Wnt10b Gain-of-Function Improves Cardiac Repair by Arteriole Formation and Attenuation of Fibrosis

Transcriptome analysis of cardiac endothelial cells after myocardial infarction reveals temporal changes and long-term deficits

Endothelial cells (ECs) have essential roles in cardiac tissue repair after myocardial infarction (MI). To establish stage-specific and long-term effects of the ischemic injury on cardiac ECs, we analyzed their transcriptome at landmark time points after MI in mice. We found that early EC response at Day 2 post-MI centered on metabolic changes, acquisition of proinflammatory phenotypes, initiation of the S phase of cell cycle, and activation of stress-response pathways, followed by progression to mitosis (M/G2 phase) and acquisition of proangiogenic and mesenchymal properties during scar formation at Day 7. In contrast, genes involved in vascular physiology and maintenance of vascular tone were suppressed. Importantly, ECs did not return to pre-injury phenotypes after repair has been completed but maintained inflammatory, fibrotic and thrombotic characteristics and lost circadian rhythmicity. We discovered that the highest induced transcript is the mammalian-specific Sh2d5 gene that promoted migration and invasion of ECs through Rac1 GTPase. Our results revealed a synchronized, temporal activation of disease phenotypes, metabolic pathways, and proliferation in quiescent ECs after MI, indicating that precisely-timed interventions are necessary to optimize cardiac tissue repair and improve outcomes. Furthermore, long-term effects of acute ischemic injury on ECs may contribute to vascular dysfunction and development of heart failure.

Wnt10b protects cardiomyocytes against doxorubicin-induced cell death via MAPK modulation

BACKGROUND

Doxorubicin, an anthracycline chemotherapeutic known to incur heart damage, decreases heart function in up to 11% of patients. Recent investigations have implicated the Wnt signaling cascade as a key modulator of cardiac tissue repair after myocardial infarction. Wnt upregulation in murine models resulted in stimulation of angiogenesis and suppression of fibrosis after ischemic insult. However, the molecular mechanisms of Wnt in mitigating doxorubicin-induced cardiac insult require further investigation. Identifying cardioprotective mechanisms of Wnt is imperative to reducing debilitating cardiovascular adverse events in oncologic patients undergoing treatment.

METHODS

Exposing human cardiomyocyte AC16 cells to varying concentrations of Wnt10b and DOX, we observed key metrics of cell viability. To assess the viability and apoptotic rates, we utilized MTT and TUNEL assays. We quantified cell and mitochondrial membrane stability via LDH release and JC-1 staining. To investigate how Wnt10b mitigates doxorubicin-induced apoptosis, we introduced pharmacologic inhibitors of key enzymes involved in apoptosis: FR180204 and SB203580, ERK1/2 and p38 inhibitors. Further, we quantified apoptotic executor enzymes, caspase 3/7, via immunofluorescence.

RESULTS

AC16 cells exposed solely to doxorubicin were shrunken with distorted morphology. Cardioprotective effects of Wnt10b were demonstrated via a reduction in apoptosis, from 70.1% to 50.1%. LDH release was also reduced between doxorubicin and combination groups from 2.27-fold to 1.56-fold relative to the healthy AC16 control group. Mitochondrial membrane stability was increased from 0.67-fold in the doxorubicin group to 5.73 in co-treated groups relative to control. Apoptotic protein expression was stifled by Wnt10b, with caspase3/7 expression reduced from 2.4- to 1.3-fold, and both a 20% decrease in p38 and 40% increase in ERK1/2 activity.

CONCLUSION

Our data with the AC16 cell model demonstrates that Wnt10b provides defense mechanisms against doxorubicin-induced cardiotoxicity and apoptosis. Further, we explain a mechanism of this beneficial effect involving the mitochondria through simultaneous suppression of pro-apoptotic p38 and anti-apoptotic ERK1/2 activities.

New Insights into the Reparative Angiogenesis after Myocardial Infarction

Myocardial infarction (MI) causes massive loss of cardiac myocytes and injury to the coronary microcirculation, overwhelming the limited capacity of cardiac regeneration. Cardiac repair after MI is finely organized by complex series of procedures involving a robust angiogenic response that begins in the peri-infarcted border area of the infarcted heart, concluding with fibroblast proliferation and scar formation. Efficient neovascularization after MI limits hypertrophied myocytes and scar extent by the reduction in collagen deposition and sustains the improvement in cardiac function. Compelling evidence from animal models and classical in vitro angiogenic approaches demonstrate that a plethora of well-orchestrated signaling pathways involving Notch, Wnt, PI3K, and the modulation of intracellular Ca2+ concentration through ion channels, regulate angiogenesis from existing endothelial cells (ECs) and endothelial progenitor cells (EPCs) in the infarcted heart. Moreover, cardiac repair after MI involves cell-to-cell communication by paracrine/autocrine signals, mainly through the delivery of extracellular vesicles hosting pro-angiogenic proteins and non-coding RNAs, as microRNAs (miRNAs). This review highlights some general insights into signaling pathways activated under MI, focusing on the role of Ca2+ influx, Notch activated pathway, and miRNAs in EC activation and angiogenesis after MI.

The role of WNT10B in physiology and disease: A 10-year update

WNT10B, a member of the WNT family of secreted glycoproteins, activates the WNT/β-catenin signaling cascade to control proliferation, stemness, pluripotency, and cell fate decisions. WNT10B plays roles in many tissues, including bone, adipocytes, skin, hair, muscle, placenta, and the immune system. Aberrant WNT10B signaling leads to several diseases, such as osteoporosis, obesity, split-hand/foot malformation (SHFM), fibrosis, dental anomalies, and cancer. We reviewed WNT10B a decade ago, and here we provide a comprehensive update to the field. Novel research on WNT10B has expanded to many more tissues and diseases. WNT10B polymorphisms and mutations correlate with many phenotypes, including bone mineral density, obesity, pig litter size, dog elbow dysplasia, and cow body size. In addition, the field has focused on the regulation of WNT10B using upstream mediators, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). We also discussed the therapeutic implications of WNT10B regulation. In summary, research conducted during 2012-2022 revealed several new, diverse functions in the role of WNT10B in physiology and disease.

Bone Marrow-Derived Mesenchymal Stem Cells Transplantation Attenuates Renal Fibrosis Following Acute Kidney Injury in Rats by Diminishing Pericyte-Myofibroblast Transition and Extracellular Matrix Augment

BACKGROUND

Renal fibrosis is a common chronic outcome of acute kidney injury (AKI). Pericyte-myofibroblasts transition and production of abundant extracellular matrix are the important pathologic basis. This study investigated the effect of bone marrow-derived mesenchymal stem cells (BMSCs) transplantation on the AKI kidney fibrosis and the possible mechanisms.

METHODS

By constructing the animal and cell model of AKI pericyte injury, the therapeutic effect of BMSCs on pericyte-myofibroblasts transition was detected. The production and accumulation of extracellular matrix, including collagen I, collagen III, and fibronectin were also tested. The mechanism was revealed by means of analysis of signal pathway.

RESULTS

After AKI insult, many myofibroblasts emerged in the renal interstitium together with a large amount of extracellular matrix components. The BMSCs transplantation significantly decreased the number of myofibroblasts trans-differentiated from pericytes in the AKI model. The changes of vascular endothelial growth factor subtypes and Ang-I/AngII secreted by pericytes were also significantly reduced after BMSCs co-culture. At the same time, extracellular matrix components, including collagen I, collagen III, and fibronectin, decreased significantly. Transplantation treatment alleviated the fibrosis score. The transforming growth factor β (TGF-β) concentration decreased as well as the levels of Smad2/3 and p-Smad2/3 with the presence of BMSCs therapy.

CONCLUSIONS

Bone marrow-derived mesenchymal stem cells transplantation diminished pericyte-myofibroblast transition and extracellular matrix augment after AKI by regulating the TGF-β/Smad2/3 signaling pathway. It may be used as a novel therapeutic method for retarding renal fibrosis, which is worthy of further study.

Galunisertib-Loaded Gelatin Methacryloyl Hydrogel Microneedle Patch for Cardiac Repair after Myocardial Infarction

Uncontrolled and excessive fibrosis after myocardial infarction (MI) in the peri-infarct zone leads to left ventricular remodeling and deterioration of cardiac function. Inhibiting fibroblast activation during the mature phase of cardiac repair improves cardiac remodeling and function after MI. Here, we engineered a biocompatible microneedle (MN) patch using gelatin methacryloyl and loaded it with galunisertib, a transforming growth factor-beta (TGF-β)-specific inhibitor, to treat excessive cardiac fibrosis after MI. The MN patch could sustainably release galunisertib for more than 2 weeks and provide mechanical support for the fragile ventricular wall. After being applied to a rat model of MI, the galunisertib-loaded MN patch improved long-term cardiac function and reduced cardiac fibrosis by effectively inhibiting TGF-β depending on fibroblast activation. This strategy shows the potential of the MN patch as an advanced platform to locally deliver direct antifibrotic drugs to prevent myocardial fibrosis for the treatment of MI and the promotion of cardiac repair.

Wnt Signaling in Heart Development and Regeneration

PURPOSE OF REVIEW

Cardiovascular diseases are the leading cause of death worldwide, largely due to the limited regenerative capacity of the adult human heart. In contrast, teleost zebrafish hearts possess natural regeneration capacity by proliferation of pre-existing cardiomyocytes after injury. Hearts of mice can regenerate if injured in a few days after birth, which coincides with the transient capacity for cardiomyocyte proliferation. This review tends to elaborate the roles and mechanisms of Wnt/β-catenin signaling in heart development and regeneration in mammals and non-mammalian vertebrates.

RECENT FINDINGS

Studies in zebrafish, mice, and human embryonic stem cells demonstrate the binary effect for Wnt/β-catenin signaling during heart development. Both Wnts and Wnt antagonists are induced in multiple cell types during cardiac development and injury repair. In this review, we summarize composites of the Wnt signaling pathway and their different action routes, followed by the discussion of their involvements in cardiac specification, proliferation, and patterning. We provide overviews about canonical and non-canonical Wnt activity during heart homeostasis, remodeling, and regeneration. Wnt/β-catenin signaling exhibits biphasic and antagonistic effects on cardiac specification and differentiation depending on the stage of embryogenesis. Inhibition of Wnt signaling is beneficial for cardiac wound healing and functional recovery after injury. Understanding of the roles and mechanisms of Wnt signaling pathway in injured animal hearts will contribute to the development of potential therapeutics for human diseased hearts.

Signaling cascades in the failing heart and emerging therapeutic strategies

Chronic heart failure is the end stage of cardiac diseases. With a high prevalence and a high mortality rate worldwide, chronic heart failure is one of the heaviest health-related burdens. In addition to the standard neurohormonal blockade therapy, several medications have been developed for chronic heart failure treatment, but the population-wide improvement in chronic heart failure prognosis over time has been modest, and novel therapies are still needed. Mechanistic discovery and technical innovation are powerful driving forces for therapeutic development. On the one hand, the past decades have witnessed great progress in understanding the mechanism of chronic heart failure. It is now known that chronic heart failure is not only a matter involving cardiomyocytes. Instead, chronic heart failure involves numerous signaling pathways in noncardiomyocytes, including fibroblasts, immune cells, vascular cells, and lymphatic endothelial cells, and crosstalk among these cells. The complex regulatory network includes protein-protein, protein-RNA, and RNA-RNA interactions. These achievements in mechanistic studies provide novel insights for future therapeutic targets. On the other hand, with the development of modern biological techniques, targeting a protein pharmacologically is no longer the sole option for treating chronic heart failure. Gene therapy can directly manipulate the expression level of genes; gene editing techniques provide hope for curing hereditary cardiomyopathy; cell therapy aims to replace dysfunctional cardiomyocytes; and xenotransplantation may solve the problem of donor heart shortages. In this paper, we reviewed these two aspects in the field of failing heart signaling cascades and emerging therapeutic strategies based on modern biological techniques.

Elevated Wnt2 and Wnt4 activate NF-κB signaling to promote cardiac fibrosis by cooperation of Fzd4/2 and LRP6 following myocardial infarction

Background

Acute myocardial infarction (AMI)-induced excessive myocardial fibrosis exaggerates cardiac dysfunction. However, serum Wnt2 or Wnt4 level in AMI patients, and the roles in cardiac fibrosis are largely unkown.

Methods

AMI and non-AMI patients were enrolled to examine serum Wnt2 and Wnt4 levels by ELISA analysis. The AMI patients were followed-up for one year. MI mouse model was built by ligation of left anterior descending branch (LAD).

Findings

Serum Wnt2 or Wnt4 level was increased in patients with AMI, and the elevated Wnt2 and Wnt4 were correlated to adverse outcome of these patients. Knockdown of Wnt2 and Wnt4 significantly attenuated myocardial remodeling and cardiac dysfunction following experimental MI. In vitro, hypoxia enhanced the secretion and expression of Wnt2 and Wnt4 in neonatal rat cardiac myocytes (NRCMs) or fibroblasts (NRCFs). Mechanistically, the elevated Wnt2 or Wnt4 activated β-catenin /NF-κB signaling to promote pro-fibrotic effects in cultured NRCFs. In addition, Wnt2 or Wnt4 upregulated the expression of these Wnt co-receptors, frizzled (Fzd) 2, Fzd4 and (ow-density lipoprotein receptor-related protein 6 (LRP6). Further analysis revealed that Wnt2 or Wnt4 activated β-catenin /NF-κB by the co-operation of Fzd4 or Fzd2 and LRP6 signaling, respectively.

Interpretation

Elevated Wnt2 and Wnt4 activate β-catenin/NF-κB signaling to promote cardiac fibrosis by cooperation of Fzd4/2 and LRP6 in fibroblasts, which contributes to adverse outcome of patients with AMI, suggesting that systemic inhibition of Wnt2 and Wnt4 may improve cardiac dysfunction after MI.

The association between cardiovascular drugs and depression/anxiety in patients with cardiovascular disease: A meta-analysis

This study aimed to investigate the association between cardiovascular drugs and depression/anxiety in patients with cardiovascular disease (CVD). This meta-analysis was registered in PROSPERO (International Prospective Register of Systematic Reviews; CRD42020197839) and conducted in accordance with the MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines. The PubMed, EMBASE, Web of Science, China National Knowledge Infrastructure, Wanfang, and VIP databases were systematically searched to identify all available studies on this topic. Random-effects multivariate meta-regression was performed to investigate the sources of study heterogeneity. Review Manager version 5.3 and Stata 12.0 were used for data analyses. This meta-analysis included 54 studies with a total number of 212,640 patients. Overall, in patients with CVD, aspirin (odds ratio [OR]:0.91, 95% confidence interval [CI]:0.86-0.96, P = 0.02) was associated with a lower risk of depression, while calcium channel blockers (CCB) (OR:1.21, 95%CI:1.05-1.38, P = 0.008), diuretics (OR:1.34, 95%CI:1.14-1.58, P = 0.0005), and nitrate esters (OR:1.32, 95%CI:1.08-1.61, P = 0.006) were associated with a higher risk of depression, additionally, statin (OR:0.79, 95%CI:0.71-0.88, P < 0.0001) was associated with a lower risk of anxiety, but diuretics (OR:1.39, 95%CI:1.26-1.52, P < 0.00001) was associated with a higher risk of anxiety. Subgroup analysis presented that, in patients with hypertension, β-blockers were associated with a higher risk of depression (OR:1.45, 95%CI:1.26-1.67, P < 0.00001); in patients with coronary artery disease (CAD), statin (OR:0.77, 95%CI:0.59-0.99, P = 0.04), and aspirin (OR:0.85, 95%CI:0.75-0.97, P = 0.02) were associated with a lower risk of depression, while CCB (OR:1.32, 95%CI:1.15-1.51, P < 0.0001) and diuretics (OR:1.36, 95%CI:1.12-1.64, P = 0.002) were associated with a higher risk of depression, additionally, diuretics was associated with a higher risk of anxiety (OR:1.41, 95%CI:1.28-1.55, P < 0.00001); in patients with heart failure, nitrate esters (OR:1.93, 95%CI:1.19-3.13, P = 0.007), and diuretics (OR:1.58, 95%CI: 1.02-2.43, P = 0.04) were associated with a higher risk of depression. The use of cardiovascular drugs should be considered when evaluating depression or anxiety in patients with CVD to improve the care and treatment of these patients.

Inhibition of Wnt10b/β-catenin signaling alleviates pulmonary fibrogenesis induced by paraquat in vivo and in vitro

Pulmonary fibrosis (PF) caused by paraquat remains a critical issue, and the molecular mechanisms are still unclear. Epithelial-mesenchymal transition (EMT) is regarded as a hallmark of PF, conferring alveolar epithelial cells partial mesenchymal characteristics, facilitating migration, expressing excessive extracellular matrix components, and participating in lung parenchyma remodeling and stiffening. Aberration of Wnt signaling has been identified in EMT and PF, and Wnt protein family consists of 19 ligands. The relationship of the specific Wnt ligands and fibrogenesis induced by PQ was not well defined. In current study, PQ-induced lung fibrosis rat model and EMT cell model were utilized to investigate the underlying molecular mechanisms both in vivo and in vitro. The results demonstrated that canonical Wnt/β-catenin signaling was highly activated and Wnt10b was the most affected. Additionally, suppression of Wnt10b by RNA interference could reverse EMT in vitro and detain the process of PF in vivo. These data establish Wnt10b as the key regulator of EMT and lung fibrogenesis, and suggest the potential of targeted interference against Wnt10b as a promising therapeutic strategy for lung fibrosis.

The roles of signaling pathways in cardiac regeneration

In recent years, knowledge of cardiac regeneration mechanisms has dramatically expanded. Regeneration can replace lost parts of organs, common among animal species. The heart is commonly considered an organ with terminal development, which has no reparability potential during post-natal life; however, some intrinsic regeneration capacity has been reported for cardiac muscle, which opens novel avenues in cardiovascular disease treatment. Different endogenous mechanisms were studied for cardiac repairing and regeneration in recent decades. Survival, proliferation, inflammation, angiogenesis, cell-cell communication, cardiomyogenesis, and anti-aging pathways are the most important mechanisms that have been studied in this regard. Several in vitro and animal model studies focused on proliferation induction for cardiac regeneration reported promising results. These studies have mainly focused on promoting proliferation signaling pathways and demonstrated various signaling pathways such as Wnt, PI3K/Akt, IGF-1, TGF-β, Hippo, and VEGF signaling cardiac regeneration. Therefore, in this review, we intended to discuss the connection between different critical signaling pathways in cardiac repair and regeneration.

Identification of candidate biomarkers and therapeutic agents for heart failure by bioinformatics analysis

INTRODUCTION

Heart failure (HF) is a heterogeneous clinical syndrome and affects millions of people all over the world. HF occurs when the cardiac overload and injury, which is a worldwide complaint. The aim of this study was to screen and verify hub genes involved in developmental HF as well as to explore active drug molecules.

METHODS

The expression profiling by high throughput sequencing of GSE141910 dataset was downloaded from the Gene Expression Omnibus (GEO) database, which contained 366 samples, including 200 heart failure samples and 166 non heart failure samples. The raw data was integrated to find differentially expressed genes (DEGs) and were further analyzed with bioinformatics analysis. Gene ontology (GO) and REACTOME enrichment analyses were performed via ToppGene; protein-protein interaction (PPI) networks of the DEGs was constructed based on data from the HiPPIE interactome database; modules analysis was performed; target gene-miRNA regulatory network and target gene-TF regulatory network were constructed and analyzed; hub genes were validated; molecular docking studies was performed.

RESULTS

A total of 881 DEGs, including 442 up regulated genes and 439 down regulated genes were observed. Most of the DEGs were significantly enriched in biological adhesion, extracellular matrix, signaling receptor binding, secretion, intrinsic component of plasma membrane, signaling receptor activity, extracellular matrix organization and neutrophil degranulation. The top hub genes ESR1, PYHIN1, PPP2R2B, LCK, TP63, PCLAF, CFTR, TK1, ECT2 and FKBP5 were identified from the PPI network. Module analysis revealed that HF was associated with adaptive immune system and neutrophil degranulation. The target genes, miRNAs and TFs were identified from the target gene-miRNA regulatory network and target gene-TF regulatory network. Furthermore, receiver operating characteristic (ROC) curve analysis and RT-PCR analysis revealed that ESR1, PYHIN1, PPP2R2B, LCK, TP63, PCLAF, CFTR, TK1, ECT2 and FKBP5 might serve as prognostic, diagnostic biomarkers and therapeutic target for HF. The predicted targets of these active molecules were then confirmed.

CONCLUSION

The current investigation identified a series of key genes and pathways that might be involved in the progression of HF, providing a new understanding of the underlying molecular mechanisms of HF.

LRP5 Regulates HIF-1α Stability via Interaction with PHD2 in Ischemic Myocardium

Low-density lipoprotein receptor-related protein 5 (LRP5) has been studied as a co-receptor for Wnt/β-catenin signaling. However, its role in the ischemic myocardium is largely unknown. Here, we show that LRP5 may act as a negative regulator of ischemic heart injury via its interaction with prolyl hydroxylase 2 (PHD2), resulting in hypoxia-inducible factor-1α (HIF-1α) degradation. Overexpression of LRP5 in cardiomyocytes promoted hypoxia-induced apoptotic cell death, whereas LRP5-silenced cardiomyocytes were protected from hypoxic insult. Gene expression analysis (mRNA-seq) demonstrated that overexpression of LRP5 limited the expression of HIF-1α target genes. LRP5 promoted HIF-1α degradation, as evidenced by the increased hydroxylation and shorter stability of HIF-1α under hypoxic conditions through the interaction between LRP5 and PHD2. Moreover, the specific phosphorylation of LRP5 at T1492 and S1503 is responsible for enhancing the hydroxylation activity of PHD2, resulting in HIF-1α degradation, which is independent of Wnt/β-catenin signaling. Importantly, direct myocardial delivery of adenoviral constructs, silencing LRP5 in vivo, significantly improved cardiac function in infarcted rat hearts, suggesting the potential value of LRP5 as a new target for ischemic injury treatment.

Possible role of WNT10B in increased proliferation and tubule formation of human umbilical vein endothelial cell cultures treated with hypoxic conditioned medium from human adipocytes

Regulation of angiogenesis plays an important role in adipose tissue expansion and function. The Wnt pathway and WNT10B, the main member of Wnt family, participate in angiogenesis in cancer tumors, but there is limited evidence to support the regulatory role of WNT10B in human adipose tissue angiogenesis. Subcutaneous white adipose tissue (scWAT) of 80 participants including obese and non-obese subjects was obtained and the expression of WNT10B and VEGFA genes were evaluated using qPCR. Human adipose-derived stem cells (hADSC) were differentiated to adipocytes and incubated under either hypoxic or normoxic conditions. The conditioned media of these adipocytes were collected and used as growth media for human umbilical vein endothelial cells (HUVEC) in Matrigel. We evaluated the proliferation, cell cycle phases, tubule formation and β-catenin activation of these treated cells. We found a significant correlation between WNT10B and VEGFA expression in the scWAT of both obese and non-obese subjects. Proliferation and tubule formation of HUVEC treated with conditioned media of hypoxic adipocytes (hCM) in the S-phase were increased significantly compared to the HUVEC treated with the conditioned media of normoxic adipocytes (nCM). The expression of WNT10B and VEGFA was enhanced in hypoxic adipocytes compared to normoxic adipocytes; also, activation and nuclear translocation of β-catenin was enhanced in the HUVEC treated with hCM compared to nCM. WNT10B acts as an angiogenic protein in scWAT under hypoxic conditions. Hypoxia induced WNT10B increases VEGFA expression and causes tube formation by HUVECs and angiogenesis in adipose tissue via the canonical Wnt/β-catenin pathway.

A genome-wide analysis of cardiac lesions of pigs that die during transport: Is heart failure of in-transit-loss pigs associated with a heritable cardiomyopathy?

While heart failure is a primary cause of death for many in-transit-loss (ITL) pigs, the underlying cause of these deaths is not known. Cardiomyopathies are considered a common cause of heart failure in humans and often have a genetic component. The objective of this study was to determine if genes associated with cardiomyopathies could be identified in ITL pigs. Samples from the hearts of pigs that died during transport to an abattoir in Ontario, Canada were collected and genotyped along with samples from pigs that did not die during transport (ILT hearts: n = 149; non-ITL/control hearts: n = 387). Genome-wide analyses were carried out on each of the determined phenotypes (gross cardiac lesions) using a medium density single nucleotide polymorphism (SNP) chip and 500 kb windows/regions for analysis, with 250 kb regions of overlap. The distribution derived by a multidimensional scaling (MDS) analysis of all phenotypes demonstrated a lack of complete separation between phenotypes of affected and unaffected animals, which made diagnosis difficult. Although genetic differences were small, a few genes associated with dilated cardiomyopathy (DCM) and arrhythmogenic right ventricular cardiomyopathy (ARVM) were identified. In addition, multiple genes associated with cardiac arrhythmias and ventricular hypertrophy were identified that can possibly result in heart failure. The results of this preliminary study did not provide convincing evidence that a single, heritable cardiomyopathy is the cause of heart failure in ITL pigs.

Targeting 5-HT2B Receptor Signaling Prevents Border Zone Expansion and Improves Microstructural Remodeling After Myocardial Infarction

BACKGROUND

Myocardial infarction (MI) induces an intense injury response that ultimately generates a collagen-dominated scar. Although required to prevent ventricular rupture, the fibrotic process is often sustained in a manner detrimental to optimal recovery. Cardiac myofibroblasts are the cells tasked with depositing and remodeling collagen and are a prime target to limit the fibrotic process after MI. Serotonin 2B receptor (5-HT2B) signaling has been shown to be harmful in a variety of cardiopulmonary pathologies and could play an important role in mediating scar formation after MI.

METHODS

We used 2 pharmacological antagonists to explore the effect of 5-HT2B inhibition on outcomes after MI and characterized the histological and microstructural changes involved in tissue remodeling. Inducible 5-HT2B ablation driven by Tcf21MCM and PostnMCM was used to evaluate resident cardiac fibroblast- and myofibroblast-specific contributions of 5-HT2B, respectively. RNA sequencing was used to motivate subsequent in vitro analyses to explore cardiac fibroblast phenotype.

RESULTS

5-HT2B antagonism preserved cardiac structure and function by facilitating a less fibrotic scar, indicated by decreased scar thickness and decreased border zone area. 5-HT2B antagonism resulted in collagen fiber redistribution to thinner collagen fibers that were more anisotropic, enhancing left ventricular contractility, whereas fibrotic tissue stiffness was decreased, limiting the hypertrophic response of uninjured cardiomyocytes. Using a tamoxifen-inducible Cre, we ablated 5-HT2B from Tcf21-lineage resident cardiac fibroblasts and saw similar improvements to the pharmacological approach. Tamoxifen-inducible Cre-mediated ablation of 5-HT2B after onset of injury in Postn-lineage myofibroblasts also improved cardiac outcomes. RNA sequencing and subsequent in vitro analyses corroborate a decrease in fibroblast proliferation, migration, and remodeling capabilities through alterations in Dnajb4 expression and Src phosphorylation.

CONCLUSIONS

Together, our findings illustrate that 5-HT2B expression in either cardiac fibroblasts or activated myofibroblasts directly contributes to excessive scar formation, resulting in adverse remodeling and impaired cardiac function after MI.

Effect of Interventions in WNT Signaling on Healing of Cardiac Injury: A Systematic Review

The wound healing that follows myocardial infarction is a complex process involving multiple mechanisms, such as inflammation, angiogenesis and fibrosis. In the last two decades, the involvement of WNT signaling has been extensively studied and effects on virtually all aspects of this wound healing have been reported. However, as often is the case in a newly emerging field, inconsistent and sometimes even contradictory findings have been reported. The aim of this systematic review is to provide a comprehensive overview of studies in which the effect of interventions in WNT signaling were investigated in in vivo models of cardiac injury. To this end, we used different search engines to perform a systematic search of the literature using the key words "WNT and myocardial and infarction". We categorized the interventions according to their place in the WNT signaling pathway (ligand, receptor, destruction complex or nuclear level). The most consistent improvements of the wound healing response were observed in studies in which the acylation of WNT proteins was inhibited by administering porcupine inhibitors, by inhibiting of the downstream glycogen synthase kinase-3β (GSK3β) and by intervening in the β-catenin-mediated gene transcription. Interestingly, in several of these studies, evidence was presented for activation of cardiomyocyte proliferation around the infarct area. These findings indicate that inhibition of WNT signaling can play a valuable role in the repair of cardiac injury, thereby improving cardiac function and preventing the development of heart failure.

Single-Cell RNA Sequencing Unveils Unique Transcriptomic Signatures of Organ-Specific Endothelial Cells

BACKGROUND

Endothelial cells (ECs) display considerable functional heterogeneity depending on the vessel and tissue in which they are located. Whereas these functional differences are presumably imprinted in the transcriptome, the pathways and networks that sustain EC heterogeneity have not been fully delineated.

METHODS

To investigate the transcriptomic basis of EC specificity, we analyzed single-cell RNA sequencing data from tissue-specific mouse ECs generated by the Tabula Muris consortium. We used a number of bioinformatics tools to uncover markers and sources of EC heterogeneity from single-cell RNA sequencing data.

RESULTS

We found a strong correlation between tissue-specific EC transcriptomic measurements generated by either single-cell RNA sequencing or bulk RNA sequencing, thus validating the approach. Using a graph-based clustering algorithm, we found that certain tissue-specific ECs cluster strongly by tissue (eg, liver, brain), whereas others (ie, adipose, heart) have considerable transcriptomic overlap with ECs from other tissues. We identified novel markers of tissue-specific ECs and signaling pathways that may be involved in maintaining their identity. Sex was a considerable source of heterogeneity in the endothelial transcriptome and we discovered Lars2 to be a gene that is highly enriched in ECs from male mice. We found that markers of heart and lung ECs in mice were conserved in human fetal heart and lung ECs. We identified potential angiocrine interactions between tissue-specific ECs and other cell types by analyzing ligand and receptor expression patterns.

CONCLUSIONS

We used single-cell RNA sequencing data generated by the Tabula Muris consortium to uncover transcriptional networks that maintain tissue-specific EC identity and to identify novel angiocrine and functional relationships between tissue-specific ECs.

Cardiac fibrosis

Myocardial fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix proteins, is a common pathophysiologic companion of many different myocardial conditions. Fibrosis may reflect activation of reparative or maladaptive processes. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. Immune cells, vascular cells and cardiomyocytes may also acquire a fibrogenic phenotype under conditions of stress, activating fibroblast populations. Fibrogenic growth factors (such as transforming growth factor-β and platelet-derived growth factors), cytokines [including tumour necrosis factor-α, interleukin (IL)-1, IL-6, IL-10, and IL-4], and neurohumoral pathways trigger fibrogenic signalling cascades through binding to surface receptors, and activation of downstream signalling cascades. In addition, matricellular macromolecules are deposited in the remodelling myocardium and regulate matrix assembly, while modulating signal transduction cascades and protease or growth factor activity. Cardiac fibroblasts can also sense mechanical stress through mechanosensitive receptors, ion channels and integrins, activating intracellular fibrogenic cascades that contribute to fibrosis in response to pressure overload. Although subpopulations of fibroblast-like cells may exert important protective actions in both reparative and interstitial/perivascular fibrosis, ultimately fibrotic changes perturb systolic and diastolic function, and may play an important role in the pathogenesis of arrhythmias. This review article discusses the molecular mechanisms involved in the pathogenesis of cardiac fibrosis in various myocardial diseases, including myocardial infarction, heart failure with reduced or preserved ejection fraction, genetic cardiomyopathies, and diabetic heart disease. Development of fibrosis-targeting therapies for patients with myocardial diseases will require not only understanding of the functional pluralism of cardiac fibroblasts and dissection of the molecular basis for fibrotic remodelling, but also appreciation of the pathophysiologic heterogeneity of fibrosis-associated myocardial disease.

WNT11-Conditioned Medium Promotes Angiogenesis through the Activation of Non-Canonical WNT-PKC-JNK Signaling Pathway

BACKGROUND

We demonstrated that the transduction of Wnt11 into mesenchymal stem cells (MSCs) (MSCWnt11) promotes these cells differentiation into cardiac phenotypes. In the present study, we investigated the paracrine effects of MSCWnt11 on cardiac function and angiogenesis.

METHODS AND RESULTS

Conditioned medium was collected from MSCWnt11 (CdMWnt11) and their control cells (CdMGFP). CdMWnt11, especially obtained from MSCWnt11 exposed to hypoxia, significantly promoted human umbilical vein endothelial cells (HUVECs) migration and increased capillary-like tube (CLT) formation, which was blocked by Wnt11 neutralizing antibody. Wnt11 protein was significantly higher in CdMWnt11 compared to that in CdMGFP. Directly treating HUVECs with recombinant Wnt11 protein significantly increased CLT formation, which was abrogated by treating cells with the JNK inhibitor SP600125, as well as the PKC inhibitor Calphostin-C. Moreover, the transfection of Wnt11 to HUVECs (HWnt11) significantly increased CLT formation and HUVEC migration, as well as upregulated p-pan-PKC and p-JNK expression. Injection of CdMWnt11 into the peri-infarct region in a rat acute myocardial infarction (AMI) model significantly improved cardiac function, reduced infarct size, and increased myocardial blood flow and blood vessel density in the ischemic area.

CONCLUSION

Wnt11 released from MSCWnt11 increased angiogenesis and improved cardiac function via non-canonical Wnt-PKC-JNK dependent pathways.

Angiogenesis after acute myocardial infarction

Acute myocardial infarction (MI) inflicts massive injury to the coronary microcirculation leading to vascular disintegration and capillary rarefication in the infarct region. Tissue repair after MI involves a robust angiogenic response that commences in the infarct border zone and extends into the necrotic infarct core. Technological advances in several areas have provided novel mechanistic understanding of postinfarction angiogenesis and how it may be targeted to improve heart function after MI. Cell lineage tracing studies indicate that new capillary structures arise by sprouting angiogenesis from pre-existing endothelial cells (ECs) in the infarct border zone with no meaningful contribution from non-EC sources. Single-cell RNA sequencing shows that ECs in infarcted hearts may be grouped into clusters with distinct gene expression signatures, likely reflecting functionally distinct cell populations. EC-specific multicolour lineage tracing reveals that EC subsets clonally expand after MI. Expanding EC clones may arise from tissue-resident ECs with stem cell characteristics that have been identified in multiple organs including the heart. Tissue repair after MI involves interactions among multiple cell types which occur, to a large extent, through secreted proteins and their cognate receptors. While we are only beginning to understand the full complexity of this intercellular communication, macrophage and fibroblast populations have emerged as major drivers of the angiogenic response after MI. Animal data support the view that the endogenous angiogenic response after MI can be boosted to reduce scarring and adverse left ventricular remodelling. The improved mechanistic understanding of infarct angiogenesis therefore creates multiple therapeutic opportunities. During preclinical development, all proangiogenic strategies should be tested in animal models that replicate both cardiovascular risk factor(s) and the pharmacotherapy typically prescribed to patients with acute MI. Considering that the majority of patients nowadays do well after MI, clinical translation will require careful selection of patients in need of proangiogenic therapies.

A Unique Population of Regulatory T Cells in Heart Potentiates Cardiac Protection From Myocardial Infarction

BACKGROUND

Regulatory T cells (Tregs), traditionally recognized as potent suppressors of immune response, are increasingly attracting attention because of a second major function: residing in parenchymal tissues and maintaining local homeostasis. However, the existence, unique phenotype, and function of so-called tissue Tregs in the heart remain unclear.

METHODS

In mouse models of myocardial infarction (MI), myocardial ischemia/reperfusion injury, or cardiac cryoinjury, the dynamic accumulation of Tregs in the injured myocardium was monitored. The bulk RNA sequencing was performed to analyze the transcriptomic characteristics of Tregs from the injured myocardium after MI or ischemia/reperfusion injury. Photoconversion, parabiosis, single-cell T-cell receptor sequencing, and adoptive transfer were applied to determine the source of heart Tregs. The involvement of the interleukin-33/suppression of tumorigenicity 2 axis and Sparc (secreted acidic cysteine-rich glycoprotein), a molecule upregulated in heart Tregs, was further evaluated in functional assays.

RESULTS

We showed that Tregs were highly enriched in the myocardium of MI, ischemia/reperfusion injury, and cryoinjury mice. Transcriptomic data revealed that Tregs isolated from the injured hearts had plenty of differentially expressed transcripts in comparison with their lymphoid counterparts, including heart-draining lymphoid nodes, with a phenotype of promoting infarct repair, indicating a unique characteristic. The heart Tregs were accumulated mainly because of recruitment from the circulating Treg pool, whereas local proliferation also contributed to their expansion. Moreover, a remarkable case of repeatedly detected T-cell receptor of heart Tregs, more than that of spleen Tregs, suggests a model of clonal expansion. Besides, Helios^highNrp-1^high phenotype proved the mainly thymic origin of heart Tregs, with a small contribution of phenotypic conversion of conventional CD4⁺ T cells, proved by the analysis of T-cell receptor repertoires and conventional CD4⁺ T cells adoptive transfer experiments. The interleukin-33/suppression of tumorigenicity 2 axis was essential for sustaining heart Treg populations. Last, we demonstrated that Sparc, which was highly expressed by heart Tregs, acted as a critical factor to protect the heart against MI by increasing collagen content and boosting maturation in the infarct zone.

CONCLUSIONS

We identified and characterized a phenotypically and functionally unique population of heart Tregs that may lay the foundation to harness Tregs for cardioprotection in MI and other cardiac diseases.

Single-cell RNA sequencing in cardiovascular development, disease and medicine

Advances in single-cell RNA sequencing (scRNA-seq) technologies in the past 10 years have had a transformative effect on biomedical research, enabling the profiling and analysis of the transcriptomes of single cells at unprecedented resolution and throughput. Specifically, scRNA-seq has facilitated the identification of novel or rare cell types, the analysis of single-cell trajectory construction and stem or progenitor cell differentiation, and the comparison of healthy and disease-related tissues at single-cell resolution. These applications have been critical in advances in cardiovascular research in the past decade as evidenced by the generation of cell atlases of mammalian heart and blood vessels and the elucidation of mechanisms involved in cardiovascular development and stem or progenitor cell differentiation. In this Review, we summarize the currently available scRNA-seq technologies and analytical tools and discuss the latest findings using scRNA-seq that have substantially improved our knowledge on the development of the cardiovascular system and the mechanisms underlying cardiovascular diseases. Furthermore, we examine emerging strategies that integrate multimodal single-cell platforms, focusing on future applications in cardiovascular precision medicine that use single-cell omics approaches to characterize cell-specific responses to drugs or environmental stimuli and to develop effective patient-specific therapeutics.

TGF-β and WNT signaling pathways in cardiac fibrosis: non-coding RNAs come into focus

Cardiac fibrosis describes the inappropriate proliferation of cardiac fibroblasts (CFs), leading to accumulation of extracellular matrix (ECM) proteins in the cardiac muscle, which is found in many pathophysiological heart conditions. A range of molecular components and cellular pathways, have been implicated in its pathogenesis. In this review, we focus on the TGF-β and WNT signaling pathways, and their mutual interaction, which have emerged as important factors involved in cardiac pathophysiology. The molecular and cellular processes involved in the initiation and progression of cardiac fibrosis are summarized. We focus on TGF-β and WNT signaling in cardiac fibrosis, ECM production, and myofibroblast transformation. Non-coding RNAs (ncRNAs) are one of the main players in the regulation of multiple pathways and cellular processes. MicroRNAs, long non-coding RNAs, and circular long non-coding RNAs can all interact with the TGF-β/WNT signaling axis to affect cardiac fibrosis. A better understanding of these processes may lead to new approaches for diagnosis and treatment of many cardiac conditions. Video Abstract.

Wnt/β-catenin in ischemic myocardium: interactions and signaling pathways as a therapeutic target

Cardiovascular disease (CVD) is still a factor of mortality in the whole world. Through canonical and noncanonical pathways and with different receptors, the Wnt/β-catenin signaling pathway plays an essential role in response to heart injuries. Wnt regulates the mobilization and proliferation of cells in endothelium and epicardium in an infarcted heart. Therefore, with its profibrotic effects as well as its antagonism with other proteins, Wnt/β-catenin signaling pathway leads to beneficial effects on fibrosis and cardiac remodeling in myocardium. In addition, Wnt increases the proliferation and differentiation of cardiac progenitors in an ischemic heart. Complex interactions and dual activity of Wnt, the changes in its expression, and mutations that can change its activity during heart development have an adverse effect on cardiac myocardium after injury. However, targeting the Wnt in myocardium with cellular and molecular pathways can be suggested to improve and repair ischemic heart. Given these challenges, in this review article, we deal with the role of Wnt/β-catenin signaling pathway as well as its interactions with other cells and molecules in an ischemic myocardium.

The effect of extrinsic Wnt/β-catenin signaling in Muller glia on retinal ganglion cell neurite growth

Muller glia are the predominant glial cell type in the retina, and they structurally and metabolically support retinal neurons. Wnt/β-catenin signaling pathways play essential roles in the central nervous system, including glial and neuronal differentiation, axonal growth, and neuronal regeneration. We previously demonstrated that Wnt signaling activation in retinal ganglion cells (RGC) induces axonal regeneration after injury. However, whether Wnt signaling within the adjacent Muller glia plays an axongenic role is not known. In this study, we characterized the effect of Wnt signaling in Muller glia on RGC neurite growth. Primary Muller glia and RGC cells were grown in transwell co-cultures and adenoviral constructs driving Wnt regulatory genes were used to activate and inhibit Wnt signaling specifically in primary Muller glia. Our results demonstrated that activation of Wnt signaling in Muller glia significantly increased RGC average neurite length and branch site number. In addition, the secretome of Muller glia after induction or inhibition of Wnt signaling was characterized using protein profiling of conditioned media by Q Exactive mass spectrometry. The Muller glia secretome after activation of Wnt signaling had distinct and more numerous proteins involved in regulation of axon extension, axon projection and cell adhesion. Furthermore, we showed highly redundant expression of Wnt signaling ligands in Muller glia and Frizzled receptors in RGCs and Muller glia. Therefore, this study provides new information about potential neurite growth promoting molecules in the Muller glia secretome, and identified Wnt-dependent target proteins that may mediate the axonal growth.

Wnt10b-overexpressing umbilical cord mesenchymal stem cells promote critical size rat calvarial defect healing by enhanced osteogenesis and VEGF-mediated angiogenesis

Background/objectives

Accelerating the process of bone regeneration is of great interest for surgeons and basic scientists alike. Recently, umbilical cord mesenchymal stem cells (UCMSCs) are considered clinically applicable for tissue regeneration due to their noninvasive harvesting and better viability. Nonetheless, the bone regenerative ability of human UCMSCs (HUCMSCs) is largely unknown. This study aimed to investigate whether Wnt10b-overexpressing HUCMSCs have enhanced bone regeneration ability in a rat model.

Method

A rat calvarial defect was performed on 8-week old male Sprague Dawley rats. Commercially purchased HUCMSCs^Emp in hydrogel, HUCMSCs^Wnt10b in hydrogel and HUCMSCs^Wnt10b with IWR-1 were placed in the calvarial bone defect right after surgery on rats (N = 8 rats for each group). Calvaria were harvested for micro-CT analysis and histology four weeks after surgery. CFU-F and multi-differentiation assay by oil red staining, alizarin red staining and RT-PCR (real-time polymerase chain reaction) were performed on HUCMSCs^Emp and HUCMSCs^Wnt10bin vitro. Conditioned media from HUCMSCs^Emp and HUCMSCs^Wnt10b were collected and used to treat human umbilical cord vein endothelial cells in Matrigel to access vessel formation capacity by tube formation assay.

Results

Alizarin red staining, oil red staining and RT-PCR results showed robust osteogenic differentiation but poor adipogenic differentiation ability of HUCMSCs^Wnt10b. Furthermore, HUCMSCs^Wnt10b could accelerate bone defect healing, which was likely due to enhanced angiogenesis after the HUCMSCs^Wnt10b treatment, because more CD31+ vessels and increased vascular endothelial growth factor-A (VEGF-A) expression were observed, compared with the HUCMSCs^Emp treatment. Conditioned media from HUCMSCs^Wnt10b also induced endothelial cells to form vessel tubes in a tube formation assay, which could be abolished by SU5416, an angiogenesis inhibitor.

Conclusion

To our knowledge, this is the first study providing empirical evidence that HUCMSCs^Wnt10b can enhance their ability to heal calvarial bone defects via VEGF-mediated angiogenesis.

The translational potential of this article

HUCMSCs^Wnt10b can accelerate critical size calvaria and are a new promising therapeutic cell source for fracture nonunion healing.

Multiple Roles of sFRP2 in Cardiac Development and Cardiovascular Disease

The Wnt signaling pathway plays important roles in organ development and disease processes. Secreted frizzled-related protein 2 (sFRP2), a vital molecule of Wnt signaling, can regulate cardiac development and cardiovascular disease. Recent studies have suggested that sFRP2 is not only an antagonist of the canonical Wnt signaling pathway, but also has a more complex relationship in myocardial fibrosis, angiogenesis, cardiac hypertrophy and cardiac regeneration. Here, we review the role of sFRP2 and Wnt signaling in cardiac development and cardiovascular disease.

Interventions in WNT Signaling to Induce Cardiomyocyte Proliferation: Crosstalk with Other Pathways

Myocardial infarction is a frequent cardiovascular event and a major cause for cardiomyocyte loss. In adult mammals, cardiomyocytes are traditionally considered to be terminally differentiated cells, unable to proliferate. Therefore, the wound-healing response in the infarct area typically yields scar tissue rather than newly formed cardiomyocytes. In the last decade, several lines of evidence have challenged the lack of proliferative capacity of the differentiated cardiomyocyte: studies in zebrafish and neonatal mammals have convincingly demonstrated the regenerative capacity of cardiomyocytes. Moreover, multiple signaling pathways have been identified in these models that-when activated in adult mammalian cardiomyocytes-can reactivate the cell cycle in these cells. However, cardiomyocytes frequently exit the cell cycle before symmetric division into daughter cells, leading to polyploidy and multinucleation. Now that there is more insight into the reactivation of the cell cycle machinery, other prerequisites for successful symmetric division of cardiomyocytes, such as the control of sarcomere disassembly to allow cytokinesis, require more investigation. This review aims to discuss the signaling pathways involved in cardiomyocyte proliferation, with a specific focus on wingless/int-1 protein signaling. Comparing the conflicting results from in vitro and in vivo studies on this pathway illustrates that the interaction with other cells and structures around the infarct is likely to be essential to determine the outcome of these interventions. The extensive crosstalk with other pathways implicated in cardiomyocyte proliferation calls for the identification of nodal points in the cell signaling before cardiomyocyte proliferation can be moved forward toward clinical application as a cure of cardiac disease. SIGNIFICANCE STATEMENT: Evidence is mounting that proliferation of pre-existing cardiomyocytes can be stimulated to repair injury of the heart. In this review article, an overview is provided of the different signaling pathways implicated in cardiomyocyte proliferation with emphasis on wingless/int-1 protein signaling, crosstalk between the pathways, and controversial results obtained in vitro and in vivo.

Cadherin-11 blockade reduces inflammation-driven fibrotic remodeling and improves outcomes after myocardial infarction

Over one million Americans experience myocardial infarction (MI) annually, and the resulting scar and subsequent cardiac fibrosis gives rise to heart failure. A specialized cell-cell adhesion protein, cadherin-11 (CDH11), contributes to inflammation and fibrosis in rheumatoid arthritis, pulmonary fibrosis, and aortic valve calcification but has not been studied in myocardium after MI. MI was induced by ligation of the left anterior descending artery in mice with either heterozygous or homozygous knockout of CDH11, wild-type mice receiving bone marrow transplants from Cdh11-deficient animals, and wild-type mice treated with a functional blocking antibody against CDH11 (SYN0012). Flow cytometry revealed significant CDH11 expression in noncardiomyocyte cells after MI. Animals given SYN0012 had improved cardiac function, as measured by echocardiogram, reduced tissue remodeling, and altered transcription of inflammatory and proangiogenic genes. Targeting CDH11 reduced bone marrow-derived myeloid cells and increased proangiogenic cells in the heart 3 days after MI. Cardiac fibroblast and macrophage interactions increased IL-6 secretion in vitro. Our findings suggest that CDH11-expressing cells contribute to inflammation-driven fibrotic remodeling after MI and that targeting CDH11 with a blocking antibody improves outcomes by altering recruitment of bone marrow-derived cells, limiting the macrophage-induced expression of IL-6 by fibroblasts and promoting vascularization.

WNT Signaling in Disease. Cells. 2019;8:826. [PMID: 31382613 PMCID: PMC6721652 DOI: 10.3390/cells8080826]

Developmental signaling pathways control a vast array of biological processes during embryogenesis and in adult life. The WNT pathway was discovered simultaneously in cancer and development. Recent advances have expanded the role of WNT to a wide range of pathologies in humans. Here, we discuss the WNT pathway and its role in human disease and some of the advances in WNT-related treatments.

The role of Wnt signaling in the healing myocardium: a focus on cell specificity

Various cell types are involved in the healing process after myocardial infarction (MI). Besides cardiac resident cells (such as cardiomyocytes, fibroblasts and endothelial cells) already present at the lesion site, a massive influx of leukocytes (mainly monocytes and neutrophils) is observed within hours after the ischemic event. So far, little is known about modes of interaction of these cells. Wnt signaling is an evolutionary conserved signaling cassette known to play an important role in cell-cell communication. While the overall reactivation of Wnt signaling upon ischemic injury is well described, the precise expression pattern of Wnt proteins, however, is far from understood. We here describe known Wnt components that partake in MI healing and differentiate cell-specific aspects. The secretion of Wnt proteins and their antagonists in the context of cardiac inflammation after MI appear to be tightly regulated in a spatial-temporal manner. Overall, we aim to stress the importance of elucidating not only Wnt component-specific aspects, but also their sometimes contradicting effects in different target cells. A better understanding of Wnt signaling in MI healing may eventually lead to the development of successful therapeutic approaches in an often considered "un-druggable" pathway.

The epicardium as a hub for heart regeneration

After decades of directed research, no effective regenerative therapy is currently available to repair the injured human heart. The epicardium, a layer of mesothelial tissue that envelops the heart in all vertebrates, has emerged as a new player in cardiac repair and regeneration. The epicardium is essential for muscle regeneration in the zebrafish model of innate heart regeneration, and the epicardium also participates in fibrotic responses in mammalian hearts. This structure serves as a source of crucial cells, such as vascular smooth muscle cells, pericytes, and fibroblasts, during heart development and repair. The epicardium also secretes factors that are essential for proliferation and survival of cardiomyocytes. In this Review, we describe recent advances in our understanding of the biology of the epicardium and the effect of these findings on the candidacy of this structure as a therapeutic target for heart repair and regeneration.

Large-Scale Single-Cell RNA-Seq Reveals Molecular Signatures of Heterogeneous Populations of Human Induced Pluripotent Stem Cell-Derived Endothelial Cells

RATIONALE

Human-induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) have risen as a useful tool in cardiovascular research, offering a wide gamut of translational and clinical applications. However, inefficiency of the currently available iPSC-EC differentiation protocol and underlying heterogeneity of derived iPSC-ECs remain as major limitations of iPSC-EC technology.

OBJECTIVE

Here, we performed droplet-based single-cell RNA sequencing (scRNA-seq) of the human iPSCs after iPSC-EC differentiation. Droplet-based scRNA-seq enables analysis of thousands of cells in parallel, allowing comprehensive analysis of transcriptional heterogeneity.

METHODS AND RESULTS

Bona fide iPSC-EC cluster was identified by scRNA-seq, which expressed high levels of endothelial-specific genes. iPSC-ECs, sorted by CD144 antibody-conjugated magnetic sorting, exhibited standard endothelial morphology and function including tube formation, response to inflammatory signals, and production of NO. Nonendothelial cell populations resulting from the differentiation protocol were identified, which included immature cardiomyocytes, hepatic-like cells, and vascular smooth muscle cells. Furthermore, scRNA-seq analysis of purified iPSC-ECs revealed transcriptional heterogeneity with 4 major subpopulations, marked by robust enrichment of CLDN5, APLNR, GJA5, and ESM1 genes, respectively.

CONCLUSIONS

Massively parallel, droplet-based scRNA-seq allowed meticulous analysis of thousands of human iPSCs subjected to iPSC-EC differentiation. Results showed inefficiency of the differentiation technique, which can be improved with further studies based on identification of molecular signatures that inhibit expansion of nonendothelial cell types. Subtypes of bona fide human iPSC-ECs were also identified, allowing us to sort for iPSC-ECs with specific biological function and identity.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

Wenyang Huazhuo Tongluo formula inhibits fibrosis via suppressing Wnt/β-catenin signaling pathway in a Bleomycin-induced systemic sclerosis mouse model

Background

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. So far, no Western medicine treatment can completely inhibit or reverse the progress of SSc, while at the same time, our previous series of studies have shown that the treatment of SSc by the Wenyang Huazhuo Tongluo formula (WYHZTL), a Chinese herbal decoction, shows a delightful prospect. The aim of this study is to further investigate the mechanism of anti-fibrosis of WYHZTL formula in SSc mouse model.

Methods

The Bleomycin-induced SSc mouse model was treated with saline (BLM), high-dosage of WYHZTL formula (WYHZTL-H), medium-dosage of WYHZTL formula (WYHZTL-M), low-dosage of WYHZTL formula (WYHZTL-L) and XAV-939, a small molecule inhibitor of Wnt/β-catenin signaling pathway, by the intragastric administration and intraperitoneal injection, respectively. The mRNA and protein levels of Wnt/β-catenin signaling pathway associated genes, fibrosis markers and histopathology were detected by reverse transcription-quantitative polymerase chain reaction, Western blotting and hematoxylin/eosin-staining. The levels of Wnt1, CTGF and DKK1 protein in serum were detected by enzyme-linked immunosorbent assay.

Results

Compared with BLM group, the WYHZTL formula and XAV-939 could significantly inhibit the thickness of the skin tissue of the SSc mouse model. The mRNA expression levels of GSK3β and DKK1 in the WYHZTL formula and XAV-939-treated group were significantly higher than those in the BLM group, while Wnt1, β-catenin, TCF4, cyclin D1, survivin, VEGF, CTGF, FN1, collagen I/III were decreased. Compared with BLM group, the protein expression levels of GSK3β and DKK1 in the WYHZTL formula and XAV-939-treated group were upregulated, while Wnt1, β-catenin, cyclin D1, survivin, CTGF, FN1, collagen I/III were downregulated. WYHZTL formula and XAV-939 could inhibit expression of Wnt1 and CTGF, but promoted DKK1 in serum. Furthermore, WYHZTL-H seemed more effective than WYHZTL-M and/or XAV-939 on regulating Wnt1, β-catenin, TCF4, GSK3β, DKK1, cyclin D1, survivin, VEGF, CTGF, FN1 and collagen I/III.

Conclusion

This present study demonstrates that WYHZTL formula has anti-fibrosis effect in Bleomycin-induced SSc mouse model in a dosage-dependent manner, and the molecular mechanism may be related to the inhibition of Wnt/β-catenin signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s13020-018-0175-z) contains supplementary material, which is available to authorized users.

ErbB2 promotes endothelial phenotype of human left ventricular epicardial highly proliferative cells (eHiPC)

The adult human heart contains a subpopulation of highly proliferative cells. The role of ErbB receptors in these cells has not been studied. From human left ventricular (LV) epicardial biopsies, we isolated highly proliferative cells (eHiPC) to characterize the cell surface expression and function of ErbB receptors in the regulation of cell proliferation and phenotype. We found that human LV eHiPC express all four ErbB receptor subtypes. However, the expression of ErbB receptors varied widely among eHiPC isolated from different subjects. eHiPC with higher cell surface expression of ErbB2 reproduced the phenotype of endothelial cells and were characterized by endothelial cell-like functional properties. We also found that EGF/ErbB1 induces VEGFR2 expression, while ligands for both ErbB1 and ErbB3/4 induce expression of Tie2. The number of CD31posCD45neg endothelial cells is higher in LV biopsies from subjects with high ErbB2 (ErbB2high) eHiPC compared to low ErbB2 (ErbB2low) eHiPC. These findings have important implications for potential strategies to increase the efficacy of cell-based revascularization of the injured heart, through promotion of an endothelial phenotype in cardiac highly proliferative cells.

WNT Signaling in Cardiac and Vascular Disease

WNT signaling is an elaborate and complex collection of signal transduction pathways mediated by multiple signaling molecules. WNT signaling is critically important for developmental processes, including cell proliferation, differentiation and tissue patterning. Little WNT signaling activity is present in the cardiovascular system of healthy adults, but reactivation of the pathway is observed in many pathologies of heart and blood vessels. The high prevalence of these pathologies and their significant contribution to human disease burden has raised interest in WNT signaling as a potential target for therapeutic intervention. In this review, we first will focus on the constituents of the pathway and their regulation and the different signaling routes. Subsequently, the role of WNT signaling in cardiovascular development is addressed, followed by a detailed discussion of its involvement in vascular and cardiac disease. After highlighting the crosstalk between WNT, transforming growth factor-β and angiotensin II signaling, and the emerging role of WNT signaling in the regulation of stem cells, we provide an overview of drugs targeting the pathway at different levels. From the combined studies we conclude that, despite the sometimes conflicting experimental data, a general picture is emerging that excessive stimulation of WNT signaling adversely affects cardiovascular pathology. The rapidly increasing collection of drugs interfering at different levels of WNT signaling will allow the evaluation of therapeutic interventions in the pathway in relevant animal models of cardiovascular diseases and eventually in patients in the near future, translating the outcomes of the many preclinical studies into a clinically relevant context.

Exosomes Generated From iPSC-Derivatives: New Direction for Stem Cell Therapy in Human Heart Diseases

Cardiovascular disease (CVD) is the leading cause of death in modern society. The adult heart innately lacks the capacity to repair and regenerate the damaged myocardium from ischemic injury. Limited understanding of cardiac tissue repair process hampers the development of effective therapeutic solutions to treat CVD such as ischemic cardiomyopathy. In recent years, rapid emergence of induced pluripotent stem cells (iPSC) and iPSC-derived cardiomyocytes presents a valuable opportunity to replenish the functional cells to the heart. The therapeutic effects of iPSC-derived cells have been investigated in many preclinical studies. However, the underlying mechanisms of iPSC-derived cell therapy are still unclear, and limited engraftment of iPSC-derived cardiomyocytes is well known. One facet of their mechanism is the paracrine effect of the transplanted cells. Microvesicles such as exosomes secreted from the iPSC-derived cardiomyocytes exert protective effects by transferring the endogenous molecules to salvage the injured neighboring cells by regulating apoptosis, inflammation, fibrosis, and angiogenesis. In this review, we will focus on the current advances in the exosomes from iPSC derivatives and discuss their therapeutic potential in the treatment of CVD.

Wnt Signaling in Cardiac Remodeling and Heart Failure

Wnt signaling plays an essential role during development, but is also activated in diseases as diverse as neurodegeneration, osteoporosis, and cancer. Accumulating evidence demonstrates that Wnt signaling is also activated during cardiac remodeling and heart failure. In this chapter, we will provide a brief overview of Wnt signaling in all its complexity. Then we will discuss the evidence for its involvement in the development of cardiac hypertrophy, the wound healing after myocardial infarction (MI) and heart failure. Finally, we will provide an overview of the drugs that are available to target Wnt signaling at different levels of the signaling cascade and the results of these pharmacological interventions in cardiac disease.

Wnt/β-catenin pathway in tissue injury: roles in pathology and therapeutic opportunities for regeneration

The Wnt/β-catenin pathway is an evolutionarily conserved set of signals with critical roles in embryonic and neonatal development across species. In mammals the pathway is quiescent in many organs. It is reactivated in response to injury and is reported to play complex and contrasting roles in promoting regeneration and fibrosis. We review the current understanding of the role of the Wnt/β-catenin pathway in injury of various mammalian organs and discuss the current advances and potential of Wnt inhibitory therapeutics toward promoting tissue regeneration and reducing fibrosis.-Bastakoty, D., Young, P. P. Wnt/β-catenin pathway in tissue injury: roles in pathology and therapeutic opportunities for regeneration.

BMP Antagonist Gremlin 2 Limits Inflammation After Myocardial Infarction

RATIONALE

We have recently shown that the bone morphogenetic protein (BMP) antagonist Gremlin 2 (Grem2) is required for early cardiac development and cardiomyocyte differentiation. Our initial studies discovered that Grem2 is strongly induced in the adult heart after experimental myocardial infarction (MI). However, the function of Grem2 and BMP-signaling inhibitors after cardiac injury is currently unknown.

OBJECTIVE

To investigate the role of Grem2 during cardiac repair and assess its potential to improve ventricular function after injury.

METHODS AND RESULTS

Our data show that Grem2 is transiently induced after MI in peri-infarct area cardiomyocytes during the inflammatory phase of cardiac tissue repair. By engineering loss- (Grem2(-/-)) and gain- (TG(Grem2)) of-Grem2-function mice, we discovered that Grem2 controls the magnitude of the inflammatory response and limits infiltration of inflammatory cells in peri-infarct ventricular tissue, improving cardiac function. Excessive inflammation in Grem2(-/-) mice after MI was because of overactivation of canonical BMP signaling, as proven by the rescue of the inflammatory phenotype through administration of the canonical BMP inhibitor, DMH1. Furthermore, intraperitoneal administration of Grem2 protein in wild-type mice was sufficient to reduce inflammation after MI. Cellular analyses showed that BMP2 acts with TNFα to induce expression of proinflammatory proteins in endothelial cells and promote adhesion of leukocytes, whereas Grem2 specifically inhibits the BMP2 effect.

CONCLUSIONS

Our results indicate that Grem2 provides a molecular barrier that controls the magnitude and extent of inflammatory cell infiltration by suppressing canonical BMP signaling, thereby providing a novel mechanism for limiting the adverse effects of excessive inflammation after MI.

Temporary, Systemic Inhibition of the WNT/β-Catenin Pathway promotes Regenerative Cardiac Repair following Myocardial Infarct

AIMS

The WNT/β-catenin pathway is temporarily activated in the heart following myocardial infarction (MI). Despite data from genetic models indicating both positive and negative roles for the WNT pathway depending on the model used, the effect of therapeutic inhibition of WNT pathway on post-injury outcome and the cellular mediators involved are not completely understood. Using a newly available, small molecule, GNF-6231, which averts WNT pathway activation by blocking secretion of all WNT ligands, we sought to investigate whether therapeutic inhibition of the WNT pathway temporarily after infarct can mitigate post injury cardiac dysfunction and fibrosis and the cellular mechanisms responsible for the effects.

METHODS AND RESULTS

Pharmacologic inhibition of the WNT pathway by post-MI intravenous injection of GNF-6231 in C57Bl/6 mice significantly reduced the decline in cardiac function (Fractional Shortening at day 30: 38.71 ± 4.13% in GNF-6231 treated vs. 34.89 ± 4.86% in vehicle-treated), prevented adverse cardiac remodeling, and reduced infarct size (9.07 ± 3.98% vs. 17.18 ± 4.97%). WNT inhibition augmented proliferation of interstitial cells, particularly in the distal myocardium, inhibited apoptosis of cardiomyocytes, and reduced myofibroblast proliferation in the peri-infarct region. In vitro studies showed that WNT inhibition increased proliferation of Sca1⁺ cardiac progenitors, improved survival of cardiomyocytes, and inhibited collagen I synthesis by cardiac myofibroblasts.

CONCLUSION

Systemic, temporary pharmacologic inhibition of the WNT pathway using an orally bioavailable drug immediately following MI resulted in improved function, reduced adverse remodeling and reduced infarct size in mice. Therapeutic WNT inhibition affected multiple aspects of infarct repair: it promoted proliferation of cardiac progenitors and other interstitial cells, inhibited myofibroblast proliferation, improved cardiomyocyte survival, and reduced collagen I gene expression by myofibroblasts. Our data point to a promising role for WNT inhibitory therapeutics as a new class of drugs to drive post-MI repair and prevent heart failure.