Biology subjects

Laimbacher, A.

Publications and source records attributed to Laimbacher, A..

7 recordsLinked to original sources

bioRxiv2026

Pulmonary pressure load shapes right ventricular molecular remodelling in dilated cardiomyopathy

Right ventricular (RV) adaptation to pulmonary hypertension determines outcome in dilated cardiomyopathy (DCM), but the molecular mechanisms of the transition to decompensation remain unclear. We analysed RV tissue from explanted hearts of patients with end-stage DCM using single-nucleus RNA sequencing (n=21), mass spectrometry and Olink Reveal proteomics (both n=44), and integrated these molecular profiles with echocardiographic and right-heart catheterisation measures to identify molecular correlates of RV dysfunction. Mean pulmonary arterial pressure was the dominant correlate of RV transcriptional remodelling, particularly in cardiomyocytes, where higher pressure was associated with contractile remodelling, autophagy, vesicle trafficking and glucose metabolism. In contrast, RV decompensation was characterised by immune activation and reduced oxidative phosphorylation exclusively at the proteomic level. Integrative multi-omics factor analysis (MOFA) further identified fibrosis as the dominant molecular program shared across transcriptomic and proteomic layers. Together, these findings indicate molecular adaptation to pressure load and tissue fibrosis during progression towards RV failure.

physiology↗

bioRxiv2026

Lanifibranor (IVA-337) - a pan-PPAR agonist suppresses TGF-β1-induced cardiac fibrosis and rescues cardiomyocyte function

Background: Cardiac fibrosis is a hallmark of many cardiovascular diseases, driven by sustained fibroblast activation and excessive extracellular matrix deposition, leading to myocardial stiffening and impaired contractility. Current therapies inadequately address this process. This study evaluated the antifibrotic potential of lanifibranor, a balanced pan-peroxisome proliferator-activated receptors (PPARs) agonist, in TGF-beta1-induced cardiac fibrosis. Methods: Human cardiac microtissues, along with 2D and 3D cardiac fibroblast and cardiomyocyte cultures, were used to assess cell viability, structure, metabolism, contractility, and gene expression. Results: Lanifibranor reduced TGF-beta1-induced fibrosis by limiting fibroblast activation and matrix deposition without affecting viability. In fibroblasts, these effects were associated with partial restoration of mitochondrial respiration and reduced focal adhesion maturation. In cardiac microtissues, lanifibranor improved contraction kinetics, decreased profibrotic transcriptional activity, and preserved bioenergetic homeostasis despite altered nucleotide balance. In cardiomyocytes, treatment normalized contractility and calcium handling while maintaining metabolic stability. Conclusions: Lanifibranor attenuates TGF-beta1-driven cardiac fibrosis by combining antifibrotic effects with metabolic and functional improvements in human models.

pharmacology and toxicology↗

bioRxiv2026

The dual PPAR-α/δ agonist elafibranor attenuates TGF-β1-induced cardiac fibrosis through redox-metabolic and bioenergetic reprogramming in human cardiac models

BackgroundCardiac fibrosis drives adverse myocardial remodelling through persistent fibroblast activation, ECM deposition, and impaired cardiac function. Current therapies offer limited protection against cardiac fibrosis progression. Elafibranor is a dual PPAR-/{delta} agonist approved for the treatment of liver disease. However, its effects in human models of cardiac fibrosis remain insufficiently explored. MethodsElafibranor was evaluated in complementary human in vitro TGF-{beta}1-induced cardiac fibrosis models: 2D primary fibroblasts, 3D fibroblast spheroids, spontaneously contracting 3D cardiac microtissues, and hiPSC-derived cardiomyocytes. Viability, apoptosis, fibroblast activation, ECM remodelling, mitochondrial respiration, nucleotide and NAD pools, calcium handling, contractility, and transcriptomic profiles were assessed. ResultsAt non-cytotoxic concentrations, elafibranor attenuated TGF-{beta}1-driven cardiac fibrosis responses. In 2D cardiac fibroblasts, it reduced myofibroblast differentiation, procollagen 11 secretion, and partially restored mitochondrial respiratory capacity. In 3D spheroids, it preserved viability, attenuated caspase-3/7 activation, and suppressed procollagen 11 release. In cardiac microtissues, elafibranor reduced ECM accumulation, shifted transcriptomic profiles toward redox-metabolic/cytoprotective pathways, altered adenine nucleotide and NAD pools, and partially recovered contraction parameters. In hiPSC-derived cardiomyocytes, elafibranor modulated calcium handling, contractility, and mitochondrial respiration. ConclusionsElafibranor mitigates TGF-{beta}1-driven cardiac fibrosis by suppressing fibroblast activation and ECM remodelling while promoting adaptive metabolic, redox, and bioenergetic responses, supporting balanced PPAR-/{delta} activation as a potential therapeutic strategy for cardiac fibrosis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/745425v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@2de670org.highwire.dtl.DTLVardef@173fea6org.highwire.dtl.DTLVardef@537e7aorg.highwire.dtl.DTLVardef@194b846_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

Dysferlin is a novel regulator of COMP-positive matrifibrocytes in heart failure

Background and AimsCardiac fibrosis is a major contributor to heart failure (HF), yet mechanisms limiting pathological fibroblast activation remain incompletely understood. We identified dysferlin (DYSF), a membrane repair protein, as highly induced in HF fibroblasts and investigated its role in regulating profibrotic responses. MethodsCardiac fibroblasts from patients with end-stage HF and unaffected donor hearts were analysed by liquid chromatography-tandem mass spectrometry and bulk RNA sequencing. Dysferlin expression was validated in independent cohorts. Selected gene/protein expression was validated using single-cell/single-nucleus RNA sequencing and multiplex immunofluorescence of human myocardium from dilated cardiomyopathy (DCM), ischaemic cardiomyopathy (ICM), acute myocardial infarction (AMI), and unaffected hearts. Functional studies were performed in human and mouse cardiac fibroblasts using siRNA-mediated silencing and TGF-{beta} stimulation, and in engineered human 3D cardiac microtissues. Fibrotic remodelling, autophagy, apoptosis, and contractile function were assessed by molecular, histological, biochemical and functional analyses. ResultsDysferlin abundance was markedly increased in HF fibroblasts. Across HF myocardium, DYSF was enriched in activated fibroblasts but largely excluded from COMP-enriched fibrotic regions, consistent with a role in restraining fibroblast state transitions. Although induced by TGF-{beta}, DYSF silencing enhanced extracellular matrix production, increased FOSL2 expression, and promoted differentiation into COMP-positive matrifibrocytes. In engineered human cardiac microtissues, DYSF silencing exacerbated fibrosis, increased apoptosis, and impaired contractility. Mechanistically, dysferlin restrained the TGF-{beta}-FOSL2-autophagy signalling axis, whereas FOSL2 suppressed DYSF expression, defining a reciprocal regulatory circuit. Silencing FOSL2 or MXRA5 increased dysferlin levels, while mRNA-protein discordance implicated S-acylation as a potential regulator of dysferlin protein abundance. ConclusionsDysferlin is a stress-inducible antifibrotic regulator that limits maladaptive fibroblast differentiation and myocardial fibrosis, thereby representing a potential therapeutic target to attenuate adverse cardiac remodelling in HF. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=122 SRC="FIGDIR/small/745492v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@46ae02org.highwire.dtl.DTLVardef@4a0b99org.highwire.dtl.DTLVardef@13fa574org.highwire.dtl.DTLVardef@18777d4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

Comparison of Culture Systems for Mouse Living Myocardial Slices in Cardiac Fibrosis Research

Living myocardial slices (LMS) are a highly relevant ex vivo model for investigating cardiac physiology and disease, as they preserve the native three-dimensional architecture, cellular diversity, and extracellular matrix of the heart. In addition, LMS enable longitudinal functional and molecular analyses. In this study, we established and compared two LMS culture approaches: an air-liquid interface system and a biomimetic culture system. We further examined how different slicing techniques affect tissue quality and longevity within the biomimetic setup. To develop a fibrosis model, LMS were stimulated with transforming growth factor-beta1 (TGF-beta1) and/or exposed to increased mechanical load. Tissue viability was assessed using LIVE/DEAD staining and the MTT assay, while cytotoxicity was evaluated with the LDH-Glo-TM Cytotoxicity assay. Contractile function was measured, and fibrotic remodelling was analysed using RT-qPCR, ELISA, and immunohistochemistry. Our results demonstrate that LMS cultured in the biomimetic system exhibit superior viability, structural integrity, and functional performance compared with those maintained at the air-liquid interface. Mouse LMS could be stably cultured for up to one week in the biomimetic system. Importantly, sample preparation, particularly the slicing method, had a significant impact on tissue quality and culture duration. While TGF-beta1 stimulation alone did not consistently induce fibrosis, combining TGF-beta1 treatment with increased mechanical load led to more pronounced fibrotic remodelling in LMS. These findings highlight the importance of biomechanical cues in modelling cardiac fibrosis ex vivo and support the biomimetic system as a robust platform for functional and disease-relevant studies.

cell biology↗

bioRxiv2026

Compartmental Profiling of PDE4B in Systemic Sclerosis

ObjectivesThe preferential phosphodiesterase 4B (PDE4B) inhibitor nerandomilast was recently approved for treatment of idiopathic pulmonary fibrosis (IPF) and progressive pulmonary fibrosis. Its proposed immunomodulatory, anti-fibrotic, and endothelial-stabilising actions target all three cardinal features of SSc, yet PDE4B expression has not been systematically characterised in SSc tissue. We aimed to define PDE4B expression across fibrotic organs and cellular compartments in SSc. MethodsPDE4B expression was profiled in SSc lung, peripheral blood mononuclear cells (PBMCs) and skin on the transcript level using single-cell RNA sequencing data and on the protein level using immunohistochemistry, immunofluorescence and multiplexed immunofluorescent stainings. ResultsPDE4B was consistently dysregulated in immune cells across SSc tissue and PBMCs, with compartment-specific direction and distribution. In SSc-ILD lung, expression was increased in CD8 and CD4 memory T-cells. In PBMCs, expression was increased in B cells, monocytes, and CD8 T-cells, and stratified patients into three endotypes (PDE4B//hi) not distinguishable by clinical variables. In skin, bulk RNA-seq showed a significant global increase, which localized to myeloid cells in scRNA-seq data. Approximately 90% of FAP activated fibroblasts co-expressed PDE4B at the protein level in SSc skin, identifying the activated fibroblast compartment as a candidate target for PDE4B inhibition. No PDE4B dysregulation was detected in vascular cell types. ConclusionsThis first cell-type-resolved characterisation of PDE4B in SSc demonstrates consistent immune-cell dysregulation across tissues and protein-level enrichment in activated fibroblasts. This provides a human-tissue rationale for the immunomodulatory and anti-fibrotic effects of PDE4B inhibition and supporting PDE4B as a disease-relevant therapeutic target in SSc. Key messagesO_ST_ABSWhat is already known on this topicC_ST_ABSO_LINerandomilast (BI 1015550), a PDE4B-preferential inhibitor, was approved for idiopathic pulmonary fibrosis and progressive pulmonary fibrosis. C_LIO_LIPre-clinical studies indicate that PDE4B inhibition may act on all cardinal features of SSc. C_LI What this study addsO_LIFirst cell-type-resolved characterization of PDE4B expression across SSc-affected lung, PBMCs, and skin. C_LIO_LIPBMC PDE4B expression is heterogeneous, stratifying patients into PDE4B// endotypes independent of standard clinical variables. C_LIO_LIscRNA-seq shows increased myeloid PDE4B expression in SSc skin, while [~]90% of FAP activated fibroblasts in SSc skin express PDE4B protein. C_LI How this study might affect research, practice or policyO_LIThe study strengthens the human-level evidence underpinning the target rationale for PDE4B inhibition in SSc. C_LI

molecular biology↗

bioRxiv2025

Disease-specific fibroblast-myeloid interactions in rheumatoid arthritis synovium

Rheumatoid arthritis (RA) is characterized by profound remodeling of the synovial microenvironment. Here we show that enhanced fibroblast-macrophage cross-talk distinguishes RA from psoriatic arthritis (PsA). MerTK-SPP1 macrophages represent the dominant inflammatory myeloid population in RA, interacting with expanded fibroblast subsets through SPP1-mediated signaling. Lining fibroblasts display induction of antigen-presentation and IL-6/JAK-STAT pathways, while a CHI3L1-producing fibroblast population arises specifically in RA and may act as a source of autoantigens. These stromal populations interact closely with FABP5 iDC3 cells and T cells within a disrupted synovial lining, creating a niche driving adaptive immune activation. In contrast, PsA exhibits increased fibroblast- endothelial interactions without major endothelial transcriptional changes. Our data identify SPP1 signaling and fibroblast-myeloid-dendritic interactions as core drivers of RA synovial inflammation that links innate immune activation to the initiation of autoimmunity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/688477v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@c76e39org.highwire.dtl.DTLVardef@11563a9org.highwire.dtl.DTLVardef@141f3fborg.highwire.dtl.DTLVardef@f90742_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗