Cardiac matrix: a clue for future therapy

Investigation of crucial genes and mitochondrial function impairment in diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) is a special type of cardiovascular disease, termed as a situation of abnormal myocardial structure and function that occurs in diabetic patients. However, the most fundamental mechanisms of DCM have not been fully explicated, and useful targets for the therapeutic strategies still need to be explored.

METHODS

In the present study, we combined bioinformatics analysis and in vitro experiments throughout the process of DCM. Differentially Expressed Genes (DEGs) analysis was performed and the weighted gene co-expression network analysis (WGCNA) was constructed to determine the crucial genes that were tightly connected to DCM. Additionally, Functional enrichment analysis was conducted to define biological pathways. To identify the specific molecular mechanism, the human cardiomyocyte cell line (AC16) was stimulated by high glucose (HG, 50 mM D-glucose) and used to imitate DCM condition. Then, we tentatively examined the effect of high glucose on cardiomyocytes, the expression levels of crucial genes were further validated by in vitro experiments.

RESULTS

Generally, NPPA, IGFBP5, SERPINE1, and C3 emerged as potential therapeutic targets. Functional enrichment analysis performed by bioinformatics indicated that the pathogenesis of DCM is mainly related to heart muscle contraction and calcium (Ca2+) release activation. In vitro, we discovered that high glucose treatment induced cardiomyocyte injury and exacerbated mitochondrial dysfunction remarkably.

CONCLUSION

Our research defined four crucial genes, as well as determined that mitochondrial function impairment compromises calcium homeostasis ultimately resulting in contractile dysfunction is a central contributor to DCM progression. Hopefully, this study will offer more effective biomarkers for DCM diagnosis and treatment.

Estimating the impact of drug addiction causes heart damage

To date, few studies have investigated the toxicological effects of the combined use of amphetamine and heroin in the heart. Hence, the aim of this study was to identify indicators for clinical evaluation and prevention of cardiac injury induced by the combined use of amphetamine and heroin. Four different groups were analyzed: (1) normal group (n＝25；average age＝35 ± 6.8); (2) heart disease group (n＝25；average age＝58 ± 17.2); (3) drug abusers (n = 27; average age = 37 ± 7.7); (4) drug abstainers (previous amphetamine-heroin users who had been drug-free for more than two weeks; n = 22; average age = 35 ± 5.6). The activity of MMPs, and levels of TNF-α, IL-6, GH, IGF-I, and several serum biomarkers were examined to evaluate the impact of drug abuse on the heart. The selected plasma biomarkers and classic cardiac biomarkers were significantly increased compared to the normal group. The zymography data showed the changes in cardiac-remodeling enzymes MMP-9 and MMP-2 among combined users of amphetamine and heroin. The levels of TNF-α and IL-6 only increased in the heart disease group. Growth hormone was increased; however, IGF-I level decreased with drug abuse and the level was not restored by abstinence. We speculated that the amphetamine-heroin users might pose risk to initiate heart disease even though the users abstained for more than two weeks. The activity change of MMP-9 and MMP-2 can be a direct reason affecting heart function. The indirect reason may be related to liver damage by drug abuse reduce IGF-1 production to protect heart function.

Role of ADMA in the pathogenesis of microvascular complications in type 2 diabetes mellitus

Diabetic microangiopathy is a typical and severe problem in diabetics, including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, and diabetic cardiomyopathy. Patients with type 2 diabetes and diabetic microvascular complications have significantly elevated levels of Asymmetric dimethylarginine (ADMA), which is an endogenous inhibitor of nitric oxide synthase (NOS). ADMA facilitates the occurrence and progression of microvascular complications in type 2 diabetes through its effects on endothelial cell function, oxidative stress damage, inflammation, and fibrosis. This paper reviews the association between ADMA and microvascular complications of diabetes and elucidates the underlying mechanisms by which ADMA contributes to these complications. It provides a new idea and method for the prevention and treatment of microvascular complications in type 2 diabetes.

Proteomic Analysis of Estrogen-Mediated Enhancement of Mesenchymal Stem Cell-Induced Angiogenesis In Vivo

Therapeutic use of mesenchymal stem cells (MSCs) for tissue repair has great potential. MSCs from multiple sources, including those derived from human umbilical matrix, namely Wharton’s jelly, may serve as a resource for obtaining MSCs. However, low in vivo engraftment efficacy of MSCs remains a challenging limitation. To improve clinical outcomes using MSCs, an in-depth understanding of the mechanisms and factors involved in successful engraftment is required. We recently demonstrated that 17β-estradiol (E2) improves MSCs in vitro proliferation, directed migration and engraftment in murine heart slices. Here, using a proteomics approach, we investigated the angiogenic potential of MSCs in vivo and the modulatory actions of E2 on mechanisms involved in tissue repair. Specifically, using a Matrigel^® plug assay, we evaluated the effects of E2 on MSCs-induced angiogenesis in ovariectomized (OVX) mice. Moreover, using proteomics we investigated the potential pro-repair processes, pathways, and co-mechanisms possibly modified by the treatment of MSCs with E2. Using RT-qPCR, we evaluated mRNA expression of pro-angiogenic molecules, including endoglin, Tie-2, ANG, and VEGF. Hemoglobin levels, a marker for blood vessel formation, were increased in plugs treated with E2 + MSCs, suggesting increased capillary formation. This conclusion was confirmed by the histological analysis of capillary numbers in the Matrigel^® plugs treated with E2 + MSC. The LC-MS screening of proteins obtained from the excised Matrigel^® plugs revealed 71 proteins that were significantly altered following E2 exposure, 57 up-regulated proteins and 14 down-regulated proteins. A major result was the association of over 100 microRNA molecules (miRNAs) involved in cellular communication, vesicle transport, and metabolic and energy processes, and the high percentage of approximately 25% of genes involved in unknown biological processes. Together, these data provide evidence for increased angiogenesis by MSCs treated with the sex hormone E2. In conclusion, E2 treatment may increase the engraftment and repair potential of MSCs into tissue, and may promote MSC-induced angiogenesis after tissue injury.

The Diabetic Cardiomyopathy: The Contributing Pathophysiological Mechanisms

Individuals with diabetes mellitus (DM) disclose a higher incidence and a poorer prognosis of heart failure (HF) than non-diabetic people, even in the absence of other HF risk factors. The adverse impact of diabetes on HF likely reflects an underlying “diabetic cardiomyopathy” (DM–CMP), which may by exacerbated by left ventricular hypertrophy and coronary artery disease (CAD). The pathogenesis of DM-CMP has been a hot topic of research since its first description and is still under active investigation, as a complex interplay among multiple mechanisms may play a role at systemic, myocardial, and cellular/molecular levels. Among these, metabolic abnormalities such as lipotoxicity and glucotoxicity, mitochondrial damage and dysfunction, oxidative stress, abnormal calcium signaling, inflammation, epigenetic factors, and others. These disturbances predispose the diabetic heart to extracellular remodeling and hypertrophy, thus leading to left ventricular diastolic and systolic dysfunction. This Review aims to outline the major pathophysiological changes and the underlying mechanisms leading to myocardial remodeling and cardiac functional derangement in DM-CMP.

The Microenvironment of Decellularized Extracellular Matrix from Heart Failure Myocardium Alters the Balance between Angiogenic and Fibrotic Signals from Stromal Primitive Cells

Cardiac adverse remodeling is characterized by biological changes that affect the composition and architecture of the extracellular matrix (ECM). The consequently disrupted signaling can interfere with the balance between cardiogenic and pro-fibrotic phenotype of resident cardiac stromal primitive cells (CPCs). The latter are important players in cardiac homeostasis and can be exploited as therapeutic cells in regenerative medicine. Our aim was to compare the effects of human decellularized native ECM from normal (dECM-NH) or failing hearts (dECM-PH) on human CPCs. CPCs were cultured on dECM sections and characterized for gene expression, immunofluorescence, and paracrine profiles. When cultured on dECM-NH, CPCs significantly upregulated cardiac commitment markers (CX43, NKX2.5), cardioprotective cytokines (bFGF, HGF), and the angiogenesis mediator, NO. When seeded on dECM-PH, instead, CPCs upregulated pro-remodeling cytokines (IGF-2, PDGF-AA, TGF-β) and the oxidative stress molecule H₂O₂. Interestingly, culture on dECM-PH was associated with impaired paracrine support to angiogenesis, and increased expression of the vascular endothelial growth factor (VEGF)-sequestering decoy isoform of the KDR/VEGFR2 receptor. Our results suggest that resident CPCs exposed to the pathological microenvironment of remodeling ECM partially lose their paracrine angiogenic properties and release more pro-fibrotic cytokines. These observations shed novel insights on the crosstalk between ECM and stromal CPCs, suggesting also a cautious use of non-healthy decellularized myocardium for cardiac tissue engineering approaches.

Mechanisms of diabetic cardiomyopathy and potential therapeutic strategies: preclinical and clinical evidence

The pathogenesis and clinical features of diabetic cardiomyopathy have been well-studied in the past decade, but effective approaches to prevent and treat this disease are limited. Diabetic cardiomyopathy occurs as a result of the dysregulated glucose and lipid metabolism associated with diabetes mellitus, which leads to increased oxidative stress and the activation of multiple inflammatory pathways that mediate cellular and extracellular injury, pathological cardiac remodelling, and diastolic and systolic dysfunction. Preclinical studies in animal models of diabetes have identified multiple intracellular pathways involved in the pathogenesis of diabetic cardiomyopathy and potential cardioprotective strategies to prevent and treat the disease, including antifibrotic agents, anti-inflammatory agents and antioxidants. Some of these interventions have been tested in clinical trials and have shown favourable initial results. In this Review, we discuss the mechanisms underlying the development of diabetic cardiomyopathy and heart failure in type 1 and type 2 diabetes mellitus, and we summarize the evidence from preclinical and clinical studies that might provide guidance for the development of targeted strategies. We also highlight some of the novel pharmacological therapeutic strategies for the treatment and prevention of diabetic cardiomyopathy.

Micromechanobiology: Focusing on the Cardiac Cell-Substrate Interface

Engineered, in vitro cardiac cell and tissue systems provide test beds for the study of cardiac development, cellular disease processes, and drug responses in a dish. Much effort has focused on improving the structure and function of engineered cardiomyocytes and heart tissues. However, these parameters depend critically on signaling through the cellular microenvironment in terms of ligand composition, matrix stiffness, and substrate mechanical properties-that is, matrix micromechanobiology. To facilitate improvements to in vitro microenvironment design, we review how cardiomyocytes and their microenvironment change during development and disease in terms of integrin expression and extracellular matrix (ECM) composition. We also discuss strategies used to bind proteins to common mechanobiology platforms and describe important differences in binding strength to the substrate. Finally, we review example biomaterial approaches designed to support and probe cell-ECM interactions of cardiomyocytes in vitro, as well as open questions and challenges.

MMP9 mediates acute hyperglycemia-induced human cardiac stem cell death by upregulating apoptosis and pyroptosis in vitro

Providing a conducive microenvironment is critical to increase survival of transplanted stem cells in regenerative therapy. Hyperglycemia promotes stem cell death impairing cardiac regeneration in the diabetic heart. Understanding the molecular mechanisms of high glucose-induced stem cell death is important for improving cardiac regeneration in diabetic patients. Matrix metalloproteinase-9 (MMP9), a collagenase, is upregulated in the diabetic heart, and ablation of MMP9 decreases infarct size in the non-diabetic myocardial infarction heart. In the present study, we aim to investigate whether MMP9 is a mediator of hyperglycemia-induced cell death in human cardiac stem cells (hCSCs) in vitro. We created MMP9^−/− hCSCs to test the hypothesis that MMP9 mediates hyperglycemia-induced oxidative stress and cell death via apoptosis and pyroptosis in hCSCs, which is attenuated by the lack of MMP9. We found that hyperglycemia induced oxidative stress and increased cell death by promoting pyroptosis and apoptosis in hCSCs, which was prevented in MMP9^−/− hCSCs. These findings revealed a novel intracellular role of MMP9 in mediating stem cell death and provide a platform to assess whether MMP9 inhibition could improve hCSCs survival in stem cell therapy at least in acute hyperglycemic microenvironment.

Insulin-like growth factor-1 short-period therapy improves cardiomyopathy stimulating cardiac progenitor cells survival in obese mice

BACKGROUND AND AIMS

Cardiovascular diseases are the main cause of mortality in obesity. Despite advanced understanding, the mechanisms that regulate cardiac progenitor cells (CPC) survival in pathological conditions are not clear. Low IGF-1 plasma levels are correlated to obesity, cardiomyopathy and CPC death, so this work aimed to investigate IGF-1 therapeutic potential on cardiomyopathy and its relationship with the survival, proliferation and differentiation of CPC in Western diet-induced obesity.

METHODS AND RESULTS

Male Swiss mice were divided into control group (CG, n = 8), fed with standard diet; and obese group (OG, n = 16), fed with Western diet, for 12 weeks. At 11th week, OG was subdivided to receive a daily subcutaneous injection of human recombinant IGF-1 (100 μg.Kg^-1) for seven consecutive days (OG + IGF1, n = 8). Results showed that IGF-1 therapy improved the metabolic parameters negatively impacted by western diet in OG, reaching levels similar to CG. OG + IGF-1 also demonstrated restored heart energetic metabolism, fibrosis resolution, decreased apoptosis level, restored cardiac gap junctions and intracellular calcium balance. Cardiomyopathy improvement was accompanied by increased CPC survival, proliferation and newly cardiomyocytes formation related to increased pAkt/Akt ratio.

CONCLUSION

These results suggest that only one week of IGF-1 therapy has cardioprotective effects through Akt pathway upregulation, ensuring CPC survival and differentiation, contributing to heart failure rescue.

Extracellular Matrix in Regulation of Contractile System in Cardiomyocytes

The contractile apparatus of cardiomyocytes is considered to be a stable system. However, it undergoes strong rearrangements during heart development as cells progress from their non-muscle precursors. Long-term culturing of mature cardiomyocytes is also accompanied by the reorganization of their contractile apparatus with the conversion of typical myofibrils into structures of non-muscle type. Processes of heart development as well as cell adaptation to culture conditions in cardiomyocytes both involve extracellular matrix changes, which appear to be crucial for the maturation of contractile apparatus. The aim of this review is to analyze the role of extracellular matrix in the regulation of contractile system dynamics in cardiomyocytes. Here, the remodeling of actin contractile structures and the expression of actin isoforms in cardiomyocytes during differentiation and adaptation to the culture system are described along with the extracellular matrix alterations. The data supporting the regulation of actin dynamics by extracellular matrix are highlighted and the possible mechanisms of such regulation are discussed.

Hyperhomocysteinemia and myocardial remodeling in the sand rat, Psammomys obesus

OBJECTIVE

Numerous studies have shown that a methionine-rich diet induces hyperhomocysteinemia (Hhcy), a risk factor for cardiovascular diseases. The objective of the present study was to determine the involvement of Hhcy in cardiac remodeling in the sand rat Psammomys obesus.

MATERIALS AND METHODS

An experimental Hhcy was induced, in the sand rat Psammomys obesus, by intraperitoneal injection of 300 mg/kg of body weight/day of methionine for 1 month. The impact of Hhcy on the cellular and matricial structures of the myocardium was analyzed with histological techniques (Masson trichrome and Sirius red staining). Immunohistochemistry allowed us to analyze several factors involved in myocardial remodeling, such as fibrillar collagen I and III, metalloproteases (MMP-2 and -9) and their inhibitors (TIMP-1 and -2), TGF-β1 and activated caspase 3.

RESULTS

Our results show that Hhcy induced by an excess of methionine causes, in the myocardium of Psammomys obesus, a significant accumulation of fibrillar collagens I and III at the interstitial and perivascular scales, indicating the appearance of fibrosis, which is associated with an immuno-expression increase of TGF-β1, MMP-9 and TIMP-2 and an immuno-expression decrease of MMP-2 and TIMP-1. Also, Hhcy induces apoptosis of some cardiomyocytes and cardiac fibroblasts by increasing of activated caspase 3 expression. These results highlight a remodeling of cardiac tissue in hyperhomocysteinemic Psammomys obesus.

Intermittent hypoxia induces beneficial cardiovascular remodeling in left ventricular function of type 1 diabetic rat

OBJECTIVE

Depressed mechanical activity is a marked complication in diabetics. Hypoxia has properties for novel diagnostic and therapeutic strategies, while intermittent hypoxia (IH) provides early functional and histologic remodeling, including some cardio benefits in early hemodynamic alterations with histologic remodeling and delayed changes in peripheral vasoreactivity. Therefore, we aimed to examine whether IH application presents a cardioprotective effect, via stabilization of hypoxia-inducible factor (HIF) in streptozotocin (STZ)-induced diabetic rat heart.

METHODS

Male 10-week-old Wistar rats were randomly assigned as control group (C), IH group, (STZ)-induced diabetic group (DM) and IH applied DM group (DM+IH). Diabetes duration was kept 6 weeks and IH groups were exposed to hypobaric hypoxia at about 70 kPa (including ~14% PO2; 6 h/day for 6-weeks).

RESULTS

Depressed left ventricular developed pressure (LVDP) and prolonged contraction and relaxation of Langendorff-perfused hearts, as well as increased total oxidative status from streptozotocin (STZ)-induced diabetic rats were markedly prevented with IH application. IH application induced significant increase in protein expression levels of both HIF-1α and vascular endothelial growth factor (VEGF), in both control and diabetic rat hearts, whereas there were significant decreases in the protein levels of prolyl-4 hydroxylase domain enzymes, PHD2, and PHD3 in diabetic hearts. Furthermore, IH application induced marked increases in protein levels of matrix metalloproteinases, MMP-2 and MMP-9 and capillary density in left ventricle of diabetic rats.

CONCLUSION

Overall, we presented how IH application has a beneficial cardiovascular remodeling effect in left ventricular function of diabetic rats, at most, via affecting increased oxidative stress and HIF-VEGF related angiogenesis, providing information on hyperglycemia associated new targets and therapeutic strategies.

Decellularized Extracellular Matrix Materials for Cardiac Repair and Regeneration

Decellularized extracellular matrix (dECM) is a promising biomaterial for repairing cardiovascular tissue, as dECM most effectively captures the complex array of proteins, glycosaminoglycans, proteoglycans, and many other matrix components that are found in native tissue, providing ideal cues for regeneration and repair of damaged myocardium. dECM can be used in a variety of forms, such as solid scaffolds that maintain native matrix structure, or as soluble materials that can form injectable hydrogels for tissue repair. dECM has found recent success in many regeneration and repair therapies, such as for musculoskeletal, neural, and liver tissues. This review focuses on dECM in the context of cardiovascular applications, with variations in tissue and species sourcing, and specifically discusses advances in solid and soluble dECM development, in vitro studies, in vivo implementation, and clinical translation.

The Role of Osteoprotegerin and Its Ligands in Vascular Function

The superfamily of tumor necrosis factor (TNF) receptors includes osteoprotegerin (OPG) and its ligands, which are receptor activators of nuclear factor kappa-B ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL). The OPG/RANKL/RANK system plays an active role in pathological angiogenesis and inflammation as well as cell survival. It has been demonstrated that there is crosstalk between endothelial cells and osteoblasts during osteogenesis, thus establishing a connection between angiogenesis and osteogenesis. This OPG/RANKL/RANK/TRAIL system acts on specific cell surface receptors, which are then able to transmit their signals to other intracellular components and modify gene expression. Cytokine production and activation of their receptors induce mechanisms to recruit monocytes and neutrophils as well as endothelial cells. Data support the role of an increased OPG/RANKL ratio as a possible marker of progression of endothelial dysfunction in metabolic disorders in relationship with inflammatory marker levels. We review the role of the OPG/RANKL/RANK triad in vascular function as well as molecular mechanisms related to the etiology of vascular diseases. The potential therapeutic strategies may be very promising in the future.

A New Era of Cardiac Cell Therapy: Opportunities and Challenges

Myocardial infarction (MI), caused by coronary heart disease (CHD), remains one of the most common causes of death in the United States. Over the last few decades, scientists have invested considerable resources on the study and development of cell therapies for myocardial regeneration after MI. However, due to a number of limitations, they are not yet readily available for clinical applications. Mounting evidence supports the theory that paracrine products are the main contributors to the regenerative effects attributed to these cell therapies. The next generation of cell-based MI therapies will identify and isolate cell products and derivatives, integrate them with biocompatible materials and technologies, and use them for the regeneration of damaged myocardial tissue. This review discusses the progress made thus far in pursuit of this new generation of cell therapies. Their fundamental regenerative mechanisms, their potential to combine with other therapeutic products, and their role in shaping new clinical approaches for heart tissue engineering, are addressed.

TFAM overexpression reduces pathological cardiac remodeling

Heart failure (HF) is a functional lack of myocardial performance due to a loss of molecular control over increases in calcium and ROS, resulting in proteolytic degradative advances and cardiac remodeling. Mitochondria are the molecular powerhouse of cells, shifting the sphere of cardiomyocyte stability and performance. Functional mitochondria rely on the molecular abilities of safety factors such as TFAM to maintain physiological parameters. Mitochondrial transcription factor A (TFAM) creates a mitochondrial nucleoid structure around mtDNA, protecting it from mutation, inhibiting NFAT (ROS activator/hypertrophic stimulator), and transcriptionally activates Serca2a to decrease calcium mishandling. Calpain1 and MMP9 are proteolytic degratory factors that play a major role in cardiomyocyte decline in HF. Current literature depicts major decreases in TFAM as HF progresses. We aim to assess TFAM function against Calpain1 and MMP9 proteolytic activity and its role in cardiac remodeling. To this date, no publication has surfaced describing the effects of aortic banding (AB) as a surgical HF model in TFAM-TG mice. HF models were created via AB in TFAM transgenic (TFAM-TG) and C57BLJ-6 (WT) mice. Eight weeks post AB, functional analysis revealed a successful banding procedure, resulting in cardiac hypertrophy as observed via echocardiography. Pulse wave and color doppler show increased aortic flow rates as well as turbulent flow at the banding site. Preliminary results of cardiac tissue immuno-histochemistry of HF-control mice show decreased TFAM and compensatory increases in Serca2a fluorescent expression, along with increased Calpain1 and MMP9 expression. Protein, RNA, and IHC analysis will further assess TFAM-TG results post-banding. Echocardiography shows more cardiac stability and functionality in HF-induced TFAM-TG mice than the control counterpart. These findings complement our published in vitro results. Overall, this suggests that TFAM has molecular therapeutic potential to reduce protease expression.

Intermittent Hypoxia Mimicking Sleep Apnea Increases Passive Stiffness of Myocardial Extracellular Matrix. A Multiscale Study

Background: Tissue hypoxia-reoxygenation characterizes obstructive sleep apnea (OSA), a very prevalent respiratory disease associated with increased cardiovascular morbidity and mortality. Experimental studies indicate that intermittent hypoxia (IH) mimicking OSA induces oxidative stress and inflammation in heart tissue at the cell and molecular levels. However, it remains unclear whether IH modifies the passive stiffness of the cardiac tissue extracellular matrix (ECM). Aim: To investigate multiscale changes of stiffness induced by chronic IH in the ECM of left ventricular (LV) myocardium in a murine model of OSA. Methods: Two-month and 18-month old mice (N = 10 each) were subjected to IH (20% O₂ 40 s-6% O₂ 20 s) for 6 weeks (6 h/day). Corresponding control groups for each age were kept under normoxia. Fresh LV myocardial strips (∼7 mm × 1 mm × 1 mm) were prepared, and their ECM was obtained by decellularization. Myocardium ECM macroscale mechanics were measured by performing uniaxial stress-strain tensile tests. Strip macroscale stiffness was assessed as the stress value (σ) measured at 0.2 strain and Young's modulus (E_M) computed at 0.2 strain by fitting Fung's constitutive model to the stress-strain relationship. ECM stiffness was characterized at the microscale as the Young's modulus (E_m) measured in decellularized tissue slices (∼12 μm tick) by atomic force microscopy. Results: Intermittent hypoxia induced a ∼1.5-fold increase in σ (p < 0.001) and a ∼2.5-fold increase in E_M (p < 0.001) of young mice as compared with normoxic controls. In contrast, no significant differences emerged in E_m among IH-exposed and normoxic mice. Moreover, the mechanical effects of IH on myocardial ECM were similar in young and aged mice. Conclusion: The marked IH-induced increases in macroscale stiffness of LV myocardium ECM suggests that the ECM plays a role in the cardiac dysfunction induced by OSA. Furthermore, absence of any significant effects of IH on the microscale ECM stiffness suggests that the significant increases in macroscale stiffening are primarily mediated by 3D structural ECM remodeling.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Targeting miRNA for Therapy of Juvenile and Adult Diabetic Cardiomyopathy

Prevalence of diabetes mellitus (DM), a multifactorial disease often diagnosed with high blood glucose levels, is rapidly increasing in the world. Association of DM with multi-organ dysfunction including cardiomyopathy makes it a leading cause of morbidity and mortality. There are two major types of DM: type 1 DM (T1D) and type 2 DM (T2D). T1D is diagnosed by reduced levels of insulin and high levels of glucose in the blood. It is caused due to pancreatic beta cell destruction/loss, and mostly found in juveniles (juvenile DM). T2D is diagnosed by increased levels of insulin and glucose in the blood. It is caused due to insulin receptor dysfunction, and mostly found in the adults (adult DM). Both T1D and T2D impair cardiac muscle function, which is referred to as diabetic cardiomyopathy. We and others have reported that miRNAs, a novel class of tiny non-coding regulatory RNAs, are differentially expressed in the diabetic heart and they contribute to diabetic cardiomyopathy. Here, we elaborated the biogenesis of miRNA, how miRNA regulates a gene, cardioprotective roles of different miRNAs including miRNAs present in exosomes, underlying molecular mechanisms by which miRNA ameliorates diabetic cardiomyopathy, and the role of miRNA as a potential therapeutic target for juvenile and adult diabetic cardiomyopathy.

Dihydrotestosterone induces pro-angiogenic factors and assists homing of MSC into the cardiac tissue

The use of mesenchymal stem cells (MSC) as a therapeutic tool in cardiovascular diseases is promising. Since androgens exert some beneficial actions on the cardiovascular system, we tested our hypothesis that this hormone could promote MSC-mediated repair processes, also. Cultured MSCs isolated from Wharton's jelly were exposed to 30 nM dihydrotestosterone (DHT) for 1 or 4 days and the effects of the hormone on their growth/migration/adhesion and the underlying mechanisms were assessed. Results were obtained by real-time cell impedance measurements, and DNA quantification showed that DHT increased MSC proliferation by ~30%. As determined by xCELLigence system, DHT augmented (~2 folds) the migration of MSC toward cardiac tissue slices (at 12 h), and this effect was blocked by flutamide, an androgen receptor (AR) antagonist. Exposure of cells to DHT, upregulated the gene and protein expression of AR, EMMPRIN and MMP-9 and downregulated the expression of MMP-2 DHT significantly induced the release of nitric oxide by MSC (≥2-fold) and flutamide blocked this effect. When MSCs were co-cultured with cardiac slices, immunohistochemical analysis and qRT-PCR showed that the integration of DHT-stimulated MSC was significantly higher than that of in controls. In conclusion, our findings provide the first evidence that DHT promotes MSC growth, migration and integration into the cardiac slices. The modulating effects of DHT were associated with upregulation of ARs and of key molecules known to promote tissue remodeling and angiogenesis. Our findings suggest that priming of MSC with DHT may potentially increase their capability to regenerate cardiac tissue; in vivo studies are needed to confirm our in vitro findings.

Stem Cell-Derived Exosomes, Autophagy, Extracellular Matrix Turnover, and miRNAs in Cardiac Regeneration during Stem Cell Therapy

Stem cell therapy (SCT) raises the hope for cardiac regeneration in ischemic hearts. However, underlying molecular mechanisms for repair of dead myocardium by SCT in the ischemic heart is poorly understood. Growing evidences suggest that cardiac matrix stiffness and differential expressions of miRNAs play a crucial role in stem cell survival and differentiation. However, their roles on transplanted stem cells, for myocardial repair of the ischemic heart, remain unclear. Transplanted stem cells may act in an autocrine and/or paracrine manner to regenerate the dead myocardium. Paracrine mediators such as stem cell-derived exosomes are emerging as a novel therapeutic strategy to overcome some of the limitations of SCT. These exosomes carry microRNAs (miRNAs) that may regulate stem cell differentiation into a specific lineage. MicroRNAs may also contribute to stiffness of surrounding matrix by regulating extracellular matrix (ECM) turnover. The survival of transplanted stem cell depends on its autophagic process that maintains cellular homeostasis. Therefore, exosomes, miRNAs, extracellular matrix turnover, and autophagy may have an integral role in improving the efficacy of SCT. This review elaborates the specific roles of these regulatory components on cardiac regeneration in the ischemic heart during SCT.

Sphingosine 1-Phosphate Receptors: Do They Have a Therapeutic Potential in Cardiac Fibrosis?

Sphingosine 1-phosphate (S1P) is a bioactive lipid that is characterized by a peculiar mechanism of action. In fact, S1P, which is produced inside the cell, can act as an intracellular mediator, whereas after its export outside the cell, it can act as ligand of specific G-protein coupled receptors, which were initially named endothelial differentiation gene (Edg) and eventually renamed sphingosine 1-phosphate receptors (S1PRs). Among the five S1PR subtypes, S1PR1, S1PR2 and S1PR3 isoforms show broad tissue gene expression, while S1PR4 is primarily expressed in immune system cells, and S1PR5 is expressed in the central nervous system. There is accumulating evidence for the important role of S1P as a mediator of many processes, such as angiogenesis, carcinogenesis and immunity, and, ultimately, fibrosis. After a tissue injury, the imbalance between the production of extracellular matrix (ECM) and its degradation, which occurs due to chronic inflammatory conditions, leads to an accumulation of ECM and, consequential, organ dysfunction. In these pathological conditions, many factors have been described to act as pro- and anti-fibrotic agents, including S1P. This bioactive lipid exhibits both pro- and anti-fibrotic effects, depending on its site of action. In this review, after a brief description of sphingolipid metabolism and signaling, we emphasize the involvement of the S1P/S1PR axis and the downstream signaling pathways in the development of fibrosis. The current knowledge of the therapeutic potential of S1PR subtype modulators in the treatment of the cardiac functions and fibrinogenesis are also examined.

Naturally Engineered Maturation of Cardiomyocytes

Ischemic heart disease remains one of the most prominent causes of mortalities worldwide with heart transplantation being the gold-standard treatment option. However, due to the major limitations associated with heart transplants, such as an inadequate supply and heart rejection, there remains a significant clinical need for a viable cardiac regenerative therapy to restore native myocardial function. Over the course of the previous several decades, researchers have made prominent advances in the field of cardiac regeneration with the creation of in vitro human pluripotent stem cell-derived cardiomyocyte tissue engineered constructs. However, these engineered constructs exhibit a functionally immature, disorganized, fetal-like phenotype that is not equivalent physiologically to native adult cardiac tissue. Due to this major limitation, many recent studies have investigated approaches to improve pluripotent stem cell-derived cardiomyocyte maturation to close this large functionality gap between engineered and native cardiac tissue. This review integrates the natural developmental mechanisms of cardiomyocyte structural and functional maturation. The variety of ways researchers have attempted to improve cardiomyocyte maturation in vitro by mimicking natural development, known as natural engineering, is readily discussed. The main focus of this review involves the synergistic role of electrical and mechanical stimulation, extracellular matrix interactions, and non-cardiomyocyte interactions in facilitating cardiomyocyte maturation. Overall, even with these current natural engineering approaches, pluripotent stem cell-derived cardiomyocytes within three-dimensional engineered heart tissue still remain mostly within the early to late fetal stages of cardiomyocyte maturity. Therefore, although the end goal is to achieve adult phenotypic maturity, more emphasis must be placed on elucidating how the in vivo fetal microenvironment drives cardiomyocyte maturation. This information can then be utilized to develop natural engineering approaches that can emulate this fetal microenvironment and thus make prominent progress in pluripotent stem cell-derived maturity toward a more clinically relevant model for cardiac regeneration.

Current Understanding of the Pathophysiology of Myocardial Fibrosis and Its Quantitative Assessment in Heart Failure

Myocardial fibrosis is an important part of cardiac remodeling that leads to heart failure and death. Myocardial fibrosis results from increased myofibroblast activity and excessive extracellular matrix deposition. Various cells and molecules are involved in this process, providing targets for potential drug therapies. Currently, the main detection methods of myocardial fibrosis rely on serum markers, cardiac magnetic resonance imaging, and endomyocardial biopsy. This review summarizes our current knowledge regarding the pathophysiology, quantitative assessment, and novel therapeutic strategies of myocardial fibrosis.

Pathophysiological Fundamentals of Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) was first recognized more than four decades ago and occurred independent of cardiovascular diseases or hypertension in both type 1 and type 2 diabetic patients. The exact mechanisms underlying this disease remain incompletely understood. Several pathophysiological bases responsible for DCM have been proposed, including the presence of hyperglycemia, nonenzymatic glycosylation of large molecules (e.g., proteins), energy metabolic disturbance, mitochondrial damage and dysfunction, impaired calcium handling, reactive oxygen species formation, inflammation, cardiac cell death, and cardiac hypertrophy and fibrosis, leading to impairment of cardiac contractile functions. Increasing evidence also indicates the phenomenon called "metabolic memory" for diabetes-induced cardiovascular complications, for which epigenetic modulation seemed to play an important role, suggesting that the aforementioned pathogenic bases may be regulated by epigenetic modification. Therefore, this review aims at briefly summarizing the current understanding of the pathophysiological bases for DCM. Although how epigenetic mechanisms play a role remains incompletely understood now, extensive clinical and experimental studies have implicated its importance in regulating the cardiac responses to diabetes, which are believed to shed insight into understanding of the pathophysiological and epigenetic mechanisms for the development of DCM and its possible prevention and/or therapy. © 2017 American Physiological Society. Compr Physiol 7:693-711, 2017.

Role of microRNA in metabolic shift during heart failure

Heart failure (HF) is an end point resulting from a number of disease states. The prognosis for HF patients is poor with survival rates precipitously low. Energy metabolism is centrally linked to the development of HF, and it involves the proteomic remodeling of numerous pathways, many of which are targeted to the mitochondrion. microRNAs (miRNA) are noncoding RNAs that influence posttranscriptional gene regulation. miRNA have garnered considerable attention for their ability to orchestrate changes to the transcriptome, and ultimately the proteome, during HF. Recently, interest in the role played by miRNA in the regulation of energy metabolism at the mitochondrion has emerged. Cardiac proteome remodeling during HF includes axes impacting hypertrophy, oxidative stress, calcium homeostasis, and metabolic fuel transition. Although it is established that the pathological environment of hypoxia and hemodynamic stress significantly contribute to the HF phenotype, it remains unclear as to the mechanistic underpinnings driving proteome remodeling. The aim of this review is to present evidence highlighting the role played by miRNA in these processes as a means for linking pathological stimuli with proteomic alteration. The differential expression of proteins of substrate transport, glycolysis, β-oxidation, ketone metabolism, the citric acid cycle (CAC), and the electron transport chain (ETC) are paralleled by the differential expression of miRNA species that modulate these processes. Identification of miRNAs that translocate to cardiomyocyte mitochondria (miR-181c, miR-378) influencing the expression of the mitochondrial genome-encoded transcripts as well as suggested import modulators are discussed. Current insights, applications, and challenges of miRNA-based therapeutics are also described.

Reversal of Phospholamban Inhibition of the Sarco(endo)plasmic Reticulum Ca2+-ATPase (SERCA) Using Short, Protein-interacting RNAs and Oligonucleotide Analogs

The sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) and phospholamban (PLN) complex regulates heart relaxation through its removal of cytosolic Ca²⁺ during diastole. Dysfunction of this complex has been related to many heart disorders and is therefore a key pharmacological target. There are currently no therapeutics that directly target either SERCA or PLN. It has been previously reported that single-stranded DNA binds PLN with strong affinity and relieves inhibition of SERCA in a length-dependent manner. In the current article, we demonstrate that RNAs and single-stranded oligonucleotide analogs, or xeno nucleic acids (XNAs), also bind PLN strongly (K_d <10 nm) and relieve inhibition of SERCA. Affinity for PLN is sequence-independent. Relief of PLN inhibition is length-dependent, allowing SERCA activity to be restored incrementally. The improved in vivo stability of XNAs offers more realistic pharmacological potential than DNA or RNA. We also found that microRNAs (miRNAs) 1 and 21 bind PLN strongly and relieve PLN inhibition of SERCA to a greater extent than a similar length random sequence RNA mixture. This may suggest that miR-1 and miR-21 have evolved to contain distinct sequence elements that are more effective at relieving PLN inhibition than random sequences.

Effects of Matrix Metalloproteinases on the Performance of Platelet Fibrin Gel Spiked With Cardiac Stem Cells in Heart Repair

Stem cells and biomaterials have been studied for therapeutic cardiac repair. Previous studies have shown the beneficial effects of platelet fibrin gel and cardiac stem cells when cotransplanted into rodent hearts with myocardial infarction (MI). We hypothesized that matrix metalloproteinases (MMPs) play an important role in such protection. Thus, the present study is designed to elucidate the effects of MMP inhibition on the therapeutic benefits of intramyocardial injection of platelet fibrin gel spiked with cardiac stem cells (cell-gel) in a rat model of acute MI. In vitro, broad-spectrum MMP inhibitor GM6001 undermines cell spreading and cardiomyocyte contraction. In a syngeneic rat model of myocardial infarction, MMP inhibition blunted the recruitment of endogenous cardiovascular cells into the injected biomaterials, therefore hindering de novo angiogenesis and cardiomyogenesis. Echocardiography and histology 3 weeks after treatment revealed that metalloproteinase inhibition diminished the functional and structural benefits of cell-gel in treating MI. Reduction of host angiogenesis, cardiomyocyte cycling, and MMP-2 activities was evident in animals treated with GM6001. Our findings suggest that MMPs play a critical role in the therapeutic benefits of platelet fibrin gel spiked with cardiac stem cells for treating MI.

SIGNIFICANCE

In this study, the effects of matrix metalloproteinase inhibition on the performance of platelet gel spiked with cardiac stem cells (cell-gel) for heart regeneration are explored. The results demonstrate that matrix metalloproteinases are required for cell-gel to exert its benefits in cardiac repair. Inhibition of matrix metalloproteinases reduces cell engraftment, host angiogenesis, and recruitment of endogenous cardiovascular cells in rats with heart attack.

Regulation and involvement of matrix metalloproteinases in vascular diseases

Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases whose main function is to degrade and deposit structural proteins within the extracellular matrix (ECM). A dysregulation of MMPs is linked to vascular diseases. MMPs are classified into collagenases, gelatinases, membrane-type, metalloelastase, stromelysins, matrilysins, enamelysins, and unclassified subgroups. The production of MMPs is stimulated by factors such as oxidative stress, growth factors and inflammation which lead to its up- or down-regulation with subsequent ECM remodeling. Normally, excess activation of MMPs is controlled by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). An imbalance of MMPs and TIMPs has been implicated in hypertension, atherosclerotic plaque formation and instability, aortic aneurysms and varicose vein wall remodeling. Also, recent evidence suggests epigenetic regulation of some MMPs in angiogenesis and atherosclerosis. Over the years, pharmacological inhibitors of MMPs have been used to modify or prevent the development of the disease with some success. In this review, we discuss recent advances in MMP biology, and their involvement in the manifestation of vascular disease.

Porous nanofibrous poly(L-lactic acid) scaffolds supporting cardiovascular progenitor cells for cardiac tissue engineering

Myocardial infarction (MI) is the irreversible necrosis of heart with approximately 1.5 million cases every year in the United States. Tissue engineering offers a promising strategy for cardiac repair after MI. However, the optimal cell source for heart tissue regeneration and the ideal scaffolds to support cell survival, differentiation, and integration, remain to be developed. To address these issues, we developed the technology to induce cardiovascular progenitor cells (CPCs) derived from mouse embryonic stem cells (ESCs) towards desired cardiomyocytes as well as smooth muscle cells and endothelial cells. We fabricated extracellular matrix (ECM)-mimicking nanofibrous poly(l-lactic acid) (PLLA) scaffolds with porous structure of high interconnection for cardiac tissue formation. The CPCs were seeded into the scaffolds to engineer cardiac constructs in vitro. Fluorescence staining and RT-PCR assay showed that the scaffolds facilitated cell attachment, extension, and differentiation. Subcutaneous implantation of the cell/scaffold constructs in a nude mouse model showed that the scaffolds favorably supported survival of the grafted cells and their commitment to the three desired lineages in vivo. Thus, our study suggested that the porous nanofibrous PLLA scaffolds support cardiac tissue formation from CPCs. The integration of CPCs with the nanofibrous PLLA scaffolds represents a promising tissue engineering strategy for cardiac repair.

STATEMENT OF SIGNIFICANCE

Myocardial infarction is the irreversible necrosis of heart with approximately 1.5 million cases every year in the United States. Tissue engineering offers a promising strategy for cardiac repair after MI. However, the optimal cell source for heart tissue regeneration and the ideal scaffolds to support cell survival, differentiation, and integration, remain to be developed. To address these issues, we developed porous nanofibrous PLLA scaffolds that mimic natural extracellular matrix to support cardiac tissue formation from CPCs. The integration of CPCs with the nanofibrous PLLA scaffolds represents a promising tissue engineering strategy for cardiac repair.

Effects of angiotensin-(1-7) on the proliferation and collagen synthesis of arginine vasopressin-stimulated rat cardiac fibroblasts: role of mas receptor-calcineurin-NF-κB signaling pathway

: Interstitial fibrosis is a common pathological change in various heart diseases, especially cardiac hypertrophy. Arginine vasopressin (AVP), one of the hallmarks of heart failure, exhibits a profibrotic effect by promoting the proliferation and differentiation of cardiac fibroblasts (CFs). In contrast, angiotensin-(1-7) [Ang-(1-7)] was reported to be beneficial for cardiac remodeling by its antifibrotic effect. To evaluate the effect of Ang-(1-7) on AVP-stimulated CFs and the subsequent signaling molecules involved, CFs isolated from neonatal rat hearts were incubated with AVP and treated with or without Ang-(1-7). Cell proliferation, cell cycle, collagen production, and related cellular signaling molecules were then assessed. The results showed that Ang-(1-7) dose-dependently inhibited cell proliferation and collagen production in AVP-stimulated CFs. In addition, Ang-(1-7) also significantly suppressed calcineurin activity in a dose-dependent manner in AVP-stimulated CFs, which was associated with reduced collagen production. Accordingly, the nuclear translocation and transcriptional activity of nuclear factor-kappa B (NF-κB), downstream signal of calcineurin, were also notably restrained by Ang-(1-7) in AVP-stimulated CFs. Furthermore, the inhibitory effect of Ang-(1-7) on AVP-activated calcineurin-NF-κB signaling was completely reversed by the Mas receptor antagonist A-799. These findings suggest that Ang-(1-7) exerts an antifibrotic effect by inhibiting AVP-stimulated CF proliferation and collagen synthesis by inactivating Mas receptor-calcineurin-NF-κB signaling pathway.

Cardioprotective Signature of Short-Term Caloric Restriction

Objective

To understand the molecular pathways underlying the cardiac preconditioning effect of short-term caloric restriction (CR).

Background

Lifelong CR has been suggested to reduce the incidence of cardiovascular disease through a variety of mechanisms. However, prolonged adherence to a CR life-style is difficult. Here we reveal the pathways that are modulated by short-term CR, which are associated with protection of the mouse heart from ischemia.

Methods

Male 10-12 wk old C57bl/6 mice were randomly assigned to an ad libitum (AL) diet with free access to regular chow, or CR, receiving 30% less food for 7 days (d), prior to myocardial infarction (MI) via permanent coronary ligation. At d8, the left ventricles (LV) of AL and CR mice were collected for Western blot, mRNA and microRNA (miR) analyses to identify cardioprotective gene expression signatures. In separate groups, infarct size, cardiac hemodynamics and protein abundance of caspase 3 was measured at d2 post-MI.

Results

This short-term model of CR was associated with cardio-protection, as evidenced by decreased infarct size (18.5±2.4% vs. 26.6±1.7%, N=10/group; P=0.01). mRNA and miR profiles pre-MI (N=5/group) identified genes modulated by short-term CR to be associated with circadian clock, oxidative stress, immune function, apoptosis, metabolism, angiogenesis, cytoskeleton and extracellular matrix (ECM). Western blots pre-MI revealed CR-associated increases in phosphorylated Akt and GSK3ß, reduced levels of phosphorylated AMPK and mitochondrial related proteins PGC-1α, cytochrome C and cyclooxygenase (COX) IV, with no differences in the levels of phosphorylated eNOS or MAPK (ERK1/2; p38). CR regimen was also associated with reduced protein abundance of cleaved caspase 3 in the infarcted heart and improved cardiac function.

Adiponectin protects rat heart from left ventricular remodeling induced by chronic intermittent hypoxia via inhibition of TGF-β/smad2/3 pathway

OBJECTIVE

Obstructive sleep apnea syndrome (OSAS) is associated with many cardiovascular disorders. Chronic intermittent hypoxia (CIH) is the primary player in OSAS of the many associated factors. This study was in order to investigate the effects of the Adiponectin (Ad) on left ventricular remodeling induced by CIH.

METHODS

Forty-five rats were randomly divided into three groups: normal control (NC) group, CIH group and CIH plus Ad supplemented (CIH + Ad) group. After 35 days' CIH exposure, masson analysis was used to detect the left ventricular fibrosis and western blot was used to measure the protein expression of collagen I, collagen III and TGF-β/smad2/3 pathway. Gene analysis by RT-PCR was used to study the MMP2 and TIMP2.

RESULTS

After CIH exposure, the fibrosis of left ventricular in CIH group was significantly remarkable than that in both NC and CIH + Ad groups (P<0.05), although statistical difference existed between NC and CIH + Ad groups (P<0.05). In addition, the protein expression of collagen I as well as collagen III and the ratio of mRNA levels of MMP2/TIMP2 were the highest in CIH group but the lowest in NC group, with CIH + Ad group in between. There was a significant difference among three groups (all P<0.05). The TGF-β/smad2/3 pathway was activated obviously in CIH group, but less noticeably in CIH + Ad group (P<0.05) with a significant difference in the two groups.

CONCLUSIONS

The present study showed that Ad could ameliorate the left ventricular remodeling induced by CIH via inhibition of the expression of TGF-β/smad2/3 pathway.

Pressure overload induces IL-18 and IL-18R expression, but markedly suppresses IL-18BP expression in a rabbit model. IL-18 potentiates TNF-α-induced cardiomyocyte death

Recurrent or sustained inflammation plays a causal role in the development and progression of left ventricular hypertrophy (LVH) and its transition to failure. Interleukin (IL)-18 is a potent pro-hypertrophic inflammatory cytokine. We report that induction of pressure overload in the rabbit, by constriction of the descending thoracic aorta induces compensatory hypertrophy at 4weeks (mass/volume ratio: 1.7±0.11) and ventricular dilatation indicative of heart failure at 6weeks (mass/volume ratio: 0.7±0.04). In concordance with this, fractional shortening was preserved at 4weeks, but markedly attenuated at 6weeks. We cloned rabbit IL-18, IL-18Rα, IL-18Rβ, and IL-18 binding protein (IL-18BP) cDNA, and show that pressure overload, while enhancing IL-18 and IL-18R expression in hypertrophied and failing hearts, markedly attenuated the level of expression of the endogenous IL-18 antagonist IL-18BP. Cyclical mechanical stretch (10% cyclic equibiaxial stretch, 1Hz) induced hypertrophy of primary rabbit cardiomyocytes in vitro and enhanced ANP, IL-18, and IL-18Rα expression. Further, treatment with rhIL-18 induced its own expression and that of IL-18Rα via AP-1 activation, and induced cardiomyocyte hypertrophy in part via PI3K/Akt/GATA4 signaling. In contrast, IL-18 potentiated TNF-α-induced cardiomyocyte death, and by itself induced cardiac endothelial cell death. These results demonstrate that pressure overload is associated with enhanced IL-18 and its receptor expression in hypertrophied and failingrabbit hearts. Since IL-18BP expression is markedly inhibited, our results indicate a positive amplification in IL-18 proinflammatory signaling during pressure overload, and suggest IL-18 as a potential therapeutic target in pathological hypertrophy and cardiac failure.

Stable, covalent attachment of laminin to microposts improves the contractility of mouse neonatal cardiomyocytes

The mechanical output of contracting cardiomyocytes, the muscle cells of the heart, relates to healthy and disease states of the heart. Culturing cardiomyocytes on arrays of elastomeric microposts can enable inexpensive and high-throughput studies of heart disease at the single-cell level. However, cardiomyocytes weakly adhere to these microposts, which limits the possibility of using biomechanical assays of single cardiomyocytes to study heart disease. We hypothesized that a stable covalent attachment of laminin to the surface of microposts improves cardiomyocyte contractility. We cultured cells on polydimethylsiloxane microposts with laminin covalently bonded with the organosilanes 3-glycidoxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane with glutaraldehyde. We measured displacement of microposts induced by the contractility of mouse neonatal cardiomyocytes, which attach better than mature cardiomyocytes to substrates. We observed time-dependent changes in contractile parameters such as micropost deformation, contractility rates, contraction and relaxation speeds, and the times of contractions. These parameters were affected by the density of laminin on microposts and by the stability of laminin binding to micropost surfaces. Organosilane-mediated binding resulted in higher laminin surface density and laminin binding stability. 3-glycidoxypropyltrimethoxysilane provided the highest laminin density but did not provide stable protein binding with time. Higher surface protein binding stability and strength were observed with 3-aminopropyltriethoxysilane with glutaraldehyde. In cultured cardiomyocytes, contractility rate, contraction speeds, and contraction time increased with higher laminin stability. Given these variations in contractile function, we conclude that binding of laminin to microposts via 3-aminopropyltriethoxysilane with glutaraldehyde improves contractility observed by an increase in beating rate and contraction speed as it occurs during the postnatal maturation of cardiomyocytes. This approach is promising for future studies to mimic in vivo tissue environments.

Decellularized matrices for cardiovascular tissue engineering

Cardiovascular disease (CVD) is one of the leading causes of death in the Western world. The replacement of damaged vessels and valves has been practiced since the 1950's. Synthetic grafts, usually made of bio-inert materials, are long-lasting and mechanically relevant, but fail when it comes to "biointegration". Decellularized matrices, instead, can be considered biological grafts capable of stimulating in vivo migration and proliferation of endothelial cells (ECs), recruitment and differentiation of mural cells, finally, culminating in the formation of a biointegrated tissue. Decellularization protocols employ osmotic shock, ionic and non-ionic detergents, proteolitic digestions and DNase/RNase treatments; most of them effectively eliminate the cellular component, but show limitations in preserving the native structure of the extracellular matrix (ECM). In this review, we examine the current state of the art relative to decellularization techniques and biological performance of decellularized heart, valves and big vessels. Furthermore, we focus on the relevance of ECM components, native and resulting from decellularization, in mediating in vivo host response and determining repair and regeneration, as opposed to graft corruption.

STAT3, a key regulator of cell-to-cell communication in the heart

The signal transducer and activator of transcription 3 (STAT3) is fundamental for physiological homeostasis and stress-induced remodelling of the heart as deregulated STAT3 circuits are sufficient to induce dilated and peripartum cardiomyopathy and adverse remodelling after myocardial infarction. STAT3 activity depends on multiple post-translational modifications (phosphorylation, acetylation, and dimerization). It is regulated by multiple receptor systems, which are coupled to positive and negative feedback loops to ensure physiological and beneficial action. Its intracellular functions are diverse as it acts as a signalling protein, a transcription factor but also participates in mitochondria energy production and protection. STAT3 modulates proliferation, differentiation, survival, oxidative stress, and/or metabolism in cardiomyocytes, fibroblasts, endothelial cells, progenitor cells, and various inflammatory cells. By regulating the secretome of these cardiac cells, STAT3 influences a broad range of intercellular communication systems. It thereby impacts on the communication between cardiomyocytes, the plasticity of the cardiac microenvironment, the vasculature, the extracellular matrix, and the inflammation in response to physiological and pathophysiological stress. Here, we sum up current knowledge on STAT3-mediated intra- and intercellular communication within the heterogeneous cellular network of the myocardium to co-ordinate complex biological processes and discuss STAT3-dependent targets as novel therapeutic concepts to treat various forms of heart disease.

Docosahexaenoic acid reverses angiotensin II-induced RECK suppression and cardiac fibroblast migration

The omega-3 polyunsaturated fatty acids (ω-3 fatty acids) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been reported to inhibit or delay the progression of cardiovascular diseases, including myocardial fibrosis. Recently we reported that angiotensin II (Ang II) promotes cardiac fibroblast (CF) migration by suppressing the MMP regulator reversion-inducing-cysteine-rich protein with Kazal motifs (RECK), through a mechanism dependent on AT1, ERK, and Sp1. Here we investigated the role of miR-21 in Ang II-mediated RECK suppression, and determined whether the ω-3 fatty acids reverse these effects. Ang II induced miR-21 expression in primary mouse cardiac fibroblasts (CFs) via ERK-dependent AP-1 and STAT3 activation, and while a miR-21 inhibitor reversed Ang II-induced RECK suppression, a miR-21 mimic inhibited both RECK expression and Ang II-induced CF migration. Moreover, Ang II suppressed the pro-apoptotic PTEN, and the ERK negative regulator Sprouty homologue 1 (SPRY1), but induced the metalloendopeptidase MMP2, all in a manner that was miR-21-dependent. Further, forced expression of PTEN inhibited Akt phosphorylation, Sp1 activation, and MMP2 induction. Notably, while both EPA and DHA reversed Ang II-mediated RECK suppression, DHA appeared to be more effective, and reversed Ang II-induced miR-21 expression, RECK suppression, MMP2 induction, and CF migration. These results indicate that Ang II-induced CF migration is differentially regulated by miR-21-mediated MMP induction and RECK suppression, and that DHA has the potential to upregulate RECK, and therefore may exert potential beneficial effects in cardiac fibrosis.