SPARC mediates early extracellular matrix remodeling following myocardial infarction

Exploring the roles of SPARC as a proinflammatory factor and its potential as a novel therapeutic target against cardiovascular disease

Cardiovascular disease (CVD) is a leading cause of death worldwide, and the number of patients with CVD continues to increase despite extensive research and developments in this field. Chronic inflammation is a pivotal pathological component of CVD, and unveiling new proinflammatory factors will help devise novel preventive and therapeutic strategies. The extracellular matrix (ECM) not only provides structural support between cells but also contributes to cellular functions. Secreted protein acidic and rich in cysteine (SPARC) is a collagen-binding matricellular protein that is particularly induced during development and tissue remodeling. A proinflammatory role for SPARC has been demonstrated in various animal models, such as in the lipopolysaccharide-induced footpad model and dextran sodium sulfate-induced colitis model. Recent clinical studies reported a positive correlation between elevated plasma SPARC levels and hypertension, obesity, and the inflammatory marker high-sensitive C-reactive protein. In addition, SPARC gene deletion attenuates the cardiac injury induced by aging, myocardial infarction, and pressure load, suggesting that SPARC has deleterious effects on CVD. This review summarizes the regulatory and proinflammatory mechanisms of SPARC on CVD, chronic kidney disease (CKD), and cerebrovascular disease and discusses the rationale behind measuring SPARC as a biomarker of CVD and the effects of inhibition of SPARC in the prevention and treatment of CVD.

Evaluation of lamin A/C mechanotransduction under different surface topography in LMNA related muscular dystrophy

Most of the single point mutations of the LMNA gene are associated with distinct muscular dystrophies, marked by heterogenous phenotypes but primarily the loss and symmetric weakness of skeletal muscle tissue. The molecular mechanism and phenotype-genotype relationships in these muscular dystrophies are poorly understood. An effort has been here to delineating the adaptation of mechanical inputs into biological response by mutant cells of lamin A associated muscular dystrophy. In this study, we implement engineered smooth and pattern surfaces of particular young modulus to mimic muscle physiological range. Using fluorescence and atomic force microscopy, we present distinct architecture of the actin filament along with abnormally distorted cell and nuclear shape in mutants, which showed a tendency to deviate from wild type cells. Topographic features of pattern surface antagonize the binding of the cell with it. Correspondingly, from the analysis of genome wide expression data in wild type and mutant cells, we report differential expression of the gene products of the structural components of cell adhesion as well as LINC (linkers of nucleoskeleton and cytoskeleton) protein complexes. This study also reveals mis expressed downstream signaling processes in mutant cells, which could potentially lead to onset of the disease upon the application of engineered materials to substitute the role of conventional cues in instilling cellular behaviors in muscular dystrophies. Collectively, these data support the notion that lamin A is essential for proper cellular mechanotransduction from extracellular environment to the genome and impairment of the muscle cell differentiation in the pathogenic mechanism for lamin A associated muscular dystrophy.

Modified mRNA-Mediated CCN5 Gene Transfer Ameliorates Cardiac Dysfunction and Fibrosis without Adverse Structural Remodeling

Modified mRNAs (modRNAs) are an emerging delivery method for gene therapy. The success of modRNA-based COVID-19 vaccines has demonstrated that modRNA is a safe and effective therapeutic tool. Moreover, modRNA has the potential to treat various human diseases, including cardiac dysfunction. Acute myocardial infarction (MI) is a major cardiac disorder that currently lacks curative treatment options, and MI is commonly accompanied by fibrosis and impaired cardiac function. Our group previously demonstrated that the matricellular protein CCN5 inhibits cardiac fibrosis (CF) and mitigates cardiac dysfunction. However, it remains unclear whether early intervention of CF under stress conditions is beneficial or more detrimental due to potential adverse effects such as left ventricular (LV) rupture. We hypothesized that CCN5 would alleviate the adverse effects of myocardial infarction (MI) through its anti-fibrotic properties under stress conditions. To induce the rapid expression of CCN5, ModRNA-CCN5 was synthesized and administrated directly into the myocardium in a mouse MI model. To evaluate CCN5 activity, we established two independent experimental schemes: (1) preventive intervention and (2) therapeutic intervention. Functional analyses, including echocardiography and magnetic resonance imaging (MRI), along with molecular assays, demonstrated that modRNA-mediated CCN5 gene transfer significantly attenuated cardiac fibrosis and improved cardiac function in both preventive and therapeutic models, without causing left ventricular rupture or any adverse cardiac remodeling. In conclusion, early intervention in CF by ModRNA-CCN5 gene transfer is an efficient and safe therapeutic modality for treating MI-induced heart failure.

Global research trends and emerging opportunities for integrin adhesion complexes in cardiac repair: a scientometric analysis

Objective

Cardiac regenerative medicine has gained significant attention in recent years, and integrins are known to play a critical role in mediating cardiac development and repair, especially after an injury from the myocardial infarction (MI). Given the extensive research history and interdisciplinary nature of this field, a quantitative retrospective analysis and visualization of related topics is necessary.

Materials and methods

We performed a scientometric analysis of published papers on cardiac integrin adhesion complexes (IACs), including analysis of annual publications, disciplinary evolution, keyword co-occurrence, and literature co-citation.

Results

A total of 2,664 publications were finally included in the past 20 years. The United States is the largest contributor to the study and is leading this area of research globally. The journal Circulation Research attracts the largest number of high-quality publications. The study of IACs in cardiac repair/regenerative therapies involves multiple disciplines, particularly in materials science and developmental biology. Keywords of research frontiers were represented by Tenasin-C (2019-2023) and inflammation (2020-2023).

Conclusion

Integrins are topics with ongoing enthusiasm in biological development and tissue regeneration. The rapidly emerging role of matricellular proteins and non-protein components of the extracellular matrix (ECM) in regulating matrix structure and function may be a further breakthrough point in the future; the emerging role of IACs and their downstream molecular signaling in cardiac repair are also of great interest, such as induction of cardiac proliferation, differentiation, maturation, and metabolism, fibroblast activation, and inflammatory modulation.

Macrophages in cardiac remodelling after myocardial infarction

Myocardial infarction (MI), as a result of thrombosis or vascular occlusion, is the most prevalent cause of morbidity and mortality among all cardiovascular diseases. The devastating consequences of MI are compounded by the complexities of cellular functions involved in the initiation and resolution of early-onset inflammation and the longer-term effects related to scar formation. The resultant tissue damage can occur as early as 1 h after MI and activates inflammatory signalling pathways to elicit an immune response. Macrophages are one of the most active cell types during all stages after MI, including the cardioprotective, inflammatory and tissue repair phases. In this Review, we describe the phenotypes of cardiac macrophage involved in MI and their cardioprotective functions. A specific subset of macrophages called resident cardiac macrophages (RCMs) are derived from yolk sac progenitor cells and are maintained as a self-renewing population, although their numbers decrease with age. We explore sophisticated sequencing techniques that demonstrate the cardioprotective properties of this cardiac macrophage phenotype. Furthermore, we discuss the interactions between cardiac macrophages and other important cell types involved in the pathology and resolution of inflammation after MI. We summarize new and promising therapeutic approaches that target macrophage-mediated inflammation and the cardioprotective properties of RCMs after MI. Finally, we discuss future directions for the study of RCMs in MI and cardiovascular health in general.

Identification of Hub Genes in the Remodeling of Non-Infarcted Myocardium Following Acute Myocardial Infarction

(1) Background: There are few diagnostic and therapeutic targets for myocardial remodeling in the salvageable non-infarcted myocardium. (2) Methods: Hub genes were identified through comprehensive bioinformatics analysis (GSE775, GSE19322, and GSE110209 from the gene expression omnibus (GEO) database) and the biological functions of hub genes were examined by gene ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Furthermore, the differential expression of hub genes in various cell populations between the acute myocardial infarction (AMI) and sham-operation groups was analyzed by processing scRNA data (E-MTAB-7376 from the ArrayExpress database) and RNA-seq data (GSE183168). (3) Results: Ten strongly interlinked hub genes (Timp1, Sparc, Spp1, Tgfb1, Decr1, Vim, Serpine1, Serpina3n, Thbs2, and Vcan) were identified by the construction of a protein-protein interaction network from 135 differentially expressed genes identified through comprehensive bioinformatics analysis and their reliability was verified using GSE119857. In addition, the 10 hub genes were found to influence the ventricular remodeling of non-infarcted tissue by modulating the extracellular matrix (ECM)-mediated myocardial fibrosis, macrophage-driven inflammation, and fatty acid metabolism. (4) Conclusions: Ten hub genes were identified, which may provide novel potential targets for the improvement and treatment of AMI and its complications.

Single-cell and spatial transcriptomics of the infarcted heart define the dynamic onset of the border zone in response to mechanical destabilization

The border zone (BZ) of the infarcted heart is a geographically complex and biologically enigmatic interface separating poorly perfused infarct zones (IZs) from remote zones (RZs). The cellular and molecular mechanisms of myocardial BZs are not well understood because microdissection inevitably combines them with uncontrolled amounts of RZs and IZs. Here, we use single-cell/nucleus RNA sequencing, spatial transcriptomics and multiplexed RNA fluorescence in situ hybridization to redefine the BZ based on cardiomyocyte transcriptomes. BZ1 (Nppa + Xirp2 -) forms a hundreds-of-micrometer-thick layer of morphologically intact cells adjacent to RZs that are detectable within an hour of injury. Meanwhile, BZ2 (Nppa + Xirp2 +) forms a near-single-cell-thick layer of morphologically distorted cardiomyocytes at the IZ edge that colocalize with matricellular protein-expressing myofibroblasts and express predominantly mechanotransduction genes. Surprisingly, mechanical injury alone is sufficient to induce BZ genes. We propose a 'loss of neighbor' hypothesis to explain how ischemic cell death mechanically destabilizes the BZ to induce its transcriptional response.

Full-Length Spatial Transcriptomics Reveals the Unexplored Isoform Diversity of the Myocardium Post-MI

We introduce Single-cell Nanopore Spatial Transcriptomics (scNaST), a software suite to facilitate the analysis of spatial gene expression from second- and third-generation sequencing, allowing to generate a full-length near-single-cell transcriptional landscape of the tissue microenvironment. Taking advantage of the Visium Spatial platform, we adapted a strategy recently developed to assign barcodes to long-read single-cell sequencing data for spatial capture technology. Here, we demonstrate our workflow using four short axis sections of the mouse heart following myocardial infarction. We constructed a de novo transcriptome using long-read data, and successfully assigned 19,794 transcript isoforms in total, including clinically-relevant, but yet uncharacterized modes of transcription, such as intron retention or antisense overlapping transcription. We showed a higher transcriptome complexity in the healthy regions, and identified intron retention as a mode of transcription associated with the infarct area. Our data revealed a clear regional isoform switching among differentially used transcripts for genes involved in cardiac muscle contraction and tissue morphogenesis. Molecular signatures involved in cardiac remodeling integrated with morphological context may support the development of new therapeutics towards the treatment of heart failure and the reduction of cardiac complications.

The Role of Matrix Proteins in Cardiac Pathology

The extracellular matrix (ECM) and ECM-regulatory proteins mediate structural and cell-cell interactions that are crucial for embryonic cardiac development and postnatal homeostasis, as well as organ remodeling and repair in response to injury. These proteins possess a broad functionality that is regulated by multiple structural domains and dependent on their ability to interact with extracellular substrates and/or cell surface receptors. Several different cell types (cardiomyocytes, fibroblasts, endothelial and inflammatory cells) within the myocardium elaborate ECM proteins, and their role in cardiovascular (patho)physiology has been increasingly recognized. This has stimulated robust research dissecting the ECM protein function in human health and disease and replicating the genetic proof-of-principle. This review summarizes recent developments regarding the contribution of ECM to cardiovascular disease. The clear importance of this heterogeneous group of proteins in attenuating maladaptive repair responses provides an impetus for further investigation into these proteins as potential pharmacological targets in cardiac diseases and beyond.

Sex-related differences of early cardiac functional and proteomic alterations in a rat model of myocardial ischemia

BACKGROUND

Reduced cardiovascular risk in premenopausal women has been the focus of research in recent decades. Previous hypothesis-driven experiments have highlighted the role of sex hormones on distinct inflammatory responses, mitochondrial proteins, extracellular remodeling and estrogen-mediated cardioprotective signaling pathways related to post-ischemic recovery, which were associated with better cardiac functional outcomes in females. We aimed to investigate the early, sex-specific functional and proteomic changes following myocardial ischemia in an unbiased approach.

METHODS

Ischemia was induced in male (M-Isch) and female (F-Isch) rats with sc. injection of isoproterenol (85 mg/kg) daily for 2 days, while controls (M-Co, F-Co) received sc. saline solution. At 48 h after the first injection pressure-volume analysis was carried out to assess left ventricular function. FFPE tissue slides were scanned and analyzed digitally, while myocardial proteins were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using isobaric labeling. Concentrations of circulating steroid hormones were measured with LC-MS/MS. Feature selection (PLS and PLS-DA) was used to examine associations among functional, proteomic and hormonal datasets.

RESULTS

Induction of ischemia resulted in 38% vs 17% mortality in M-Isch and F-Isch respectively. The extent of ischemic damage to surviving rats was comparable between the sexes. Systolic dysfunction was more pronounced in males, while females developed a more severe impairment of diastolic function. 2224 proteins were quantified, with 520 showing sex-specific differential regulation. Our analysis identified transcriptional, cytoskeletal, contractile, and mitochondrial proteins, molecular chaperones and the extracellular matrix as sources of disparity between the sexes. Bioinformatics highlighted possible associations of estrogens and their metabolites with early functional and proteomic alterations.

CONCLUSIONS

Our study has highlighted sex-specific alterations in systolic and diastolic function shortly after ischemia, and provided a comprehensive look at the underlying proteomic changes and the influence of estrogens and their metabolites. According to our bioinformatic analysis, inflammatory, mitochondrial, chaperone, cytoskeletal, extracellular and matricellular proteins are major sources of intersex disparity, and may be promising targets for early sex-specific pharmacologic interventions.

Intestinal production of secreted protein acidic and rich in cysteine (SPARC) in patients with ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) is an inflammatory disease of the intestine. The genetics factors play an important role in the pathogenesis of UC. SPARC exacerbates colonic inflammatory symptoms in dextran sodium sulphate-induced murine colitis. The aim of the study was to measure the gene expression and intestinal production of SPARC in patients with UC and controls as well as, to determine its correlation with histological activity.

METHODS

We included 40 patients with confirmed diagnosis of UC, and 20 controls without endoscopic evidence of any type of colitis or neoplasia. The relative quantification of the gene expression was performed by real time PCR. GAPDH was used as housekeeping gene for normalization purposes and quality controls. Protein expression was determined by immunohistochemistry.

RESULTS

The gene expression of SPARC was increased in patients with active UC vs in remission UC and vs. controls (P = 0.005). There was no significant difference between patients with remission UC and controls. The overexpression of SPARC in patients with active UC correlated significantly with mild histological activity (P = 0.06, OR = 7.77, IC = 0.77-77.9) moderate (P = 0.06, OR = 8.1, IC 95%=0.79-82.73), and severe (P = 0.03, OR = 6.5, IC 95%=1.09-38.6). Double positive SPARC+/CD16+ cells were localized mainly in submucosa, muscular layer, and adventitia, and in perivascular inflammatory infiltrates in patients with active UC.

CONCLUSION

The gene and protein expression of SPARC is increased in active UC. SPARC could be a marker of intestinal inflammation and its expression correlates with histological activity.

Recapitulating Cardiac Structure and Function In Vitro from Simple to Complex Engineering

Cardiac tissue engineering aims to generate in vivo-like functional tissue for the study of cardiac development, homeostasis, and regeneration. Since the heart is composed of various types of cells and extracellular matrix with a specific microenvironment, the fabrication of cardiac tissue in vitro requires integrating technologies of cardiac cells, biomaterials, fabrication, and computational modeling to model the complexity of heart tissue. Here, we review the recent progress of engineering techniques from simple to complex for fabricating matured cardiac tissue in vitro. Advancements in cardiomyocytes, extracellular matrix, geometry, and computational modeling will be discussed based on a technology perspective and their use for preparation of functional cardiac tissue. Since the heart is a very complex system at multiscale levels, an understanding of each technique and their interactions would be highly beneficial to the development of a fully functional heart in cardiac tissue engineering.

Myocardial Infarction Induces Cardiac Fibroblast Transformation within Injured and Noninjured Regions of the Mouse Heart

Heart failure (HF) is associated with pathological remodeling of the myocardium, including the initiation of fibrosis and scar formation by activated cardiac fibroblasts (CFs). Although early CF-dependent scar formation helps prevent cardiac rupture by maintaining the heart's structural integrity, ongoing deposition of the extracellular matrix in the remote and infarct regions can reduce tissue compliance, impair cardiac function, and accelerate progression to HF. In our study, we conducted mass spectrometry (MS) analysis to identify differentially altered proteins and signaling pathways between CFs isolated from 7 day sham and infarcted murine hearts. Surprisingly, CFs from both the remote and infarct regions of injured hearts had a wide number of similarly altered proteins and signaling pathways that were consistent with fibrosis and activation into pathological myofibroblasts. Specifically, proteins enriched in CFs isolated from MI hearts were involved in pathways pertaining to cell-cell and cell-matrix adhesion, chaperone-mediated protein folding, and collagen fibril organization. These results, together with principal component analyses, provided evidence of global CF activation postinjury. Interestingly, however, direct comparisons between CFs from the remote and infarct regions of injured hearts identified 15 differentially expressed proteins between MI remote and MI infarct CFs. Eleven of these proteins (Gpc1, Cthrc1, Vmac, Nexn, Znf185, Sprr1a, Specc1, Emb, Limd2, Pawr, and Mcam) were higher in MI infarct CFs, whereas four proteins (Gstt1, Gstm1, Tceal3, and Inmt) were higher in MI remote CFs. Collectively, our study shows that MI injury induced global changes to the CF proteome, with the magnitude of change reflecting their relative proximity to the site of injury.

Extracellular Matrix in Ischemic Heart Disease, Part 4/4: JACC Focus Seminar

Myocardial ischemia and infarction, both in the acute and chronic phases, are associated with cardiomyocyte loss and dramatic changes in the cardiac extracellular matrix (ECM). It has long been appreciated that these changes in the cardiac ECM result in altered mechanical properties of ischemic or infarcted myocardial segments. However, a growing body of evidence now clearly demonstrates that these alterations of the ECM not only affect the structural properties of the ischemic and post-infarct heart, but they also play a crucial and sometimes direct role in mediating a range of biological pathways, including the orchestration of inflammatory and reparative processes, as well as the pathogenesis of adverse remodeling. This final part of a 4-part JACC Focus Seminar reviews the evidence on the role of the ECM in relation to the ischemic and infarcted heart, as well as its contribution to cardiac dysfunction and adverse clinical outcomes.

Cardiac fibrosis

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

Cardiac fibroblast activation during myocardial infarction wound healing: Fibroblast polarization after MI

Cardiac wound healing after myocardial infarction (MI) evolves from pro-inflammatory to anti-inflammatory to reparative responses, and the cardiac fibroblast is a central player during the entire transition. The fibroblast mirrors changes seen in the left ventricle infarct by undergoing a continuum of polarization phenotypes that follow pro-inflammatory, anti-inflammatory, and pro-scar producing profiles. The development of each phenotype transition is contingent upon the MI environment into which the fibroblast enters. In this mini-review, we summarize our current knowledge regarding cardiac fibroblast activation during MI and highlight key areas where gaps remain.

Regulation of Myocardial Extracellular Matrix Dynamic Changes in Myocardial Infarction and Postinfarct Remodeling

The article represents literature review dedicated to molecular and cellular mechanisms underlying clinical manifestations and outcomes of acute myocardial infarction. Extracellular matrix adaptive changes are described in detail as one of the most important factors contributing to healing of damaged myocardium and post-infarction cardiac remodeling. Extracellular matrix is reviewed as dynamic constantly remodeling structure that plays a pivotal role in myocardial repair. The role of matrix metalloproteinases and their tissue inhibitors in fragmentation and degradation of extracellular matrix as well as in myocardium healing is discussed. This review provides current information about fibroblasts activity, the role of growth factors, particularly transforming growth factor β and cardiotrophin-1, colony-stimulating factors, adipokines and gastrointestinal hormones, various matricellular proteins. In conclusion considering the fact that dynamic transformation of extracellular matrix after myocardial ischemic damage plays a pivotal role in myocardial infarction outcomes and prognosis, we suggest a high importance of further investigation of mechanisms underlying extracellular matrix remodeling and cell-matrix interactions in cardiovascular diseases.

Understanding the mechanisms that determine extracellular matrix remodeling in the infarcted myocardium

Myocardial Infarction (MI) initiates a series of wound healing events that begins with up-regulation of an inflammatory response and culminates in scar formation. The extracellular matrix (ECM) is intricately involved in all stages from initial break down of existing ECM to synthesis of new ECM to form the scar. This review will summarize our current knowledge on the processes involved in ECM remodeling after MI and identify the gaps that still need to be filled.

Matrix metalloproteinases regulate ECM accumulation but not larval heart growth in Drosophila melanogaster

The Drosophila heart provides a simple model to examine the remodelling of muscle insertions with growth, extracellular matrix (ECM) turnover, and fibrosis. Between hatching and pupation, the Drosophila heart increases in length five-fold. If major cardiac ECM components are secreted remotely, how is ECM "self assembly" regulated? We explored whether ECM proteases were required to maintain the morphology of a growing heart while the cardiac ECM expanded. An increase in expression of Drosophila's single tissue inhibitor of metalloproteinase (TIMP), or reduced function of metalloproteinase MMP2, resulted in fibrosis and ectopic deposition of two ECM Collagens; type-IV and fibrillar Pericardin. Significant accumulations of Collagen-IV (Viking) developed on the pericardium and in the lumen of the heart. Congenital defects in Pericardin deposition misdirected further assembly in the larva. Reduced metalloproteinase activity during growth also increased Pericardin fibre accumulation in ECM suspending the heart. Although MMP2 expression was required to remodel and position cardiomyocyte cell junctions, reduced MMP function did not impair expansion of the heart. A previous study revealed that MMP2 negatively regulates the size of the luminal cell surface in the embryonic heart. Cardiomyocytes align at the midline, but do not adhere to enclose a heart lumen in MMP2 mutant embryos. Nevertheless, these embryos hatch and produce viable larvae with bifurcated hearts, indicating a secondary pathway to lumen formation between ipsilateral cardiomyocytes. MMP-mediated remodelling of the ECM is required for organogenesis, and to prevent assembly of excess or ectopic ECM protein during growth. MMPs are not essential for normal growth of the Drosophila heart.

Towards better definition, quantification and treatment of fibrosis in heart failure. A scientific roadmap by the Committee of Translational Research of the Heart Failure Association (HFA) of the European Society of Cardiology

Fibrosis is a pivotal player in heart failure development and progression. Measurements of (markers of) fibrosis in tissue and blood may help to diagnose and risk stratify patients with heart failure, and its treatment may be effective in preventing heart failure and its progression. A lack of pathophysiological insights and uniform definitions has hampered the research in fibrosis and heart failure. The Translational Research Committee of the Heart Failure Association discussed several aspects of fibrosis in their workshop. Early insidious perturbations such as subclinical hypertension or inflammation may trigger first fibrotic events, while more dramatic triggers such as myocardial infarction

and myocarditis give rise to full blown scar formation and ongoing fibrosis in diseased hearts. Aging itself is also associated with a cardiac phenotype that includes fibrosis. Fibrosis is an extremely heterogeneous phenomenon, as several stages of the fibrotic process exist, each with different fibrosis subtypes and a different composition of various cells and proteins — resulting in a very complex pathophysiology. As a result, detection of fibrosis, e.g. using current cardiac imaging modalities or plasma biomarkers, will detect only specific subforms of fibrosis, but cannot capture all aspects of the complex fibrotic process. Furthermore, several anti‐fibrotic therapies are under investigation, but such therapies generally target aspecific aspects of the fibrotic process and suffer from a lack of precision. This review discusses the mechanisms and the caveats and proposes a roadmap for future research.

Extracellular matrix roles in cardiorenal fibrosis: Potential therapeutic targets for CVD and CKD in the elderly

Whereas hypertension, diabetes, and dyslipidemia are age-related risk factors for cardiovascular disease (CVD) and chronic kidney disease (CKD), aging alone is an independent risk factor. With advancing age, the heart and kidney gradually but significantly undergo inflammation and subsequent fibrosis, which eventually results in an irreversible decline in organ physiology. Through cardiorenal network interactions, cardiac dysfunction leads to and responds to renal injury, and both facilitate aging effects. Thus, a comprehensive strategy is needed to evaluate the cardiorenal aging network. Common hallmarks shared across systems include extracellular matrix (ECM) accumulation, along with upregulation of matrix metalloproteinases (MMPs) including MMP-9. The wide range of MMP-9 substrates, including ECM components and inflammatory cytokines, implicates MMP-9 in a variety of pathological and age-related processes. In particular, there is strong evidence that inflammatory cell-derived MMP-9 exacerbates cardiorenal aging. This review explores the potential therapeutic targets against CVD and CKD in the elderly, focusing on ECM and MMP roles.

The Mouse Heart Attack Research Tool 1.0 database

The generation of big data has enabled systems-level dissections into the mechanisms of cardiovascular pathology. Integration of genetic, proteomic, and pathophysiological variables across platforms and laboratories fosters discoveries through multidisciplinary investigations and minimizes unnecessary redundancy in research efforts. The Mouse Heart Attack Research Tool (mHART) consolidates a large data set of over 10 yr of experiments from a single laboratory for cardiovascular investigators to generate novel hypotheses and identify new predictive markers of progressive left ventricular remodeling after myocardial infarction (MI) in mice. We designed the mHART REDCap database using our own data to integrate cardiovascular community participation. We generated physiological, biochemical, cellular, and proteomic outputs from plasma and left ventricles obtained from post-MI and no-MI (naïve) control groups. We included both male and female mice ranging in age from 3 to 36 mo old. After variable collection, data underwent quality assessment for data curation (e.g., eliminate technical errors, check for completeness, remove duplicates, and define terms). Currently, mHART 1.0 contains >888,000 data points and includes results from >2,100 unique mice. Database performance was tested, and an example is provided to illustrate database utility. This report explains how the first version of the mHART database was established and provides researchers with a standard framework to aid in the integration of their data into our database or in the development of a similar database. NEW & NOTEWORTHY The Mouse Heart Attack Research Tool combines >888,000 cardiovascular data points from >2,100 mice. We provide this large data set as a REDCap database to generate novel hypotheses and identify new predictive markers of adverse left ventricular remodeling following myocardial infarction in mice and provide examples of use. The Mouse Heart Attack Research Tool is the first database of this size that integrates data sets across platforms that include genomic, proteomic, histological, and physiological data.

Myocardial infarction remodeling that progresses to heart failure: a signaling misunderstanding

After myocardial infarction, remodeling of the left ventricle involves a wound-healing orchestra involving a variety of cell types. In order for wound healing to be optimal, appropriate communication must occur; these cells all need to come in at the right time, be activated at the right time in the right amount, and know when to exit at the right time. When this occurs, a new homeostasis is obtained within the infarct, such that infarct scar size and quality are sufficient to maintain left ventricular size and shape. The ideal scenario does not always occur in reality. Often, miscommunication can occur between infarct and remote spaces, across the temporal wound-healing spectrum, and across organs. When miscommunication occurs, adverse remodeling can progress to heart failure. This review discusses current knowledge gaps and recent development of the roles of inflammation and the extracellular matrix in myocardial infarction remodeling. In particular, the macrophage is one cell type that provides direct and indirect regulation of both the inflammatory and scar-forming responses. We summarize current research efforts focused on identifying biomarker indicators that reflect the status of each component of the wound-healing process to better predict outcomes.

Roles of SPARC in urothelial carcinogenesis, progression and metastasis

Secreted Protein Acidic and Rich in Cysteine (SPARC) is a matricellular glycoprotein that is implicated in myriad physiological and pathological conditions characterized by extensive remodeling and plasticity. The functions and disease association of SPARC in cancer is being increasingly appreciated as it plays multi-faceted contextual roles depending on the cancer type, cell of origin and the unique cancer milieu at both primary and metastatic sites. Herein we will review our current knowledge of the role of SPARC in the multistep cascades of urinary bladder carcinogenesis, progression and metastasis from preclinical models and clinical data and shine the light on its prognostic and therapeutic potentials.

Understanding cardiac extracellular matrix remodeling to develop biomarkers of myocardial infarction outcomes

Cardiovascular Disease (CVD) is the most common cause of death in industrialized countries, and myocardial infarction (MI) is a major CVD with significant morbidity and mortality. Following MI, the left ventricle (LV) undergoes a wound healing response to ischemia that results in extracellular matrix (ECM) scar formation to replace necrotic myocytes. While ECM accumulation following MI is termed cardiac fibrosis, this is a generic term that does not differentiate between ECM accumulation that occurs in the infarct region to form a scar that is structurally necessary to preserve left ventricle (LV) wall integrity and ECM accumulation that increases LV wall stiffness to exacerbate dilation and stimulate the progression to heart failure. This review focuses on post-MI LV ECM remodeling, targeting the discussion on ECM biomarkers that could be useful for predicting MI outcomes.

Cardiac CD68+ and stabilin-1+ macrophages in wound healing following myocardial infarction: From experiment to clinic

Myocardial infarction (MI) remains the leading cause of mortality and morbidity throughout the world. Macrophages are key innate immune cells that play a significant role in transition from the inflammatory to the regenerative phase during wound healing following MI. The scavenger receptor stabilin-1 is one of the most interesting macrophage biomarkers. This receptor contributes to wound healing, angiogenesis, and tissue remodeling. We suggested a research protocol using macrophage biomarkers to study the cellular basis of cardiac remodeling and healing in patients with acute MI. The purpose of the research was to translate experimental knowledge regarding macrophage subsets and their biomarkers in post-infarction myocardial regeneration into results observed in clinical settings. The study included 41 patients with fatal MI type 1. All patients were divided into four groups according to the timeline of MI histopathology. In addition to routine histopathological analysis, macrophage infiltration was assessed by immunohistochemistry. We used CD68 as a marker for the cells of the macrophage lineage and stabilin-1 as an M2-like macrophage biomarker. The number of CD68+ and stabilin-1+ macrophages in the infarct area increased and peaked in the regenerative phase and did not decrease in the late stage of MI. In the peri-infarct area, the number of CD68+ macrophages increased in the inflammatory phase, peaked during the reparative phase, and did not decrease in the late phase, while the number of stabilin-1+ macrophages increased in the regenerative phase and remained unchanged. Additionally, in the reparative phase, we observed increase in the number of CD68+ and stabilin-1+ macrophages in the non-infarct area. The research protocol suggested allowed us to translate experimental knowledge regarding macrophage subsets and their biomarkers in post-infarction myocardial regeneration into clinical data. Taken together, these results demonstrated biphasic cardiac macrophage response following acute MI somewhat similar to that in a murine model. The increase in stabilin-1+ macrophage infiltration noticed in the myocardium during the regenerative phase and the strong positive correlation between the number of these cells and timeline of MI histopathology enabled us to propose stabilin-1 as a diagnostic macrophage biomarker in myocardium wound healing in patients with acute MI.

Temporal dynamics of cardiac hypertrophic growth in response to pressure overload

Hypertension is one of the most important risk factors of heart failure. In response to high blood pressure, the left ventricle manifests hypertrophic growth to ameliorate wall stress, which may progress into decompensation and trigger pathological cardiac remodeling. Despite the clinical importance, the temporal dynamics of pathological cardiac growth remain elusive. Here, we took advantage of the puromycin labeling approach to measure the relative rates of protein synthesis as a way to delineate the temporal regulation of cardiac hypertrophic growth. We first identified the optimal treatment conditions for puromycin in neonatal rat ventricular myocyte culture. We went on to demonstrate that myocyte growth reached its peak rate after 8-10 h of growth stimulation. At the in vivo level, with the use of an acute surgical model of pressure-overload stress, we observed the maximal growth rate to occur at day 7 after surgery. Moreover, RNA sequencing analysis supports that the most profound transcriptomic changes occur during the early phase of hypertrophic growth. Our results therefore suggest that cardiac myocytes mount an immediate growth response in reply to pressure overload followed by a gradual return to basal levels of protein synthesis, highlighting the temporal dynamics of pathological cardiac hypertrophic growth.NEW & NOTEWORTHY We determined the optimal conditions of puromycin incorporation in cardiac myocyte culture. We took advantage of this approach to identify the growth dynamics of cardiac myocytes in vitro. We went further to discover the protein synthesis rate in vivo, which provides novel insights about cardiac temporal growth dynamics in response to pressure overload.

Plasma follistatin-like protein 1 is correlated with disease severity in patients with acute pulmonary embolism and predicts short-term mortality

We investigated the plasma levels of follistatin-like protein 1 (FSTL1) in patients with acute pulmonary embolism (PE) and whether it could predict short-term mortality. A prospective observational cohort study was conducted in patients with acute PE (n = 220). FSTL1 was measured in plasma samples using enzyme-linked immunosorbent assay. Plasma FSTL1 levels were significantly increased in patients with acute PE, and positively correlated with disease severity (rs = 0.7171). Sensitivity and specificity rates for high-risk PE at a specific FSTL1 cutoff point (23 ng/ml) were 79.3% and 92.9%. Multivariant Cox regression analysis showed that FSTL1 was independently associated with 30-day mortality rate. Addition of FSTL1 to the PE severity index (PESI) scoring system significantly improved the predictive value for 30-day mortality. These results indicate that the plasma level of FSTL1 is correlated with disease severity in patients with acute PE and predicts short-term mortality.

The extracellular matrix in myocardial injury, repair, and remodeling

The cardiac extracellular matrix (ECM) not only provides mechanical support, but also transduces essential molecular signals in health and disease. Following myocardial infarction, dynamic ECM changes drive inflammation and repair. Early generation of bioactive matrix fragments activates proinflammatory signaling. The formation of a highly plastic provisional matrix facilitates leukocyte infiltration and activates infarct myofibroblasts. Deposition of matricellular proteins modulates growth factor signaling and contributes to the spatial and temporal regulation of the reparative response. Mechanical stress due to pressure and volume overload and metabolic dysfunction also induce profound changes in ECM composition that contribute to the pathogenesis of heart failure. This manuscript reviews the role of the ECM in cardiac repair and remodeling and discusses matrix-based therapies that may attenuate remodeling while promoting repair and regeneration.

Systems biology-opportunities and challenges: the application of proteomics to study the cardiovascular extracellular matrix

Systems biology approaches including proteomics are becoming more widely used in cardiovascular research. In this review article, we focus on the application of proteomics to the cardiac extracellular matrix (ECM). ECM remodelling is a hallmark of many cardiovascular diseases. Proteomic techniques using mass spectrometry (MS) provide a platform for the comprehensive analysis of ECM proteins without a priori assumptions. Proteomics overcomes various constraints inherent to conventional antibody detection. On the other hand, studies that use whole tissue lysates for proteomic analysis mask the identification of the less abundant ECM constituents. In this review, we first discuss decellularization-based methods that enrich for ECM proteins in cardiac tissue, and how targeted MS allows for accurate protein quantification. The second part of the review will focus on post-translational modifications including hydroxylation and glycosylation and on the release of matrix fragments with biological activity (matrikines), all of which can be interrogated by proteomic techniques.

Follistatin-like 1 promotes cardiac fibroblast activation and protects the heart from rupture

Follistatin‐like 1 (Fstl1) is a secreted protein that is acutely induced in heart following myocardial infarction (MI). In this study, we investigated cell type‐specific regulation of Fstl1 and its function in a murine model of MI. Fstl1 was robustly expressed in fibroblasts and myofibroblasts in the infarcted area compared to cardiac myocytes. The conditional ablation of Fstl1 in S100a4‐expressing fibroblast lineage cells (Fstl1‐cfKO mice) led to a reduction in injury‐induced Fstl1 expression and increased mortality due to cardiac rupture during the acute phase. Cardiac rupture was associated with a diminished number of myofibroblasts and decreased expression of extracellular matrix proteins. The infarcts of Fstl1‐cfKO mice displayed weaker birefringence, indicative of thin and loosely packed collagen. Mechanistically, the migratory and proliferative capabilities of cardiac fibroblasts were attenuated by endogenous Fstl1 ablation. The activation of cardiac fibroblasts by Fstl1 was mediated by ERK1/2 but not Smad2/3 signaling. This study reveals that Fstl1 is essential for the acute repair of the infarcted myocardium and that stimulation of early fibroblast activation is a novel function of Fstl1.

Effects of vascular endothelial growth factor on osteoblasts and osteoclasts

INTRODUCTION

Bone remodeling is crucial to the success of many dental procedures and is tightly regulated. Vascular endothelial growth factor (VEGF), a key cytokine for angiogenesis, is also an important regulator of bone remodeling. We aimed to examine the mechanisms by which VEGF induces bone remodeling by studying its effects on cultured osteoblasts and osteoclasts.

METHODS

Preosteoblastic MC3T3-E1 cells were treated with vehicle or VEGF-A165. Cell proliferation, migration, and invasion potentials were assessed. Preosteoclastic RAW264.7 cells were treated with vehicle or VEGF with or without the receptor activator of nuclear factor kappa-B ligand (RANKL), and osteoclast formation was measured with tartrate-resistant acid phosphatase staining. Conditioned media from vehicle-treated or VEGF-treated MC3T3-E1 cells were tested for the levels of RANKL and osteoprotegerin (OPG) and were used to treat RAW264.7 cells to observe osteoclast formation.

RESULTS

VEGF significantly induced MC3T3-E1 cell proliferation, migration, and invasion. VEGF did not directly induce osteoclastogenesis but significantly increased the RANKL/OPG ratio in the conditioned media from the MC3T3-E1 cultures; this significantly increased osteoclast formation.

CONCLUSIONS

VEGF stimulates osteoclast differentiation by increasing the osteoblastic RANKL/OPG ratio but has no direct effect on osteoclast precursor cells, and it induces osteoblast proliferation, migration, and invasion potentials in vitro.

Differential impact of mechanical unloading on structural and nonstructural components of the extracellular matrix in advanced human heart failure

Adverse remodeling of the extracellular matrix (ECM) is a significant characteristic of heart failure. Reverse remodeling of the fibrillar ECM secondary to mechanical unloading of the left ventricle (LV) by left ventricular assist device (LVAD) has been subject of intense investigation; however, little is known about the impacts on nonfibrillar ECM and matricellular proteins that also contribute to disease progression. Explanted failing hearts were procured from patients with nonischemic dilated cardiomyopathy (DCM) with or without LVAD support, and compared to nonfailing control hearts. LV free wall specimens were formalin-fixed, flash-frozen or optimum cutting temperature-mount frozen. Histologic and biochemical assessment of fibrillar ECM showed that LVAD support was associated with lower levels of insoluble collagen, collagen type I mRNA, and collagen I/III ratio compared with no-LVAD hearts. A disintegrin and Metalloproteinase with Thrombospondin Motifs-2 (ADAM-TS2), a procollagen endopeptidase, was reduced in no-LVAD but not in LVAD hearts. The rise in ECM proteolytic activities was significantly lower in LVAD hearts. Matrix metalloproteinases (MMP1, MMP2, MMP8, MMP13, and MT1-MMP/MMP14) were comparable between DCM hearts. Tissue inhibitor of metalloproteinase (TIMP)3 and TIMP4 messenger RNA and protein showed the greatest reduction in no-LVAD hearts. Basement membrane proteins exhibited less severe disarray of laminin and fibronectin-1 in LVAD-supported hearts. The rise in matricellular protein, osteopontin, was suppressed in LVAD hearts, whereas secreted protein, acidic, cysteine-rich (SPARC) levels was unaffected by LVAD. Mechanical unloading of the failing DCM hearts can restore the fibrillar ECM and the basement membrane, contributing toward improved clinical outcomes. However, persistent elevation of matricellular proteins such as SPARC could contribute to the relapse of failing hearts on removal of LVAD support.

Increased ADAMTS1 mediates SPARC-dependent collagen deposition in the aging myocardium

Secreted protein acidic and rich in cysteine (SPARC) is a collagen-binding matricellular protein highly expressed during fibrosis. Fibrosis is a prominent component of cardiac aging that reduces myocardial elasticity. Previously, we reported that SPARC deletion attenuated myocardial stiffness and collagen deposition in aged mice. To investigate the mechanisms by which SPARC promotes age-related cardiac fibrosis, we evaluated six groups of mice (n = 5-6/group): young (3-5 mo old), middle-aged (10-12 mo old), and old (18-29 mo old) C57BL/6 wild type (WT) and SPARC-null (Null) mice. Collagen content, determined by picrosirius red staining, increased in an age-dependent manner in WT but not in Null mice. A disintegrin and metalloproteinase with thrombospondin-like motifs 1 (ADAMTS1) increased in middle-aged and old WT compared with young, whereas in Null mice only old animals showed increased ADAMTS1 expression. Versican, a substrate of ADAMTS1, decreased with age only in WT. To assess the mechanisms of SPARC-induced collagen deposition, we stimulated cardiac fibroblasts with SPARC. SPARC treatment increased secretion of collagen I and ADAMTS1 (both the 110-kDa latent and 87-kDa active forms) into the conditioned media as well as the cellular expression of transforming growth factor-β1-induced protein (Tgfbi) and phosphorylated Smad2. An ADAMTS1 blocking antibody suppressed the SPARC-induced collagen I secretion, indicating that SPARC promoted collagen production directly through ADAMTS1 interaction. In conclusion, ADAMTS1 is an important mediator of SPARC-regulated cardiac aging.

Predictive value of circulating osteonectin in patients with ischemic symptomatic chronic heart failure

Background

Osteonectin (OSN) plays a pivotal role in cardiac remodeling, but predictive value for OSN in ischemic chronic heart failure (CHF) has not been defined. The aim of the study was to evaluate the prognostic value of OSN for cumulative survival and hospitalization among patients with ischemic-induced CHF.

Methods

A total of 154 patients with ischemic symptomatic moderate-to-severe CHF were enrolled in the study at discharge from the hospital. Observation period was up to 3 years (156 weeks). Blood samples for biomarkers measurements were collected at baseline prior to study entry. ELISA methods for measurements of circulating level of OSN were used.

Results

During a median follow-up of 2.18 years, 21 participants died and 106 subjects were re-admitted. Medians of circulating levels of OSN in survival and died patient cohorts were 670.96 ng/mL (95% confidence interval [CI] = 636.53–705.35 ng/mL) and 907.84 ng/mL (95% CI = 878.02–937.60 ng/mL). Receiver operation characteristic curve analysis has shown that cut off point of OSN concentration for cumulative survival function was 845.15 ng/mL. It has been found a significant divergence of Kaplan–Meier survival curves in patients with high (>845.15 ng/mL) and low (<845.15 ng/mL) concentrations of OSN. Circulating OSN independently predicted all-cause mortality (odds ratio [OR] = 1.23; 95% CI = 1.10–1.36; p < 0.001), CHF-related death (OR = 1.46; 95% CI = 1.22–1.80; p < 0.001), and also CHF-related re-admission (OR = 1.92; 95% CI = 1.77–2.45; p < 0.001) within 3 years of observation period.

Conclusion

Increased circulating secreted protein acidic and rich in cysteine family member OSN associates with increased 3-year CHF-related death, all-cause mortality, and risk for recurrent hospitalization due to CHF.

The two faces of invariant natural killer T cells

In this issue of the Biomedical Journal, we take a look at some of the immune system's most peculiar cells, invariant natural killer T cells, which have features of both innate and adaptive cells. We also highlight a clinical study revealing that high serum phosphate levels could show that it's time to start dialysis in patients with chronic kidney diseases. Finally, this issue also includes some case reports, including an unusual case of aspergillosis related to long-term inhaler use.

The role of secreted protein acidic and rich in cysteine (SPARC) in cardiac repair and fibrosis: Does expression of SPARC by macrophages influence outcomes?

Secreted protein acidic and rich in cysteine (SPARC) is a matricellular, collagen-binding protein. Matricellular proteins are described as extracellular matrix-associated proteins that do not serve classical structural roles in the matrix such as those ascribed to laminins and collagens. The family of matricellular proteins modulates cell:extracellular matrix interactions and is actively expressed during tissue remodeling. Functional activities attributed to SPARC in cultured cells include regulation of cell adhesion, cytoskeletal rearrangement, proliferation, and matrix assembly. The primary phenotype characteristic of SPARC-null mice is a deficit in amounts of fibrillar collagen and fibril morphology. Strikingly, SPARC-null mice demonstrate a blunted fibrotic response in a number of different tissue settings. The role of monocyte/macrophages as an important component of tissue fibrosis is becoming increasingly appreciated. Expression of SPARC by bone marrow derived inflammatory cells raises the interesting proposition that SPARC produced by infiltrating leukocytes might contribute to the course of inflammation and tissue fibrosis in the heart. This review will summarize results from studies defining the function of SPARC in myocardial repair and fibrosis and results from other non-cardiac tissues that shed light onto possible consequences of SPARC expression by monocyte/macrophages in the setting of heart disease.

Anti-remodeling and anti-fibrotic effects of the neuregulin-1β glial growth factor 2 in a large animal model of heart failure

BACKGROUND

Neuregulin-1β (NRG-1β) is a growth factor critical for cardiac development and repair with therapeutic potential for heart failure. We previously showed that the glial growth factor 2 (GGF2) isoform of NRG-1β improves cardiac function in rodents after myocardial infarction (MI), but its efficacy in a large animal model of cardiac injury has not been examined. We therefore sought to examine the effects of GGF2 on ventricular remodeling, cardiac function, and global transcription in post-MI swine, as well as potential mechanisms for anti-remodeling effects.

METHODS AND RESULTS

MI was induced in anesthetized swine (n=23) by intracoronary balloon occlusion. At 1 week post-MI, survivors (n=13) received GGF2 treatment (intravenous, biweekly for 4 weeks; n=8) or were untreated (n=5). At 5 weeks post-MI, fractional shortening was higher (32.8% versus 25.3%, P=0.019), and left ventricular (LV) end-diastolic dimension lower (4.5 versus 5.3 cm, P=0.003) in GGF2-treated animals. Treatment altered expression of 528 genes, as measured by microarrays, including collagens, basal lamina components, and matricellular proteins. GGF2-treated pigs exhibited improvements in LV cardiomyocyte mitochondria and intercalated disk structures and showed less fibrosis, altered matrix structure, and fewer myofibroblasts (myoFbs), based on trichrome staining, electron microscopy, and immunostaining. In vitro experiments with isolated murine and rat cardiac fibroblasts demonstrate that NRG-1β reduces myoFbs, and suppresses TGFβ-induced phospho-SMAD3 as well as αSMA expression.

CONCLUSIONS

These results suggest that GGF2/NRG-1β prevents adverse remodeling after injury in part via anti-fibrotic effects in the heart.

Integrative genomic analyses of secreted protein acidic and rich in cysteine and its role in cancer prediction

Secreted protein acidic and rich in cysteine (SPARC), also termed osteonectin or basement‑membrane‑40 (BM‑40), is a matrix‑associated protein that elicits changes in cell shape, inhibits cell‑cycle progression and affects the synthesis of extracellular matrix (ECM). The final mature SPARC protein has 286 amino acids with three distinct domains, including an NH2‑terminal acidic domain (NT), follistatin‑like domain (FS) and C terminus domain (EC). The present study identified SPARC genes from 14 vertebrate genomes and revealed that SPARC existed in all types of vertebrates, including fish, amphibians, birds and mammals. In total, 21 single nucleotide polymorphisms (SNPs) causing missense mutations were identified, which may affect the formation of the truncated form of the SPARC protein. The human SPARC gene was found to be expressed in numerous tissues or organs, including in the bone marrow, whole blood, lymph node, thymus, brain, cerebellum, retina, heart, smooth muscle, skeletal muscle, spinal cord, intestine, colon, adipocyte, kidney, liver, pancreas, thyroid, salivary gland, skin, ovary, uterus, placenta, cervix and prostate. When searched in the PrognoScan database, the human SPARC gene was also found to be expressed in bladder, blood, breast, glioma, esophagus, colorectal, head and neck, ovarian, lung and skin cancer tissues. It was revealed that the association between the expression of SPARC and prognosis varied in different types of cancer, and even in the same cancer from different databases. It implied that the function of SPARC in these tumors may be multidimensional, functioning not just as a tumor suppressor or oncogene.

Myofibroblasts and the extracellular matrix network in post-myocardial infarction cardiac remodeling

The cardiac extracellular matrix (ECM) fills the space between cells, supports tissue organization, and transduces mechanical, chemical, and biological signals to regulate homeostasis of the left ventricle (LV). Following myocardial infarction (MI), a multitude of ECM proteins are synthesized to replace myocyte loss and form a reparative scar. Activated fibroblasts (myofibroblasts) are the primary source of ECM proteins, thus playing a key role in cardiac repair. A balanced turnover of ECM through regulation of synthesis by myofibroblasts and degradation by matrix metalloproteinases (MMPs) is critical for proper scar formation. In this review, we summarize the current literature on the roles of myofibroblasts, MMPs, and ECM proteins in MI-induced LV remodeling. In addition, we discuss future research directions that are needed to further elucidate the molecular mechanisms of ECM actions to optimize cardiac repair.

Dynamic changes in myocardial matrix and relevance to disease: translational perspectives

The cardiac extracellular matrix (ECM) provides the architectural scaffold to support efficient contraction and relaxation of cardiomyocytes. The elegant design of the ECM facilitates optimal force transduction, electric transmission, intercellular communication, and metabolic exchange within the myocardial microenvironment. In the setting of increased wall stress, injury, or disease, the ECM can undergo a series of dynamic changes that lead to favorable chamber remodeling and functional adaptation. Over time, sustained matrix remodeling can impair diastolic and systolic function caused by excess deposition of interstitial fibrous tissue. These pathological alterations in ECM structure/function are considered central to the evolution of adverse cardiac remodeling and the development of heart failure. This review discusses the complex dynamics of the cardiac ECM in the setting of myocardial infarction, pressure overload, and volume overload. We also summarize the current status of ECM biomarkers that may have clinical value in prognosticating cardiac disease progression in patients. Finally, we discuss the most current status of drugs under evaluation for use in cardiac fibrosis.

Cardiac fibroblast-derived 3D extracellular matrix seeded with mesenchymal stem cells as a novel device to transfer cells to the ischemic myocardium

PURPOSE

Demonstrate a novel manufacturing method to generate extracellular matrix scaffolds from cardiac fibroblasts (CF-ECM) as a therapeutic mesenchymal stem cell-transfer device.

MATERIALS AND METHODS

Rat CF were cultured at high-density (~1.6×10⁵/cm²) for 10-14 days. Cell sheets were removed from the culture dish by incubation with EDTA and decellularized with water and peracetic acid. CF-ECM was characterized by mass spectrometry, immunofluorescence and scanning electron microscopy. CF-ECM seeded with human embryonic stem cell derived mesenchymal stromal cells (hEMSCs) were transferred into a mouse myocardial infarction model. 48 hours later, mouse hearts were excised and examined for CF-ECM scaffold retention and cell transfer.

RESULTS

CF-ECM scaffolds are composed of fibronectin (82%), collagens type I (13%), type III (3.4%), type V (0.2%), type II (0.1%) elastin (1.3%) and 18 non-structural bioactive molecules. Scaffolds remained intact on the mouse heart for 48 hours without the use of sutures or glue. Identified hEMSCs were distributed from the epicardium to the endocardium.

CONCLUSIONS

High density cardiac fibroblast culture can be used to generate CF-ECM scaffolds. CF-ECM scaffolds seeded with hEMSCs can be maintained on the heart without suture or glue. hEMSC are successfully delivered throughout the myocardium.

Dissection of the human multipotent adult progenitor cell secretome by proteomic analysis

Multipotent adult progenitor cells (MAPCs) are adult adherent stromal stem cells currently being assessed in acute graft versus host disease clinical trials with demonstrated immunomodulatory capabilities and the potential to ameliorate detrimental autoimmune and inflammation-related processes. Our previous studies documented that MAPCs secrete factors that play a role in regulating T-cell activity. Here we expand our studies using a proteomics approach to characterize and quantify MAPC secretome components secreted over 72 hours in vitro under steady-state conditions and in the presence of the inflammatory triggers interferon-γ and lipopolysaccharide, or a tolerogenic CD74 ligand, RTL1000. MAPCs differentially responded to each of the tested stimuli, secreting molecules that regulate the biological activity of the extracellular matrix (ECM), including proteins that make up the ECM itself, proteins that regulate its construction/deconstruction, and proteins that serve to attach and detach growth factors from ECM components for redistribution upon appropriate stimulation. MAPCs secreted a wide array of proteases, some detectable in their zymogen forms. MAPCs also secreted protease inhibitors that would regulate protease activity. MAPCs secreted chemokines and cytokines that could provide molecular guidance cues to various cell types, including neutrophils, macrophages, and T cells. In addition, MAPCs secreted factors involved in maintenance of a homeostatic environment, regulating such diverse programs as innate immunity, angiogenesis/angiostasis, targeted delivery of growth factors, and the matrix-metalloprotease cascade.

Using proteomics to uncover extracellular matrix interactions during cardiac remodeling

The left ventricle (LV) responds to a myocardial infarction with an orchestrated sequence of events that result in fundamental changes to both the structure and function of the myocardium. This collection of responses is termed as LV remodeling. Myocardial ischemia resulting in necrosis is the initiating event that culminates in the formation of an extracellular matrix (ECM) rich infarct scar that replaces necrotic myocytes. While the cardiomyocyte is the major cell type that responds to ischemia, infiltrating leukocytes and cardiac fibroblasts coordinate the subsequent wound healing response. The matrix metalloproteinase family of enzymes regulates the inflammatory and ECM responses that modulate scar formation. Matridomics is the proteomic evaluation focused on ECM, while degradomics is the proteomic evaluation of proteases as well as their inhibitors and substrates. This review will summarize the use of proteomics to better understand matrix metalloproteinase roles in post myocardial infarction LV remodeling.

Function and fate of myofibroblasts after myocardial infarction

The importance of cardiac fibroblasts in the regulation of myocardial remodelling following myocardial infarction (MI) is becoming increasingly recognised. Studies over the last few decades have reinforced the concept that cardiac fibroblasts are much more than simple homeostatic regulators of extracellular matrix turnover, but are integrally involved in all aspects of the repair and remodelling of the heart that occurs following MI. The plasticity of fibroblasts is due in part to their ability to undergo differentiation into myofibroblasts. Myofibroblasts are specialised cells that possess a more contractile and synthetic phenotype than fibroblasts, enabling them to effectively repair and remodel the cardiac interstitium to manage the local devastation caused by MI. However, in addition to their key role in cardiac restoration and healing, persistence of myofibroblast activation can drive pathological fibrosis, resulting in arrhythmias, myocardial stiffness and progression to heart failure. The aim of this review is to give an appreciation of both the beneficial and detrimental roles of the myofibroblast in the remodelling heart, to describe some of the major regulatory mechanisms controlling myofibroblast differentiation including recent advances in the microRNA field, and to consider how this cell type could be exploited therapeutically.

Matrix metalloproteinases: drug targets for myocardial infarction

Myocardial infarction (MI) remains a major cause of morbidity and mortality worldwide. Rapid advances in the treatment of acute MI have significantly improved short-term outcomes in patients, due in large part to successes in preventing myocardial cell death and limiting infarct area during the time of ischemia and subsequent reperfusion. Matrix metalloproteases (MMPs) play key roles in post-MI cardiac remodeling and in the development of adverse outcomes. This review highlights the importance of MMPs in the injury and remodeling response of the left ventricle and also discusses their potential as therapeutic targets Additional pre-clinical and clinical research is needed to further investigate and understand the cardioprotective effects of MMPs inhibitors.

Interleukin-1 has opposing effects on connective tissue growth factor and tenascin-C expression in human cardiac fibroblasts

Cardiac fibroblasts (CF) play a central role in the repair and remodeling of the heart following injury and are important regulators of inflammation and extracellular matrix (ECM) turnover. ECM-regulatory matricellular proteins are synthesized by several myocardial cell types including CF. We investigated the effects of pro-inflammatory cytokines on matricellular protein expression in cultured human CF. cDNA array analysis of matricellular proteins revealed that interleukin-1α (IL-1α, 10ng/ml, 6h) down-regulated connective tissue growth factor (CTGF/CCN2) mRNA by 80% and up-regulated tenascin-C (TNC) mRNA levels by 10-fold in human CF, without affecting expression of thrombospondins 1-3, osteonectin or osteopontin. Western blotting confirmed these changes at the protein level. In contrast, tumor necrosis factor α (TNFα) did not modulate CCN2 expression and had only a modest stimulatory effect on TNC levels. Signaling pathway inhibitor studies suggested an important role for the p38 MAPK pathway in suppressing CCN2 expression in response to IL-1α. In contrast, multiple signaling pathways (p38, JNK, PI3K/Akt and NFκB) contributed to IL-1α-induced TNC expression. In conclusion, IL-1α reduced CCN2 expression and increased TNC expression in human CF. These observations are of potential value for understanding how inflammation and ECM regulation are linked at the level of the CF.