Fibroblasts in the Infarcted, Remodeling, and Failing Heart

Assessment of left ventricular systolic function and pathological changes using layer-specific strain in rats with myocardial hypertrophy at various disease stages

PURPOSE

Although layer-specific strains are effective for assessing cardiac function, their application in rat models at different stages of myocardial hypertrophy (MH) is immature, and their relationship with MH and myocardial fibrosis (MF) is unclear. This study aimed to investigate changes in layer-specific strains across different disease stages and analyze their association with pathological changes.

METHODS

A progressive MH rat model was established using isoproterenol injection and categorized into baseline, 1-week, 2-week, 3-week, and 4-week groups. Echocardiographic indices and pathological differences between the five groups were assessed. The correlation between layer-specific strain parameters and cardiomyocyte hypertrophy and MF was analyzed.

RESULTS

As the disease progressed, the left ventricular (LV) dilated, with the LV wall thickening and then thinning. The left ventricular ejection fraction declined significantly in the fourth week. The endo-myocardial, mid-myocardium and epi-myocardial global longitudinal strain, along with endo-myocardial global circumferential strain (GCS) and the transmural gradient, significantly decreased in the first week, the mid-myocardium GCS in the second week, and continued to decrease as the disease progressed. The epi-myocardial GCS increased in the first week, but then decreased, becoming significantly lower than the baseline group in the third week. The degrees of MH and MF were correlated with the layer-specific strain parameters.

CONCLUSION

Layer-specific strains maybe are valuable for early and effective monitoring of LV systolic function and pathological changes in rats with MH. Longitudinal strain is more sensitive to functional changes; endomyocardial strain reflects early LV remodeling and circumferential strain perhaps indicates disease progression and severity.

From cancer to heart fibrosis - GLIPR1 highlights a subset of myofibroblasts responsive to mesenchymal stem cell therapy after myocardial infarction

Despite recent advances in pre-clinical research on cardiac remodeling following myocardial infarction (MI), the precise molecular pathways remain poorly understood and effective therapies for heart failure are still delayed in development. Aged animal models may more accurately reflect the clinical scenario, as aging alters the cellular identities and impedes cardiac repair. In this manuscript, we investigated the expression profile of mouse cardiac fibroblasts following myocardial infarction, using both young and aged animals to enhance the translational significance. The initial studies aimed to identify fibroblast changes common to both young and old animals. Additionally, a group of young animals that underwent mesenchymal stem cells (MSC) therapy after MI surgery was included to help identify the molecular changes amenable to therapeutic modulation. The analysis uncovered Glioma- Pathogenesis Related Protein 1 (GLIPR1) activation during the post-MI maturation phase in a subset of myofibroblasts, localized to the infarct zone in young subjects and widespread throughout the ventricle in aged animals. Further investigations indicated that the inflammatory environment post-MI induced the upregulation of GLIPR1, which in turn promoted increased TIMP3 expression. These findings provide valuable insights for future research aimed at exploring the therapeutic potential of targeting GLIPR1 to reduce cardiac fibrosis post-MI.

A cell type-specific expression atlas of small and total RNA in the heart after myocardial infarction

Acute myocardial infarction (AMI) is a leading cause of mortality worldwide. MicroRNAs (miRNAs), among other small non-coding RNAs, shape the transcriptome and control cellular functions. Although single-cell technologies are now available to study myocardial ischemia response, the study of small RNA regulation is limited by depth of expression, capture efficiency and lack of full coverage of transcripts. In addition, the kinetic expression of miRNAs is unknown. Using paired small and total RNA sequencing, we built an expression atlas to study the temporal dynamics of miRNAs and genes in four major heart cell types after AMI. Expression dynamics reveal enriched functions highlighting cell type-specific AMI stress responses. Many deregulated mouse genes after AMI overlap with known human cardiovascular disease genes. The dataset is highly valuable for additional research on small and long non-coding RNAs, such as regulation of RNA variants by splicing or alternative ORFs. All in all, the RNA expression atlas provides a useful resource to study different roles of RNAs in major cell types of the heart after AMI.

NLRP3 inflammasome: structure, mechanism, drug-induced organ toxicity, therapeutic strategies, and future perspectives

Drug-induced toxicity is an important issue in clinical medicine, which typically results in organ dysfunction and adverse health consequences. The family of NOD-like receptors (NLRs) includes intracellular proteins involved in recognizing pathogens and triggering innate immune responses, including the activation of the NLRP3 inflammasome. The NLRP3 (nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3) inflammasome is a critical component for both innate and adaptive immune responses and has been implicated in various drug-induced toxicities, including hepatic, renal, and cardiovascular diseases. The unusual activation of the NLRP3 inflammasome causes the release of pro-inflammatory cytokines, such as IL-1β and IL-18, which can lead to more damage to tissues. Targeting NLRP3 inflammasome is a potential therapeutic endeavour for suppressing drug-induced toxicity. This review provides insights into the mechanism, drug-induced organ toxicity, therapeutic strategies, and prospective therapeutic approaches of the NLRP3 inflammasome and summarizes the developing therapies that target the inflammasome unit. This review has taken up one of the foremost endeavours in understanding and inhibiting the NLRP3 inflammasome as a means of generating safer pharmacological therapies.

Emerging Epigenetic Therapies for the Treatment of Cardiac Fibrosis

Fibrosis is a pathological process characterized by excessive extracellular matrix (ECM) deposition, leading to tissue stiffening and organ dysfunction. It is a major contributor to chronic diseases affecting various organs, with limited therapeutic options available. Among the different forms of fibrosis, cardiac fibrosis is particularly relevant due to its impact on cardiovascular diseases (CVDs), which remain the leading cause of morbidity and mortality worldwide. This process is driven by activated cardiac fibroblasts (CFs), which promote ECM accumulation in response to chronic stressors. Epigenetic mechanisms, including DNA methylation, histone modifications, and chromatin remodeling, are key regulators of fibroblast activation and fibrotic gene expression. Enzymes such as DNA methyltransferases (DNMTs), histone methyltransferases (HMTs), histone acetyltransferases (HATs), and histone deacetylases (HDACs) have emerged as potential therapeutic targets, and epigenetic inhibitors have shown promise in modulating these enzymes to attenuate fibrosis by controlling fibroblast function and ECM deposition. These small-molecule compounds offer advantages such as reversibility and precise temporal control, making them attractive candidates for therapeutic intervention. This review aims to provide a comprehensive overview of the mechanisms by which epigenetic regulators influence cardiac fibrosis and examines the latest advances in preclinical epigenetic therapies. By integrating recent data from functional studies, single-cell profiling, and drug development, it highlights key molecular targets, emerging therapeutic strategies, and current limitations, offering a critical framework to guide future research and clinical translation.

Cocultured amniotic stem cells and cardiomyocytes in a 3-D acellular heart patch reduce the infarct size and left ventricle remodeling: promote angiogenesis in a porcine acute myocardial infarction model

BACKGROUND

Acute myocardial infarction (AMI) induces significant myocardial damage, ultimately leading to heart failure as the surrounding healthy myocardial tissue undergoes progressive deterioration due to excessive mechanical stress.

METHODS

This study aimed to investigate myocardial regeneration in a porcine model of AMI using an acellular amniotic membrane with fibrin-termed an amnion bilayer (AB) or heart patch-as a cellular delivery system using porcine amniotic stem cells (pASCs) and autologous porcine cardiomyocytes (pCardios). Fifteen pigs (aged 2-4 months, weighing 50-60 kg) were randomly assigned to three experimental groups (n = 5): control group (AMI induction only), pASC group (pASC transplantation only), and coculture group (pASC and pCardio transplantation). AMI was induced via posterior left ventricular artery ligation and confirmed through standard biomarkers. After eight weeks, histological and molecular analyses were conducted to assess myocardial regeneration.

RESULTS

Improvement in regional wall motion abnormality (RWMA) was observed in 60% of the coculture group, 25% of the pASC group, and none in the control group. Histological analysis of the control group revealed extensive fibrosis with pronounced lipomatosis, particularly at the infarct center. In contrast, pASC and coculture groups exhibited minimal fibrotic scarring at both the infarct center and border regions. Immunofluorescence analysis demonstrated positive α-actinin expression in both the pASC and coculture groups, with the coculture group displaying sarcomeric structures-an organization absent in control group. RNA expression levels of key cardiomyogenic markers, including cardiac troponin T (cTnT), myosin heavy chain (MHC), and Nkx2.5, were significantly elevated in the treatment groups compared to the controls, with the coculture group exhibiting the highest MHC expression. The expression of c-Kit was also increased in both treatment groups relative to the control. Conversely, apoptotic markers p21 and Caspase-9 were highest in the control group, while coculture group exhibited the lowest p53 expression.

CONCLUSION

Epicardial transplantation of an acellular amniotic heart patch cocultured with cardiomyocytes and pASCs demonstrated superior cardiomyogenesis after eight weeks compared to pASC transplantation alone or control conditions. The coculture system was found to enhance the cardiac regeneration process, as evidenced by improved RWMA, distinct sarcomeric organization, reduced fibrotic scarring, and lower apoptotic gene expression.

Formyl-peptide receptor type 2 activation mitigates heart and lung damage in inflammatory arthritis

Rheumatoid arthritis (RA) is associated with heart and lung dysfunction. Current therapies fail to attenuate such complications. Here, we identify formyl-peptide receptor type 2 (FPR2) as a therapeutic target to treat heart and lung dysfunction associated with inflammatory arthritis. Arthritic mice on high levels of dietary homocysteine develop cardiac diastolic dysfunction and reduced lung compliance, mirroring two comorbidities in RA. Therapeutic administration of a small molecule FPR2 agonist (BMS986235) to hyper-homocysteine arthritic mice prevented diastolic dysfunction (monitored by echocardiography) and restored lung compliance. These tissue-specific effects were secondary to reduced neutrophil infiltration, modulation of fibroblast activation and phenotype (in the heart) and attenuation of monocyte and macrophage numbers (in the lung). A dual FPR1/2 agonist (compound 43) failed to prevent the reduction in lung compliance of arthritic mice and promoted the accumulation of inflammatory monocytes and pro-fibrotic macrophages in lung parenchyma. This cellular response lies downstream of FPR1-mediated potentiation of CCL2-dependent monocyte chemotaxis and activation. This finding supports the therapeutic development of selective FPR2 agonists to mitigate two impactful comorbidities associated with inflammatory arthritides.

The SGLT2 inhibitor canagliflozin attenuates mitochondrial oxidative stress and alterations of calcium handling induced by high glucose in human cardiac fibroblasts

Cardiac fibrosis and remodeling are critical contributors to heart failure, particularly in the context of diabetes, where hyperglycemia (HG) exacerbates pathological fibroblast activity. Despite the known cardiovascular benefits of canagliflozin (CANA), its specific effects on human cardiac fibroblasts (HCFs) under HG conditions remain unexplored. We investigated whether CANA could mitigate HG-induced detrimental responses in HCFs. Dose-response assays revealed that 100 nM CANA significantly reduced HG-induced proliferation and migration of HCFs. Furthermore, CANA attenuated mitochondrial reactive oxygen species (ROS) production, a key driver of myofibroblast differentiation, and suppressed HG-induced expression of SMAD2, a critical activator of cardiac fibroblasts. Additionally, HG disrupted calcium (Ca2+) homeostasis, which was ameliorated by CANA treatment. These findings collectively demonstrate that CANA exerts protective effects on HCFs by improving mitochondrial function, restoring Ca2+ handling, and reducing fibroblast proliferation, migration, and activation under HG conditions.

Proteome Alterations in Cardiac Fibroblasts: Insights from Experimental Myocardial Infarction and Clinical Ischaemic Cardiomyopathy

Ischaemic heart disease (IHD) is a chronic condition that can cause pathological cardiac remodelling and heart failure (HF). In this study, we sought to determine how cardiac fibroblasts were altered post-experimental myocardial infarction (MI). Female C57BL6 mice underwent experimental MI by permanent left coronary artery ligation. Cardiac fibroblasts were isolated from extracted heart tissue of experimental MI mice and subsequently treated with the pro-fibrotic cytokine, TGF-β, for 24 h and analysed using high throughput LC-MS/MS analysis. Findings were validated using mass spectrometry data generated from human left ventricular tissue analysis, which were collected from patients with ischaemic cardiomyopathy (ISCM) and age/sex-matched patients without clinical HF (NF). Proteomic analysis revealed significant protein expression changes in mouse cardiac fibroblasts after MI. These changes were most pronounced at 1 month post-MI, compared to earlier time points (3 days and 1 week). TGF-β treatment profoundly affected fibroblast cells extracted from MI mice, indicating a heightened sensitivity to pro-fibrotic factors after myocardial injury. Extracellular matrix (ECM) proteins significantly altered in MI fibroblasts following TGF-β treatment were significantly associated with cardiac remodelling. Notably, Lox was significantly changed in both isolated fibroblasts treated with TGF-β from experiment MI mice and human ISCM. Isolated cardiac fibroblasts from MI mice are more susceptible to developing pathogenic traits following TGF-β treatment than isolated fibroblasts from normal heart tissue. ECM proteins associated with these enhanced fibroblast activities and functions are evident. These altered proteins may play a functional role in MI-associated cardiac dysfunction.

The epigenetic regulation of crosstalk between cardiac fibroblasts and other cardiac cell types during stress

With the global impact of cardiovascular disease, there is a dire need to understand the mechanisms in the heart during injury and stress. It has been shown that the regulation of the extracellular matrix via cardiac fibroblasts plays a major role in the progression of heart failure and worsening function of the heart. Importantly, it has been suggested that crosstalk between other cardiac cells like cardiomyocytes, immune cells, and endothelial cells are influenced by the pathological function of the fibroblasts. This decline in function across all cardiac cells is seemingly irreversible. However, epigenetic mechanisms have been shown to regulate functionality across cardiac cells and improve outcomes during stress or injury. This epigenetic regulation has also been shown to control communication between different cell types and influence the role of multiple cardiac cell types during injury. The goal of this review is to summarize and discuss the current research of epigenetic regulation of cardiac fibroblasts and the subsequent crosstalk with other cardiac cell types in cardiovascular disease states.

Rescue of mitochondrial dysfunction through alteration of extracellular matrix composition in barth syndrome cardiac fibroblasts

Fibroblast-ECM (dys)regulation is associated with a plethora of diseases. The ECM acts as a reservoir of inflammatory factors and cytokines that mediate molecular mechanisms within cardiac cell populations. The role of ECM-mitochondria crosstalk in the development and progression of cardiac disorders remains uncertain. We evaluated the influence of ECM produced by stromal cells from patients with the mitochondrial cardiomyopathy (Barth syndrome, BTHS) and unaffected healthy controls on cardiac fibroblast (CF) metabolic function. To do this, cell-derived matrices CDMs were generated from BTHS and healthy human pluripotent stem cell-derived CFs (hPSC-CF) and used as cell culture substrates. BTHS CDMs negatively impacted the mitochondrial function of healthy hPSC-CFs while healthy CDMs improved mitochondrial function in BTHS hPSC-CFs. Mass spectrometry comparisons identified 5 matrisome proteins differentially expressed in BTHS compared to healthy CDM. Our results highlight a key role for the ECM in disease through its impact on mitochondrial function.

Targeting cardiac fibrosis with Chimeric Antigen Receptor-Engineered Cells

Cardiac fibrosis poses a significant challenge in cardiovascular diseases due to its intricate pathogenesis, and there is currently no standardized and effective treatment approach. The fibrotic process entails the involvement of various cell types and molecular mechanisms, such as fibroblast activation and proliferation, increased collagen synthesis, and extracellular matrix rearrangement. Traditional therapies often fall short in efficacy or carry substantial side effects. However, recent studies have shown that Chimeric Antigen Receptor T (CAR-T) cells can selectively target and eliminate activated cardiac fibroblasts (CFs) in mice, leading to reduced cardiac fibrosis and improved myocardial tissue compliance. This breakthrough presents a new and promising avenue for treating cardiac fibrosis. Currently, CAR-T cell-based therapy for cardiac fibrosis is undergoing animal experimentation, indicating ample scope for enhancement. Future investigations could explore the application of CAR cell therapy in cardiac fibrosis treatment, including the potential of CAR-natural killer (CAR-NK) cells and CAR macrophages (CAR-M), offering novel insights and strategies for combating cardiac fibrosis.

Myocardial inflammation is associated with impaired mitochondrial oxidative capacity in ischaemic cardiomyopathy

AIMS

Myocardial inflammation and impaired mitochondrial oxidative capacity are hallmarks of heart failure (HF) pathophysiology. The extent of myocardial inflammation in patients suffering from ischaemic cardiomyopathy (ICM) or dilated cardiomyopathy (DCM) and its association with mitochondrial energy metabolism are unknown. We aimed at establishing a relevant role of cardiac inflammation in the impairment of mitochondrial energy production in advanced ischaemic and non-ischaemic HF.

METHODS

We included 81 patients with stage D HF (ICM, n = 44; DCM, n = 37) undergoing left ventricular assist device implantation (n = 59) or heart transplantation (n = 22) and obtained left ventricular tissue samples during open heart surgery. We quantified mitochondrial oxidative capacity, citrate synthase activity (CSA) and fibrosis and lymphocytic infiltration. We considered infiltration of >14 CD3+ cells/mm2 relevant inflammation.

RESULTS

Patients with ICM or DCM did not differ regarding age (61.5 ± 5.7 vs. 56.5 ± 12.7 years, P = 0.164), sex (86% vs. 84% male, P = 0.725), type 2 diabetes mellitus (34% vs. 18%, P = 0.126) or chronic kidney disease (8% vs. 11%, P = 0.994). ICM exhibited oxidative capacity reduced by 23% compared to DCM (108.6 ± 41.4 vs. 141.9 ± 59.9 pmol/(s*mg), P = 0.006). Maximum production of reactive oxygen species was not significantly different between ICM and DCM (0.59 ± 0.28 vs. 0.69 ± 0.36 pmol/(s*ml), P = 0.196). Mitochondrial content, detected by CSA, was lower in ICM (359.6 ± 164.1 vs. 503.0 ± 198.5 nmol/min/mg protein, P = 0.002). Notably, relevant inflammation was more common in ICM (27% vs. 6%, P = 0.024), and the absolute number of infiltrating leucocytes correlated with lower oxidative capacity (r = -0.296, P = 0.019). Fibrosis was more prevalent in ICM (20.9 ± 21.2 vs. 7.2 ± 5.6% of area, P = 0.002), but not associated with oxidative capacity (r = -0.13, P = 0.327).

CONCLUSIONS

More than every fourth ICM patient with advanced HF displays myocardial inflammation in the range of inflammatory cardiomyopathy associated with reduced mitochondrial oxidative capacity. Future studies may evaluate inflammation in ICM at earlier stages in standardised fashion to explore the therapeutic potential of immunosuppression to influence trajectories of HF in ICM.

Spatial FAP Expression as Detected by 68 Ga-FAPI-46 Identifies Myofibroblasts Beyond the Infarct Scar After Reperfusion

PURPOSE

Myocardial infarction (MI) triggers complex cellular responses essential for tissue repair and remodeling, including myofibroblast activation. Fibroblast activation protein alpha (FAP) identifies activated myofibroblasts post-MI, however its spatial distribution relative to the scar and area at risk (AAR) is unclear. Non-invasive FAP-imaging with PET radiotracer 68 Ga-FAPI-46 shows uptake beyond the infarct scar. We therefore aimed to characterize FAP expression in the AAR using a myocardial ischemia-reperfusion (MI/R) model in mice.

PROCEDURES

We induced MI/R in male C57BL/6N mice. The AAR was identified by in vivo lectin staining, and expression of FAP, CD68, and hypoxic tissues were measured using immunohistochemistry. Spatial FAP was further interrogated by 68 Ga-FAPI-46 in mice by autoradiography and humans by PET. Additionally, human cardiac tissues from acute MI patients were examined for fibroblasts and inflammatory cells by expression of FAP, CD13, and α-smooth muscle actin.

RESULTS

FAP expression peaked three days post-MI/R predominantly within the AAR (p < 0.05 vs. d0). Consistent between murine models and human tissues, FAP+ myofibroblasts accumulated within the infarct scar and borderzone, occasionally extending into non-ischemic myocardium. CD68+ macrophages peaked similarly at three days post-MI/R (p < 0.05 vs. d0). FAP expression weakly correlated with CD68 but not with extent of ischemic or hypoxic territory post-MI/R. FAP imaging in mice and humans revealed aligned non-uniform 68 Ga-FAPI-46 uptake extending from the infarct scar into surviving myocardium after MI.

CONCLUSIONS

Our findings demonstrate a distinct FAP expression pattern post-MI/R. The alignment of ex vivo 68 Ga-FAPI-46 signal with myofibroblasts in the AAR supports its identification of a unique substrate in myocardial injury complementing other non-invasive imaging measurements of perfusion, viability and fibrosis.

Preclinical extracellular matrix-based treatment strategies for myocardial infarction: a systematic review and meta-analysis

BACKGROUND

Administrating extracellular matrix (ECM) to restore cardiac function post-myocardial infarction (MI) shows promise, however study variability obscures its true impact. We therefore conducted a systematic review and meta-analysis of preclinical studies to assess the effects of ECM treatments on cardiac function and tissue homeostasis post-MI.

METHODS

We searched PubMed and SCOPUS from inception to June 28, 2024, for animal studies describing ECM treatment post-MI (pre-registered on PROSPERO, CRD42022368400). Random effects meta-analyses compared ECM treatment to controls regarding left ventricular ejection fraction (LVEF), fractional shortening, infarct size, stroke volume, and left ventricular wall thickness. Subgroup analyses examined the influence of sex, species, ECM source, and administration method. Funnel plots and Egger's regression assessed publication bias.

RESULTS

We identify 88 articles which meet our inclusion criteria. These studies describe the use of rats (51%), mice (38%), and pigs (11%). 44% of studies use males, 34% females, 5% both sexes, and 17% did not report sex. Most studies employ permanent MI models (85%) over ischemia reperfusion models (15%), and deliver ECM via intramyocardial injection (59%), cardiac patch (39%), cardiac sleeve (1%), or osmotic pump (1%). Our meta-analysis demonstrates that ECM treatment significantly improves LVEF (MD: 10.9%, 95% CI: [8.7%;13.0%]; p = 8.057e-24), fractional shortening (MD: 8.2%, 95% CI: [5.6%; 10.9%]; p = 1.751e-09), stroke volume (SMD 0.6, 95% CI: [0.2;1.0], p = 0.004), left ventricular wall thickening (SMD 1.2, 95% CI: [0.9; 1.5], p = 1.321e-17), while reducing infarct size (-11.7%, 95% CI: [-14.7%;-8.6%], p = 3.699e-14). We find no significant differences between the various subgroups and no indication of publication bias.

CONCLUSIONS

ECM-based treatments significantly enhance cardiac function and tissue homeostasis in preclinical post-MI models, supporting further research toward clinical translation.

Cardiac Fibrosis in the Multi-Omics Era: Implications for Heart Failure

Cardiac fibrosis, a hallmark of heart failure and various cardiomyopathies, represents a complex pathological process that has long challenged therapeutic intervention. High-throughput omics technologies have begun revolutionizing our understanding of the molecular mechanisms driving cardiac fibrosis and are providing unprecedented insights into its heterogeneity and progression. This review provides a comprehensive analysis of how techniques-encompassing genomics, epigenomics, transcriptomics, proteomics, and metabolomics-are providing insight into our understanding of cardiac fibrosis. Genomic studies have identified novel genetic variants and regulatory networks associated with fibrosis susceptibility and progression, and single-cell transcriptomics has unveiled distinct cardiac fibroblast subpopulations with unique molecular signatures. Epigenomic profiling has revealed dynamic chromatin modifications controlling fibroblast activation states, and proteomic analyses have identified novel biomarkers and potential therapeutic targets. Metabolomic studies have uncovered important alterations in cardiac energetics and substrate utilization during fibrotic remodeling. The integration of these multi-omic data sets has led to the identification of previously unrecognized pathogenic mechanisms and potential therapeutic targets, including cell-type-specific interventions and metabolic modulators. We discuss how these advances are driving the development of precision medicine approaches for cardiac fibrosis while highlighting current challenges and future directions in translating multi-omic insights into effective therapeutic strategies. This review provides a systems-level perspective on cardiac fibrosis that may inform the development of more effective, personalized therapeutic approaches for heart failure and related cardiovascular diseases.

TGFβ-activated kinase 1 signaling controls acquisition of the inflammatory fibroblast phenotype and regulates cardiac remodeling after myocardial infarction

Organ health and function depend on communication between cell types to coordinate tissue growth and repair. Recent studies have indicated that fibroblasts are critical to this process; however, their role in regulating inflammatory responses to injury have remained ambiguous. Here, we demonstrate that transforming growth factor β-activated kinase 1 (TAK1) is a gatekeeper of the inflammatory cardiac fibroblast phenotype. We find that TAK1 propagates IL-1β and TNF-α signaling in cardiac fibroblasts and coordinates the synthesis and secretion of chemokines as well as inflammatory and pro-resolving lipid mediators. Deletion of TAK1 in fibroblasts decreased immune cell recruitment after MI, which was associated with improved cardiac structural and functional remodeling in male mice. Nevertheless, we found the effects of TAK1 deletion to be sexually dimorphic in nature, providing support to the idea that the protected phenotype of the female sex may be based in disparate immune and inflammatory responses. Moreover, TAK1 signaling controlled the acquisition of novel markers of the inflammatory fibroblast phenotype, having a biological basis in redox stress, chemokine and lipid mediator biosynthesis, metalloproteinase activity, and damage-associated molecular pattern recognition. Collectively, these results further resolve the nature and function of inflammatory cardiac fibroblasts in cardiac responses to injury and identify TAK1 signaling in fibroblasts as a potential target for therapy.

Shared molecular, cellular, and environmental hallmarks in cardiovascular disease and cancer: Any place for drug repurposing?

Cancer and cardiovascular disease (CVD) are the 2 biggest killers worldwide. Specific treatments have been developed for the 2 diseases. However, mutual therapeutic targets should be considered because of the overlap of cellular and molecular mechanisms. Cancer research has grown at a fast pace, leading to an increasing number of new mechanistic treatments. Some of these drugs could prove useful for treating CVD, which realizes the concept of cancer drug repurposing. This review provides a comprehensive outline of the shared hallmarks of cancer and CVD, primarily ischemic heart disease and heart failure. We focus on chronic inflammation, altered immune response, stromal and vascular cell activation, and underlying signaling pathways causing pathological tissue remodeling. There is an obvious scope for targeting those shared mechanisms, thereby achieving reciprocal preventive and therapeutic benefits. Major attention is devoted to illustrating the logic, advantages, challenges, and viable examples of drug repurposing and discussing the potential influence of sex, gender, age, and ethnicity in realizing this approach. Artificial intelligence will help to refine the personalized application of drug repurposing for patients with CVD. SIGNIFICANCE STATEMENT: Cancer and cardiovascular disease (CVD), the 2 biggest killers worldwide, share several underlying cellular and molecular mechanisms. So far, specific therapies have been developed to tackle the 2 diseases. However, the development of new cardiovascular drugs has been slow compared with cancer drugs. Understanding the intersection between pathological mechanisms of the 2 diseases provides the basis for repurposing cancer therapeutics for CVD treatment. This approach could allow the rapid development of new drugs for patients with CVDs.

Plumbagin improves myocardial fibrosis after myocardial infarction by inhibiting the AKT/mTOR pathway to upregulate autophagy levels

Cardiac fibrosis is a chronic inflammatory response that considerably impacts cardiac function following myocardial infarction (MI). Although Plumbagin, a natural compound, has been shown to have anti-fibrotic effects by suppresses the ROS and NF-κB pathways in liver fibrosis, its role in regulating cardiac function and cardiac fibrosis post-MI remains unknown. In this study, we demonstrate that Plumbagin effectively inhibits TGF-β1-induced myocardial fibroblast fibrosis and promotes autophagy activation by suppressing the AKT/mTOR pathway. Consistent results were obtained from MI mouse model, which demonstrated that Plumbagin improved cardiac function in mice after MI, reduced the myocardial scar area, and downregulated the expression of fibrosis-related genes. These findings align with our in vitro results, as Plumbagin also inhibited AKT/mTOR activity and increased autophagy levels. Furthermore, we artificially elevated p-mTOR expression in vitro using an mTOR agonist, which reversed the therapeutic effects of Plumbagin, as evidenced by decreased autophagy levels and increased expression of fibrosis-related genes. Our results show that Plumbagin can partially reduce cardiac fibrosis by activating autophagy through modulation of the AKT/mTOR pathway.

Efficacy of Colchicine in Reducing NT-proBNP, Caspase-1, TGF-β, and Galectin-3 Expression and Improving Echocardiography Parameters in Acute Myocardial Infarction: A Multi-Center, Randomized, Placebo-Controlled, Double-Blinded Clinical Trial

Background: Caspase-1 (reflects NOD-like receptor protein 3 inflammasome activity), transforming growth factor-β (TGF-β), and Galectin-3 play significant roles in post-AMI fibrosis and inflammation. Recently, colchicine was shown to dampen inflammation after AMI; however, its direct benefit remains controversial. Objectives: This study aimed to analyze the benefit of colchicine in reducing NT-proBNP, Caspase-1, TGF-β,and Galectin-3 expression and improving systolic-diastolic echocardiography parameters among AMI patients. Methods: A double-blinded, placebo-controlled, randomized, multicenter clinical trial was conducted at three hospitals in East Java, Indonesia: Dr. Saiful Anwar Hospital Malang, Dr. Soebandi Hospital Jember, and Dr. Iskak Hospital Tulungagung, between 1 June and 31 December 2023. A total of 161 eligible AMI subjects were randomly allocated 1:1 to colchicine (0.5 mg daily) or standard treatment for 30 days. Caspase-1, TGF-β, and Galectin-3 were tested on day 1 and day 5 by ELISA, while NT-proBNP was tested on days 5 and 30. Transthoracic echocardiography was also performed on day 5 and day 30. Results: By day 30, no significant improvements in systolic-diastolic echocardiography parameters had been shown in the colchicine group. However, colchicine reduced the level of NT-proBNP on day 30 more than placebo (ΔNT-proBNP: -73.74 ± 87.53 vs. -75.75 ± 12.44 pg/mL; p < 0.001). Moreover, colchicine lowered the level of Caspase-1 expression on day 5 and the levels of TGF-β and Galectin-3 expression on day 1. Conclusions: Colchicine can reduce NT-proBNP, Caspase-1, TGF-β, and Galectin-3 expression significantly among AMI patients. Colchicine administration was capable of reducing post-AMI inflammation, ventricular dysfunction, and heart failure but did not improve systolic-diastolic echocardiography parameters (ClinicalTrials.gov identifier: NCT06426537).

A Vaccine Against Fibroblast Activation Protein Improves Murine Cardiac Fibrosis by Preventing the Accumulation of Myofibroblasts

BACKGROUND

Myofibroblasts are primary cells involved in chronic response-induced cardiac fibrosis. Fibroblast activation protein (FAP) is a relatively specific marker of activated myofibroblasts and a potential target molecule. This study aimed to clarify whether a vaccine targeting FAP could eliminate myofibroblasts in chronic cardiac stress model mice and reduce cardiac fibrosis.

METHODS

We coadministered a FAP peptide vaccine with a cytosine-phosphate-guanine (CpG) K3 oligonucleotide adjuvant to male C57/BL6J mice and confirmed an elevation in the anti-FAP antibody titer. After continuous angiotensin II and phenylephrine administration for 28 days, we evaluated the degree of cardiac fibrosis and the number of myofibroblasts in cardiac tissues.

RESULTS

We found that cardiac fibrosis was significantly decreased in the FAP-vaccinated mice compared with the angiotensin II and phenylephrine control mice (3.45±1.11% versus 8.62±4.79%; P=4.59×10-3) and that the accumulation of FAP-positive cells was also significantly decreased, as indicated by FAP immunohistochemical staining (4077±1746 versus 7327±1741 cells/mm2; FAP vaccine versus angiotensin II and phenylephrine control; P=6.67×10-3). No systemic or organ-specific inflammation due to antibody-dependent cell cytotoxicity induced by the FAP vaccine was observed. Although the transient activation of myofibroblasts has an important role in maintaining the structural robustness in the process of tissue repair, the FAP vaccine showed no adverse effects in myocardial infarction and skin injury models.

CONCLUSIONS

Our study demonstrates the FAP vaccine can be a therapeutic tool for cardiac fibrosis.

Emerging Role of Macrophage-Fibroblast Interactions in Cardiac Homeostasis and Remodeling

As major noncardiomyocyte components in cardiac tissues, macrophages and fibroblasts play crucial roles in maintaining cardiac homeostasis, orchestrating reparative responses after cardiac injuries, facilitating adaptive cardiac remodeling, and contributing to adverse cardiac remodeling, owing to their inherent heterogeneity and plasticity. Recent advances in research methods have yielded novel insights into the intricate interactions between macrophages and fibroblasts in the cardiac context. This review aims to comprehensively examine the molecular mechanisms governing macrophage-fibroblast interactions in cardiac homeostasis and remodeling, emphasize recent advancements in the field, and offer an evaluation from a translational standpoint.

Novel Therapeutic Strategies Targeting Fibroblasts to Improve Heart Disease

Cardiac fibrosis represents the terminal pathological manifestation of various heart diseases, with the formation of fibroblasts playing a pivotal role in this process. Consequently, targeting the formation and function of fibroblasts holds significant potential for improving outcomes in heart disease. Recent research reveals the considerable potential of fibroblasts in ameliorating cardiac conditions, demonstrating different functional characteristics at various time points and spatial locations. Therefore, precise modulation of fibroblast activity may offer an effective approach for treating cardiac fibrosis and achieving targeted therapeutic outcomes. In this review, we focus on the fate and inhibition of fibroblasts, analyze their dynamic changes in cardiac diseases, and propose a framework for identifying markers of fibroblast activation mechanisms and selecting optimal time windows for therapeutic intervention. By synthesizing research findings in these areas, we aim to provide new strategies and directions for the precise treatment of fibroblasts in cardiac diseases.

Extracellular PKM2 Preserves Cardiomyocytes and Reduces Cardiac Fibrosis During Myocardial Infarction

Substantial loss of cardiomyocytes during heart attacks and onset of other cardiovascular diseases is a major cause of mortality. Preservation of cardiomyocytes during cardiac injury would be the most effective strategy to manage these diseases in clinic. However, there is no effective treatment strategy that is able to prevent cardiomyocyte loss. We demonstrate here that the systemic administration of a recombinant PKM2 mutant (G415R) preserves cardiomyocytes and reduces cardiac fibrosis during myocardial infarction. G415R preserves cardiomyocytes by protecting the cardiomyocytes from dying and by promoting cardiomyocyte proliferation. Preservation of cardiomyocytes by extracellular PKM2 (EcPKM2) reduces cardiac fibrosis because of the decreased activation of cardiac fibroblasts. Our experiments show that EcPKM2 (G415R) exerts its action by interacting with integrin avb3 on cardiomyocytes. EcPKM2(G415R) activates the integrin-FAK-PI3K signaling axis, which subsequently suppresses PTEN expression and consequently regulates cardiomyocyte apoptosis resistance and proliferation under hypoxia and oxidative stress conditions. Our studies uncover an important cardiomyocyte protection mechanism. More importantly, the activity/action of EcPKM2 (G415R) in preserving cardiomyocyte suggesting a possible therapeutic strategy and target for the treatment of heart attacks and other cardiovascular diseases.

Macrophages suppress cardiac reprogramming of fibroblasts in vivo via IFN-mediated intercellular self-stimulating circuit

Direct conversion of cardiac fibroblasts (CFs) to cardiomyocytes (CMs) in vivo to regenerate heart tissue is an attractive approach. After myocardial infarction (MI), heart repair proceeds with an inflammation stage initiated by monocytes infiltration of the infarct zone establishing an immune microenvironment. However, whether and how the MI microenvironment influences the reprogramming of CFs remains unclear. Here, we found that in comparison with cardiac fibroblasts (CFs) cultured in vitro, CFs that transplanted into infarct region of MI mouse models resisted to cardiac reprogramming. RNA-seq analysis revealed upregulation of interferon (IFN) response genes in transplanted CFs, and subsequent inhibition of the IFN receptors increased reprogramming efficiency in vivo. Macrophage-secreted IFN-β was identified as the dominant upstream signaling factor after MI. CFs treated with macrophage-conditioned medium containing IFN-β displayed reduced reprogramming efficiency, while macrophage depletion or blocking the IFN signaling pathway after MI increased reprogramming efficiency in vivo. Co-IP, BiFC and Cut-tag assays showed that phosphorylated STAT1 downstream of IFN signaling in CFs could interact with the reprogramming factor GATA4 and inhibit the GATA4 chromatin occupancy in cardiac genes. Furthermore, upregulation of IFN-IFNAR-p-STAT1 signaling could stimulate CFs secretion of CCL2/7/12 chemokines, subsequently recruiting IFN-β-secreting macrophages. Together, these immune cells further activate STAT1 phosphorylation, enhancing CCL2/7/12 secretion and immune cell recruitment, ultimately forming a self-reinforcing positive feedback loop between CFs and macrophages via IFN-IFNAR-p-STAT1 that inhibits cardiac reprogramming in vivo. Cumulatively, our findings uncover an intercellular self-stimulating inflammatory circuit as a microenvironmental molecular barrier of in situ cardiac reprogramming that needs to be overcome for regenerative medicine applications.

Role for the F-box proteins in heart diseases

The maintenance of cardiac homeostasis necessitates proper protein turnover, which is regulated by the ubiquitin-proteasome system. F-box proteins are one type of E3 ubiquitin ligases, and accumulating evidence suggests that dysregulation of FBPs exacerbates heart diseases. Therefore, in this review, we summarized the F-box proteins present in the heart, which can be divided into three types based on their repeated sequences, namely FBXO (Fbxo32, Fbxo25, Fbxo44, Fbxo27 and Fbxo28), FBXW (Fbxw7 and Fbxw5), and FBXL (Fbxl1, Fbxl10, Fbxl16 and Fbxl2). Moreover, the physiological and pathological roles and the functional mechanisms of these F-box proteins were elucidated within the cardiac context, providing new theories and strategies for the prevention and treatment of heart diseases.

Importance of long non-coding RNAs in the pathogenesis, diagnosis, and treatment of myocardial infarction

Myocardial infarction (MI), a major global cause of mortality and morbidity, continues to pose a significant burden on public health. Despite advances in understanding its pathogenesis, there remains a need to elucidate the intricate molecular mechanisms underlying MI progression. Long non-coding RNAs (lncRNAs) have emerged as key regulators in diverse biological processes, yet their specific roles in MI pathophysiology remain elusive. Conducting a thorough review of literature using PubMed and Google Scholar databases, we investigated the involvement of lncRNAs in MI, focusing on their regulatory functions and downstream signaling pathways. Our analysis revealed extensive dysregulation of lncRNAs in MI, impacting various biological processes through diverse mechanisms. Notably, lncRNAs act as crucial modulators of gene expression and signaling cascades, functioning as decoys, regulators, and scaffolds. Furthermore, studies identified the multifaceted roles of lncRNAs in modulating inflammation, apoptosis, autophagy, necrosis, fibrosis, remodeling, and ischemia-reperfusion injury during MI progression. Recent research highlights the pivotal contribution of lncRNAs to MI pathogenesis, offering novel insights into potential therapeutic interventions. Moreover, the identification of circulating lncRNA signatures holds promise for the development of non-invasive diagnostic biomarkers. In summary, findings underscore the significance of lncRNAs in MI pathophysiology, emphasizing their potential as therapeutic targets and diagnostic tools for improved patient management and outcomes.

Molecular mechanisms of lipid droplets-mitochondria coupling in obesity and metabolic syndrome: insights and pharmacological implications

Abnormal lipid accumulation is a fundamental contributor to obesity and metabolic disorders. Lipid droplets (LDs) and mitochondria (MT) serve as organelle chaperones in lipid metabolism and energy balance. LDs play a crucial role in lipid storage and mobilization, working in conjunction with MT to regulate lipid metabolism within the liver, brown adipose tissue, and skeletal muscle, thereby maintaining metabolic homeostasis. The novelty of our review is the comprehensive description of LD and MT interaction mechanisms. We also focus on the current drugs that target this metabolism, which provide novel approaches for obesity and related metabolism disorder treatment.

Harnessing the regenerative potential of interleukin11 to enhance heart repair

Balancing between regenerative processes and fibrosis is crucial for heart repair, yet strategies regulating this balance remain a barrier to developing therapies. The role of Interleukin 11 (IL11) in heart regeneration remains controversial, as both regenerative and fibrotic functions have been reported. We uncovered that il11a, an Il11 homolog in zebrafish, can trigger robust regenerative programs in zebrafish hearts, including cardiomyocytes proliferation and coronary expansion, even in the absence of injury. Notably, il11a induction in uninjured hearts also activates the quiescent epicardium to produce epicardial progenitor cells, which later differentiate into cardiac fibroblasts. Consequently, prolonged il11a induction indirectly leads to persistent fibroblast emergence, resulting in cardiac fibrosis. While deciphering the regenerative and fibrotic effects of il11a, we found that il11-dependent fibrosis, but not regeneration, is mediated through ERK activity, suggesting to potentially uncouple il11a dual effects on regeneration and fibrosis. To harness the il11a's regenerative ability, we devised a combinatorial treatment through il11a induction with ERK inhibition. This approach enhances cardiomyocyte proliferation with mitigated fibrosis, achieving a balance between regenerative processes and fibrosis. Thus, we unveil the mechanistic insights into regenerative il11 roles, offering therapeutic avenues to foster cardiac repair without exacerbating fibrosis.

Multi-modality deep learning-based [68Ga]Ga-DOTA-FAPI-04 PET polar map generation: potential value in detecting reactive fibrosis after myocardial infarction

PURPOSE

Generating polar map (PM) from [68Ga]Ga-DOTA-FAPI-04 PET images is challenging and inaccurate using existing automatic methods that rely on the myocardial anatomical integrity in PET images. This study aims to enhance the accuracy of PM generated from [68Ga]Ga-DOTA-FAPI-04 PET images and explore the potential value of PM in detecting reactive fibrosis after myocardial infarction and assessing its relationship with cardiac function.

METHODS

We proposed a deep-learning-based method that fuses multi-modality images to compensate for the cardiac structural information lost in [68Ga]Ga-DOTA-FAPI-04 PET images and accurately generated PMs. We collected 133 pairs of [68Ga]Ga-DOTA-FAPI-04 PET/MR images from 87 ST-segment elevated myocardial infarction patients for training and evaluation purposes. Twenty-six patients were selected for longitudinal analysis, further examining the clinical value of PM-related imaging parameters.

RESULTS

The quantitative comparison demonstrated that our method was comparable with the manual method and surpassed the commercially available software-PMOD in terms of accuracy in generating PMs for [68Ga]Ga-DOTA-FAPI-04 PET images. Clinical analysis revealed the effectiveness of [68Ga]Ga-DOTA-FAPI-04 PET PM in detecting reactive myocardial fibrosis. Significant correlations were demonstrated between the difference of baseline PM FAPI% and PM LGE%, and the change in cardiac function parameters (all p < 0.001), including LVESV% (r = 0.697), LVEDV% (r = 0.621) and LVEF% (r = -0.607).

CONCLUSION

The [68Ga]Ga-DOTA-FAPI-04 PET PMs generated by our method are comparable to manually generated and sufficient for clinical use. The PMs generated by our method have potential value in detecting reactive fibrosis after myocardial infarction and were associated with cardiac function, suggesting the possibility of enhancing clinical diagnostic practices.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04723953). Registered 26 January 2021.

Recent Clinical Implications of FAPI: Imaging and Therapy

ABSTRACT

The fibroblast activation protein (FAP) is a biomarker that is selectively overexpressed on cancer-associated fibroblasts (CAFs) in various types of tumoral tissues and some nonmalignant diseases, including fibrosis, arthritis, cardiovascular, and metabolic diseases. FAP plays a critical role in tumor microenvironment through facilitating proliferation, invasion, angiogenesis, immunosuppression, and drug resistance. Recent studies reveal that FAP might be regarded as a promising target for cancer diagnosis and treatment. FAP-targeted imaging modalities, especially PET, have shown high sensitivity and specificity in detecting FAP-expressing tumors. FAP-targeted imaging can potentially enhance tumor detection, staging, and monitoring of treatment response, and facilitate the development of personalized treatment strategies. This study provides a comprehensive view of FAP and its function in the pathophysiology of cancer and nonmalignant diseases. It also will discuss the characteristics of radiolabeled FAP inhibitors, particularly those based on small molecules, their recent clinical implications in imaging and therapy, and the associated clinical challenges with them. In addition, we present the results of imaging and biodistribution radiotracer 68 Ga-FAPI-46 in patients with nonmalignant diseases, including interstitial lung disease, primary biliary cirrhosis, and myocardial infarction, who were referred to our department. Our results show that cardiac FAP-targeted imaging can provide a novel potential biomarker for managing left ventricle remodeling. Moreover, this study has been organized and presented in a manner that offers a comprehensive overview of the current status and prospects of FAPI inhibitors in the diagnosis and treatment of diseases.

From exosomes to mitochondria and myocardial infarction: Molecular insight and therapeutic challenge

Myocardial infarction (MI) remains a leading cause of mortality worldwide. Despite patients with MI benefit from timely reperfusion therapies, the rates of mortality and morbidity remain substantial, suggesting an enduring need for the development of new approaches. Molecular mechanisms underlying myocardial ischemic injury are associated with both cardiomyocytes and non-cardiomyocytes. Exosomes are nano-sized extracellular vesicles released by almost all eukaryotic cells. They facilitate the communication between various cells by transferring information via their cargo and altering different biological activities in recipient cells. Studies have created great prospects for therapeutic applications of exosomes in MI, as demonstrated through their beneficial effect on heart function and reducing ventricular remodeling in association with fibrosis, angiogenesis, apoptosis, and inflammation. Of note, myocardial ischemic injury is primarily due to restricted blood flow, reducing oxygen availability, and causing inefficient utilization of energy substrates. However, the impact of exosomes on cardiac energy metabolism has not been adequately investigated. Although exosomes have been engineered for targeted delivery to enhance clinical efficacy, challenges must be overcome to utilize them reliably in the clinic. In this review, we summarize the research progress of exosomes for MI with a focus on the known and unknown regarding the role of exosomes in energy metabolism in cardiomyocytes and non-cardiomyocytes; as well as potential research avenues of exosome-mitochondrial energy regulation as well as therapeutic challenges. We aim to help identify more efficient molecular targets that may promote the clinical application of exosomes.

Possible mechanisms of SARS-CoV-2-associated myocardial fibrosis: reflections in the post-pandemic era

Since December 2019, coronavirus disease 2019 (COVID-19) has been spreading worldwide with devastating immediate or long-term effects on people's health. Although the lungs are the primary organ affected by COVID-19, individuals infected with SARS-CoV-2 also develop systemic lesions involving multiple organs throughout the body, such as the cardiovascular system. Emerging evidence reveals that COVID-19 could generate myocardial fibrosis, termed "COVID-19-associated myocardial fibrosis." It can result from the activation of fibroblasts via the renin-angiotensin-aldosterone system (RAAS), transforming growth factor-β1 (TGF-β1), microRNAs, and other pathways, and can also occur in other cellular interactions with SARS-CoV-2, such as immunocytes, endothelial cells. Nonetheless, to gain a more profound insight into the natural progression of COVID-19-related myocardial fibrosis, additional investigations are necessary. This review delves into the underlying mechanisms contributing to COVID-19-associated myocardial fibrosis while also examining the antifibrotic potential of current COVID-19 treatments, thereby offering guidance for future clinical trials of these medications. Ultimately, we propose future research directions for COVID-19-associated myocardial fibrosis in the post-COVID-19 era, such as artificial intelligence (AI) telemedicine. We also recommend that relevant tests be added to the follow-up of COVID-19 patients to detect myocardial fibrosis promptly.

The Participation of Ferroptosis in Fibrosis of the Heart and Kidney Tissues in Dahl Salt-Sensitive Hypertensive Rats

BACKGROUND

Salt-sensitive hypertension is often more prone to induce damage to target organs such as the heart and kidneys. Abundant recent studies have demonstrated a close association between ferroptosis and cardiovascular diseases. Therefore, we hypothesize that ferroptosis may be closely associated with organ damage in salt-sensitive hypertension. This study aimed to investigate whether ferroptosis is involved in the occurrence and development of myocardial fibrosis and renal fibrosis in salt-sensitive hypertensive rats.

METHODS

Ten 7-week-old male Dahl salt-sensitive (Dahl-SS) rats were adaptively fed for 1 week, then randomly divided into two groups and fed either a normal diet (0.3% NaCl, normal diet group) or a high-salt diet (8% NaCl, high-salt diet group) for 8 weeks. Blood pressure of the rats was observed, and analysis of the hearts and kidneys of Dahl-SS rats was conducted via hematoxylin-eosin (HE) staining, Masson staining, Prussian blue staining, transmission electron microscopy, tissue iron content detection, malondialdehyde content detection, immunofluorescence, and Western blot.

RESULTS

Compared to the normal diet group, rats in the high-salt diet group had increases in systolic blood pressure and diastolic blood pressure (P < 0.05); collagen fiber accumulation was observed in the heart and kidney tissues (P < 0.01), accompanied by alterations in mitochondrial ultrastructure, reduced mitochondrial volume, and increased density of the mitochondrial double membrane. Additionally, there were significant increases in both iron content and malondialdehyde levels (P < 0.05). Immunofluorescence and Western blot results both indicated significant downregulation (P < 0.05) of xCT and GPX4 proteins associated with ferroptosis in the high-salt diet group.

CONCLUSIONS

Ferroptosis is involved in the damage and fibrosis of the heart and kidney tissues in salt-sensitive hypertensive rats.

Metabolism and bioenergetics in the pathophysiology of organ fibrosis

Fibrosis is the tissue scarring characterized by excess deposition of extracellular matrix (ECM) proteins, mainly collagens. A fibrotic response can take place in any tissue of the body and is the result of an imbalanced reaction to inflammation and wound healing. Metabolism has emerged as a major driver of fibrotic diseases. While glycolytic shifts appear to be a key metabolic switch in activated stromal ECM-producing cells, several other cell types such as immune cells, whose functions are intricately connected to their metabolic characteristics, form a complex network of pro-fibrotic cellular crosstalk. This review purports to clarify shared and particular cellular responses and mechanisms across organs and etiologies. We discuss the impact of the cell-type specific metabolic reprogramming in fibrotic diseases in both experimental and human pathology settings, providing a rationale for new therapeutic interventions based on metabolism-targeted antifibrotic agents.

Long-term inhaling ultrafine zinc particles increases cardiac wall stresses elevated by myocardial infarction

The analysis of cardiac wall mechanics is of importance for understanding coronary heart diseases (CHD). The inhalation of ultrafine particles could deteriorate CHD. The aim of the study is to investigate the effects of cardiac wall mechanics on rats of myocardial infarction (MI) after long-term inhalation of ultrafine Zn particles. Cardiac wall stresses and strains were computed, based on echocardiographic and hemodynamic measurements. It was found that MI resulted in the significantly elevated stresses and the reduced strains. The short-term inhalation of ultrafine Zn particles decreased stresses and increased strains in MI rats, but the long-term inhalation had the opposite effects. Hence, the short-term inhalation of ultrafine Zn particles could alleviate the MI-induced LV dysfunction while the long-term inhalation impaired it.

The Role and Potential Mechanisms of Rehabilitation Exercise Improving Cardiac Remodeling

Rehabilitation exercise is a crucial non-pharmacological intervention for the secondary prevention and treatment of cardiovascular diseases, effectively ameliorating cardiac remodeling in patients. Exercise training can mitigate cardiomyocyte apoptosis, reduce extracellular matrix deposition and fibrosis, promote angiogenesis, and regulate inflammatory response to improve cardiac remodeling. This article presents a comprehensive review of recent research progress, summarizing the pivotal role and underlying mechanism of rehabilitation exercise in improving cardiac remodeling and providing valuable insights for devising effective rehabilitation treatment programs. Graphical Abstract.

Nuclear ATP-citrate lyase regulates chromatin-dependent activation and maintenance of the myofibroblast gene program

Differentiation of cardiac fibroblasts to myofibroblasts is necessary for matrix remodeling and fibrosis in heart failure. We previously reported that mitochondrial calcium signaling drives α-ketoglutarate-dependent histone demethylation, promoting myofibroblast formation. Here we investigate the role of ATP-citrate lyase (ACLY), a key enzyme for acetyl-CoA biosynthesis, in histone acetylation regulating myofibroblast fate and persistence in cardiac fibrosis. We show that inactivation of ACLY prevents myofibroblast differentiation and reverses myofibroblasts towards quiescence. Genetic deletion of Acly in post-activated myofibroblasts prevents fibrosis and preserves cardiac function in pressure-overload heart failure. TGFβ stimulation enhances ACLY nuclear localization and ACLY-SMAD2/3 interaction, and increases H3K27ac at fibrotic gene loci. Pharmacological inhibition of ACLY or forced nuclear expression of a dominant-negative ACLY mutant prevents myofibroblast formation and H3K27ac. Our data indicate that nuclear ACLY activity is necessary for myofibroblast differentiation and persistence by maintaining histone acetylation at TGFβ-induced myofibroblast genes. These findings provide targets to prevent and reverse pathological fibrosis.

WISP-1 Regulates Cardiac Fibrosis by Promoting Cardiac Fibroblasts' Activation and Collagen Processing

Hypertension induces cardiac fibrotic remodelling characterised by the phenotypic switching of cardiac fibroblasts (CFs) and collagen deposition. We tested the hypothesis that Wnt1-inducible signalling pathway protein-1 (WISP-1) promotes CFs' phenotypic switch, type I collagen synthesis, and in vivo fibrotic remodelling. The treatment of human CFs (HCFs, n = 16) with WISP-1 (500 ng/mL) induced a phenotypic switch (α-smooth muscle actin-positive) and type I procollagen cleavage to an intermediate form of collagen (pC-collagen) in conditioned media after 24h, facilitating collagen maturation. WISP-1-induced collagen processing was mediated by Akt phosphorylation via integrin β1, and disintegrin and metalloproteinase with thrombospondin motifs 2 (ADAMTS-2). WISP-1 wild-type (WISP-1+/+) mice and WISP-1 knockout (WISP-1-/-) mice (n = 5-7) were subcutaneously infused with angiotensin II (AngII, 1000 ng/kg/min) for 28 days. Immunohistochemistry revealed the deletion of WISP-1 attenuated type I collagen deposition in the coronary artery perivascular area compared to WISP-1+/+ mice after a 28-day AngII infusion, and therefore, the deletion of WISP-1 attenuated AngII-induced cardiac fibrosis in vivo. Collectively, our findings demonstrated WISP-1 is a critical mediator in cardiac fibrotic remodelling, by promoting CFs' activation via the integrin β1-Akt signalling pathway, and induced collagen processing and maturation via ADAMTS-2. Thereby, the modulation of WISP-1 levels could provide potential therapeutic targets in clinical treatment.

Characterizing the immune response to myocardial infarction in pigs

Though myocardial infarction (MI) in pigs is a well-established translational large animal model, it has not yet been widely used for immunotherapy studies, and a comprehensive description of the immune response to MI in this species is lacking. We induced MI in Landrace pigs by balloon occlusion of the left anterior descending artery over 90 min. Within 14 days, the necrotic myocardium was progressively replaced by scar tissue with involvement of myofibroblasts. We characterized the immune response in the heart ex vivo by (immuno)histology, flow cytometry, and RNA sequencing of myocardial tissue on days 3, 7, and 14 after MI. Besides a clear predominance of myeloid cells among heart-infiltrating leukocytes, we detected activated T cells and an increasing proportion of CD4+ Foxp3+ regulatory T cells (Treg), especially in the infarct core-findings that closely mirror what has been observed in mice and humans after MI. Transcriptome data indicated inflammatory activity that was persistent but markedly changing in character over time and linked to extracellular matrix biology. Analysis of lymphocytes in heart-draining lymph nodes revealed significantly higher proliferation rates of T helper cell subsets, including Treg on day 7 after MI, compared to sham controls. Elevated frequencies of myeloid progenitors in the spleen suggest that it might be a site of emergency myelopoiesis after MI in pigs, as previously shown in mice. We thus provide a first description of the immune response to MI in pigs, and our results can aid future research using the species for preclinical immunotherapy studies.

Fibroblast Diversity and Epigenetic Regulation in Cardiac Fibrosis

Cardiac fibrosis, a process characterized by excessive extracellular matrix (ECM) deposition, is a common pathological consequence of many cardiovascular diseases (CVDs) normally resulting in organ failure and death. Cardiac fibroblasts (CFs) play an essential role in deleterious cardiac remodeling and dysfunction. In response to injury, quiescent CFs become activated and adopt a collagen-secreting phenotype highly contributing to cardiac fibrosis. In recent years, studies have been focused on the exploration of molecular and cellular mechanisms implicated in the activation process of CFs, which allow the development of novel therapeutic approaches for the treatment of cardiac fibrosis. Transcriptomic analyses using single-cell RNA sequencing (RNA-seq) have helped to elucidate the high cellular diversity and complex intercellular communication networks that CFs establish in the mammalian heart. Furthermore, a significant body of work supports the critical role of epigenetic regulation on the expression of genes involved in the pathogenesis of cardiac fibrosis. The study of epigenetic mechanisms, including DNA methylation, histone modification, and chromatin remodeling, has provided more insights into CF activation and fibrotic processes. Targeting epigenetic regulators, especially DNA methyltransferases (DNMT), histone acetylases (HAT), or histone deacetylases (HDAC), has emerged as a promising approach for the development of novel anti-fibrotic therapies. This review focuses on recent transcriptomic advances regarding CF diversity and molecular and epigenetic mechanisms that modulate the activation process of CFs and their possible clinical applications for the treatment of cardiac fibrosis.

Novel cardiac extracellular matrix biomarkers in STEMI: Associations with ischemic injury and long-term mortality

BACKGROUND

We aimed to determine whether serum levels of proteins related to changes in cardiac extracellular matrix (ECM) were associated with ischemic injury assessed by cardiac magnetic resonance (CMR) and mortality in patients with ST-elevation myocardial infarction (STEMI).

METHODS

The concentrations of six ECM-related proteins (periostin, osteopontin, syndecan-1, syndecan-4, bone morphogenetic protein 7, and growth differentiation factor (GDF)-15) were measured in serum samples from patients on Day 1 and Month 4 after STEMI (n = 239). Ischemic injury was assessed by myocardial salvage index, microvascular obstruction, infarct size, and left ventricular function measured by CMR conducted during the initial admission (median 2 days after admission) and after 4 months. All-cause mortality was recorded after a median follow-up time of 70 months.

RESULTS

Levels of periostin increased from Day 1 to Month 4 after hospitalization, while the levels of GDF-15, osteopontin, syndecan-1, and syndecan-4 declined. At both time points, high levels of syndecan-1 were associated with microvascular obstruction, large infarct size, and reduced left ventricular ejection fraction, whereas high levels of syndecan-4 at Month 4 were associated with a higher myocardial salvage index and less dilatation of the left ventricle. Higher mortality rates were associated with periostin levels at both time points, low syndecan-4 levels at Month 4, or high GDF-15 levels at Month 4.

CONCLUSIONS

In patients with STEMI, we found an association between serum levels of ECM biomarkers and ischemic injury and mortality. The results provide new insight into the role ECM components play in ischemic injury following STEMI and suggests a potential for these biomarkers in prognostication after STEMI.

Cardiac and perivascular myofibroblasts, matrifibrocytes, and immune fibrocytes in hypertension; commonalities and differences with other cardiovascular diseases

Hypertension is a major cause of cardiovascular diseases such as myocardial infarction and stroke. Cardiovascular fibrosis occurs with hypertension and contributes to vascular resistance, aortic stiffness, and cardiac hypertrophy. However, the molecular mechanisms leading to fibroblast activation in hypertension remain largely unknown. There are two types of fibrosis: replacement fibrosis and reactive fibrosis. Replacement fibrosis occurs in response to the loss of viable tissue to form a scar. Reactive fibrosis occurs in response to an increase in mechanical and neurohormonal stress. Although both types of fibrosis are considered adaptive processes, they become maladaptive when the tissue loss is too large, or the stress persists. Myofibroblasts represent a subpopulation of activated fibroblasts that have gained contractile function to promote wound healing. Therefore, myofibroblasts are a critical cell type that promotes replacement fibrosis. Although myofibroblasts were recognized as the fibroblasts participating in reactive fibrosis, recent experimental evidence indicated there are distinct fibroblast populations in cardiovascular reactive fibrosis. Accordingly, we will discuss the updated definition of fibroblast subpopulations, the regulatory mechanisms, and their potential roles in cardiovascular pathophysiology utilizing new knowledge from various lineage tracing and single-cell RNA sequencing studies. Among the fibroblast subpopulations, we will highlight the novel roles of matrifibrocytes and immune fibrocytes in cardiovascular fibrosis including experimental models of hypertension, pressure overload, myocardial infarction, atherosclerosis, aortic aneurysm, and nephrosclerosis. Exploration into the molecular mechanisms involved in the differentiation and activation of those fibroblast subpopulations may lead to novel treatments for end-organ damage associated with hypertension and other cardiovascular diseases.

Exploring the molecular biology of ischemic cardiomyopathy based on ferroptosis‑related genes

Ischemic cardiomyopathy (ICM) is a serious cardiac disease with a very high mortality rate worldwide, which causes myocardial ischemia and hypoxia as the main damage. Further understanding of the underlying pathological processes of cardiomyocyte injury is key to the development of cardioprotective strategies. Ferroptosis is an iron-dependent form of regulated cell death characterized by the accumulation of lipid hydroperoxides to lethal levels, resulting in oxidative damage to the cell membrane. The current understanding of the role and regulation of ferroptosis in ICM is still limited, especially in the absence of evidence from large-scale transcriptomic data. Through comprehensive bioinformatics analysis of human ICM transcriptome data obtained from the Gene Expression Omnibus database, the present study identified differentially expressed ferroptosis-related genes (DEFRGs) in ICM. Subsequently, their potential biological mechanisms and cross-talk were analyzed, and hub genes were identified by constructing protein-protein interaction networks. Ferroptosis features such as reactive oxygen species generation, changes in ferroptosis marker proteins, iron ion aggregation and lipid oxidation, were identified in the H9c2 anoxic reoxygenation injury model. Finally, the diagnostic ability of Gap junction alpha-1 (GJA1), Solute carrier family 40 member 1 (SLC40A1), Alpha-synuclein (SNCA) were identified through receiver operating characteristic curves and the expression of DEFRGs was verified in an in vitro model. Furthermore, potential drugs (retinoic acid) that could regulate ICM ferroptosis were predicted based on key DEFRGs. The present article presents new insights into the role of ferroptosis in ICM, investigating the regulatory role of ferroptosis in the pathological process of ICM and advocating for ferroptosis as a potential novel therapeutic target for ICM based on evidence from the ICM transcriptome.

[A transcriptomic analysis of correlation between mitochondrial function and energy metabolism remodeling in mice with myocardial fibrosis following myocardial infarction]

OBJECTIVE

To investigate the changes of mitochondrial respiratory function during myocardial fibrosis in mice with myocardial infarction (MI) and its correlation with the increase of glycolytic flux.

METHODS

Forty C57BL/6N mice were randomized into two equal groups to receive sham operation or ligation of the left anterior descending coronary artery to induce acute MI. At 28 days after the operation, 5 mice from each group were euthanized and left ventricular tissue samples were collected for transcriptomic sequencing. FPKM method was used to calculate gene expression levels to identify the differentially expressed genes (DEGs) in MI mice, which were analyzed using GO and KEGG databases to determine the pathways affecting the disease process. Heat maps were drawn to show the differential expressions of the pathways and the related genes in the enrichment analysis. In primary cultures of neonatal mouse cardiac fibroblasts (CFs), the changes in mitochondrial respiration and glycolysis levels in response to treatment with the pro-fibrotic agonist TGF-β1 were analyzed using Seahorse experiment.

RESULTS

The mouse models of MI showed significantly increased diastolic and systolic left ventricular diameter (P < 0.05) and decreased left ventricular ejection fraction (P < 0.0001). A total of 124 up-regulated and 106 down-regulated DEGs were identified in the myocardial tissues of MI mice, and GO and KEGG enrichment analysis showed that these DEGs were significantly enriched in fatty acid metabolism, organelles and other metabolic pathways and in the mitochondria. Heat maps revealed fatty acid beta oxidation, mitochondrial dysfunction and increased glycolysis levels in MI mice. In the primary culture of CFs, treatment with TGF-β1 significantly reduced the basal and maximum respiratory levels and increased the basal and maximum glycolysis levels (P < 0.0001).

CONCLUSION

During myocardial fibrosis, energy metabolism remodeling occurs in the CFs, manifested by lowered mitochondrial function and increased energy generation through glycolysis.

The role of fibrosis in cardiomyopathies: An opportunity to develop novel biomarkers of disease activity

Cardiomyopathies encompass a spectrum of heart disorders with diverse causes and presentations. Fibrosis stands out as a shared hallmark among various cardiomyopathies, reflecting a common thread in their pathogenesis. This prevalent fibrotic response is intricately linked to the consequences of dysregulated extracellular matrix (ECM) remodeling, emphasizing its significance in the development and progression the disease. This review explores the ECM involvement in various cardiomyopathies and its impact on myocardial stiffness and fibrosis. Additionally, we discuss the potential of ECM fragments as early diagnosis, prognosis, and risk stratification. Biomarkers deriving from turnover of collagens and other ECM proteins hold promise in clinical applications. We outline current clinical management, future directions, and the potential for personalized ECM-targeted therapies with specific focus on microRNAs. In summary, this review examines the role of the fibrosis in cardiomyopathies, highlighting the potential of ECM-derived biomarkers in improving disease management with implications for precision medicine.

HTRA1-driven detachment of type I collagen from endoplasmic reticulum contributes to myocardial fibrosis in dilated cardiomyopathy

BACKGROUND

The aberrant secretion and excessive deposition of type I collagen (Col1) are important factors in the pathogenesis of myocardial fibrosis in dilated cardiomyopathy (DCM). However, the precise molecular mechanisms underlying the synthesis and secretion of Col1 remain unclear.

METHODS AND RESULTS

RNA-sequencing analysis revealed an increased HtrA serine peptidase 1 (HTRA1) expression in patients with DCM, which is strongly correlated with myocardial fibrosis. Consistent findings were observed in both human and mouse tissues by immunoblotting, quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunohistochemistry, and immunofluorescence analyses. Pearson's analysis showed a markedly positive correlation between HTRA1 level and myocardial fibrosis indicators, including extracellular volume fraction (ECV), native T1, and late gadolinium enhancement (LGE), in patients with DCM. In vitro experiments showed that the suppression of HTRA1 inhibited the conversion of cardiac fibroblasts into myofibroblasts and decreased Col1 secretion. Further investigations identified the role of HTRA1 in promoting the formation of endoplasmic reticulum (ER) exit sites, which facilitated the transportation of Col1 from the ER to the Golgi apparatus, thereby increasing its secretion. Conversely, HTRA1 knockdown impeded the retention of Col1 in the ER, triggering ER stress and subsequent induction of ER autophagy to degrade misfolded Col1 and maintain ER homeostasis. In vivo experiments using adeno-associated virus-serotype 9-shHTRA1-green fluorescent protein (AAV9-shHTRA1-GFP) showed that HTRA1 knockdown effectively suppressed myocardial fibrosis and improved left ventricular function in mice with DCM.

CONCLUSIONS

The findings of this study provide valuable insights regarding the treatment of DCM-associated myocardial fibrosis and highlight the therapeutic potential of targeting HTRA1-mediated collagen secretion.

Cardiac fibrogenesis: an immuno-metabolic perspective

Cardiac fibrosis is a major and complex pathophysiological process that ultimately culminates in cardiac dysfunction and heart failure. This phenomenon includes not only the replacement of the damaged tissue by a fibrotic scar produced by activated fibroblasts/myofibroblasts but also a spatiotemporal alteration of the structural, biochemical, and biomechanical parameters in the ventricular wall, eliciting a reactive remodeling process. Though mechanical stress, post-infarct homeostatic imbalances, and neurohormonal activation are classically attributed to cardiac fibrosis, emerging evidence that supports the roles of immune system modulation, inflammation, and metabolic dysregulation in the initiation and progression of cardiac fibrogenesis has been reported. Adaptive changes, immune cell phenoconversions, and metabolic shifts in the cardiac nonmyocyte population provide initial protection, but persistent altered metabolic demand eventually contributes to adverse remodeling of the heart. Altered energy metabolism, mitochondrial dysfunction, various immune cells, immune mediators, and cross-talks between the immune cells and cardiomyocytes play crucial roles in orchestrating the transdifferentiation of fibroblasts and ensuing fibrotic remodeling of the heart. Manipulation of the metabolic plasticity, fibroblast-myofibroblast transition, and modulation of the immune response may hold promise for favorably modulating the fibrotic response following different cardiovascular pathological processes. Although the immunologic and metabolic perspectives of fibrosis in the heart are being reported in the literature, they lack a comprehensive sketch bridging these two arenas and illustrating the synchrony between them. This review aims to provide a comprehensive overview of the intricate relationship between different cardiac immune cells and metabolic pathways as well as summarizes the current understanding of the involvement of immune-metabolic pathways in cardiac fibrosis and attempts to identify some of the previously unaddressed questions that require further investigation. Moreover, the potential therapeutic strategies and emerging pharmacological interventions, including immune and metabolic modulators, that show promise in preventing or attenuating cardiac fibrosis and restoring cardiac function will be discussed.

Circadian Rhythms in Cardiovascular Metabolism

Energetic demand and nutrient supply fluctuate as a function of time-of-day, in alignment with sleep-wake and fasting-feeding cycles. These daily rhythms are mirrored by 24-hour oscillations in numerous cardiovascular functional parameters, including blood pressure, heart rate, and myocardial contractility. It is, therefore, not surprising that metabolic processes also fluctuate over the course of the day, to ensure temporal needs for ATP, building blocks, and metabolism-based signaling molecules are met. What has become increasingly clear is that in addition to classic signal-response coupling (termed reactionary mechanisms), cardiovascular-relevant cells use autonomous circadian clocks to temporally orchestrate metabolic pathways in preparation for predicted stimuli/stresses (termed anticipatory mechanisms). Here, we review current knowledge regarding circadian regulation of metabolism, how metabolic rhythms are synchronized with cardiovascular function, and whether circadian misalignment/disruption of metabolic processes contribute toward the pathogenesis of cardiovascular disease.

Heart-on-a-chip systems: disease modeling and drug screening applications

Cardiovascular disease (CVD) is the leading cause of death worldwide, casting a substantial economic footprint and burdening the global healthcare system. Historically, pre-clinical CVD modeling and therapeutic screening have been performed using animal models. Unfortunately, animal models oftentimes fail to adequately mimic human physiology, leading to a poor translation of therapeutics from pre-clinical trials to consumers. Even those that make it to market can be removed due to unforeseen side effects. As such, there exists a clinical, technological, and economical need for systems that faithfully capture human (patho)physiology for modeling CVD, assessing cardiotoxicity, and evaluating drug efficacy. Heart-on-a-chip (HoC) systems are a part of the broader organ-on-a-chip paradigm that leverages microfluidics, tissue engineering, microfabrication, electronics, and gene editing to create human-relevant models for studying disease, drug-induced side effects, and therapeutic efficacy. These compact systems can be capable of real-time measurements and on-demand characterization of tissue behavior and could revolutionize the drug development process. In this review, we highlight the key components that comprise a HoC system followed by a review of contemporary reports of their use in disease modeling, drug toxicity and efficacy assessment, and as part of multi-organ-on-a-chip platforms. We also discuss future perspectives and challenges facing the field, including a discussion on the role that standardization is expected to play in accelerating the widespread adoption of these platforms.