calcium homeostasis dysregulation, though how specific mutations disrupt calcium homeostasis remains unclear.

METHODS

To evaluate the effects of early intervention in calcium homeostasis, we used 2 mouse models of sarcomeric HCM (cardiac troponin T R92L and R92W) with differential myocellular calcium dysregulation and disease presentation. Two modes of intervention were tested: inhibition of the autoactivated calcium-dependent kinase (calmodulin kinase II [CaMKII]) via the AC3I peptide and diltiazem, an L-type calcium channel antagonist. Two-dimensional echocardiography was used to determine cardiac function and left ventricular remodeling, and atrial remodeling was monitored via atrial mass. Sarcoplasmic reticulum Ca2+ATPase activity was measured as an index of myocellular calcium handling and coupled to its regulation via the phosphorylation status of phospholamban.

RESULTS

We measured an increase in phosphorylation of CaMKII in R92W animals by 6 months of age, indicating increased autonomous activity of the kinase in these animals. Inhibition of CaMKII led to recovery of diastolic function and partially blunted atrial remodeling in R92W mice. This improved function was coupled to increased sarcoplasmic reticulum Ca2+ATPase activity in the R92W animals despite reduction of CaMKII activation, likely indicating improvement in myocellular calcium handling. In contrast, inhibition of CaMKII in R92L animals led to worsened myocellular calcium handling, remodeling, and function. Diltiazem-HCl arrested diastolic dysfunction progression in R92W animals only, with no improvement in cardiac remodeling in either genotype.

CONCLUSIONS

We propose a highly specific, mutation-dependent role of activated CaMKII in HCM progression and a precise therapeutic target for clinical management of HCM in selected cohorts. Moreover, the mutation-specific response elicited with diltiazem highlights the necessity to understand mutation-dependent progression at a molecular level to precisely intervene in disease progression.

Characterization of Endothelial Cilia Distribution During Cerebral-Vascular Development in Zebrafish ( Danio rerio)

Objective- Endothelial cells (ECs) sense and respond to flow-induced mechanical stress, in part, via microtubule-based projections called primary cilia. However, many critical steps during vascular morphogenesis occur independent of flow. The involvement of cilia in regulating these stages of cranial vascular morphogenesis is poorly understood because cilia have not been visualized in primary head vessels. The objective of this study was to investigate involvement of cilia in regulating the early stages of cranial vascular morphogenesis. Approach and Results- Using high-resolution imaging of the Tg(kdrl:mCherry-CAAX) y171 ;(bactin::Arl13b:GFP) zebrafish line, we showed that cilia are enriched in the earliest formed cranial vessels that assemble via vasculogenesis and in angiogenic hindbrain capillaries. Cilia were more prevalent around the boundaries of putative intravascular spaces in primary and angiogenic vessels. Loss of cardiac contractility and blood flow, because of knockdown of cardiac troponin T type 2a ( tnnt2a) expression, did not affect the distribution of cilia in primary head vasculature. In later stages of development, cilia were detected in retinal vasculature, areas of high curvature, vessel bifurcation points, and during vessel anastomosis. Loss of genes crucial for cilia biogenesis ( ift172 and ift81) induced intracerebral hemorrhages in an EC-autonomous manner. Exposure to high shear stress induced premature cilia disassembly in brain ECs and was associated with intracerebral hemorrhages. Conclusions- Our study suggests a functional role for cilia in brain ECs, which is associated with the emergence and remodeling of the primary cranial vasculature. This cilia function is flow-independent, and cilia in ECs are required for cerebral-vascular stability.