Roles of FGF Signals in Heart Development, Health, and Disease

FGF9 is required for Purkinje cell development and function in the cerebellum

Fibroblast growth factor 9 (FGF9) is a member of the fibroblast growth factor family, which is widely expressed in the central nervous system (CNS). It has been reported that deletion of FGF9 leads to defects in cerebellum development, including Purkinje cell defect. However, it is not clear how FGF9 regulating cerebellar development remains to be determined. Our results showed that in addition to disrupt Bergmann fiber scaffold formation and granule neuron migration, deletion of neuronal FGF9 led to ataxia defects. It affected development and function of Purkinje cells, and also changed the action potential threshold and excitation frequency. Mechanistically, depletion of FGF9 significantly changed neurotransmitter contents in Purkinje cells and led to preferential increase in inflammation, even downregulation in ERK signaling. Together, the data demonstrate that neuronal FGF9 is required for the development and function of Purkinje cells in the cerebellum. Insufficient FGF9 during cerebellum development will cause ataxia defects.

In-Depth Genomic Analysis: The New Challenge in Congenital Heart Disease

The use of next-generation sequencing has provided new insights into the causes and mechanisms of congenital heart disease (CHD). Examinations of the whole exome sequence have detected detrimental gene variations modifying single or contiguous nucleotides, which are characterised as pathogenic based on statistical assessments of families and correlations with congenital heart disease, elevated expression during heart development, and reductions in harmful protein-coding mutations in the general population. Patients with CHD and extracardiac abnormalities are enriched for gene classes meeting these criteria, supporting a common set of pathways in the organogenesis of CHDs. Single-cell transcriptomics data have revealed the expression of genes associated with CHD in specific cell types, and emerging evidence suggests that genetic mutations disrupt multicellular genes essential for cardiogenesis. Metrics and units are being tracked in whole-genome sequencing studies.

Transcriptome Profiling Identifies Differentially Expressed Genes in Skeletal Muscle Development in Native Chinese Ducks

China boasts a rich diversity of indigenous duck species, some of which exhibit desirable economic traits. Here, we generated transcriptome sequencing datasets of breast muscle tissue samples from 1D of four groups: Pekin duck pure breeding group (P), Jinling White duck breeding group (J), P ♂ × J ♀ orthogonal group (PJ) and J ♂ × P ♀ reciprocal-cross group (JP) (n = 3), chosen based on the distinctive characteristics of duck muscle development during the embryonic period. We identified 5053 differentially expressed genes (DEGs) among the four groups. Network prediction analysis showed that ribosome and oxidative phosphorylation-related genes were the most enriched, and muscular protein-related genes were found in the 14-day-old embryonic group. We found that previously characterized functional genes, such as FN1, AGRN, ADNAMST3, APOB and FGF9, were potentially involved in muscle development in 14-day-old embryos. Functional enrichment analysis suggested that genes that participated in molecular function and cell component and key signaling pathways (e.g., hippo, ribosome, oxidative phosphorylation) were significantly enriched in the development of skeletal muscle at 14 days of embryonic age. These results indicate a possible role of muscle metabolism and myoglobin synthesis in skeletal muscle development in both duck parents and hybrids.

The role of BMP4 in adipose-derived stem cell differentiation: A minireview

Bone morphogenetic protein 4 (BMP4) is a member of the transforming growth factor beta (TGF-β) superfamily of cytokines responsible for stem cells’ commitment to differentiation, proliferation, and maturation. To date, various studies have utilized BMP4 as a chemical inducer for in vitro differentiation of human mesenchymal stem cells (MSCs) based on its potential. BMP4 drives in vitro differentiation of ADSC via TGF-β signaling pathway by interactions with BMP receptors leading to the activation of smad-dependent and smad-independent pathways. The BMP4 signaling pathways are regulated by intracellular and extracellular BMP4 antagonists. Extracellular BMP4 antagonist prevents interaction between BMP4 ligand to its receptors, while intracellular BMP4 antagonist shutdowns the smad-dependent pathways through multiple mechanisms. BMP4 proved as one of the popular differentiation factors to induce ADSC differentiation into cell from mesodermal origin. However, addition of all-trans retinoic acid is also needed in trans-differentiation of ADSC into ectodermal lineage cells. Suggesting that both BMP4 and RA signaling pathways may be necessary to be activated for in vitro trans-differentiation of ADSC.

Fibroblast growth factor 21 is associated with widening QRS complex and prolonged corrected QT interval in patients with stable angina

BACKGROUND

Fibroblast growth factor 21 (FGF21) is produced by cardiac cells, may acts in an autocrine manner, and was suggested to has a cardioprotective role in atherosclerosis. Wide QRS complex and heart rate-corrected QT interval (QTc interval) prolongation are associated to dangerous ventricular arrhythmias and cardiovascular disease mortality. Yet, the role of FGF21 in cardiac arrhythmia has never been studied. The aim of the study was to investigate the relationship between plasma FGF21 and the QRS duration and QTc interval in patients with stable angina.

METHODS

Three hundred twenty-one consecutive stable angina patients were investigated. Plasma FGF21 was measured through ELISA, and each subject underwent 12-lead electrocardiography.

RESULTS

FGF21 plasma levels were positively associated with the QRS duration (β = 0.190, P = 0.001) and QTc interval (β = 0.277, P < 0.0001). With increasing FGF21 tertiles, the patients had higher frequencies of wide QRS complex and prolonged QTc interval. After adjusting for patients' anthropometric parameters, the corresponding odd ratios (ORs) for wide QRS complex of the medium and high of FGF21 versus the low of FGF21 were 1.39 (95% CI 0.51-3.90) and 4.41 (95% CI 1.84-11.59), respectively, and p for trend was 0.001. Furthermore, multiple logistic regression analysis also showed the corresponding odd ratios (ORs) for prolonged QTc interval of the medium and high of FGF21 versus the low of FGF21 were 1.02 (95% CI 0.53-1.78) and 1.93 (95% CI 1.04-3.60) respectively with the p for trend of 0.037. In addition, age- and sex-adjusted FGF21 levels were positively associated with fasting glucose, HbA1c, creatinine, and adiponectin, but negatively associated with albumin, and the estimated glomerular filtration rate.

CONCLUSIONS

This study indicates that plasma FGF21 is associated with wide QRS complex and prolonged corrected QT interval in stable angina patients, further study is required to investigate the role of plasma FGF21 for the underlying pathogenesis.

Fibroblast growth factor receptor signaling in cardiomyocytes is protective in the acute phase following ischemia-reperfusion injury

Fibroblast growth factor receptors (FGFRs) are expressed in multiple cell types in the adult heart. Previous studies have shown a cardioprotective effect of some FGF ligands in cardiac ischemia-reperfusion (I/R) injury and a protective role for endothelial FGFRs in post-ischemic vascular remodeling. To determine the direct role FGFR signaling in cardiomyocytes in acute cardiac I/R injury, we inactivated Fgfr1 and Fgfr2 (CM-DCKO) or activated FGFR1 (CM-caFGFR1) in cardiomyocytes in adult mice prior to I/R injury. In the absence of injury, inactivation of Fgfr1 and Fgfr2 in adult cardiomyocytes had no effect on cardiac morphometry or function. When subjected to I/R injury, compared to controls, CM-DCKO mice had significantly increased myocyte death 1 day after reperfusion, and increased infarct size, cardiac dysfunction, and myocyte hypertrophy 7 days after reperfusion. No genotype-dependent effect was observed on post-ischemic cardiomyocyte cross-sectional area and vessel density in areas remote to the infarct. By contrast, transient activation of FGFR1 signaling in cardiomyocytes just prior to the onset of ischemia did not affect outcomes after cardiac I/R injury at 1 day and 7 days after reperfusion. These data demonstrate that endogenous cell-autonomous cardiomyocyte FGFR signaling supports the survival of cardiomyocytes in the acute phase following cardiac I/R injury and that this cardioprotection results in continued improved outcomes during cardiac remodeling. Combined with the established protective role of some FGF ligands and endothelial FGFR signaling in I/R injury, this study supports the development of therapeutic strategies that promote cardiomyocyte FGF signaling after I/R injury.

Phenotypic spectrum of FGF10-related disorders: a systematic review

FGF10, as an FGFR2b-specific ligand, plays a crucial role during cell proliferation, multi-organ development, and tissue injury repair. The developmental importance of FGF10 has been emphasized by the identification of FGF10 abnormalities in human congenital disorders affecting different organs and systems. Single-nucleotide variants in FGF10 or FGF10-involving copy-number variant deletions have been reported in families with lacrimo-auriculo-dento-digital syndrome, aplasia of the lacrimal and salivary glands, or lethal lung developmental disorders. Abnormalities involving FGF10 have also been implicated in cleft lip and palate, myopia, or congenital heart disease. However, the exact developmental role of FGF10 and large phenotypic heterogeneity associated with FGF10 disruption remain incompletely understood. Here, we review human and animal studies and summarize the data on FGF10 mechanism of action, expression, multi-organ function, as well as its variants and their usefulness for clinicians and researchers.

FGF22 deletion causes hidden hearing loss by affecting the function of inner hair cell ribbon synapses

Ribbon synapses are important structures in transmitting auditory signals from the inner hair cells (IHCs) to their corresponding spiral ganglion neurons (SGNs). Over the last few decades, deafness has been primarily attributed to the deterioration of cochlear hair cells rather than ribbon synapses. Hearing dysfunction that cannot be detected by the hearing threshold is defined as hidden hearing loss (HHL). The relationship between ribbon synapses and FGF22 deletion remains unknown. In this study, we used a 6-week-old FGF22 knockout mice model (Fgf22^–/–) and mainly focused on alteration in ribbon synapses by applying the auditory brainstem response (ABR) test, the immunofluorescence staining, the patch-clamp recording, and quantitative real-time PCR. In Fgf22^–/– mice, we found the decreased amplitude of ABR wave I, the reduced vesicles of ribbon synapses, and the decreased efficiency of exocytosis, which was suggested by a decrease in the capacitance change. Quantitative real-time PCR revealed that Fgf22^–/– led to dysfunction in ribbon synapses by downregulating SNAP-25 and Gipc3 and upregulating MEF2D expression, which was important for the maintenance of ribbon synapses’ function. Our research concluded that FGF22 deletion caused HHL by affecting the function of IHC ribbon synapses and may offer a novel therapeutic target to meet an ever-growing demand for deafness treatment.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Cardioprotection by selective SGLT-2 inhibitors in a non-diabetic mouse model of myocardial ischemia/reperfusion injury: a class or a drug effect?

Major clinical trials with sodium glucose co-transporter-2 inhibitors (SGLT-2i) exhibit protective effects against heart failure events, whereas inconsistencies regarding the cardiovascular death outcomes are observed. Therefore, we aimed to compare the selective SGLT-2i empagliflozin (EMPA), dapagliflozin (DAPA) and ertugliflozin (ERTU) in terms of infarct size (IS) reduction and to reveal the cardioprotective mechanism in healthy non-diabetic mice. C57BL/6 mice randomly received vehicle, EMPA (10 mg/kg/day) and DAPA or ERTU orally at the stoichiometrically equivalent dose (SED) for 7 days. 24 h-glucose urinary excretion was determined to verify SGLT-2 inhibition. IS of the region at risk was measured after 30 min ischemia (I), and 120 min reperfusion (R). In a second series, the ischemic myocardium was collected (10th min of R) for shotgun proteomics and evaluation of the cardioprotective signaling. In a third series, we evaluated the oxidative phosphorylation capacity (OXPHOS) and the mitochondrial fatty acid oxidation capacity by measuring the respiratory rates. Finally, Stattic, the STAT-3 inhibitor and wortmannin were administered in both EMPA and DAPA groups to establish causal relationships in the mechanism of protection. EMPA, DAPA and ERTU at the SED led to similar SGLT-2 inhibition as inferred by the significant increase in glucose excretion. EMPA and DAPA but not ERTU reduced IS. EMPA preserved mitochondrial functionality in complex I&II linked oxidative phosphorylation. EMPA and DAPA treatment led to NF-kB, RISK, STAT-3 activation and the downstream apoptosis reduction coinciding with IS reduction. Stattic and wortmannin attenuated the cardioprotection afforded by EMPA and DAPA. Among several upstream mediators, fibroblast growth factor-2 (FGF-2) and caveolin-3 were increased by EMPA and DAPA treatment. ERTU reduced IS only when given at the double dose of the SED (20 mg/kg/day). Short-term EMPA and DAPA, but not ERTU administration at the SED reduce IS in healthy non-diabetic mice. Cardioprotection is not correlated to SGLT-2 inhibition, is STAT-3 and PI3K dependent and associated with increased FGF-2 and Cav-3 expression.

Induction of Stem-Cell-Derived Cardiomyogenesis by Fibroblast Growth Factor 10 (FGF10) and Its Interplay with Cardiotrophin-1 (CT-1)

Simple Summary

Cardiovascular diseases are worldwide one of the leading contributors of mortality, and among multiple therapeutic approaches, stem cell therapy has been introduced as a robust therapeutic strategy to alleviate related symptoms and restore cardiac functions. Prior to this, however, for successful cell therapy, an adequate number of functional and safe cardiac cells needs to be generated. For this purpose, our approach was boosting the proliferative capacity of stem cell-derived cardiomyocytes using growth factors, such as fibroblast growth factor 10 (FGF10) and cardiotrophin-1 (CT-1). Our results demonstrated that FGF10 and CT-1 substantially increased the number of cardiac cells that originated from stem cells. In molecular assays, to assess RNA and protein level alterations, the enhanced presence of specific markers for cardiac cells after treatment of stem cells with FGF10 and/or CT-1 was confirmed. This inducing potential of cardiac cells can particularly be applicable in the cell replacement-based therapies of cardiac infarction. This research sheds light on the putative effect of FGF10 and CT-1 in the transition of stem cells to cardiac cells, leading to the repair and survival of the heart.

Abstract

For heart regeneration purposes, embryonic stem cell (ES)-based strategies have been developed to induce the proliferation of cardiac progenitor cells towards cardiomyocytes. Fibroblast growth factor 10 (FGF10) contributes to cardiac development and induces cardiomyocyte differentiation in vitro. Yet, among pro-cardiogenic factors, including cardiotrophin-1 (CT-1), the hyperplastic function of FGF10 in cardiomyocyte turnover remains to be further characterized. We investigated the proliferative effects of FGF10 on ES-derived cardiac progenitor cells in the intermediate developmental stage and examined the putative interplay between FGF10 and CT-1 in cardiomyocyte proliferation. Mouse ES cells were treated with FGF10 and/or CT-1. Differential expression of cardiomyocyte-specific gene markers was analyzed at transcript and protein levels. Substantial upregulation of sarcomeric α-actinin was detected by qPCR, flow cytometry, Western blot and immunocytochemistry. FGF10 enhanced the expression of other structural proteins (MLC-2a, MLC-2v and TNNT2), transcriptional factors (NKX2-5 and GATA4), and proliferation markers (Aurora B and YAP-1). FGF10/CT-1 co-administration led to an upregulation of proliferation markers, suggesting the synergistic potential of FGF10 + CT-1 on cardiomyogenesis. In summary, we provided evidence that FGF10 and CT-1 induce cardiomyocyte structural proteins, associated transcription factors, and cardiac cell proliferation, which could be applicable in therapies to replenish damaged cardiomyocytes.

Genomic frontiers in congenital heart disease

The application of next-generation sequencing to study congenital heart disease (CHD) is increasingly providing new insights into the causes and mechanisms of this prevalent birth anomaly. Whole-exome sequencing analysis identifies damaging gene variants altering single or contiguous nucleotides that are assigned pathogenicity based on statistical analyses of families and cohorts with CHD, high expression in the developing heart and depletion of damaging protein-coding variants in the general population. Gene classes fulfilling these criteria are enriched in patients with CHD and extracardiac abnormalities, evidencing shared pathways in organogenesis. Developmental single-cell transcriptomic data demonstrate the expression of CHD-associated genes in particular cell lineages, and emerging insights indicate that genetic variants perturb multicellular interactions that are crucial for cardiogenesis. Whole-genome sequencing analyses extend these observations, identifying non-coding variants that influence the expression of genes associated with CHD and contribute to the estimated ~55% of unexplained cases of CHD. These approaches combined with the assessment of common and mosaic genetic variants have provided a more complete knowledge of the causes and mechanisms of CHD. Such advances provide knowledge to inform the clinical care of patients with CHD or other birth defects and deepen our understanding of the complexity of human development. In this Review, we highlight known and candidate CHD-associated human genes and discuss how the integration of advances in developmental biology research can provide new insights into the genetic contributions to CHD.

The Role of Fibroblast Growth Factor (FGF) Signaling in Tissue Repair and Regeneration

Fibroblast growth factors (FGFs) are a large family of secretory molecules that act through tyrosine kinase receptors known as FGF receptors. They play crucial roles in a wide variety of cellular functions, including cell proliferation, survival, metabolism, morphogenesis, and differentiation, as well as in tissue repair and regeneration. The signaling pathways regulated by FGFs include RAS/mitogen-activated protein kinase (MAPK), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)–protein kinase B (AKT), phospholipase C gamma (PLCγ), and signal transducer and activator of transcription (STAT). To date, 22 FGFs have been discovered, involved in different functions in the body. Several FGFs directly or indirectly interfere with repair during tissue regeneration, in addition to their critical functions in the maintenance of pluripotency and dedifferentiation of stem cells. In this review, we summarize the roles of FGFs in diverse cellular processes and shed light on the importance of FGF signaling in mechanisms of tissue repair and regeneration.

Protein tyrosine phosphatase receptor zeta 1 deletion triggers defective heart morphogenesis in mice and zebrafish

Protein tyrosine phosphatase receptor-ζ1 (PTPRZ1) is a transmembrane tyrosine phosphatase receptor highly expressed in embryonic stem cells. In the present work, gene expression analyses of Ptprz1^−/− and Ptprz1^+/+ mice endothelial cells and hearts pointed to an unidentified role of PTPRZ1 in heart development through the regulation of heart-specific transcription factor genes. Echocardiography analysis in mice identified that both systolic and diastolic functions are affected in Ptprz1^−/− compared with Ptprz1^+/+ hearts, based on a dilated left ventricular (LV) cavity, decreased ejection fraction and fraction shortening, and increased angiogenesis in Ptprz1^−/− hearts, with no signs of cardiac hypertrophy. A zebrafish ptprz1^−/− knockout was also generated and exhibited misregulated expression of developmental cardiac markers, bradycardia, and defective heart morphogenesis characterized by enlarged ventricles and defected contractility. A selective PTPRZ1 tyrosine phosphatase inhibitor affected zebrafish heart development and function in a way like what is observed in the ptprz1^−/− zebrafish. The same inhibitor had no effect in the function of the adult zebrafish heart, suggesting that PTPRZ1 is not important for the adult heart function, in line with data from the human cell atlas showing very low to negligible PTPRZ1 expression in the adult human heart. However, in line with the animal models, Ptprz1 was expressed in many different cell types in the human fetal heart, such as valvar, fibroblast-like, cardiomyocytes, and endothelial cells. Collectively, these data suggest that PTPRZ1 regulates cardiac morphogenesis in a way that subsequently affects heart function and warrant further studies for the involvement of PTPRZ1 in idiopathic congenital cardiac pathologies.

NEW & NOTEWORTHY Protein tyrosine phosphatase receptor ζ1 (PTPRZ1) is expressed in fetal but not adult heart and seems to affect heart development. In both mouse and zebrafish animal models, loss of PTPRZ1 results in dilated left ventricle cavity, decreased ejection fraction, and fraction shortening, with no signs of cardiac hypertrophy. PTPRZ1 also seems to be involved in atrioventricular canal specification, outflow tract morphogenesis, and heart angiogenesis. These results suggest that PTPRZ1 plays a role in heart development and support the hypothesis that it may be involved in congenital cardiac pathologies.

Reawakening the Intrinsic Cardiac Regenerative Potential: Molecular Strategies to Boost Dedifferentiation and Proliferation of Endogenous Cardiomyocytes

Despite considerable efforts carried out to develop stem/progenitor cell-based technologies aiming at replacing and restoring the cardiac tissue following severe damages, thus far no strategies based on adult stem cell transplantation have been demonstrated to efficiently generate new cardiac muscle cells. Intriguingly, dedifferentiation, and proliferation of pre-existing cardiomyocytes and not stem cell differentiation represent the preponderant cellular mechanism by which lower vertebrates spontaneously regenerate the injured heart. Mammals can also regenerate their heart up to the early neonatal period, even in this case by activating the proliferation of endogenous cardiomyocytes. However, the mammalian cardiac regenerative potential is dramatically reduced soon after birth, when most cardiomyocytes exit from the cell cycle, undergo further maturation, and continue to grow in size. Although a slow rate of cardiomyocyte turnover has also been documented in adult mammals, both in mice and humans, this is not enough to sustain a robust regenerative process. Nevertheless, these remarkable findings opened the door to a branch of novel regenerative approaches aiming at reactivating the endogenous cardiac regenerative potential by triggering a partial dedifferentiation process and cell cycle re-entry in endogenous cardiomyocytes. Several adaptations from intrauterine to extrauterine life starting at birth and continuing in the immediate neonatal period concur to the loss of the mammalian cardiac regenerative ability. A wide range of systemic and microenvironmental factors or cell-intrinsic molecular players proved to regulate cardiomyocyte proliferation and their manipulation has been explored as a therapeutic strategy to boost cardiac function after injuries. We here review the scientific knowledge gained thus far in this novel and flourishing field of research, elucidating the key biological and molecular mechanisms whose modulation may represent a viable approach for regenerating the human damaged myocardium.

Repression of Osmr and Fgfr1 by miR-1/133a prevents cardiomyocyte dedifferentiation and cell cycle entry in the adult heart

Dedifferentiation of cardiomyocytes is part of the survival program in the remodeling myocardium and may be essential for enabling cardiomyocyte proliferation. In addition to transcriptional processes, non-coding RNAs play important functions for the control of cell cycle regulation in cardiomyocytes and cardiac regeneration. Here, we demonstrate that suppression of FGFR1 and OSMR by miR-1/133a is instrumental to prevent cardiomyocyte dedifferentiation and cell cycle entry in the adult heart. Concomitant inactivation of both miR-1/133a clusters in adult cardiomyocytes activates expression of cell cycle regulators, induces a switch from fatty acid to glycolytic metabolism, and changes expression of extracellular matrix genes. Inhibition of FGFR and OSMR pathways prevents most effects of miR-1/133a inactivation. Short-term miR-1/133a depletion protects cardiomyocytes against ischemia, while extended loss of miR-1/133a causes heart failure. Our results demonstrate a crucial role of miR-1/133a–mediated suppression of Osmr and Ffgfr1 in maintaining the postmitotic differentiated state of cardiomyocytes.

Modeling Hypoxic Stress In Vitro Using Human Embryonic Stem Cells Derived Cardiomyocytes Matured by FGF4 and Ascorbic Acid Treatment

Mature cardiomyocytes (CMs) obtained from human pluripotent stem cells (hPSCs) have been required for more accurate in vitro modeling of adult-onset cardiac disease and drug discovery. Here, we found that FGF4 and ascorbic acid (AA) induce differentiation of BG01 human embryonic stem cell–cardiogenic mesoderm cells (hESC-CMCs) into mature and ventricular CMs. Co-treatment of BG01 hESC-CMCs with FGF4+AA synergistically induced differentiation into mature and ventricular CMs. FGF4+AA-treated BG01 hESC-CMs robustly released acute myocardial infarction (AMI) biomarkers (cTnI, CK-MB, and myoglobin) into culture medium in response to hypoxic injury. Hypoxia-responsive genes and potential cardiac biomarkers proved in the diagnosis and prognosis of coronary artery diseases were induced in FGF4+AA-treated BG01 hESC-CMs in response to hypoxia based on transcriptome analyses. This study demonstrates that it is feasible to model hypoxic stress in vitro using hESC-CMs matured by soluble factors.

Fibroblast Growth Factor 21 Ameliorates NaV1.5 and Kir2.1 Channel Dysregulation in Human AC16 Cardiomyocytes

Infarcted myocardium is predisposed to cause lethal ventricular arrhythmias that remain the main cause of death in patients suffering myocardial ischemia. Liver-derived fibroblast growth factor 21 (FGF21) is an endocrine regulator, which exerts metabolic actions by favoring glucose and lipids metabolism. Emerging evidence has shown a beneficial effect of FGF21 on cardiovascular diseases, but the role of FGF21 on ventricular arrhythmias following myocardial infarction (MI) in humans has never been addressed. This study was conducted to investigate the pharmacological effects of FGF21 on cardiomyocytes after MI in humans. Patients with arrhythmia in acute MI and healthy volunteers were enrolled in this study. Serum samples were collected from these subjects on day 1 and days 7–10 after the onset of MI for measuring FGF21 levels using ELISA. Here, we found that the serum level of FGF21 was significantly increased on day 1 after the onset of MI and it returned to normal on days 7–10, relative to the Control samples. In order to clarify the regulation of FGF21 on arrhythmia, two kinds of arrhythmia animal models were established in this study, including ischemic arrhythmia model (MI rat model) and nonischemic arrhythmia model (ouabain-induced guinea pig arrhythmia model). The results showed that the incidence and duration time of ischemic arrhythmias in rhbFGF21-treated MI rats were significantly reduced at different time point after MI compared with normal saline-treated MI rats. Moreover, the onset of the first ventricular arrhythmias was delayed and the numbers of VF and maintenance were attenuated by FGF21 compared to the rhbFGF21-untreated group in the ouabain model. Consistently, in vitro study also demonstrated that FGF21 administration was able to shorten action potential duration (APD) in hydrogen peroxide-treated AC16 cells. Mechanically, FGF21 can ameliorate the electrophysiological function of AC16 cells, which is characterized by rescuing the expression and dysfunction of cardiac sodium current (I_Na) and inward rectifier potassium (I_k1) in AC16 cells induced by hydrogen peroxide. Moreover, the restorative effect of FGF21 on Na_V1.5 and Kir2.1 was eliminated when FGF receptors were inhibited. Collectively, FGF21 has the potential role of ameliorating transmembrane ion channels remodeling through the Na_V1.5/Kir2.1 pathway by FGF receptors and thus reducing life-threatening postinfarcted arrhythmias, which provides new strategies for antiarrhythmic therapy in clinics.

Recent Advances in Gene Therapy for Cardiac Tissue Regeneration

Cardiovascular diseases (CVDs) are responsible for enormous socio-economic impact and the highest mortality globally. The standard of care for CVDs, which includes medications and surgical interventions, in most cases, can delay but not prevent the progression of disease. Gene therapy has been considered as a potential therapy to improve the outcomes of CVDs as it targets the molecular mechanisms implicated in heart failure. Cardiac reprogramming, therapeutic angiogenesis using growth factors, antioxidant, and anti-apoptotic therapies are the modalities of cardiac gene therapy that have led to promising results in preclinical studies. Despite the benefits observed in animal studies, the attempts to translate them to humans have been inconsistent so far. Low concentration of the gene product at the target site, incomplete understanding of the molecular pathways of the disease, selected gene delivery method, difference between animal models and humans among others are probable causes of the inconsistent results in clinics. In this review, we discuss the most recent applications of the aforementioned gene therapy strategies to improve cardiac tissue regeneration in preclinical and clinical studies as well as the challenges associated with them. In addition, we consider ongoing gene therapy clinical trials focused on cardiac regeneration in CVDs.

Molecular mechanisms of the anti-cancer drug, LY2874455, in overcoming the FGFR4 mutation-based resistance

In recent years, many strategies have been used to overcome the fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors (TKIs) resistance caused by different mutations. LY2874455 (or 6LF) is a pan-FGFR inhibitor which is identified as the most efficient TKI for all resistant mutations in FGFRs. Here, we perform a comparative dynamics study of wild type (WT) and the FGFR4 V550L mutant for better understanding of the 6LF inhibition mechanism. Our results confirm that the pan-FGFR inhibitor 6LF can bind efficiently to both WT and V550L FGFR4. Moreover, the communication network analysis indicates that in apo-WT FGFR4, αD–αE loop behaves like a switch between open and close states of the substrate-binding pocket in searching of its ligand. In contrast, V550L mutation induces the active conformation of the FGFR4 substrate-binding pocket through disruption of αD–αE loop and αG helix anti-correlation. Interestingly, 6LF binding causes the rigidity of hinge and αD helix regions, which results in overcoming V550L induced resistance. Collectively, the results of this study would be informative for designing more efficient TKIs for more effective targeting of the FGFR signaling pathway.

Transcriptome analysis of non human primate-induced pluripotent stem cell-derived cardiomyocytes in 2D monolayer culture vs. 3D engineered heart tissue

AIMS

Stem cell therapy has shown promise for treating myocardial infarction via re-muscularization and paracrine signalling in both small and large animals. Non-human primates (NHPs), such as rhesus macaques (Macaca mulatta), are primarily utilized in preclinical trials due to their similarity to humans, both genetically and physiologically. Currently, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are delivered into the infarcted myocardium by either direct cell injection or an engineered tissue patch. Although both approaches have advantages in terms of sample preparation, cell-host interaction, and engraftment, how the iPSC-CMs respond to ischaemic conditions in the infarcted heart under these two different delivery approaches remains unclear. Here, we aim to gain a better understanding of the effects of hypoxia on iPSC-CMs at the transcriptome level.

METHODS AND RESULTS

NHP iPSC-CMs in both monolayer culture (2D) and engineered heart tissue (EHT) (3D) format were exposed to hypoxic conditions to serve as surrogates of direct cell injection and tissue implantation in vivo, respectively. Outcomes were compared at the transcriptome level. We found the 3D EHT model was more sensitive to ischaemic conditions and similar to the native in vivo myocardium in terms of cell-extracellular matrix/cell-cell interactions, energy metabolism, and paracrine signalling.

CONCLUSION

By exposing NHP iPSC-CMs to different culture conditions, transcriptome profiling improves our understanding of the mechanism of ischaemic injury.

A bioinformatics approach for identifying potential molecular mechanisms and key genes involved in COVID-19 associated cardiac remodeling

In 2019 coronavirus disease (COVID-19), whose main complication is respiratory involvement, different organs may also be affected in severe cases. However, COVID-19 associated cardiovascular manifestations are limited at present. The main purpose of this study was to identify potential candidate genes involved in COVID-19-associated heart damage by bioinformatics analysis. Differently expressed genes (DEGs) were identified using transcriptome profiles (GSE150392 and GSE4172) downloaded from the GEO database. After gene and pathway enrichment analyses, PPI network visualization, module analyses, and hub gene extraction were performed using Cytoscape software. A total of 228 (136 up and 92 downregulated) overlapping DEGs were identified at these two microarray datasets. Finally, the top hub genes (FGF2, JUN, TLR4, and VEGFA) were screened out as the critical genes among the DEGs from the PPI network. Identification of critical genes and mechanisms in any disease can lead us to better diagnosis and targeted therapy. Our findings identified core genes shared by inflammatory cardiomyopathy and SARS-CoV-2. The findings of the current study support the idea that these key genes can be used in understanding and managing the long-term cardiovascular effects of COVID-19.

Bioengineering strategies to control epithelial-to-mesenchymal transition for studies of cardiac development and disease

Epithelial-to-mesenchymal transition (EMT) is a process that occurs in a wide range of tissues and environments, in response to numerous factors and conditions, and plays a critical role in development, disease, and regeneration. The process involves epithelia transitioning into a mobile state and becoming mesenchymal cells. The investigation of EMT processes has been important for understanding developmental biology and disease progression, enabling the advancement of treatment approaches for a variety of disorders such as cancer and myocardial infarction. More recently, tissue engineering efforts have also recognized the importance of controlling the EMT process. In this review, we provide an overview of the EMT process and the signaling pathways and factors that control it, followed by a discussion of bioengineering strategies to control EMT. Important biological, biomaterial, biochemical, and physical factors and properties that have been utilized to control EMT are described, as well as the studies that have investigated the modulation of EMT in tissue engineering and regenerative approaches in vivo, with a specific focus on the heart. Novel tools that can be used to characterize and assess EMT are discussed and finally, we close with a perspective on new bioengineering methods that have the potential to transform our ability to control EMT, ultimately leading to new therapies.

The Multifunctional Contribution of FGF Signaling to Cardiac Development, Homeostasis, Disease and Repair

The current focus on cardiovascular research reflects society’s concerns regarding the alarming incidence of cardiac-related diseases and mortality in the industrialized world and, notably, an urgent need to combat them by more efficient therapies. To pursue these therapeutic approaches, a comprehensive understanding of the mechanism of action for multifunctional fibroblast growth factor (FGF) signaling in the biology of the heart is a matter of high importance. The roles of FGFs in heart development range from outflow tract formation to the proliferation of cardiomyocytes and the formation of heart chambers. In the context of cardiac regeneration, FGFs 1, 2, 9, 16, 19, and 21 mediate adaptive responses including restoration of cardiac contracting rate after myocardial infarction and reduction of myocardial infarct size. However, cardiac complications in human diseases are correlated with pathogenic effects of FGF ligands and/or FGF signaling impairment. FGFs 2 and 23 are involved in maladaptive responses such as cardiac hypertrophic, fibrotic responses and heart failure. Among FGFs with known causative (FGFs 2, 21, and 23) or protective (FGFs 2, 15/19, 16, and 21) roles in cardiac diseases, FGFs 15/19, 21, and 23 display diagnostic potential. The effective role of FGFs on the induction of progenitor stem cells to cardiac cells during development has been employed to boost the limited capacity of postnatal cardiac repair. To renew or replenish damaged cardiomyocytes, FGFs 1, 2, 10, and 16 were tested in (induced-) pluripotent stem cell-based approaches and for stimulation of cell cycle re-entry in adult cardiomyocytes. This review will shed light on the wide range of beneficiary and detrimental actions mediated by FGF ligands and their receptors in the heart, which may open new therapeutic avenues for ameliorating cardiac complications.

High-Throughput Methods in the Discovery and Study of Biomaterials and Materiobiology

The complex interaction of cells with biomaterials (i.e., materiobiology) plays an increasingly pivotal role in the development of novel implants, biomedical devices, and tissue engineering scaffolds to treat diseases, aid in the restoration of bodily functions, construct healthy tissues, or regenerate diseased ones. However, the conventional approaches are incapable of screening the huge amount of potential material parameter combinations to identify the optimal cell responses and involve a combination of serendipity and many series of trial-and-error experiments. For advanced tissue engineering and regenerative medicine, highly efficient and complex bioanalysis platforms are expected to explore the complex interaction of cells with biomaterials using combinatorial approaches that offer desired complex microenvironments during healing, development, and homeostasis. In this review, we first introduce materiobiology and its high-throughput screening (HTS). Then we present an in-depth of the recent progress of 2D/3D HTS platforms (i.e., gradient and microarray) in the principle, preparation, screening for materiobiology, and combination with other advanced technologies. The Compendium for Biomaterial Transcriptomics and high content imaging, computational simulations, and their translation toward commercial and clinical uses are highlighted. In the final section, current challenges and future perspectives are discussed. High-throughput experimentation within the field of materiobiology enables the elucidation of the relationships between biomaterial properties and biological behavior and thereby serves as a potential tool for accelerating the development of high-performance biomaterials.

Dysregulation of circulating miRNAs promotes the pathogenesis of diabetes-induced cardiomyopathy

Diabetic Cardiomyopathy (DCM) is characterized by myocardial dysfunction caused by diabetes mellitus. After-effects of diabetic cardiomyopathy are far more lethal than non-diabetic cardiomyopathy. More than 300 million people suffer from diabetes and cardiovascular disorder which is expected to be elevated to an alarming figure of 450 million by 2030. Recent studies suggested that miRNA plays important role in the onset of diabetic cardiomyopathy. This study was designed to identify the miRNA that is responsible for the onset of diabetic cardiomyopathy using in silico and in vitro approaches. In this study, to identify the miRNA responsible for the onset of diabetic cardiomyopathy, in silico analysis was done to predict the role of these circulating miRNAs in type 2 diabetic cardiomyopathy. Shared miRNAs that are present in both diseases were selected for further analysis. Total RNA and miRNA were extracted from blood samples taken from type 2 diabetic patients as well as healthy controls to analyze the expression of important genes like AKT, VEGF, IGF, FGF1, ANGPT2 using Real-time PCR. The expression of ANGPT2 was up-regulated and AKT, VEGF, IGF, FGF1 were down-regulated in DCM patients as compared to healthy controls. The miRNA expression of miR-17 was up-regulated and miR-24, miR-150, miR-199a, miR-214, and miR-320a were down-regulated in the DCM patients as compared to healthy controls. This shows that dysregulation of target genes and miRNA may contribute towards the pathogenesis of DCM and more studies should be conducted to elucidate the role of circulating miRNAs to use them as therapeutic and diagnostic options.

Cardiac Differentiation of Mesenchymal Stem Cells: Impact of Biological and Chemical Inducers

Cardiovascular disorders (CVDs) are the leading cause of global death, widely occurs due to irreparable loss of the functional cardiomyocytes. Stem cell-based therapeutic approaches, particularly the use of Mesenchymal Stem Cells (MSCs) is an emerging strategy to regenerate myocardium and thereby improving the cardiac function after myocardial infarction (MI). Most of the current approaches often employ the use of various biological and chemical factors as cues to trigger and modulate the differentiation of MSCs into the cardiac lineage. However, the recent advanced methods of using specific epigenetic modifiers and exosomes to manipulate the epigenome and molecular pathways of MSCs to modify the cardiac gene expression yield better profiled cardiomyocyte like cells in vitro. Hitherto, the role of cardiac specific inducers triggering cardiac differentiation at the cellular and molecular level is not well understood. Therefore, the current review highlights the impact and recent trends in employing biological and chemical inducers on cardiac differentiation of MSCs. Thereby, deciphering the interactions between the cellular microenvironment and the cardiac inducers will help us to understand cardiomyogenesis of MSCs. Additionally, the review also provides an insight on skeptical roles of the cell free biological factors and extracellular scaffold assisted mode for manipulation of native and transplanted stem cells towards translational cardiac research.

Artificial intelligence and leukocyte epigenomics: Evaluation and prediction of late-onset Alzheimer's disease

We evaluated the utility of leucocyte epigenomic-biomarkers for Alzheimer’s Disease (AD) detection and elucidates its molecular pathogeneses. Genome-wide DNA methylation analysis was performed using the Infinium MethylationEPIC BeadChip array in 24 late-onset AD (LOAD) and 24 cognitively healthy subjects. Data were analyzed using six Artificial Intelligence (AI) methodologies including Deep Learning (DL) followed by Ingenuity Pathway Analysis (IPA) was used for AD prediction. We identified 152 significantly (FDR p<0.05) differentially methylated intragenic CpGs in 171 distinct genes in AD patients compared to controls. All AI platforms accurately predicted AD with AUCs ≥0.93 using 283,143 intragenic and 244,246 intergenic/extragenic CpGs. DL had an AUC = 0.99 using intragenic CpGs, with both sensitivity and specificity being 97%. High AD prediction was also achieved using intergenic/extragenic CpG sites (DL significance value being AUC = 0.99 with 97% sensitivity and specificity). Epigenetically altered genes included CR1L & CTSV (abnormal morphology of cerebral cortex), S1PR1 (CNS inflammation), and LTB4R (inflammatory response). These genes have been previously linked with AD and dementia. The differentially methylated genes CTSV & PRMT5 (ventricular hypertrophy and dilation) are linked to cardiovascular disease and of interest given the known association between impaired cerebral blood flow, cardiovascular disease, and AD. We report a novel, minimally invasive approach using peripheral blood leucocyte epigenomics, and AI analysis to detect AD and elucidate its pathogenesis.

Over-expression of Fgf8 in cardiac neural crest cells leads to persistent truncus arteriosus

During cardiogenesis, the outflow tract undergoes a complicated morphogenesis, including the re-alignment of the great blood vessels, and the separation of aorta and pulmonary trunk. The deficiency of FGF8 in the morphogenesis of outflow tract has been well studied, however, the effect of over-dosed FGF8 on the development of outflow tract remains unknown. In this study, Rosa26R-Fgf8 knock-in allele was constitutively activated by Wnt1-cre transgene in the mouse neural crest cells presumptive for the endocardial cushion of outflow tract. Surprisingly, Wnt1-cre; Rosa26R-Fgf8 mouse embryos exhibited persistent truncus arteriosus and died prior to E15.5. The cardiac neural crest cells in Wnt1-cre; Rosa26R-Fgf8 truncus arteriosus did not degenerate as in WT controls, but proliferated into a thickened endocardial cushion and then, blocked the blood outflow from cardiac chambers into the lungs, which resulted in the embryonic lethality. Although the spiral aorticopulmonary septum failed to form, the differentiaion of the endothelium and smooth muscle in the Wnt1-cre; Rosa26R-Fgf8 truncus arteriosus were impacted little. However, lineage tracing assay showed that the neural crest derived cells aggregated in the cushion layer, but failed to differentiate into the endothelium of Wnt1-cre; Rosa26R-Fgf8 truncus arteriosus. Further investigation displayed the reduced p-Akt and p-Erk immunostaining, and the decreased Bmp2 and Bmp4 transcription in the endothelium of Wnt1-cre; Rosa26R-Fgf8 truncus arteriosus. Our findings suggested that Fgf8 over-expression in cardiac neural crest impaired the formation of aorticopulmonary septum by suppressing the endothelial differentiation and stimulating the proliferation of endocardial cushion cells, which implicated a novel etiology of persistent truncus arteriosus.

The FGF-AKT pathway is necessary for cardiomyocyte survival for heart regeneration in zebrafish

Zebrafish have a remarkable ability to regenerate the myocardium after injury by proliferation of pre-existing cardiomyocytes. Fibroblast growth factor (FGF) signaling is known to play a critical role in zebrafish heart regeneration through promotion of neovascularization of the regenerating myocardium. Here, we define an additional function of FGF signaling in the zebrafish myocardium after injury. We find that FGF signaling is active in a small fraction of cardiomyocytes before injury, and that the number of FGF signaling-positive cardiomyocytes increases after amputation-induced injury. We show that ERK phosphorylation is prominent in endothelial cells, but not in cardiomyocytes. In contrast, basal levels of phospho-AKT positive cardiomyocytes are detected before injury, and the ratio of phosphorylated AKT-positive cardiomyocytes increases after injury, indicating a role of AKT signaling in cardiomyocytes following injury. Inhibition of FGF signaling reduced the number of phosphorylated AKT-positive cardiomyocytes and increased cardiomyocyte death without injury. Heart injury did not induce cardiomyocyte death; however, heart injury in combination with inhibition of FGF signaling caused significant increase in cardiomyocyte death. Pharmacological inhibition of AKT signaling after heart injury also caused increased cardiomyocyte death. Our data support the idea that FGF-AKT signaling-dependent cardiomyocyte survival is necessary for subsequent heart regeneration.

Advances in Biological Functions and Clinical Studies of FGF21

Fibroblast growth factor 21 (FGF21) regulates many crucial biological processes in human and mammals, particularly metabolic modulation and protective effect after injury. Therefore, determining complex regulatory mechanisms and elucidating the signaling pathway may greatly promote the prevention, diagnosis, and treatment of related injury and metabolic diseases. This review focused on the metabolic modulation and protective effect of FGF21 and summarized the molecular mechanisms and clinical research developments.

Gelatine nanostructured lipid carrier encapsulated FGF15 inhibits autophagy and improves recovery in spinal cord injury

Gelatine nanostructured lipid carriers (GNLs) have attracted increasing attention due to their biodegradable status and capacity to capture various biologically active compounds. Many studies demonstrated that fibroblast growth factor therapies after spinal cord injury (SCI) can be used in the future for the recovery of neurons. In this study, the therapeutic effects of GNL-encapsulated fibroblast growth factor 15 (FGF15) and FGF15 were compared in SCI. The FGF15-GNLs had 88.17 ± 1.22% encapsulation efficiency and 4.82 ± 0.12% loading capacity. The effects of FGF15-GNLs and FGF15 were assessed based on the Basso–Beattie–Bresnahan (BBB) locomotion scale, inclined plane test and footprint analysis. Immunofluorescent staining was used to identify the expression of autophagy-associated proteins, GFAP (glial fibrillary acidic protein) and neurofilament 200 (NF200). FGF15-GNLs use enhanced the repair after SCI compared to the effect of FGF15. The suppression of autophagy-associated proteins LC3-II and beclin-1, and p62 enhancement by FGF15-GNLs treatment were more pronounced. Thus, the effects of FGF15-GNLs on the recovery after SCI are related to the inhibition of autophagy and glial scar, and promotion of nerve regeneration in SCI.

Cardiac Endocrinology: Heart-Derived Hormones in Physiology and Disease

The heart plays a central role in the circulatory system and provides essential oxygen, nutrients, and growth factors to the whole organism. The heart can synthesize and secrete endocrine signals to communicate with distant target organs. Studies of long-known and recently discovered heart-derived hormones highlight a shared theme and reveal a unified mechanism of heart-derived hormones in coordinating cardiac function and target organ biology. This paper reviews the biochemistry, signaling, function, regulation, and clinical significance of representative heart-derived hormones, with a focus on the cardiovascular system. This review also discusses important and exciting questions that will advance the field of cardiac endocrinology.

Differentiation of cardiomyocyte-like cells from human amniotic fluid mesenchymal stem cells by combined induction with human platelet lysate and 5-azacytidine

Human amniotic fluid mesenchymal stem cells (hAF-MSCs) have been shown to be effective in the treatment of many diseases. Platelet lysate (PL) contains multiple growth and differentiation factors; therefore, it can be used as a differentiation inducer. In this study, we attempted to evaluate the efficiency of human platelet lysate (hPL) on cell viability and the effects on cardiomyogenic differentiation of hAF-MSCs. When treating the cells with hPL, the result showed an increase in cell viability. Expressions of cardiomyogenic specific genes, including GATA4, cTnT, Cx43 and Nkx2.5, were higher in the combined treatment groups of 5-azacytidine (5-aza) and hPL than the expressions of cardiomyogenic specific genes in the control group and in the 5-aza treatment group. In terms of the results of immunofluorescence and immunoenzymatic staining, the highest expressions of cardiomyogenic specific proteins were revealed in combined treatment groups. It can be summarized that hPL may be an effective supporting cardiomyogenic supplementary factor for cardiomyogenic differentiation in hAF-MSCs.

Biomaterials Loaded with Growth Factors/Cytokines and Stem Cells for Cardiac Tissue Regeneration

Myocardial infarction causes cardiac tissue damage and the release of damage-associated molecular patterns leads to activation of the immune system, production of inflammatory mediators, and migration of various cells to the site of infarction. This complex response further aggravates tissue damage by generating oxidative stress, but it eventually heals the infarction site with the formation of fibrotic tissue and left ventricle remodeling. However, the limited self-renewal capability of cardiomyocytes cannot support sufficient cardiac tissue regeneration after extensive myocardial injury, thus, leading to an irreversible decline in heart function. Approaches to improve cardiac tissue regeneration include transplantation of stem cells and delivery of inflammation modulatory and wound healing factors. Nevertheless, the harsh environment at the site of infarction, which consists of, but is not limited to, oxidative stress, hypoxia, and deficiency of nutrients, is detrimental to stem cell survival and the bioactivity of the delivered factors. The use of biomaterials represents a unique and innovative approach for protecting the loaded factors from degradation, decreasing side effects by reducing the used dosage, and increasing the retention and survival rate of the loaded cells. Biomaterials with loaded stem cells and immunomodulating and tissue-regenerating factors can be used to ameliorate inflammation, improve angiogenesis, reduce fibrosis, and generate functional cardiac tissue. In this review, we discuss recent findings in the utilization of biomaterials to enhance cytokine/growth factor and stem cell therapy for cardiac tissue regeneration in small animals with myocardial infarction.

Betaine prevented high-fat diet-induced NAFLD by regulating the FGF10/AMPK signaling pathway in ApoE-/- mice

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is currently the leading cause of chronic liver disease in developing countries. The pathogenesis is complex, and there is currently no effective treatment. Betaine is an essential intermediate in choline catabolism and an important component of the methionine cycle. Betaine deficiency is associated with NAFLD severity, and its mechanism needs to be further elaborated.

METHODS

In this study, an NAFLD mouse model was established by feeding ApoE^-/- mice a high-fat diet. The effects of betaine on NAFLD were investigated, including its mechanism.

RESULTS

In this study, after treatment with betaine, blood lipid levels and liver damage were significantly decreased in the NAFLD mouse model. The fat infiltration of the liver tissues of high-fat diet (HFD)-fed mice after betaine administration was significantly improved. Betaine treatment significantly upregulated AMP-activated protein kinase (AMPK), fibroblast growth factor 10 (FGF10), and adipose triglyceride lipase (ATGL) protein levels both in vivo and in vitro and suppressed lipid metabolism-related genes. Furthermore, the overexpression of FGF10 increased the protein level of AMPK and decreased lipid accumulation in HepG2 cells.

CONCLUSION

Taken together, the data strongly suggest that betaine significantly prevents high-fat diet-induced NAFLD through the FGF10/AMPK signaling pathway in ApoE^-/- mice.

Delineating the molecular and histological events that govern right ventricular recovery using a novel mouse model of pulmonary artery de-banding

AIMS

The temporal sequence of events underlying functional right ventricular (RV) recovery after improvement of pulmonary hypertension-associated pressure overload is unknown. We sought to establish a novel mouse model of gradual RV recovery from pressure overload and use it to delineate RV reverse-remodelling events.

METHODS AND RESULTS

Surgical pulmonary artery banding (PAB) around a 26-G needle induced RV dysfunction with increased RV pressures, reduced exercise capacity and caused liver congestion, hypertrophic, fibrotic, and vascular myocardial remodelling within 5 weeks of chronic RV pressure overload in mice. Gradual reduction of the afterload burden through PA band absorption (de-PAB)-after RV dysfunction and structural remodelling were established-initiated recovery of RV function (cardiac output and exercise capacity) along with rapid normalization in RV hypertrophy (RV/left ventricular + S and cardiomyocyte area) and RV pressures (right ventricular systolic pressure). RV fibrotic (collagen, elastic fibres, and vimentin+ fibroblasts) and vascular (capillary density) remodelling were equally reversible; however, reversal occurred at a later timepoint after de-PAB, when RV function was already completely restored. Microarray gene expression (ClariomS, Thermo Fisher Scientific, Waltham, MA, USA) along with gene ontology analyses in RV tissues revealed growth factors, immune modulators, and apoptosis mediators as major cellular components underlying functional RV recovery.

CONCLUSION

We established a novel gradual de-PAB mouse model and used it to demonstrate that established pulmonary hypertension-associated RV dysfunction is fully reversible. Mechanistically, we link functional RV improvement to hypertrophic normalization that precedes fibrotic and vascular reverse-remodelling events.

Mutations in fibroblast growth factor (FGF8) and FGF10 identified in patients with conotruncal defects

Background

Conotruncal defects (CTDs) are a type of heterogeneous congenital heart diseases (CHDs), but little is known about their etiology. Increasing evidence has demonstrated that fibroblast growth factor (FGF) 8 and FGF10 may be involved in the pathogenesis of CTDs.

Methods

The variants of FGF8 and FGF10 in unrelated Chinese Han patients with CHDs (n = 585), and healthy controls (n = 319) were investigated. The expression and function of these patient-identified variants were detected to confirm the potential pathogenicity of the non-synonymous variants. The expression of FGF8 and FGF10 during the differentiation of human embryonic stem cells (hESCs) to cardiomyocytes and in Carnegie stage 13 human embryo was also identified.

Results

Two probable deleterious variants (p.C10Y, p.R184H) of FGF8 and one deletion mutant (p.23_24del) of FGF10 were identified in three patients with CTD. Immunofluorescence suggested that variants did not affect the intracellular localization, whereas ELISA showed that the p.C10Y and p.23_24del variants reduced the amount of secreted FGF8 and FGF10, respectively. Quantitative RT-PCR and western blotting showed that the expression of FGF8 and FGF10 variants was increased compared with wild-type; however, their functions were reduced. And we found that FGF8 and FGF10 were expressed in the outflow tract (OFT) during human embryonic development, and were dynamically expressed during the differentiation of hESCs into cardiomyocytes.

Conclusion

Our results provided evidence that damaging variants of FGF8 and FGF10 were likely contribute to the etiology of CTD. This discovery expanded the spectrum of FGF mutations and underscored the pathogenic correlation between FGF mutations and CTD.

The lateral plate mesoderm

The lateral plate mesoderm (LPM) forms the progenitor cells that constitute the heart and cardiovascular system, blood, kidneys, smooth muscle lineage and limb skeleton in the developing vertebrate embryo. Despite this central role in development and evolution, the LPM remains challenging to study and to delineate, owing to its lineage complexity and lack of a concise genetic definition. Here, we outline the processes that govern LPM specification, organization, its cell fates and the inferred evolutionary trajectories of LPM-derived tissues. Finally, we discuss the development of seemingly disparate organ systems that share a common LPM origin.

Summary: The lateral plate mesoderm is the origin of several major cell types and organ systems in the vertebrate body plan. How this mesoderm territory emerges and partitions into its downstream fates provides clues about vertebrate development and evolution.

Glucagon-Dependent Suppression of mTORC1 is Associated with Upregulation of Hepatic FGF21 mRNA Translation

Fibroblast growth factor 21 (FGF21) is a peptide hormone that acts to enhance insulin sensitivity and reverse many of the metabolic defects associated with consumption of a high-fat diet. Recent studies show that the liver is the primary source of FGF21 in the blood, and that hepatic FGF21 expression is upregulated by glucagon. Interestingly, glucagon acts to upregulate FGF21 production by primary cultures of rat hepatocytes and H4IIE and HepG2 hepatocarcinoma cells independent of changes in FGF21 mRNA abundance, suggesting that FGF21 protein expression is regulated post-transcriptionally. Based on these observations, the goal of the present study was to assess whether or not FGF21 mRNA is translationally regulated. The results show that FGF21 mRNA translation and secretion of the hormone are significantly upregulated in H4IIE cells exposed to 25 nM glucagon, independent of changes in FGF21 mRNA abundance. Furthermore, the glucagon-induced upregulation of FGF21 mRNA translation is associated with suppressed activity of the mechanistic target of rapamycin in complex 1 (mTORC1). Similarly, the results show that rapamycin-induced suppression of mTORC1 leads to upregulation of FGF21 mRNA translation with no change in FGF21 mRNA abundance. In contrast, activation of mTORC1 by refreshing the culture medium leads to downregulation of FGF21 mRNA translation. Notably, re-feeding fasted rats also leads to downregulation of FGF21 mRNA translation concomitantly with activation of mTORC1 in the liver. Overall, the findings support a model in which glucagon acts to upregulate FGF21 production by hepatocytes through suppression of mTORC1 and subsequent upregulation of FGF21 mRNA translation.

A review of fibroblast growth factor 21 in diabetic cardiomyopathy

FGF21 (fibroblast growth factor 21) is a regulator of metabolism and performs an important role in glucose and lipid metabolism and the maintenance of energy balance. FGF21 is principally expressed in the liver, but it can also be found in the pancreas, skeletal muscle, and adipose tissue. It is known that levels of serum FGF21 are significantly elevated in obese, insulin-resistant patients, and those with metabolic syndrome. Elevated levels of FGF21 in serum during the early stages of various metabolic diseases are considered a compensatory response by the organism. Therefore, FGF21 is considered a hormone in response to stress and an early diagnostic marker of disease. Diabetic cardiomyopathy is a special type of cardiac complication, characterized as a chronic myocardial disorder caused by diabetes. The pathological process includes increased oxidative stress, energy metabolism in myocardial cells, an inflammatory response, and myocardial cell apoptosis. A growing body of evidence suggests that FGF21 has the potential to be an effective drug for the treatment of diabetic cardiomyopathy. Here, we review recent progress on the characteristics of FGF21 in its protective role, especially in pathological processes such as suppressing apoptosis in the myocardium, reducing inflammation in cardiomyocytes, reducing oxidative stress, and promoting fatty acid oxidation. In addition, we explore the possibility that diabetic cardiomyopathy can be delayed through the application of FGF21, providing possible therapeutic targets of the disease.

Circulating miR-320a as a Predictive Biomarker for Left Ventricular Remodelling in STEMI Patients Undergoing Primary Percutaneous Coronary Intervention

Restoration of epicardial coronary blood flow, achieved by early reperfusion with primary percutaneous coronary intervention (PPCI), is the guideline recommended to treat patients with ST-segment-elevation myocardial infarction (STEMI). However, despite successful blood restoration, increasing numbers of patients develop left ventricular adverse remodelling (LVAR) and heart failure. Therefore, reliable prognostic biomarkers for LVAR in STEMI are urgently needed. Our aim was to investigate the role of circulating microRNAs (miRNAs) and their association with LVAR in STEMI patients following the PPCI procedure. We analysed the expression of circulating miRNAs in blood samples of 56 patients collected at admission and after revascularization (at 3, 6, 12 and 24 h). The associations between miRNAs and left ventricular end diastolic volumes at 6 months were estimated to detect LVAR. miRNAs were also analysed in samples isolated from peripheral blood mononuclear cells (PBMCs) and human myocardium of failing hearts. Kinetic analysis of miRNAs showed a fast time-dependent increase in miR-133a, miR-133b, miR-193b, miR-499, and miR-320a in STEMI patients compared to controls. Moreover, the expression of miR-29a, miR-29b, miR-324, miR-208, miR-423, miR-522, and miR-545 was differentially expressed even before PPCI in STEMI. Furthermore, the increase in circulating miR-320a and the decrease in its expression in PBMCs were significantly associated with LVAR and correlated with the expression of miR-320a in human failing myocardium from ischaemic origin. In conclusion, we determined the time course expression of new circulating miRNAs in patients with STEMI treated with PPCI and we showed that miR-320a was positively associated with LVAR.

Phosphorylation of GATA4 at serine 105 is required for left ventricular remodelling process in angiotensin II-induced hypertension in rats

In this study, we investigated whether local intramyocardial GATA4 overexpression affects the left ventricular (LV) remodelling process and the importance of phosphorylation at serine 105 (S105) for the actions of GATA4 in an angiotensin II (AngII)‐induced hypertension rat model. Adenoviral constructs overexpressing wild‐type GATA4 or GATA4 mutated at S105 were delivered into the anterior LV free wall. AngII (33.3 µg/kg/h) was administered via subcutaneously implanted minipumps. Cardiac function and structure were examined by echocardiography, followed by histological immunostainings of LV sections and gene expression measurements by RT‐qPCR. The effects of GATA4 on cultured neonatal rat ventricular fibroblasts were evaluated. In AngII‐induced hypertension, GATA4 overexpression repressed fibrotic gene expression, reversed the hypertrophic adult‐to‐foetal isoform switch of myofibrillar genes and prevented apoptosis, whereas histological fibrosis was not affected. Overexpression of GATA4 mutated at S105 resulted in LV chamber dilatation, cardiac dysfunction and had minor effects on expression of myocardial remodelling genes. Fibrotic gene expression in cardiac fibroblasts was differently affected by overexpression of wild‐type or mutated GATA4. Our results indicate that GATA4 reduces AngII‐induced responses by interfering with pro‐fibrotic and hypertrophic gene expressions. GATA4 actions on LV remodelling and fibroblasts are dependent on phosphorylation site S105.

Early angiogenic proteins associated with high risk for bronchopulmonary dysplasia and pulmonary hypertension in preterm infants

Early pulmonary vascular disease in preterm infants is associated with the subsequent development of bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH); however, mechanisms that contribute to or identify infants with increased susceptibility for BPD and/or PH are incompletely understood. Therefore, we tested if changes in circulating angiogenic peptides during the first week of life are associated with the later development of BPD and/or PH. We further sought to determine alternate peptides and related signaling pathways with the risk for BPD or PH. We prospectively enrolled infants with gestational age <34 wk and collected blood samples during their first week of life. BPD and PH were assessed at 36 wk postmenstrual age. Samples were assayed for each of the 1,121 peptides included in the SOMAscan scan technology, with subsequent pathway analysis. Of 102 infants in the study, 82 had BPD, and 13 had PH. Multiple angiogenic proteins (PF-4, VEGF121, ANG-1, bone morphogenetic protein 10 [BMP10], hepatocyte growth factor (HGF), ANG-2) were associated with the subsequent diagnosis of BPD; and FGF-19, PF-4, connective tissue activating peptide (CTAP)-III, and PDGF-AA levels were associated with BPD severity. Early increases in BMP10 was strongly associated with the late risk for BPD and PH. We found that early alterations of circulating angiogenic peptides and others were associated with the subsequent development of BPD. We further identified peptides that were associated with BPD severity and BPD-associated PH, including BMP10. We speculate that proteomic biomarkers during the first week of life may identify infants at risk for BPD and/or PH to enhance care and research.

Fibroblast growth factor 21 inhibited ischemic arrhythmias via targeting miR-143/EGR1 axis

Ventricular arrhythmia is the most common cause of sudden cardiac death in patients with myocardial infarction (MI). Fibroblast growth factor 21 (FGF21) has been shown to play an important role in cardiovascular and metabolic diseases. However, the effects of FGF21 on ventricular arrhythmias following MI have not been addressed yet. The present study was conducted to investigate the pharmacological action of FGF21 on ventricular arrhythmias after MI. Adult male mice were administrated with or without recombinant human basic FGF21 (rhbFGF21), and the susceptibility to arrhythmias was assessed by programmed electrical stimulation and optical mapping techniques. Here, we found that rhbFGF21 administration reduced the occurrence of ventricular tachycardia (VT), improved epicardial conduction velocity and shorted action potential duration at 90% (APD90) in infarcted mouse hearts. Mechanistically, FGF21 may improve cardiac electrophysiological remodeling as characterized by the decrease of INa and IK1 current density in border zone of infarcted mouse hearts. Consistently, in vitro study also demonstrated that FGF21 may rescue oxidant stress-induced dysfunction of INa and IK1 currents in cultured ventricular myocytes. We further found that oxidant stress-induced down-regulation of early growth response protein 1 (EGR1) contributed to INa and IK1 reduction in post-infarcted hearts, and FGF21 may recruit EGR1 into the SCN5A and KCNJ2 promoter regions to up-regulate NaV1.5 and Kir2.1 expression at transcriptional level. Moreover, miR-143 was identified as upstream of EGR1 and mediated FGF21-induced EGR1 up-regulation in cardiomyocytes. Collectively, rhbFGF21 administration effectively suppressed ventricular arrhythmias in post-infarcted hearts by regulating miR-143-EGR1-NaV1.5/Kir2.1 axis, which provides novel therapeutic strategies for ischemic arrhythmias in clinics.

Useful applications of growth factors for cardiovascular regenerative medicine

Novel advances for cardiovascular diseases (CVDs) include regenerative approaches for fibrosis, hypertrophy, and neoangiogenesis. Studies indicate that growth factor (GF) signaling could promote heart repair since most of the evidence is derived from preclinical models. Observational studies have evaluated GF serum/plasma levels as feasible biomarkers for risk stratification of CVDs. Noteworthy, two clinical interventional published studies showed that the administration of growth factors (GFs) induced beneficial effect on left ventricular ejection fraction (LVEF), myocardial perfusion, end-systolic volume index (ESVI). To date, large scale ongoing studies are in Phase I-II and mostly focussed on intramyocardial (IM), intracoronary (IC) or intravenous (IV) administration of vascular endothelial growth factor (VEGF) and fibroblast growth factor-23 (FGF-23) which result in the most investigated GFs in the last 10 years. Future data of ongoing randomized controlled studies will be crucial in understanding whether GF-based protocols could be in a concrete way effective in the clinical setting.

Crataegus Extract WS®1442 Stimulates Cardiomyogenesis and Angiogenesis From Stem Cells: A Possible New Pharmacology for Hawthorn?

Extracts from the leaves and flowers of Crataegus spp. (i.e., hawthorn species) have been traditionally used with documented preclinical and clinical activities in cardiovascular medicine. Based on reported positive effects on heart muscle after ischemic injury and the overall cardioprotective profile, the present study addressed potential contributions of Crataegus extracts to cardiopoietic differentiation from stem cells. The quantified Crataegus extract WS^®1442 stimulated cardiomyogenesis from murine and human embryonic stem cells (ESCs). Mechanistically, this effect was found to be induced by promoting differentiation of cardiovascular progenitor cell populations but not by proliferation. Bioassay-guided fractionation, phytochemical and analytical profiling suggested high-molecular weight ingredients as the active principle with at least part of the activity due to oligomeric procyanidines (OPCs) with a degree of polymerization between 3 and 6 (DP3–6). Transcriptome profiling in mESCs suggested two main, plausible mechanisms: These were early, stress-associated cellular events along with the modulation of distinct developmental pathways, including the upregulation of brain-derived neurotrophic factor (BDNF) and retinoic acid as well as the inhibition of transforming growth factor β/bone morphogenetic protein (TGFβ/BMP) and fibroblast growth factor (FGF) signaling. In addition, WS^®1442 stimulated angiogenesis ex vivo in Sca-1⁺ progenitor cells from adult mice hearts. These in vitro data provide evidence for a differentiation promoting activity of WS^®1442 on distinct cardiovascular stem/progenitor cells that could be valuable for therapeutic heart regeneration after myocardial infarction. However, the in vivo relevance of this new pharmacological activity of Crataegus spp. remains to be investigated and active ingredients from bioactive fractions will have to be further characterized.

Cardiac Differentiation of Adipose Tissue-Derived Stem Cells Is Driven by BMP4 and bFGF but Counteracted by 5-Azacytidine and Valproic Acid

Objective

Bone morphogenetic protein 4 (BMP4) and basic fibroblast growth factor (bFGF) play important roles in embryonic heart development. Also, two epigenetic modifying molecules, 5'-azacytidine (5'-Aza) and valproic acid (VPA) induce cardiomyogenesis in the infarcted heart. In this study, we first evaluated the role of BMP4 and bFGF in cardiac trans-differentiation and then the effectiveness of 5´-Aza and VPA in reprogramming and cardiac differentiation of human adipose tissue-derived stem cells (ADSCs).

Materials and Methods

In this experimental study, human ADSCs were isolated by collagenase I digestion. For cardiac differentiation, third to fifth-passaged ADSCs were treated with BMP4 alone or a combination of BMP4 and bFGF with or without 5'-Aza and VPA pre-treatment. After 21 days, the expression of cardiac-specific markers was evaluated by reverse transcription polymerase chain reaction (RT-PCR), quantitative real-time PCR, immunocytochemistry, flow cytometry and western blot analyses.

Results

BMP4 and more prominently a combination of BMP4 and bFGF induced cardiac differentiation of human ADSCs. Epigenetic modification of the ADSCs by 5'-Aza and VPA significantly upregulated the expression of OCT4A, SOX2, NANOG, Brachyury/T and GATA4 but downregulated GSC and NES mRNAs. Furthermore, pre-treatment with 5'-Aza and VPA upregulated the expression of TBX5, ANF, CX43 and CXCR4 mRNAs in three-week differentiated ADSCs but downregulated the expression of some cardiac-specific genes and decreased the population of cardiac troponin I-expressing cells.

Conclusion

Our findings demonstrated the inductive role of BMP4 and especially BMP4 and bFGF combination in cardiac trans-differentiation of human ADSCs. Treatment with 5'-Aza and VPA reprogrammed ADSCs toward a more pluripotent state and increased tendency of the ADSCs for mesodermal differentiation. Although pre-treatment with 5'-Aza and VPA counteracted the cardiogenic effects of BMP4 and bFGF, it may be in favor of migration, engraftment and survival of the ADSCs after transplantation.

Cardiac-mimetic cell-culture system for direct cardiac reprogramming

Rationale: Cardiovascular diseases often cause substantial heart damage and even heart failure due to the limited regenerative capacity of adult cardiomyocytes. The direct cardiac reprogramming of fibroblasts could be a promising therapeutic option for these patients. Although exogenous transcriptional factors can induce direct cardiac reprogramming, the reprogramming efficiency is too low to be used clinically. Herein, we introduce a cardiac-mimetic cell-culture system that resembles the microenvironment in the heart and provides interactions with cardiomyocytes and electrical cues to the cultured fibroblasts for direct cardiac reprogramming. Methods: Nano-thin and nano-porous membranes and heart like electric stimulus were used in the cardiac-mimetic cell-culture system. The human neonatal dermal fibroblasts containing cardiac transcription factors were plated on the membrane and cultured with the murine cardiomyocyte in the presence of the electric stimulus. The reprogramming efficiency was evaluated by qRT-PCR and immunocytochemistry. Results: Nano-thin and nano-porous membranes in the culture system facilitated interactions between fibroblasts and cardiomyocytes in coculture. The cellular interactions and electric stimulation supplied by the culture system dramatically enhanced the cardiac reprogramming efficiency of cardiac-specific transcriptional factor-transfected fibroblasts. Conclusion: The cardiac-mimetic culture system may serve as an effective tool for producing a feasible number of reprogrammed cardiomyocytes from fibroblasts.

Comparison of the Interactions of Different Growth Factors and Glycosaminoglycans

Most growth factors are naturally occurring proteins, which are signaling molecules implicated in cellular multiple functions such as proliferation, migration and differentiation under patho/physiological conditions by interacting with cell surface receptors and other ligands in the extracellular microenvironment. Many of the growth factors are heparin-binding proteins (HBPs) that have a high affinity for cell surface heparan sulfate proteoglycans (HSPG). In the present study, we report the binding kinetics and affinity of heparin interacting with different growth factors, including fibroblast growth factor (FGF) 2,7,10, hepatocyte growth factor (HGF) and transforming growth factor (TGF β-1), using a heparin chip. Surface plasmon resonance studies revealed that all the tested growth factors bind to heparin with high affinity (with K_D ranging from ~0.1 to 59 nM) and all the interactions are oligosaccharide size dependent except those involving TGF β-1. These heparin-binding growth factors also interact with other glycosaminoglycans (GAGs), as well as various chemically modified heparins. Other GAGs, including heparan sulfate, chondroitin sulfates A, B, C, D, E and keratan sulfate, showed different inhibition activities for the growth factor-heparin interactions. FGF2, FGF7, FGF10 and HGF bind heparin but the 2-O-sulfo and 6-O-sulfo groups on heparin have less impact on these interactions than do the N-sulfo groups. All the three sulfo groups (N-, 2-O and 6-O) on heparin are important for TGFβ-1-heparin interaction.