Exaggerated left ventricular dilation and reduced collagen deposition after myocardial infarction in mice lacking osteopontin

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

The critical role of osteopontin (OPN) in fibrotic diseases

Fibrosis is a pathological condition characterized by the excessive deposition of extracellular matrix components in tissues and organs, leading to progressive architectural remodelling and contributing to the development of various diseases. Osteopontin (OPN), a highly phosphorylated glycoprotein, has been increasingly recognized for its involvement in the progression of tissue fibrosis. This review provides a comprehensive overview of the genetic and protein structure of OPN and focuses on our current understanding of the role of OPN in the development of fibrosis in the lungs and other tissues. Additionally, special attention is given to the potential of OPN as a biomarker and a novel therapeutic target in the treatment of fibrosis.

Don't go breakin' my heart: cardioprotective alterations to the mechanical and structural properties of reperfused myocardium during post-infarction inflammation

Myocardial infarctions (MIs) kickstart an intense inflammatory response resulting in extracellular matrix (ECM) degradation, wall thinning, and chamber dilation that leaves the heart susceptible to rupture. Reperfusion therapy is one of the most effective strategies for limiting adverse effects of MIs, but is a challenge to administer in a timely manner. Late reperfusion therapy (LRT; 3 + hours post-MI) does not limit infarct size, but does reduce incidences of post-MI rupture and improves long-term patient outcomes. Foundational studies employing LRT in the mid-twentieth century revealed beneficial reductions in infarct expansion, aneurysm formation, and left ventricle dysfunction. The mechanism by which LRT acts, however, is undefined. Structural analyses, relying largely on one-dimensional estimates of ECM composition, have found few differences in collagen content between LRT and permanently occluded animal models when using homogeneous samples from infarct cores. Uniaxial testing, on the other hand, revealed slight reductions in stiffness early in inflammation, followed soon after by an enhanced resistance to failure for cases of LRT. The use of one-dimensional estimates of ECM organization and gross mechanical function have resulted in a poor understanding of the infarct's spatially variable mechanical and structural anisotropy. To resolve these gaps in literature, future work employing full-field mechanical, structural, and cellular analyses is needed to better define the spatiotemporal post-MI alterations occurring during the inflammatory phase of healing and how they are impacted following reperfusion therapy. In turn, these studies may reveal how LRT affects the likelihood of rupture and inspire novel approaches to guide scar formation.

Lactoferrin, Osteopontin and Lactoferrin–Osteopontin Complex: A Critical Look on Their Role in Perinatal Period and Cardiometabolic Disorders

Milk-derived bioactive proteins have increasingly gained attention and consideration throughout the world due to their high-quality amino acids and multiple health-promoting attributes. Apparently, being at the forefront of functional foods, these bioactive proteins are also suggested as potential alternatives for the management of various complex diseases. In this review, we will focus on lactoferrin (LF) and osteopontin (OPN), two multifunctional dairy proteins, as well as to their naturally occurring bioactive LF–OPN complex. While describing their wide variety of physiological, biochemical, and nutritional functionalities, we will emphasize their specific roles in the perinatal period. Afterwards, we will evaluate their ability to control oxidative stress, inflammation, gut mucosal barrier, and intestinal microbiota in link with cardiometabolic disorders (CMD) (obesity, insulin resistance, dyslipidemia, and hypertension) and associated complications (diabetes and atherosclerosis). This review will not only attempt to highlight the mechanisms of action, but it will critically discuss the potential therapeutic applications of the underlined bioactive proteins in CMD.

A molecular phenotypic screen reveals that lobetyolin alleviates cardiac dysfunction in 5/6 nephrectomized mice by inhibiting osteopontin

BACKGROUND

Cardiovascular diseases are the major cause of mortality in patients with advanced chronic kidney diseases. The predominant abnormality observed among this population is cardiac dysfunction secondary to myocardial remodelings, such as hypertrophy and fibrosis, emphasizing the need to develop potent therapies that maintain cardiac function in patients with end-stage renal disease.

AIMS

To identify potential compounds and their targets as treatments for cardiorenal syndrome type 4 (CRS) using molecular phenotyping and in vivo/in vitro experiments.

METHODS

Gene expression was assessed using bioinformatics and verified in animal experiments using 5/6 nephrectomized mice (NPM). Based on this information, a molecular phenotyping strategy was pursued to screen potential compounds. Picrosirius red staining, wheat germ agglutinin staining, Echocardiography, immunofluorescence staining, and real-time quantitative PCR (qPCR) were utilized to evaluate the effects of compounds on CRS in vivo. Furthermore, qPCR, immunofluorescence staining and flow cytometry were applied to assess the effects of these compounds on macrophages/cardiac fibroblasts/cardiomyocytes. RNA-Seq analysis was performed to locate the targets of the selected compounds. Western blotting was performed to validate the targets and mechanisms. The reversibility of these effects was tested by overexpressing Osteopontin (OPN).

RESULTS

OPN expression increased more remarkably in individuals with uremia-induced cardiac dysfunction than in other cardiomyopathies. Lobetyolin (LBT) was identified in the compound screen, and it improved cardiac dysfunction and suppressed remodeling in NPM mice. Additionally, OPN modulated the effect of LBT on cardiac dysfunction in vivo and in vitro. Further experiments revealed that LBT suppressed OPN expression via the phosphorylation of c-Jun N-terminal protein kinase (JNK) signaling pathway.

CONCLUSIONS

LBT improved CRS by inhibiting OPN expression through the JNK pathway. This study is the first to describe a cardioprotective effect of LBT and provides new insights into CRS drug discovery.

Endogenous Modulation of Extracellular Matrix Collagen during Scar Formation after Myocardial Infarction

Myocardial infarction is remains the leading cause of death in developed countries. Recent data show that the composition of the extracellular matrix might differ despite similar heart function and infarction sizes. Because collagen is the main component of the extracellular matrix, we hypothesized that changes in inflammatory cell recruitment influence the synthesis of different collagen subtypes in myofibroblasts, thus changing the composition of the scar. We found that neutrophils sustain the proliferation of fibroblasts, remodeling, differentiation, migration and inflammation, predominantly by IL-1 and PPARγ pathways (n = 3). They also significantly inhibit the mRNA expression of fibrillar collagen, maintaining a reduced stiffness in isolated myofibroblasts (n = 4-5). Reducing the neutrophil infiltration in CCR1^-/- resulted in increased mRNA expression of collagen 11, moderate expression of collagen 19 and low expression of collagen 13 and 26 in the scar 4 weeks post infarction compared with other groups (n = 3). Mononuclear cells increased the synthesis of all collagen subtypes and upregulated the NF-kB, angiotensin II and PPARδ pathways (n = 3). They increased the synthesis of collagen subtypes 1, 3, 5, 16 and 23 but reduced the expression of collagens 5 and 16 (n = 3). CCR2^-/- scar tissue showed higher levels of collagen 13 (n = 3), in association with a significant reduction in stiffness (n = 4-5). Upregulation of the inflammation-related genes in myofibroblasts mostly modulated the fibrillar collagen subtypes, with less effect on the FACIT, network-forming and globular subtypes (n = 3). The upregulation of proliferation and differentiation genes in myofibroblasts seemed to be associated only with the fibrillar collagen subtype, whereas angiogenesis-related genes are associated with fibrillar, network-forming and multiplexin subtypes. In conclusion, although we intend for our findings to deepen the understanding of the mechanism of healing after myocardial infarction and scar formation, the process of collagen synthesis is highly complex, and further intensive investigation is needed to put together all the missing puzzle pieces in this still incipient knowledge process.

Exploring the cardiac ECM during fibrosis: A new era with next-gen proteomics

Extracellular matrix (ECM) plays a critical role in maintaining elasticity in cardiac tissues. Elasticity is required in the heart for properly pumping blood to the whole body. Dysregulated ECM remodeling causes fibrosis in the cardiac tissues. Cardiac fibrosis leads to stiffness in the heart tissues, resulting in heart failure. During cardiac fibrosis, ECM proteins get excessively deposited in the cardiac tissues. In the ECM, cardiac fibroblast proliferates into myofibroblast upon various kinds of stimulations. Fibroblast activation (myofibroblast) contributes majorly toward cardiac fibrosis. Other than cardiac fibroblasts, cardiomyocytes, epithelial/endothelial cells, and immune system cells can also contribute to cardiac fibrosis. Alteration in the expression of the ECM core and ECM-modifier proteins causes different types of cardiac fibrosis. These different components of ECM culminated into different pathways inducing transdifferentiation of cardiac fibroblast into myofibroblast. In this review, we summarize the role of different ECM components during cardiac fibrosis progression leading to heart failure. Furthermore, we highlight the importance of applying mass-spectrometry-based proteomics to understand the key changes occurring in the ECM during fibrotic progression. Next-gen proteomics studies will broaden the potential to identify key targets to combat cardiac fibrosis in order to achieve precise medicine-development in the future.

Osteopontin promotes infarct repair

Understanding how macrophages promote myocardial repair can help create new therapies for infarct repair. We aimed to determine what mechanisms underlie the reparative properties of macrophages. Cytokine arrays revealed that neonatal cardiac macrophages from the injured neonatal heart secreted high amounts of osteopontin (OPN). In vitro, recombinant OPN stimulated cardiac cell outgrowth, cardiomyocyte (CM) cell-cycle re-entry, and CM migration. In addition, OPN induced nuclear translocation of the cytoplasmatic yes-associated protein 1 (YAP1) and upregulated transcriptional factors and cell-cycle genes. Significantly, by blocking the OPN receptor CD44, we eliminated the effects of OPN on CMs. OPN also activated the proliferation and migration of non-CM cells: endothelial cells and cardiac mesenchymal stromal cells in vitro. Notably, the significant role of OPN in myocardial healing was demonstrated by impaired healing in OPN-deficient neonatal hearts. Finally, in the adult mice, a single injection of OPN into the border of the ischemic zone induced CM cell-cycle re-entry, improved scar formation, local and global cardiac function, and LV remodelling 30 days after MI. In summary, we have shown, for the first time, that recombinant OPN activates cell-cycle re-entry in CMs. In addition, recombinant OPN stimulates multiple cardiac cells and improves scar formation, LV remodelling, and regional and global function after MI. Therefore, we propose OPN as a new cell-free therapy to optimize infarct repair.

Myeloid cell-specific ablation of Runx2 gene exacerbates post-infarct cardiac remodeling

Runt-related transcription factor 2 (Runx2), a regulator of osteoblast differentiation, is pathologically involved in vascular calcification; however, the significance of Runx2 in cardiac homeostasis remains unclear. Here, we investigated the roles of Runx2 in cardiac remodeling after myocardial infarction (MI). The expression of Runx2 mRNA and protein was upregulated in murine hearts after MI. Runx2 was expressed in heart-infiltrating myeloid cells, especially in macrophages, at the border zone of post-infarct myocardium. To analyze the biological functions of Runx2 in cardiac remodeling, myeloid cell-specific Runx2 deficient (CKO) mice were exposed to MI. After MI, ventricular weight/tibia length ratio was increased in CKO mice, concomitant with severe cardiac dysfunction. Cardiac fibrosis was exacerbated in CKO mice, consistent with the upregulation of collagen 1a1 expression. Mechanistically, immunohistochemical analysis using anti-CD31 antibody showed that capillary density was decreased in CKO mice. Additionally, conditioned culture media of myeloid cells from Runx2 deficient mice exposed to MI induced the tube formation of vascular endothelial cells to a lesser extent than those from control mice. RNA-sequence showed that the expression of pro-angiogenic or anti-angiogenic factors was altered in macrophages from Runx2-deficient mice. Collectively, Runx2⁺ myeloid cells infiltrate into post-infarct myocardium and prevent adverse cardiac remodeling, at least partially, by regulating endothelial cell function.

Limb-Bud and Heart (LBH) Upregulation in Cardiomyocytes under Hypoxia Promotes the Activation of Cardiac Fibroblasts via Exosome Secretion

The activation of cardiac fibroblasts (CFs) after myocardial infarction (MI) is essential for post-MI infarct healing, during which the regulation of transforming growth factor beta1 (TGF-β1) signaling is predominant. We have demonstrated that TGF-β1-mediated upregulation of LBH contributes to post-MI CF activation via modulating αB-crystallin (CRYAB), after being upregulated by TGF-β1. In this study, the effect of LBH-CRYAB signaling on the cardiac microenvironment via exosome communication and the corresponding mechanisms were investigated. The upregulation of LBH and CRYAB was verified in both cardiomyocytes (CMs) and CFs in hypoxic, post-MI peri-infarct tissues. CM-derived exosomes were isolated and identified, and LBH distribution was elevated in exosomes derived from LBH-upregulated CMs under hypoxia. Treatment with LBH+ exosomes promoted cellular proliferation, differentiation, and epithelial-mesenchymal transition-like processes in CFs. Additionally, in primary LBH^KO CFs, western blotting showed that LBH knockout partially inhibited TGF-β1-induced CF activation, while LBH-CRYAB signaling affected TGF-β1 expression and secretion through a positive feedback loop. The administration of a Smad3 phosphorylation inhibitor to LBH^KO CFs under TGF-β1 stimulation indicated that Smad3 phosphorylation partially accounted for TGF-β1-induced LBH upregulation. In conclusion, LBH upregulation in CMs in post-MI peri-infarct areas correlated with a hypoxic cardiac microenvironment and led to elevated exosomal LBH levels, promoting the activation of recipient CFs, which brings new insights into the studies and therapeutic strategies of post-MI cardiac repair.

Clinical and Molecular Implications of Osteopontin in Heart Failure

The matricellular protein osteopontin modulates cell-matrix interactions during tissue injury and healing. A complex multidomain structure of osteopontin enables it not only to bind diverse cell receptors but also to interact with various partners, including other extracellular matrix proteins, cytokines, and growth factors. Numerous studies have implicated osteopontin in the development and progression of myocardial remodeling in diverse cardiac diseases. Osteopontin influences myocardial remodeling by regulating extracellular matrix production, the activity of matrix metalloproteinases and various growth factors, inflammatory cell recruitment, myofibroblast differentiation, cardiomyocyte apoptosis, and myocardial vascularization. The exploitation of osteopontin loss- and gain-of-function approaches in rodent models provided an opportunity for assessment of the cell- and disease-specific contribution of osteopontin to myocardial remodeling. In this review, we summarize the recent knowledge on osteopontin regulation and its impact on various cardiac diseases, as well as delineate complex disease- and cell-specific roles of osteopontin in cardiac pathologies. We also discuss the current progress of therapeutics targeting osteopontin that may facilitate the development of a novel strategy for heart failure treatment.

Spatiotemporal dynamics of macrophage heterogeneity and a potential function of Trem2hi macrophages in infarcted hearts

Heart failure (HF) is a frequent consequence of myocardial infarction (MI). Identification of the precise, time-dependent composition of inflammatory cells may provide clues for the establishment of new biomarkers and therapeutic approaches targeting post-MI HF. Here, we investigate the spatiotemporal dynamics of MI-associated immune cells in a mouse model of MI using spatial transcriptomics and single-cell RNA-sequencing (scRNA-seq). We identify twelve major immune cell populations; their proportions dynamically change after MI. Macrophages are the most abundant population at all-time points (>60%), except for day 1 post-MI. Trajectory inference analysis shows upregulation of Trem2 expression in macrophages during the late phase post-MI. In vivo injection of soluble Trem2 leads to significant functional and structural improvements in infarcted hearts. Our data contribute to a better understanding of MI-driven immune responses and further investigation to determine the regulatory factors of the Trem2 signaling pathway will aid the development of novel therapeutic strategies for post-MI HF.

Serum markers of cardiac complications in a systemic sclerosis cohort

Primary cardiac involvement is one of the leading causes of mortality in systemic sclerosis (SSc), but little is known regarding circulating biomarkers for cardiac SSc. Here, we aimed to investigate potential associations between cardiac SSc and candidate serum markers. Serum samples from patients of the Oslo University SSc cohort and 100 healthy controls were screened against two custom-made candidate marker panels containing molecules deemed relevant for cardiopulmonary and/or fibrotic diseases. Left (LV) and right ventricular (RV) dysfunction was assessed by protocol echocardiography, performed within three years from serum sampling. Patients suspected of pulmonary hypertension underwent right heart catheterization. Vital status at study end was available for all patients. Descriptive analyses, logistic and Cox regressions were conducted to assess associations between cardiac SSc and candidate serum markers. The 371 patients presented an average age of 57.2 (± 13.9) years. Female sex (84%) and limited cutaneous SSc (73%) were predominant. Association between LV diastolic dysfunction and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) (OR 0.41, 95% CI 0.21-0.78, p = 0.007) was identified. LV systolic dysfunction defined by global longitudinal strain was associated with angiopoietin 2 (ANGPT2) (OR 3.42, 95% CI 1.52-7.71, p = 0.003) and osteopontin (OPN) (OR 1.95, 95% CI 1.08-3.52, p = 0.026). RV systolic dysfunction, measured by tricuspid annular plane systolic excursion, was associated to markers of LV dysfunction (ANGPT2, OPN, and TRAIL) (OR 1.67, 95% CI 1.11-2.50, p = 0.014, OR 1.86, 95% CI 1.25-2.77, p = 0.002, OR 0.32, 95% CI 0.15-0.66, p = 0.002, respectively) and endostatin (OR 1.86, 95% CI 1.22-2.84, p = 0.004). In conclusion, ANGPT2, OPN and TRAIL seem to be circulating biomarkers associated with both LV and RV dysfunction in SSc.

Fibroblast mechanotransduction network predicts targets for mechano-adaptive infarct therapies

Regional control of fibrosis after myocardial infarction is critical for maintaining structural integrity in the infarct while preventing collagen accumulation in non-infarcted areas. Cardiac fibroblasts modulate matrix turnover in response to biochemical and biomechanical cues, but the complex interactions between signaling pathways confound efforts to develop therapies for regional scar formation. We employed a logic-based ordinary differential equation model of fibroblast mechano-chemo signal transduction to predict matrix protein expression in response to canonical biochemical stimuli and mechanical tension. Functional analysis of mechano-chemo interactions showed extensive pathway crosstalk with tension amplifying, dampening, or reversing responses to biochemical stimuli. Comprehensive drug target screens identified 13 mechano-adaptive therapies that promote matrix accumulation in regions where it is needed and reduce matrix levels in regions where it is not needed. Our predictions suggest that mechano-chemo interactions likely mediate cell behavior across many tissues and demonstrate the utility of multi-pathway signaling networks in discovering therapies for context-specific disease states.

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.

Identification of a novel native peptide derived from 60S ribosomal protein L23a that translationally regulates p53 to reduce myocardial ischemia-reperfusion

Myocardial ischemia-reperfusion (I/R) is a severe disease，but its underlying mechanism is not fully elucidated and no effective clinical treatment is available. Utilizing intracellular peptidomics, we identified a novel native peptide PDRL23A (Peptide Derived from RPL23A), that is intimately related to hypoxic stress. We further show that PDRL23A effectively alleviates hypoxia-induced cardiomyocyte injury in vitro, along with improvements in mitochondrial function and redox homeostasis, including ROS accumulation, oxidative phosphorylation, and mitochondrial membrane potential. Strikingly, the in vivo results indicate that, short-term pretreatment with PDRL23A could effectively inhibit I/R-induced cardiomyocyte death, myocardial fibrosis and decreased cardiac function. Interestingly, PDRL23A was found to interact with 60 S ribosomal protein L26 (RPL26), hampering RPL26-governed p53 translation, and resulting in a reduction in the level of p53 protein, which in turn reduced p53-mediated apoptosis under hypoxic conditions. Collectively, a native peptide, PDRL23A, which translationally regulates p53 to protect against myocardial I/R injury, has been identified for the first time. Our findings provide insight into the adaptive mechanisms of hypoxia and present a potential new treatment for myocardial I/R.

Diminished PLK2 Induces Cardiac Fibrosis and Promotes Atrial Fibrillation

[Figure: see text].

Key Roles of RGD-Recognizing Integrins During Cardiac Development, on Cardiac Cells, and After Myocardial Infarction

Cardiac cells interact with the extracellular matrix (ECM) proteins through integrin mechanoreceptors that control many cellular events such as cell survival, apoptosis, differentiation, migration, and proliferation. Integrins play a crucial role in cardiac development as well as in cardiac fibrosis and hypertrophy. Integrins recognize oligopeptides present on ECM proteins and are involved in three main types of interaction, namely with collagen, laminin, and the oligopeptide RGD (Arg-Gly-Asp) present on vitronectin and fibronectin proteins. To date, the specific role of integrins recognizing the RGD has not been addressed. In this review, we examine their role during cardiac development, their role on cardiac cells, and their upregulation during pathological processes such as heart fibrosis and hypertrophy. We also examine their role in regenerative and angiogenic processes after myocardial infarction (MI) in the peri-infarct area. Specific targeting of these integrins may be a way of controlling some of these pathological events and thereby improving medical outcomes.

Osteopontin in Cardiovascular Diseases

Unprecedented advances in secondary prevention have greatly improved the prognosis of cardiovascular diseases (CVDs); however, CVDs remain a leading cause of death globally. These findings suggest the need to reconsider cardiovascular risk and optimal medical therapy. Numerous studies have shown that inflammation, pro-thrombotic factors, and gene mutations are focused not only on cardiovascular residual risk but also as the next therapeutic target for CVDs. Furthermore, recent clinical trials, such as the Canakinumab Anti-inflammatory Thrombosis Outcomes Study trial, showed the possibility of anti-inflammatory therapy for patients with CVDs. Osteopontin (OPN) is a matricellular protein that mediates diverse biological functions and is involved in a number of pathological states in CVDs. OPN has a two-faced phenotype that is dependent on the pathological state. Acute increases in OPN have protective roles, including wound healing, neovascularization, and amelioration of vascular calcification. By contrast, chronic increases in OPN predict poor prognosis of a major adverse cardiovascular event independent of conventional cardiovascular risk factors. Thus, OPN can be a therapeutic target for CVDs but is not clinically available. In this review, we discuss the role of OPN in the development of CVDs and its potential as a therapeutic target.

A combined biomarker approach for characterising extracellular matrix profiles in acute myocardial infarction

Extracellular matrix (ECM) biomarkers are useful for measuring underlying molecular activity associated with cardiac repair following acute myocardial infarction (AMI). The aim of this study was to conduct exploratory factor analysis (EFA) to examine the interrelationships between ECM biomarkers, and cluster analysis to identify if distinct ECM profiles could distinguish patient risk in AMI. Ten ECM biomarkers were measured from plasma in 140 AMI patients: MMP-2, -3, -8, -9, periostin, procollagen I N-Terminal propeptide, osteopontin, TGF-β1, TIMP-1 and -4. EFA grouped eight ECM biomarkers into a two-factor solution, which comprised three biomarkers in Factor 1 and five biomarkers in Factor 2. Notably, ECM biomarkers were not separated based on biological function. Cluster analysis grouped AMI patients into three distinct clusters. Cluster One (n = 54) had increased levels of MMP-8, MMP-9, and TGF-B1. Cluster Two (n = 43) had elevated levels of MMP-2, MMP-3, osteopontin, periostin and TIMP-1, and increased high-sensitivity troponin T and GRACE scores. Cluster Three (n = 43) had decreased levels of ECM biomarkers. Circulating ECM biomarkers demonstrated collinearity and entwined biological functions based on EFA analysis. Using cluster analysis, patients with similar clinical presentations could be separated into distinct ECM profiles that were associated with differential patient risk. Clinical significance remains to be determined.

Oral pre-treatment with thiocyanate (SCN-) protects against myocardial ischaemia-reperfusion injury in rats

Despite improvements in revascularization after a myocardial infarction, coronary disease remains a major contributor to global mortality. Neutrophil infiltration and activation contributes to tissue damage, via the release of myeloperoxidase (MPO) and formation of the damaging oxidant hypochlorous acid. We hypothesized that elevation of thiocyanate ions (SCN⁻), a competitive MPO substrate, would modulate tissue damage. Oral dosing of rats with SCN⁻, before acute ischemia–reperfusion injury (30 min occlusion, 24 h or 4 week recovery), significantly reduced the infarct size as a percentage of the total reperfused area (54% versus 74%), and increased the salvageable area (46% versus 26%) as determined by MRI imaging. No difference was observed in fractional shortening, but supplementation resulted in both left-ventricle end diastolic and left-ventricle end systolic areas returning to control levels, as determined by echocardiography. Supplementation also decreased antibody recognition of HOCl-damaged myocardial proteins. SCN⁻ supplementation did not modulate serum markers of damage/inflammation (ANP, BNP, galectin-3, CRP), but returned metabolomic abnormalities (reductions in histidine, creatine and leucine by 0.83-, 0.84- and 0.89-fold, respectively), determined by NMR, to control levels. These data indicate that elevated levels of the MPO substrate SCN⁻, which can be readily modulated by dietary means, can protect against acute ischemia–reperfusion injury.

Effluent Osteopontin levels reflect the peritoneal solute transport rate

Long-term peritoneal dialysis (PD) is accompanied by low-grade intraperitoneal inflammation and may eventually lead to peritoneal membrane injury with a high solute transport rate and ultrafiltration failure. Osteopontin (OPN) is highly expressed through the stimulation of pro-inflammatory cytokines in many cell types. This study aimed to investigate the potential of OPN as a new indicator of peritoneal deterioration. One hundred nine continuous ambulatory PD patients were analyzed. The levels of OPN and IL-6 in peritoneal effluents or serum were analyzed by ELISA kits. The mean effluent OPN concentration was 2.39 ± 1.87 ng/mL. The OPN levels in drained dialysate were correlated with D/P Cr (p < 0.0001, R = 0.54) and D/D0 glucose (p < 0.0001, R = 0.39). Logistic regression analysis showed that the OPN levels in peritoneal effluents were an independent predictive factor for the increased peritoneal solute transport rate (PSTR) obtained by the peritoneal equilibration test (p < 0.001). The area under the receiver operating characteristic curve of OPN was 0.84 (95% CI: 0.75-0.92) in predicting the increased PSTR with a sensitivity of 86% and a specificity of 67%. The joint utilization of effluent OPN with age, effluent IL-6, and serum albumin further increased the specificity (81%). Thus, OPN may be a useful indicator of peritoneal deterioration in patients with PD.

Dimethyl fumarate preserves left ventricular infarct integrity following myocardial infarction via modulation of cardiac macrophage and fibroblast oxidative metabolism

Myocardial infarction (MI) is one of the leading causes of mortality and cardiovascular disease worldwide. MI is characterized by a substantial inflammatory response in the infarcted left ventricle (LV), followed by transition of quiescent fibroblasts to active myofibroblasts, which deposit collagen to form the reparative scar. Metabolic shifting between glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) is an important mechanism by which these cell types transition towards reparative phenotypes. Thus, we hypothesized that dimethyl fumarate (DMF), a clinically approved anti-inflammatory agent with metabolic actions, would improve post-MI remodeling via modulation of macrophage and fibroblast metabolism. Adult male C57BL/6J mice were treated with DMF (10 mg/kg) for 3-7 days after MI. DMF attenuated LV infarct and non-infarct wall thinning at 3 and 7 days post-MI, and decreased LV dilation and pulmonary congestion at day 7. DMF improved LV infarct collagen deposition, myofibroblast activation, and angiogenesis at day 7. DMF also decreased pro-inflammatory cytokine expression (Tnf) 3 days after MI, and decreased inflammatory markers in macrophages isolated from the infarcted heart (Hif1a, Il1b). In fibroblasts extracted from the infarcted heart at day 3, RNA-Seq analysis demonstrated that DMF promoted an anti-inflammatory/pro-reparative phenotype. By Seahorse analysis, DMF did not affect glycolysis in either macrophages or fibroblasts at day 3, but enhanced macrophage OXPHOS while impairing fibroblast OXPHOS. Our results indicate that DMF differentially affects macrophage and fibroblast metabolism, and promotes anti-inflammatory/pro-reparative actions. In conclusion, targeting cellular metabolism in the infarcted heart may be a promising therapeutic strategy.

Limb-bud and Heart (LBH) mediates proliferation, fibroblast-to-myofibroblast transition and EMT-like processes in cardiac fibroblasts

Cardiac fibrosis is an important pathological change after myocardial infarction (MI). Its progression is essential for post-MI infarct healing, during which transforming growth factor beta1 (TGF-β1) plays a critical role. Limb-bud and Heart (LBH), a newly discovered target gene of TGF-β1, was shown to promote normal cardiogenesis. αB-crystallin (CRYAB), an LBH-interacting protein, was demonstrated to be involved in TGF-β1-induced fibrosis. The roles and molecular mechanisms of LBH and CRYAB during cardiac fibrosis remain largely unexplored. In this study, we investigated the alterations of LBH and CRYAB expression in mouse cardiac tissue after MI. LBH and CRYAB were upregulated in activated cardiac fibroblasts (CFs), while in vitro TGF-β1 stimulation induced the upregulation of LBH, CRYAB, and fibrogenic genes in primary CFs of neonatal rats. The results of the ectopic expression of LBH proved that LBH accelerated CF proliferation under hypoxia, mediated the expression of CRYAB and fibrogenic genes, and promoted epithelial-mesenchymal transition (EMT)-like processes in rat CFs, while subsequent CRYAB silencing reversed the effects induced by elevated LBH expression. We also verified the protein-protein interaction (PPI) between LBH and CRYAB in fibroblasts. In summary, our work demonstrated that LBH promotes the proliferation of CFs, mediates TGF-β1-induced fibroblast-to-myofibroblast transition and EMT-like processes through CRYAB upregulation, jointly functioning in post-MI infarct healing. These findings suggest that LBH could be a promising potential target for the study of cardiac repair and cardiac fibrosis.

Fibrosis after Myocardial Infarction: An Overview on Cellular Processes, Molecular Pathways, Clinical Evaluation and Prognostic Value

The ischemic injury caused by myocardial infarction activates a complex healing process wherein a powerful inflammatory response and a reparative phase follow and balance each other. An intricate network of mediators finely orchestrate a large variety of cellular subtypes throughout molecular signaling pathways that determine the intensity and duration of each phase. At the end of this process, the necrotic tissue is replaced with a fibrotic scar whose quality strictly depends on the delicate balance resulting from the interaction between multiple actors involved in fibrogenesis. An inflammatory or reparative dysregulation, both in term of excess and deficiency, may cause ventricular dysfunction and life-threatening arrhythmias that heavily affect clinical outcome. This review discusses cellular process and molecular signaling pathways that determine fibrosis and the imaging technique that can characterize the clinical impact of this process in-vivo.

Specific macrophage populations promote both cardiac scar deposition and subsequent resolution in adult zebrafish

Aims

A robust inflammatory response to tissue injury is a necessary part of the repair process but the deposition of scar tissue is a direct downstream consequence of this response in many tissues including the heart. Adult zebrafish not only possess the capacity to regenerate lost cardiomyocytes but also to remodel and resolve an extracellular scar within tissues such as the heart, but this scar resolution process remains poorly understood. This study aims to characterize the scarring and inflammatory responses to cardiac damage in adult zebrafish in full and investigate the role of different inflammatory subsets specifically in scarring and scar removal.

Methods and results

Using stable transgenic lines, whole organ imaging and genetic and pharmacological interventions, we demonstrate that multiple inflammatory cell lineages respond to cardiac injury in adult zebrafish. In particular, macrophage subsets (tnfα+ and tnfα−) play prominent roles with manipulation of different phenotypes suggesting that pro-inflammatory (tnfα+) macrophages promote scar deposition following cardiac injury whereas tnfα− macrophages facilitate scar removal during regeneration. Detailed analysis of these specific macrophage subsets reveals crucial roles for Csf1ra in promoting pro-inflammatory macrophage-mediated scar deposition. Additionally, the multifunctional cytokine Osteopontin (Opn) (spp1) is important for initial scar deposition but also for resolution of the inflammatory response and in late-stage ventricular collagen remodelling.

Conclusions

This study demonstrates the importance of a correctly balanced inflammatory response to facilitate scar deposition during repair but also to allow subsequent scar resolution, and full cardiac regeneration, to occur. We have identified Opn as having both pro-fibrotic but also potentially pro-regenerative roles in the adult zebrafish heart, driving Collagen deposition but also controlling inflammatory cell resolution.

RNA-Seq Expression Analysis of Chronic Asthmatic Mice with Bu-Shen-Yi-Qi Formula Treatment and Prediction of Regulated Gene Targets of Anti-Airway Remodeling

Airway remodeling is one of the typical pathological characteristics of asthma, while the structural changes of the airways in asthma are complex, which impedes the development of novel asthma targeted therapy. Our previous study had shown that Bu-Shen-Yi-Qi formula (BSYQF) could ameliorate airway remodeling in chronic asthmatic mice by modulating airway inflammation and oxidative stress in the lung. In this study, we analysed the lung transcriptome of control mice and asthmatic mouse model with/without BSYQF treatment. Using RNA-sequencing (RNA-seq) analysis, we found that 264/1746 (15.1%) of transcripts showing abnormal expression in asthmatic mice were reverted back to completely or partially normal levels by BSYQF treatment. Additionally, based on previous results, we identified 21 differential expression genes (DEGs) with fold changes (FC) > (±) 2.0 related to inflammatory, oxidative stress, mitochondria, PI3K/AKT, and MAPK signal pathways which may play important roles in the mechanism of the anti-remodeling effect of BSYQF treatment. Through inputting 21 DEGs into the IPA database to construct a gene network, we inferred Adipoq, SPP1, and TNC which were located at critical nodes in the network may be key regulators of BSYQF's anti-remodeling effect. In addition, the quantitative real-time polymerase chain reaction (qRT-PCR) result for the selected four DEGs matched those of the RNA-seq analysis. Our results provide a preliminary clue to the molecular mechanism of the anti-remodeling effect of BSYQF in asthma.

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.

MerTK Expression and ERK Activation Are Essential for the Functional Maturation of Osteopontin-Producing Reparative Macrophages After Myocardial Infarction

Background We previously reported that osteopontin plays an essential role in accelerating both reparative fibrosis and clearance of dead cells (efferocytosis) during tissue repair after myocardial infarction (MI) and galectin-3^hiCD206⁺ macrophages is the main source of osteopontin in post-MI heart. Interleukin-10- STAT3 (signal transducer and activator of transcription 3)-galectin-3 axis is essential for Spp1 (encoding osteopontin) transcriptional activation in cardiac macrophages after MI. Here, we investigated the more detailed mechanism responsible for functional maturation of osteopontin-producing macrophages. Methods and Results In post-MI hearts, Spp1 transcriptional activation occurred almost exclusively in MerTK (Mer tyrosine kinase)⁺ galectin-3^hi macrophages. The induction of MerTK on galectin-3^hi macrophages is essential for their functional maturation including efferocytosis and Spp1 transcriptional activity. MerTK⁺galectin-3^hi macrophages showed a strong activation of both STAT3 and ERK (extracellular signal-regulated kinase). STAT3 inhibition suppressed the differentiation of osteopontin-producing MerTK⁺galectin-3^hi macrophages, however, STAT3 activation was insufficient at inducing Spp1 transcriptional activity. ERK inhibition suppressed Spp1 transcriptional activation without affecting MerTK or galectin-3 expression. Concomitant activation of ERK is required for transcriptional activation of Spp1. In Il-10 knockout enhanced green fluorescent protein-Spp1 knock-in mice subjected to MI, osteopontin-producing macrophages decreased but did not disappear entirely. Interleukin-10 and macrophage colony-stimulating factor synergistically activated STAT3 and ERK and promoted the differentiation of osteopontin-producing MerTK⁺galectin-3^hi macrophages in bone marrow-derived macrophages. Coadministration of anti-interleukin-10 plus anti-macrophage colony-stimulating factor antibodies substantially reduced the number of osteopontin-producing macrophages by more than anti-interleukin-10 antibody alone in post-MI hearts. Conclusions Interleukin-10 and macrophage colony-stimulating factor act synergistically to activate STAT3 and ERK in cardiac macrophages, which in turn upregulate the expression of galectin-3 and MerTK, leading to the functional maturation of osteopontin-producing macrophages.

Nuclear Osteopontin Is a Marker of Advanced Heart Failure and Cardiac Allograft Vasculopathy: Evidence From Transplant and Retransplant Hearts

Background

Heart transplant is the gold standard therapy for patients with advanced heart failure. Over 5,500 heart transplants are performed every year worldwide. Cardiac allograft vasculopathy (CAV) is a common complication post-heart transplant which reduces survival and often necessitates heart retransplantation. Post-transplant follow-up requires serial coronary angiography and endomyocardial biopsy (EMB) for CAV and allograft rejection screening, respectively; both of which are invasive procedures. This study aims to determine whether osteopontin (OPN) protein, a fibrosis marker often present in chronic heart disease, represents a novel biomarker for CAV.

Methods

Expression of OPN was analyzed in cardiac tissue obtained from patients undergoing heart retransplantation using immunofluorescence imaging (n = 20). Tissues from native explanted hearts and three serial follow-up EMB samples of transplanted hearts were also analyzed in five of these patients.

Results

Fifteen out of 20 patients undergoing retransplantation had CAV. 13/15 patients with CAV expressed nuclear OPN. 5/5 patients with multiple tissue samples expressed nuclear OPN in both 1^st and 2^nd explanted hearts, while 0/5 expressed nuclear OPN in any of the follow-up EMBs. 4/5 of these patients had an initial diagnosis of dilated cardiomyopathy (DCM).

Conclusion

Nuclear localization of OPN in cardiomyocytes of patients with CAV was evident at the time of cardiac retransplant as well as in patients with DCM at the time of the 1^st transplant. The results implicate nuclear OPN as a novel biomarker for severe CAV and DCM.

The effects of macrophages on cardiomyocyte calcium-handling function using in vitro culture models

Following myocardial infarction (MI), myocardial inflammation plays a crucial role in the pathogenesis of MI injury and macrophages are among the key cells activated during the initial phases of the host response regulating the healing process. While macrophages have emerged as attractive effectors in tissue injury and repair, the contribution of macrophages on cardiac cell function and survival is not fully understood due to complexity of the in vivo inflammatory microenvironment. Understanding the key cells involved and how they communicate with one another is of paramount importance for the development of effective clinical treatments. Here, novel in vitro myocardial inflammation models were developed to examine how both direct and indirect interactions with polarized macrophage subsets present in the post-MI microenvironment affect cardiomyocyte function. The indirect model using conditioned medium from polarized macrophage subsets allowed examination of the effects of macrophage-derived factors on stem cell-derived cardiomyocyte function for up to 3 days. The results from the indirect model demonstrated that pro-inflammatory macrophage-derived factors led to a significant downregulation of cardiac troponin T (cTnT) and sarcoplasmic/endoplasmic reticulum calcium ATPase (Serca2) gene expression. It also demonstrated that inhibition of macrophage-secreted matricellular protein, osteopontin (OPN), led to a significant decrease in cardiomyocyte store-operated calcium entry (SOCE). In the direct model, stem cell-derived cardiomyocytes were co-cultured with polarized macrophage subsets for up to 3 days. It was demonstrated that anti-inflammatory macrophages significantly increased cardiomyocyte Ca²⁺ fractional release while macrophages independent of their subtypes led to significant downregulation of SOCE response in cardiomyocytes. This study describes simplified and controlled in vitro myocardial inflammation models, which allow examination of potential beneficial and deleterious effects of macrophages on cardiomyocytes and vise versa. This can lead to our improved understanding of the inflammatory microenvironment post-MI, otherwise difficult to directly investigate in vivo or by using currently available in vitro models.

Extracellular matrix-based biomaterials for cardiac regeneration and repair

The spectrum of ischemic heart diseases, encompassing acute myocardial infarction to heart failure, represents the leading cause of death worldwide. Although extensive progress in cardiovascular diagnoses and therapy has been made, the prevalence of the disease continues to increase. Cardiac regeneration has a promising perspective for the therapy of heart failure. Recently, extracellular matrix (ECM) has been shown to play an important role in cardiac regeneration and repair after cardiac injury. There is also evidence that the ECM could be directly used as a drug to promote cardiomyocyte proliferation and cardiac regeneration. Increasing evidence supports that applying ECM biomaterials to maintain heart function recovery is an important approach to apply the concept of cardiac regenerative medicine to clinical practice in the future. Here, we will introduce the essential role of cardiac ECM in cardiac regeneration and summarize the approaches of delivering ECM biomaterials to promote cardiac repair in this review.

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.

Syndecan-4 Protects the Heart From the Profibrotic Effects of Thrombin-Cleaved Osteopontin

Background Pressure overload of the heart occurs in patients with hypertension or valvular stenosis and induces cardiac fibrosis because of excessive production of extracellular matrix by activated cardiac fibroblasts. This initially provides essential mechanical support to the heart, but eventually compromises function. Osteopontin is associated with fibrosis; however, the underlying signaling mechanisms are not well understood. Herein, we examine the effect of thrombin-cleaved osteopontin on fibrosis in the heart and explore the role of syndecan-4 in regulating cleavage of osteopontin. Methods and Results Osteopontin was upregulated and cleaved by thrombin in the pressure-overloaded heart of mice subjected to aortic banding. Cleaved osteopontin was higher in plasma from patients with aortic stenosis receiving crystalloid compared with blood cardioplegia, likely because of less heparin-induced inhibition of thrombin. Cleaved osteopontin and the specific osteopontin peptide sequence RGDSLAYGLR that is exposed after thrombin cleavage both induced collagen production in cardiac fibroblasts. Like osteopontin, the heparan sulfate proteoglycan syndecan-4 was upregulated after aortic banding. Consistent with a heparan sulfate binding domain in the osteopontin cleavage site, syndecan-4 was found to bind to osteopontin in left ventricles and cardiac fibroblasts and protected osteopontin from cleavage by thrombin. Shedding of the extracellular part of syndecan-4 was more prominent at later remodeling phases, at which time levels of cleaved osteopontin were increased. Conclusions Thrombin-cleaved osteopontin induces collagen production by cardiac fibroblasts. Syndecan-4 protects osteopontin from cleavage by thrombin, but this protection is lost when syndecan-4 is shed in later phases of remodeling, contributing to progression of cardiac fibrosis.

Osteopontin: A Promising Therapeutic Target in Cardiac Fibrosis

Osteopontin (OPN) is recognized for its significant roles in both physiological and pathological processes. Initially, OPN was recognized as a cytokine with pro-inflammatory actions. More recently, OPN has emerged as a matricellular protein of the extracellular matrix (ECM). OPN is also known to be a substrate for proteolytic cleavage by several proteases that form an integral part of the ECM. In the adult heart under physiological conditions, basal levels of OPN are expressed. Increased expression of OPN has been correlated with the progression of cardiac remodeling and fibrosis to heart failure and the severity of the condition. The intricate process by which OPN mediates its effects include the coordination of intracellular signals necessary for the differentiation of fibroblasts into myofibroblasts, promoting angiogenesis, wound healing, and tissue regeneration. In this review, we discuss the role of OPN in contributing to the development of cardiac fibrosis and its suitability as a therapeutic target.

The potential role of senescence in limiting fibrosis caused by aging

Fibrosis-related diseases carry with them a high mortality rate and their morbidity increases with age. Recent findings indicate that induced senescence in myofibroblasts can limit or reduce myocardial fibrosis, cirrhosis, and idiopathic pulmonary fibrosis, while also accelerating wound healing. However, more senescent cells are accumulated as organisms age, which exacerbates aging-related diseases. These two contradictory theories inspired us to summarize papers on the restrictive effect of senescence on fibrosis and to input the key findings into simple software that we developed to assist with data organization and presentation. In this review, we illustrate that senescent cells secrete more matrix metalloproteinases to solubilize excess collagen, while chemokines and cytokines activate immune cells to eliminate senescent cells. In the elderly, it is perhaps more effective to limit fibrosis by inducing myofibroblast senescence and then removing senescent cells that are not cleared via normal mechanisms by antisenescence therapies.

Plasma osteopontin levels, but not its myocardial expression, reflect heart failure severity in recently diagnosed dilated cardiomyopathy

BACKGROUND

Elevated levels of the extracellular matrix glycoprotein osteopontin (OPN) may be detected in both myocardium and plasma under various pathological conditions affecting the heart. Several studies demonstrated increased plasma OPN levels in patients with heart failure due to dilated cardiomyopathy (DCM), while other studies showed high OPN expression levels in the myocardium of such patients. However, very little is known about OPN levels in both plasma and myocardium of the same individual with DCM. Therefore, we aimed to compare plasma OPN levels and levels of myocardial OPN expression in patients with recent-onset DCM (Ro-DCM).

METHODS

We examined plasma OPN as well as creatinine, C‑reactive protein (CRP), brain natriuretic peptide (BNP), and troponin I levels in 25 patients with Ro-DCM. Furthermore, all subjects underwent transthoracic echocardiography, selective coronary angiography, and endomyocardial biopsy (EMB) for the assessment of myocardial OPN expression.

RESULTS

No significant correlation between myocardial OPN expression and clinical, biochemical, or echocardiographic parameters was found. In log transformation analysis, plasma OPN levels correlated significantly with BNP levels (r = 0.46, p = 0.031), with CRP levels (r = 0.52, p = 0.015), and with early diastolic mitral annular velocity (r = -0.57, p = 0.009). There was a borderline association between the plasma OPN log value and New York Heart Association class (p = 0.053).

CONCLUSION

Plasma OPN levels reflect heart failure severity in patients with Ro-DCM. Myocardial OPN expression is not associated with either plasma OPN levels or markers of heart failure in these individuals.

The Extracellular Matrix in Ischemic and Nonischemic Heart Failure

The ECM (extracellular matrix) network plays a crucial role in cardiac homeostasis, not only by providing structural support, but also by facilitating force transmission, and by transducing key signals to cardiomyocytes, vascular cells, and interstitial cells. Changes in the profile and biochemistry of the ECM may be critically implicated in the pathogenesis of both heart failure with reduced ejection fraction and heart failure with preserved ejection fraction. The patterns of molecular and biochemical ECM alterations in failing hearts are dependent on the type of underlying injury. Pressure overload triggers early activation of a matrix-synthetic program in cardiac fibroblasts, inducing myofibroblast conversion, and stimulating synthesis of both structural and matricellular ECM proteins. Expansion of the cardiac ECM may increase myocardial stiffness promoting diastolic dysfunction. Cardiomyocytes, vascular cells and immune cells, activated through mechanosensitive pathways or neurohumoral mediators may play a critical role in fibroblast activation through secretion of cytokines and growth factors. Sustained pressure overload leads to dilative remodeling and systolic dysfunction that may be mediated by changes in the interstitial protease/antiprotease balance. On the other hand, ischemic injury causes dynamic changes in the cardiac ECM that contribute to regulation of inflammation and repair and may mediate adverse cardiac remodeling. In other pathophysiologic conditions, such as volume overload, diabetes mellitus, and obesity, the cell biological effectors mediating ECM remodeling are poorly understood and the molecular links between the primary insult and the changes in the matrix environment are unknown. This review article discusses the role of ECM macromolecules in heart failure, focusing on both structural ECM proteins (such as fibrillar and nonfibrillar collagens), and specialized injury-associated matrix macromolecules (such as fibronectin and matricellular proteins). Understanding the role of the ECM in heart failure may identify therapeutic targets to reduce geometric remodeling, to attenuate cardiomyocyte dysfunction, and even to promote myocardial regeneration.

Reactivating endogenous mechanisms of cardiac regeneration via paracrine boosting using the human amniotic fluid stem cell secretome

BACKGROUND

The adult mammalian heart retains residual regenerative capability via endogenous cardiac progenitor cell (CPC) activation and cardiomyocyte proliferation. We previously reported the paracrine cardioprotective capacity of human amniotic fluid-derived stem cells (hAFS) following ischemia or cardiotoxicity. Here we analyse the potential of hAFS secretome fractions for cardiac regeneration and future clinical translation.

METHODS

hAFS were isolated from amniotic fluid leftover samples from prenatal screening. hAFS conditioned medium (hAFS-CM) was obtained following hypoxic preconditioning. Anti-apoptotic, angiogenic and proliferative effects were evaluated on rodent neonatal cardiomyocytes (r/mNVCM), human endothelial colony forming cells (hECFC) and human CPC. Mice undergoing myocardial infarction (MI) were treated with hAFS-CM, hAFS-extracellular vesicles (hAFS-EV), or EV-depleted hAFS-CM (hAFS-DM) by single intra-myocardial administration and evaluated in the short and long term.

RESULTS

hAFS-CM improved mNVCM survival under oxidative and hypoxic damage, induced Ca²⁺-dependent angiogenesis in hECFC and triggered hCPC and rNVCM proliferation. hAFS-CM treatment after MI counteracted scarring, supported cardiac function, angiogenesis and cardiomyocyte cell cycle progression in the long term. hAFS-DM had no effect. hAFS-CM and hAFS-EV equally induced epicardium WT1+ CPC reactivation. Although no CPC cardiovascular differentiation was observed, our data suggests contribution to local angiogenesis by paracrine modulation. hAFS-EV alone were able to recapitulate all the beneficial effects exerted by hAFS-CM, except for stimulation of vessel formation.

CONCLUSIONS

hAFS-CM and hAFS-EV can improve cardiac repair and trigger cardiac regeneration via paracrine modulation of endogenous mechanisms. While both formulations are effective in sustaining myocardial renewal, hAFS-CM retains higher pro-angiogenic potential, while hAFS-EV particularly enhances cardiac function.

GPR 30 reduces myocardial infarct area and fibrosis in female ovariectomized mice by activating the PI3K/AKT pathway

AIMS

Estrogen plays an important role in cardioprotection. Animal experiments showed that the G-protein coupled estrogen receptor 30 (GPR30) specific agonist G1 could reduce post-ischemic dysfunction and inhibit cardiac fibroblast proliferation. However, the underlying mechanism of action is not clear. The current study tests the hypothesis that GPR30 reduces myocardial infarct area and fibrosis in female ovariectomized (OVX) mice by activating the PI3K/AKT pathway.

MAIN METHODS

In this study, we established a myocardial infarction (MI) animal model derived from OVX C57BL/6 female mice, and investigated the effect of G1 on cardiac function by echocardiography and Hemodynamics, morphology and expression of fibrosis-related and apoptosis-related proteins by Masson's trichrome and H&E, Immunofluorescence, Western blotting and TUNEL.

KEY FINDINGS

Combination with OVX significantly increased myocardial fibrosis and MI area compared to MI treatment alone, as determined by echocardiography and hemodynamics. Further addition of G1 changed the expression of apoptosis-related proteins, decreased the levels of tumor necrosis factor-α and interleukin-10, and reduced the degree of myocardial fibrosis and myocardial infarct area. Primary cultured cardiac fibroblasts (CFs) were subjected to hypoxia/serum deprivation (H/SD) simulating the in vivo ischemia model. When the PI3K/AKT pathway was inhibited by wortmanin in H/SD CFs, G1 failed to induce significant changes in the expression of apoptosis-related proteins.

SIGNIFICANCE

It suggested that GPR30 may improve cardiac function in female OVX mice by activating the PI3K/AKT pathway and reducing myocardial infarct size and fibrosis.

Deletion of Osteopontin Enhances β₂-Adrenergic Receptor-Dependent Anti-Fibrotic Signaling in Cardiomyocytes

Cardiac β₂-adrenergic receptors (ARs) are known to inhibit collagen production and fibrosis in cardiac fibroblasts and myocytes. The β₂AR is a Gs protein-coupled receptor (GPCR) and, upon its activation, stimulates the generation of cyclic 3′,5′-adenosine monophosphate (cAMP). cAMP has two effectors: protein kinase A (PKA) and the exchange protein directly activated by cAMP (Epac). Epac1 has been shown to inhibit cardiac fibroblast activation and fibrosis. Osteopontin (OPN) is a ubiquitous pro-inflammatory cytokine, which also mediates fibrosis in several tissues, including the heart. OPN underlies several cardiovascular pathologies, including atherosclerosis and cardiac adverse remodeling. We found that the cardiotoxic hormone aldosterone transcriptionally upregulates OPN in H9c2 rat cardiac myoblasts—an effect prevented by endogenous β₂AR activation. Additionally, CRISPR-mediated OPN deletion enhanced cAMP generation in response to both β₁AR and β₂AR activation in H9c2 cardiomyocytes, leading to the upregulation of Epac1 protein levels. These effects rendered β₂AR stimulation capable of completely abrogating transforming growth factor (TGF)-β-dependent fibrosis in OPN-lacking H9c2 cardiomyocytes. Finally, OPN interacted constitutively with G_αs subunits in H9c2 cardiac cells. Thus, we uncovered a direct inhibitory role of OPN in cardiac β₂AR anti-fibrotic signaling via cAMP/Epac1. OPN blockade could be of value in the treatment and/or prevention of cardiac fibrosis.

Osteopontin plays important roles in pulmonary arterial hypertension induced by systemic-to-pulmonary shunt

Recent studies indicated that osteopontin (OPN) was involved in the genesis and progression of pulmonary arterial hypertension (PAH); however, its role in congenital heart disease-associated PAH (CHD/PAH) remains unknown. Our results showed that OPN was increased in lungs and plasma of patients with Eisenmenger syndrome; moreover, OPN and α_Vβ₃-integrin expression levels were augmented in rat lungs exposed to systemic-to-pulmonary shunt. Cell culture assay demonstrated that distal pulmonary arterial smooth muscle cells (PASMCs) from rat lungs suffering from volume and pressure overload exhibited enhanced proliferation compared with those from healthy rats. Mechanical stretch (20% at 1 Hz) increased OPN expression and activated ERK1/2 and protein kinase B (Akt) signal pathway in distal PASMCs from healthy rats. Interestingly, OPN enhanced the proliferation and migration of PASMCs while blocking α_Vβ₃-integrin with neutralizing antibody LM609 or Arg-Gly-Asp peptidomimetic antagonist cyclo(Ala-Arg-Gly-Asp-3-aminomethylbenzoyl) (XJ735), rectified the proliferative and migratory effects of OPN, which were partially mediated via ERK1/2 and Akt signaling pathways. Furthermore, surgical correction of systemic-to-pulmonary shunt, particularly XJ735 supplementation after surgical correction of systemic-to-pulmonary shunt, significantly alleviated the pulmonary hypertensive status in terms of pulmonary hemodynamic indices, pulmonary vasculopathy, and right ventricular hypertrophy. In summary, OPN alteration in lungs exposed to systemic-to-pulmonary shunt exerts a deteriorative role in pulmonary vascular remodeling through modulating the proliferation and migration of PASMCs, at least in part, via ανβ3-ERK1/2 and ανβ3-Akt signaling pathways. Antagonizing OPN receptor ανβ3-integrin accelerated the regression of pulmonary vasculopathy after surgical correction of systemic-to-pulmonary shunt, indicating a potential therapeutic strategy for patients with CHD/PAH.-Meng, L., Liu, X., Teng, X., Gu, H., Yuan, W., Meng, J., Li, J., Zheng, Z., Wei, Y., Hu, S. Osteopontin plays important roles in pulmonary arterial hypertension induced by systemic-to-pulmonary shunt.

Inflammation and fibrosis in murine models of heart failure

Heart failure is a consequence of various cardiovascular diseases and associated with poor prognosis. Despite progress in the treatment of heart failure in the past decades, prevalence and hospitalisation rates are still increasing. Heart failure is typically associated with cardiac remodelling. Here, inflammation and fibrosis are thought to play crucial roles. During cardiac inflammation, immune cells invade the cardiac tissue and modulate tissue-damaging responses. Cardiac fibrosis, however, is characterised by an increased amount and a disrupted composition of extracellular matrix proteins. As evidence exists that cardiac inflammation and fibrosis are potentially reversible in experimental and clinical set ups, they are interesting targets for innovative heart failure treatments. In this context, animal models are important as they mimic clinical conditions of heart failure patients. The advantages of mice in this respect are short generation times and genetic modifications. As numerous murine models of heart failure exist, the selection of a proper disease model for a distinct research question is demanding. To facilitate this selection, this review aims to provide an overview about the current understanding of the pathogenesis of cardiac inflammation and fibrosis in six frequently used murine models of heart failure. Hence, it compares the models of myocardial infarction with or without reperfusion, transverse aortic constriction, chronic subjection to angiotensin II or deoxycorticosterone acetate, and coxsackievirus B3-induced viral myocarditis in this context. It furthermore provides information about the clinical relevance and the limitations of each model, and, if applicable, about the recent advancements in their methodological proceedings.

Osteopontin Expression in Cardiomyocytes Is Increased in Pediatric Patients With Sepsis or Pneumonia

Sepsis and pneumonia are major causes of death in the United States, and their pathophysiology includes infection with inflammation and immune dysfunction. Both sepsis and pneumonia cause cardiovascular dysfunction. The expression of Osteopontin (OPN) in cardiomyocytes of patients with sepsis or pneumonia, and its role the induced cardiac dysfunction have not been thoroughly investigated. OPN is a matricellular protein synthesized by multiple diseased tissues and cells including cardiomyocytes. Here, we studied the expression of OPN protein using immunofluorescence in human myocardial autopsy tissues from pediatric and mid age or elderly patients with sepsis and/or pneumonia. Fourteen human myocardial tissues from six pediatric patients and eight mid-age or elderly patients were studied. Immunofluorescence was used to investigate the expression of OPN in paraffin-embedded heart sections co-stained with the myocyte markers Actin Alpha 1 (ACTA1) and Myosin Light Chain 2 (MLC2). A quantitative analysis was performed to determine the number of ACTA1 and MLC2 positive cardiomyocytes that express OPN. The results showed that OPN expression was significantly increased in cardiomyocytes in the hearts from pediatric patients with sepsis and/or pneumonia (N = 3) relative to pediatric patients without sepsis/pneumonia (N = 3), or adult to elderly patients with sepsis/pneumonia (N = 5). Among the older septic hearts, higher levels of cardiomyocyte OPN expression was seen only in conjunction with severe coronary arterial occlusion. This is the first study to document increased OPN expression in cardiomyocytes of pediatric subjects with sepsis or pneumonia. Our findings highlight a potentially important role for OPN in sepsis- or pneumonia-mediated cardiac dysfunction in pediatric patients.

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.

The Biological Role of Nestin(+)-Cells in Physiological and Pathological Cardiovascular Remodeling

The intermediate filament protein nestin was identified in diverse populations of cells implicated in cardiovascular remodeling. Cardiac resident neural progenitor/stem cells constitutively express nestin and following an ischemic insult migrate to the infarct region and participate in angiogenesis and neurogenesis. A modest number of normal adult ventricular fibroblasts express nestin and the intermediate filament protein is upregulated during the progression of reparative and reactive fibrosis. Nestin depletion attenuates cell cycle re-entry suggesting that increased expression of the intermediate filament protein in ventricular fibroblasts may represent an activated phenotype accelerating the biological impact during fibrosis. Nestin immunoreactivity is absent in normal adult rodent ventricular cardiomyocytes. Following ischemic damage, the intermediate filament protein is induced in a modest population of pre-existing adult ventricular cardiomyocytes bordering the peri-infarct/infarct region and nestin⁽⁺⁾-ventricular cardiomyocytes were identified in the infarcted human heart. The appearance of nestin⁽⁺⁾-ventricular cardiomyocytes post-myocardial infarction (MI) recapitulates an embryonic phenotype and depletion of the intermediate filament protein inhibits cell cycle re-entry. Recruitment of the serine/threonine kinase p38 MAPK secondary to an overt inflammatory response after an ischemic insult may represent a seminal event limiting the appearance of nestin⁽⁺⁾-ventricular cardiomyocytes and concomitantly suppressing cell cycle re-entry. Endothelial and vascular smooth muscle cells (VSMCs) express nestin and upregulation of the intermediate filament protein may directly contribute to vascular remodeling. This review will highlight the biological role of nestin⁽⁺⁾-cells during physiological and pathological remodeling of the heart and vasculature and discuss the phenotypic advantage attributed to the intermediate filament protein.

Inflammatory Response During Myocardial Infarction

The occlusion of a coronary artery by a thrombus generated on a ruptured atherosclerotic plaque has been pursued in the last decades as a determining event for the clinical outcome after myocardial infarction (MI). Yet, MI causes a cell death wave front, which triggers an inflammatory response to clear cellular debris, and which in excess can double the myocardial lesion and influence the clinical prognosis in the short and long term. Accordingly, proper, timely regulated inflammatory response has now been considered a second pivotal player in cardiac recovery after MI justifying the search for pharmacological strategies to modulate inflammatory effectors. This chapter reviews the key events and the main effectors of inflammation after myocardial ischemic insult, as well as the contribution of this phenomenon to the progression of atherosclerosis.