Integration mapping of cardiac fibroblast single-cell transcriptomes elucidates cellular principles of fibrosis in diverse pathologies

Signals from the extracellular matrix: Region- and sex-specificity in cardiac aging

During aging, the cardiac extracellular matrix (ECM) undergoes gradual remodeling that reduces the heart's ability to function. Specific ECM changes cause alterations in cellular signaling pathways, eliciting maladaptive responses. Here, we provide insight into the current knowledge of how age-specific ECM changes contribute to altered ligand-receptor interactions, dysregulated mechanotransduction, and the propagation of pro-fibrotic signaling cascades that underpin dysfunction. We also highlight regional and sex differences that new biomolecular and bioengineered technologies have recently uncovered. We call for new biomaterial strategies that mimic spatiotemporal and sex-specific ECM alterations to equip researchers with the tools to unravel complex cellular signaling events. We believe this can be achieved through interdisciplinary cooperation amongst researchers spanning matrix biology, biomaterials, spatial omics, and biomedical engineering.

Dynamic molecular atlas of cardiac fibrosis at single-cell resolution shows CD248 in cardiac fibroblasts orchestrates interactions with immune cells

Post-injury remodeling is a complex process involving temporal specific cellular interactions in the injured tissue where the resident fibroblasts play multiple roles. Here, we performed single-cell and spatial transcriptome analysis in human and mouse infarcted hearts to dissect the molecular basis of these interactions. We identified a unique fibroblast subset with high CD248 expression, strongly associated with extracellular matrix remodeling. Genetic Cd248 deletion in fibroblasts mitigated cardiac fibrosis and dysfunction following ischemia/reperfusion. Mechanistically, CD248 stabilizes type I transforming growth factor beta receptor and thus upregulates fibroblast ACKR3 expression, leading to enhanced T cell retention. This CD248-mediated fibroblast-T cell interaction is required to sustain fibroblast activation and scar expansion. Disrupting this interaction using monoclonal antibody or chimeric antigen receptor T cell reduces T cell infiltration and consequently ameliorates cardiac fibrosis and dysfunction. Our findings reveal a CD248+ fibroblast subpopulation as a key regulator of immune-fibroblast cross-talk and a potential therapy to treat tissue fibrosis.

Deciphering myocardial fibrosis: a comprehensive bibliometric analysis of mechanism over the period 1992-2023

BACKGROUND

Myocardial fibrosis is a critical link in preventing the progression of heart disease. This study conducted a bibliometric analysis of its mechanism to identify trends and hotspots, aiming to provide valuable references for heart disease prevention and treatment.

METHODS

This research relies on the Web of Science Core Collection, capturing all related publications on the mechanism of myocardial fibrosis up to November 11, 2023. For the bibliometric analysis, CiteSpace 6.2.R5 (64-bit) and VOSviewer 1.6.19 software tools were utilized.

RESULTS

The mechanism of myocardial fibrosis research involves 14,931 authors from 2,370 institutions in 71 countries/regions, resulting in 2,431 published studies. Nattel Stanley is the most prolific author, while Francogianis Ng is noted for the highest co-publication frequency. The United States leads in countries/regions, with the University of California System being the top institution. Cardiovascular Research is a primary outlet for new studies, and Circulation is a key reference in this research community. Current research primarily examines how myocardial fibrosis contributes to heart failure, myocardial infarction, and myocardial hypertrophy. This emerging field also explores the role of fibroblasts in myocardial injury and investigates innovative treatments to reduce myocardial fibrosis.

CONCLUSIONS

Preventing myocardial fibrosis is a crucial strategy in the fight against heart disease. This study utilises bibliometric analysis to explore the vast array of literature on the mechanism of myocardial fibrosis, mapping the research landscape and provide literature references for potential breakthroughs in heart disease prevention and treatment strategies.

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.

Macrophage-derived SPP1 exacerbate myocardial injury by interacting with fibroblasts in viral myocarditis

BACKGROUND

Viral myocarditis (VMC) is an inflammatory myocardial condition triggered by viral infections which involves pathogenic-related damage and immune-mediated damage. However, the precise immunopathogenic mechanisms underlying VMC remain elusive.

METHODS

We performed single-cell RNA sequencing on mouse hearts during the acute phase of CVB3-induced VMC. After manually annotating cell types, functional analyses of macrophage were performed by cell ratio changes, customized gene set module scoring and CellPhoneDB. Utilizing indirect co-culture experiments in vitro, the effects of macrophage-derived SPP1 on cardiac fibroblasts were investigated. Depletion of macrophages and inhibition of SPP1 expression in mice were carried out to study the effects of macrophage-derived SPP1 on cardiac function, inflammation levels, and myocardial injury in mice with VMC.

RESULTS

Our data revealed that macrophages are the major immune cells which infiltrate the heart during the acute phase of VMC, particularly a macrophage subpopulation which highly expresses Spp1 (Spp1+ macrophages) and exhibited characteristics of peripheral blood monocytes. Spp1+ macrophages communicate extensively with fibroblasts during VMC, and that SPP1 promotes fibroblast conversion to an inflammatory phenotype with high Ccl2/Ccl7 expression. This in turn increases monocyte chemotaxis to the heart. Besides, a partial depletion of macrophages in the early stages of VMC attenuated myocardial inflammation and myocardial injury in mice. Inhibition of SPP1 reduced cardiac macrophage infiltration, attenuated myocardial inflammation, and improved cardiac function in VMC mice.

CONCLUSION

Our findings suggested that Spp1+ macrophages could self-recruit, and macrophage-derived SPP1 exacerbated myocardial immune injury by promoting high Ccl2/Ccl7 expression in fibroblasts. Our study advances understandings of VMC pathogenesis, and provides novel insight into potential immunotherapies for VMC.

Dynamic responses to rejection in the transplanted human heart revealed through spatial transcriptomics

Allograft rejection following solid-organ transplantation is a major cause of graft dysfunction and mortality. Current approaches to diagnosis rely on histology, which exhibits wide diagnostic variability and lacks access to molecular phenotypes that may stratify therapeutic response. Here, we leverage image-based spatial transcriptomics at sub-cellular resolution in longitudinal human cardiac biopsies to characterize transcriptional heterogeneity in 62 adult and pediatric heart transplant (HT) recipients during and following histologically-diagnosed rejection. Across 28 cell types, we identified significant differences in abundance in CD4 + and CD8 + T cells, fibroblasts, and endothelial cells across different biological classes of rejection (cellular, mixed, antibody-mediated). We observed a broad overlap in cellular transcriptional states across histologic rejection severity and biological class and significant heterogeneity within rejection severity grades that would qualify for immunomodulatory treatment. Individuals who had resolved rejection after therapy had a distinct transcriptomic profile relative to those with persistent rejection, including 216 genes across 6 cell types along pathways of inflammation, IL6-JAK-STAT3 signaling, IFNα/IFNγ response, and TNFα signaling. Spatial transcriptomics also identified genes linked to long-term prognostic outcomes post-HT. These results underscore importance of subtyping immunologic states during rejection to stratify immune-cardiac interactions following HT that are therapeutically relevant to short- and long-term rejection-related outcomes.

Targeting fibroblast phenotype switching in cardiac remodelling as a promising antifibrotic strategy

Myocardial fibrosis, a common feature of heart disease, remains an unsolved clinical challenge. Fibrosis resolution requires activation of cardiac fibroblasts exhibiting context-dependent beneficial and detrimental dichotomy. Here, we explored the hypothesis of fibroblast reversible transition between quiescence and activated myofibroblastic states as a manifestation of cell phenotypic switching in myocardial remodelling. In support, gene regulatory networks executing conversion of cardiac fibroblasts to myofibroblasts and vice versa in fibrosis resolution are reconstructed using TRANSPATH database. In a scenario of fibroblast activation triggered by transforming growth factor β, a cardinal mediator of tissue fibrosis, signalling cascades governing entry into or exit from specific fibroblast statures in cardiac fibrotic remodelling were dissected. It is suggested that fibroblast phenotypic switching constitutes the central gait toward guiding cell state-gating strategies to counteract adverse cardiac fibrosis, a devastating disorder with no approved therapeutic option.

The matrix protease ADAMTS1 is transcriptionally activated by KLF6 and contributes to cardiac fibrosis in non-ischemic cardiomyopathy

AIMS

Aberrant cardiac fibrosis, defined as excessive production and deposition of extracellular matrix (ECM), is mediated by myofibroblasts. ECM-producing myofibroblasts are primarily derived from resident fibroblasts during cardiac fibrosis. The mechanism underlying fibroblast-myofibroblast transition is not fully understood.

METHODS

Cardiac fibrosis was induced by transverse aortic constriction (TAC) or by angiotensin II (Ang II) infusion in C57B6/j mice. Cellular transcriptome was evaluated by RNA-seq and CUT&Tag-seq.

RESULTS

Integrated transcriptomic screening revealed that a disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) was a novel transcriptional target for Kruppel-like factor 6 (KLF6) in cardiac fibroblasts. Treatment with either TGF-β or Ang II up-regulated ADAMTS1 expression. KLF6 knockdown attenuated whereas KLF6 over-expression enhanced ADAMTS1 induction. ChIP assay and reporter assay showed that KLF6 was recruited to the ADAMTS1 promoter to activate its transcription. Consistently, ADAMTS1 knockdown suppressed fibroblast-myofibroblast transition in vitro. Importantly, myofibroblast-specific ADAMTS1 depletion attenuated cardiac fibrosis and normalized heart function in mice.

SIGNIFICANCE

In conclusion, our data demonstrate that ADAMTS1, as a downstream target of KLF6, contributes to cardiac fibrosis by regulating fibroblast-myofibroblast transition.

Decoding aging in the heart via single cell dual omics of non-cardiomyocytes

To understand heart aging at the single-cell level, we employed single-cell dual omics (scRNA-seq and scATAC-seq) in profiling non-myocytes (non-CMs) from young, middle-aged, and elderly mice. Non-CMs, vital in heart development, physiology, and pathology, are understudied compared to cardiomyocytes. Our analysis revealed aging response heterogeneity and its dynamics over time. Immune cells, notably macrophages and neutrophils, showed significant aging alterations, while endothelial cells displayed moderate changes. We identified distinct aging signatures within the cell type, including differential gene expression, transcription factor activity, and motif variation. Sub-cluster analysis revealed intra-cell type heterogeneity, characterized by diverse aging patterns. The senescence-associated secretory phenotype emerged as a key aging-related phenotype. Moreover, aging significantly influenced cell-cell communication, especially impacting a fibroblast sub-cluster with high expression of ERBB4. This study elucidates the complex cellular and molecular landscape of cardiac aging and offers guidance for potential therapeutic avenues to treat aging-related heart diseases.

Gucy1α1 specifically marks kidney, heart, lung and liver fibroblasts

Fibrosis is a common outcome of numerous pathologies, including chronic kidney disease (CKD), a progressive renal function deterioration. Current approaches to target activated fibroblasts, key effector contributors to fibrotic tissue remodeling, lack specificity. Here, we report Gucy1α1 as a specific kidney fibroblast marker. Gucy1α1 levels significantly increased over the course of two clinically relevant murine CKD models and directly correlated with established fibrosis markers. Immunofluorescent (IF) imaging showed that Gucy1α1 comprehensively labelled cortical and medullary quiescent and activated fibroblasts in the control kidney and throughout injury progression, respectively. Unlike traditionally used markers platelet derived growth factor receptor beta (Pdgfrβ) and vimentin (Vim), Gucy1α1 did not overlap with off-target populations such as podocytes. Notably, Gucy1α1 labelled kidney fibroblasts in both male and female mice. Furthermore, we observed elevated GUCY1α1 expression in the human fibrotic kidney and lung. Studies in the murine models of cardiac and liver fibrosis revealed Gucy1α1 elevation in activated Pdgfrβ-, Vim- and alpha smooth muscle actin (αSma)-expressing fibroblasts paralleling injury progression and resolution. Overall, we demonstrate Gucy1α1 as an exclusive fibroblast marker in both sexes. Due to its multiorgan translational potential, GUCY1α1 might provide a novel promising strategy to specifically target and mechanistically examine fibroblasts.

Research Progress of Fibroblasts in Human Diseases

Fibroblasts, which originate from embryonic mesenchymal cells, are the predominant cell type seen in loose connective tissue. As the main components of the internal environment that cells depend on for survival, fibroblasts play an essential role in tissue development, wound healing, and the maintenance of tissue homeostasis. Furthermore, fibroblasts are also involved in several pathological processes, such as fibrosis, cancers, and some inflammatory diseases. In this review, we analyze the latest research progress on fibroblasts, summarize the biological characteristics and physiological functions of fibroblasts, and delve into the role of fibroblasts in disease pathogenesis and explore treatment approaches for fibroblast-related diseases.