Myocardial Fibrosis: Emerging Target for Cardiac Molecular Imaging and Opportunity for Image-Guided Therapy

Investigating the NF-κB signaling pathway in heart failure: Exploring potential therapeutic approaches

Heart failure (HF) syndrome is of great interest as an emerging epidemic. Due to the increasing elderly population worldwide, the total number of HF patients is increasing every day. This disease places a significant economic burden on the healthcare and treatment systems of developing societies, and this situation is very concerning. Despite many advances in the diagnosis and treatment of cardiovascular diseases, HF is still the main cause of death worldwide. This clinical syndrome has many cellular and molecular complications, which are often aggravated by increased levels of pro-inflammatory cytokines, which lead to adverse clinical outcomes. Nuclear factor kappa B (NF-κB), a pivotal family of transcription factors, plays a crucial role in various biological processes, particularly in inflammation, immune response, cell proliferation, and cell survival. Studies show that the NF-κB signaling pathway plays a role in modulating cardiac regeneration, apoptosis, and myocardial fibrosis. It has been found that the NF-κB signaling pathway can affect heart function and HF through the regulation of matrix metalloproteinases and fibrotic mediators. Also, the NF-κB pathway regulates cell activities in cardiac cardiomyocytes and regulates the function of this organ by establishing a precise interaction between apoptosis and pyroptosis. However, the exact molecular mechanisms of this influence have not been well defined and there are many scientific gaps in this matter. This review tries to highlights potential therapeutic strategies to target NF-κB, including the use of anti-inflammatory agents and genetic modulation, which may provide new ways to reduce cardiac fibrosis and improve outcomes in HF patients. Certainly, increasing understanding of the multifaceted role of NF-κB in HF can lead to innovative treatments aimed at reducing the growing number of patients worldwide.

Circular RNAs in Cardiovascular Diseases: Molecular Mechanisms, Therapeutic Advances, and Innovations

Circular RNAs (circRNAs) have emerged as promising therapeutic targets due to their unique covalently closed-loop structures and their regulatory roles in gene expression. Despite their potential, challenges in circRNA-based therapies include ensuring stability, tissue specificity, and efficient intracellular delivery. This review explores the implications of circRNAs in cardiovascular diseases (CVDs), providing an overview of their biogenesis, molecular mechanisms, and roles in disease pathology. In addition to discussing molecular features, this review highlights therapeutic advances, including small-molecule drugs targeting circRNAs, synthetic circRNA sponges, and innovations in drug delivery systems that enhance the effectiveness of these therapies. Finally, current challenges and future directions are addressed, emphasizing the need for continued research to fully unlock the therapeutic potential of circRNA-based strategies in cardiovascular medicine.

Recent advances in positron emission tomography for detecting early fibrosis after myocardial infarction

Cardiac remodeling after myocardial infarction is one of the key factors affecting patient prognosis. Myocardial fibrosis is an important pathological link of adverse ventricular remodeling after myocardial infarction, and early fibrosis is reversible. Timely detection and intervention can effectively prevent its progression to irreversible ventricular remodeling. Although imaging modalities such as CMR and echocardiography can identify fibrosis, their sensitivity and specificity are limited, and they cannot detect early fibrosis or its activity level. Positron emission tomography (PET) allows non-invasive visualization of cellular and subcellular processes and can monitor and quantify molecules and proteins in the fibrotic pathway. It is valuable in assessing the extent of early myocardial fibrosis progression, selecting appropriate treatments, evaluating response to therapy, and determining the prognosis. In this article, we present a brief overview of mechanisms underlying myocardial fibrosis following myocardial infarction and several routine imaging techniques currently available for assessing fibrosis. Then, we focus on the application of PET molecular imaging in detecting fibrosis after myocardial infarction.

Free-breathing non-contrast T1ρ dispersion magnetic resonance imaging of myocardial interstitial fibrosis in comparison with extracellular volume fraction

BACKGROUND

Myocardial fibrosis is a common feature in various cardiac diseases. It causes adverse cardiac remodeling and is associated with poor clinical outcomes. Late gadolinium enhancement (LGE) and extracellular volume fraction (ECV) are the standard magnetic resonance imaging techniques for detecting focal and diffuse myocardial fibrosis. However, these contrast-enhanced techniques require the administration of gadolinium contrast agents, which is not applicable to patients with gadolinium contraindications. To eliminate the need for contrast agents, we developed and applied an endogenous free-breathing T1ρ dispersion imaging technique (FB-MultiMap) for diagnosing diffuse myocardial fibrosis in a cohort with suspected cardiomyopathies.

METHODS

The proposed FB-MultiMap technique, enabling T2, T1ρ, and their difference (myocardial fibrosis index [mFI]) quantification in a single scan was developed in phantoms and 15 healthy subjects. In the clinical study, 55 patients with suspected cardiomyopathies were imaged using FB-MultiMap, conventional native T1 mapping, LGE, and ECV imaging. The accuracy of the endogenous parameters for predicting increased ECV was evaluated using receiver operating characteristic curve analysis. In addition, the correlation of native T1, T1ρ, and mFI with ECV was, respectively, assessed using Pearson correlation coefficients.

RESULTS

FB-MultiMap showed a good agreement with conventional separate breath-hold mapping techniques in phantoms and healthy subjects. Considering all the patients, T1ρ was more accurate than mFI and native T1 for predicting increased ECV, with area under the curve (AUC) values of 0.91, 0.79, and 0.75, respectively, and showed a stronger correlation with ECV (correlation coefficient r: 0.72 vs 0.52 vs 0.40). In the subset of 47 patients with normal T2 values, the diagnostic performance of mFI was significantly strengthened (AUC = 0.90, r = 0.83), outperforming T1ρ and native T1.

CONCLUSION

The proposed free-breathing T1ρ dispersion imaging technique enabling simultaneous quantification of T2, T1ρ, and mFI in a single scan has shown great potential for diagnosing diffuse myocardial fibrosis in patients with complex cardiomyopathies without contrast agents.

Molecular Imaging of Heart Failure: An Update and Future Trends

Molecular imaging can detect and quantify pathophysiological processes underlying heart failure, complementing evaluation of cardiac structure and function with other imaging modalities. Targeted tracers have enabled assessment of various cellular and subcellular mechanisms of heart failure aiming for improved phenotyping, risk stratification, and personalized therapy. This review outlines the current status of molecular imaging in heart failure, accompanied with discussion on novel developments. The focus is on radionuclide methods with data from clinical studies. Imaging of myocardial metabolism can identify left ventricle dysfunction caused by myocardial ischemia that may be reversible after revascularization in the presence of viable myocardium. In vivo imaging of active inflammation and amyloid deposition have an established role in the detection of cardiac sarcoidosis and transthyretin amyloidosis. Innervation imaging has well documented prognostic value in predicting heart failure progression and arrhythmias. Tracers specific for inflammation, angiogenesis and myocardial fibrotic activity are in earlier stages of development, but have demonstrated potential value in early characterization of the response to myocardial injury and prediction of cardiac function over time. Early detection of disease activity is a key for transition from medical treatment of clinically overt heart failure towards a personalized approach aimed at supporting repair and preventing progressive cardiac dysfunction.

Imaging of Cardiac Fibrosis: How Far Have We Moved From Extracellular to Cellular?

Cardiovascular disease is the leading cause of morbidity and mortality worldwide. Myocardial fibrosis plays an important role in adverse outcomes such as heart failure and arrhythmias. As the pathological response and degree of scarring, and therefore clinical presentation varies from patient to patient, early detection of fibrosis is crucial for identifying the appropriate treatment approach and forecasting the progression of a disease along with the likelihood of disease-related mortality. Current imaging modalities provides information about either decreased function or extracellular signs of fibrosis. Targeting activated fibroblasts represents a burgeoning approach that could offer insights prior to observable functional alterations, presenting a promising focus for potential anti-fibrotic therapeutic interventions at cellular level. In this article, we provide an overview of imaging cardiac fibrosis and discuss the role of different advanced imaging modalities with the focus on novel non-invasive imaging of activated fibroblasts.

Computer-Assisted Algorithm for Quantification of Fibrosis by Native Cardiac CT: A Pilot Study

Background/Objectives: Recent advances in artificial intelligence, particularly in cardiac imaging, can potentially enhance patients' diagnosis and prognosis and identify novel imaging markers. We propose an automated, computer-aided algorithm utilizing native cardiac computed tomography (CT) imaging to identify myocardial fibrosis. This study aims to evaluate its performance compared to CMR markers of fibrosis in a cohort of patients diagnosed with breast cancer. Methods: The study included patients diagnosed with early HER2+ breast cancer, who presented LV dysfunction (LVEF < 50%) and myocardial fibrosis detected on CMR at the time of diagnosis. The patients were also evaluated by cardiac CT, and the extracted images were processed for the implementation of the automatic, computer-assisted algorithm, which marked as fibrosis every pixel that fell within the range of 60-90 HU. The percentage of pixels with fibrosis was subsequently compared with CMR parameters. Results: A total of eight patients (n = 8) were included in the study. High positive correlations between the algorithm's result and the ECV fraction (r = 0.59, p = 0.126) and native T1 (r = 0.6, p = 0.112) were observed, and a very high positive correlation with LGE of the LV(g) and the LV-LGE/LV mass percentage (r = 0.77, p = 0.025; r = 0.81, p = 0.015). A very high negative correlation was found with GLS (r = -0.77, p = 0.026). The algorithm presented an intraclass correlation coefficient of 1 (95% CI 0.99-1), p < 0.001. Conclusions: The present pilot study proposes a novel promising imaging marker for myocardial fibrosis, generated by an automatic algorithm based on native cardiac CT images.

Enhanced TfR1 Recognition of Myocardial Injury after Acute Myocardial Infarction with Cardiac Fibrosis via Pre-Degrading Excess Fibrotic Collagen

The fibrosis process after myocardial infarction (MI) results in a decline in cardiac function due to fibrotic collagen deposition and contrast agents' metabolic disorders, posing a significant challenge to conventional imaging strategies in making heart damage clear in the fibrosis microenvironment. To address this issue, we developed an imaging strategy. Specifically, we pretreated myocardial fibrotic collagen with collagenase I combined with human serum albumin (HSA-C) and subsequently visualized the site of cardiac injury by near-infrared (NIR) fluorescence imaging using an optical contrast agent (CI, CRT-indocyanine green) targeting transferrin receptor 1 peptides (CRT). The key point of this strategy is that pretreatment with HSA-C can reduce background signal interference in the fibrotic tissue while enhancing CI uptake at the heart lesion site, making the boundary between the injured heart tissue and the normal myocardium clearer. Our results showed that compared to that in the untargeted group, the normalized fluorescence intensity of cardiac damage detected by NIR in the targeted group increased 1.28-fold. The normalized fluorescence intensity increased 1.21-fold in the pretreatment group of the targeted groups. These data demonstrate the feasibility of applying pretreated fibrotic collagen and NIR contrast agents targeting TfR1 to identify ferroptosis at sites of cardiac injury, and its clinical value in the management of patients with MI needs further study.

Marein Ameliorates Myocardial Fibrosis by Inhibiting HIF-1α and TGF-β1/Smad2/3 Signaling Pathway in Isoproterenol-stimulated Mice and TGF-β1-stimulated Cardiac Fibroblasts

BACKGROUND

Myocardial fibrosis significantly contributes to the pathogenesis and progression of heart failure.

OBJECTIVE

We probe into the impact of marein, a key bioactive compound in functional food Coreopsis tinctoria, on isoproterenol-stimulated myocardial fibrotic mice and transforming growth factor β1 (TGF-β1)-stimulated cardiac fibroblasts (CFs).

METHODS

Isoproterenol was administered to the experimental mice via subcutaneous injection, and simultaneous administration of marein (25-100 mg/kg) was performed via oral gavage. CFs were stimulated with TGF- β1 to trigger differentiation and collagen synthesis, followed by treatment with marein at concentrations of 5-20 μM.

RESULTS

Treatment with marein in mice and CFs resulted in a significant reduction in the protein expression levels of α-smooth muscle actin, collagen type I, and collagen type III. Additionally, marein treatment decreased the protein expression levels of TGF-β1, hypoxia-inducible factor-1α (HIF-1α), p-Smad2/3, and Smad2/3. Notably, molecular docking analysis revealed that marein directly targets HIF-1α.

CONCLUSION

Marein might exert a protective function in isoproterenol-stimulated myocardial fibrotic mice and TGF-β1-stimulated CFs, which might result from the reduction of TGF-β1 induced HIF-1α expression, then inhibiting p-Smad2/3 and Smad2/3 expressions.