Biology subjects

Thum, T.

Publications and source records attributed to Thum, T..

9 recordsLinked to original sources

bioRxiv2026

Natural aging drives a subclinical cardiovascular phenotype in a non-human primate

Aging is an inevitable risk factor for cardiovascular disease. Profound understanding of mechanisms underlying the early stages of cardiovascular aging is essential for the development of novel therapeutics. Therefore, animal models which closely reflect the human condition are highly sought after. Here, we investigated natural cardiovascular aging in a non-human primate, comparing healthy young-adult and aged common marmosets (Callithrix jacchus). Despite preservation of most cardiac functional parameters in aged animals, significant histological alterations were found including fibrosis and microvascular rarefaction. Molecular phenotyping by single-nuclei RNA-sequencing revealed activation of cardiac stress, pro-inflammatory and fibrotic gene programs in aged hearts. Importantly, proteomic analysis of cardiac extracellular vesicles revealed a cardioprotective cargo in young animals while functionally demonstrating pro-angiogenic properties on human cardiac microvascular endothelial cells. Finally, large vessel atherosclerosis was strikingly evident in aged animals and elucidated by bulk RNA-sequencing. Overall, the aging marmoset offers a great potential for translational cardiovascular research.

physiology↗

bioRxiv2026

Single-molecule analysis sheds light on cardiac myosin dysfunction due to hypertrophic cardiomyopathy mutation A57D in ventricular myosin light chain-1 (MLC1v)

Ventricular myosin light chain-1 (MLC1v) is a key structural and function-modulating component of the {beta}-cardiac myosin ({beta}M-II) motor complex. Single-point mutations in MLC1v are linked to severe forms of hypertrophic cardiomyopathy (HCM) and sudden cardiac death (SCD) at a young age. However, the molecular mechanisms underlying the motor dysfunction responsible for HCM phenotype development are not fully understood. Here, we investigated native {beta}M-II motors isolated from septal myectomy sample of an HCM patient, harboring a rare homozygous mutation in MLC1v (A57D). Using a pure population of mutant motors (MUT), and sensitive single-molecule functional analysis approach, we directly assessed the primary functional alterations in {beta}M-II bearing A57D MLC1v mutation. In optical trap single-molecules measurements, the mutant motors displayed increased actomyosin (AM) interaction duration in strongly bound state (ton), corresponding to 3-fold reduced AM detachment rate than wild type myosin (WT). The MUT myosin also generated a shorter powerstroke size ({delta}). Ensemble average analysis of AM interaction events demonstrated that both the first powerstroke ({delta}1) associated with Pi release and the second powerstroke ({delta}2) linked to ADP release were reduced in MUT myosin. Moreover, the increased actomyosin cross-bridge stiffness in the AM.ADP state was observed for MUT compared to WT motors. Consistent with slower AM detachment rate and shorter stroke size, reconstituted human mutant {beta}M-II displayed slower actin filament gliding speed. Alterations in sarcomere-level mechanics included increased Ca2+ sensitivity of force generation and prolonged relaxation time, as predicted by FiberSim modelling. Molecular dynamics simulations indicated that the substitution of alanine by aspartate altered MLC1v interactions with myosin heavy chain (MyHC) and light chain 2 (MLC2v), affecting the curvature and flexibility of the lever arm. Overall, these studies establish the molecular mechanism underlying the primary myosin dysfunction due to A57D MLC1v mutation and further highlight the crucial role of MLC1v-mediated regulation of myosin function. Understanding the precise changes in the mutant myosins biomechanical properties is directly relevant to comprehending the initial triggers for pathological cardiac remodeling in HCM patients and designing tailored therapeutic interventions.

biophysics↗

bioRxiv2025

Nucleoside-Modified mRNA Encoding Alpha-Galactosidase A Reverses Fabry Disease Phenotypes in Human IPSC-Derived Cardiomyocytes

The lysosomal storage disorder Fabry disease results from -galactosidase A deficiency, leading to excessive glycosphingolipid substrate accumulation, primarily globotriaosylceramide (Gb3). While the underlying molecular mechanisms remain elusive, multi-systemic complications ultimately culminate in premature death, with heart failure being the leading cause of death. Current treatment options fail to treat Fabry disease adequately and only delay its progression. Preclinical studies on an alternative approach, systemic delivery of nucleoside-modified GLA mRNA (modGLA), suggest improved effectiveness over existing therapies in reducing glycosphingolipid levels in the heart. It remains unclear whether modGLA can rescue Fabry cardiomyopathy phenotypes at the cellular level, which are not faithfully recapitulated in current animal models. To address this, we investigated characteristic phenotypes in two new models of Fabry cardiomyopathy utilizing human iPSC-derived cardiomyocytes in transcriptomic and functional analyses. These human Fabry disease cardiomyocytes displayed broad transcriptional dysregulation, apoptosis, mitochondrial dysfunction, impaired reactive oxygen species handling, as well as enhanced decay parameters of calcium transients. Mechanistically, we identified hyperphosphorylated phospholamban as a major player in this calcium dysregulation. Strikingly, modGLA therapy of Fabry cardiomyocytes restored -galactosidase A enzyme activity, reduced glycosphingolipid deposition, and normalized the observed molecular alterations, supporting modGLA therapy as a promising strategy for the treatment of Fabry disease.

molecular biology↗

bioRxiv2025

Telomerase modRNA offers a novel RNA-based approach to treat human pulmonary fibrosis

Pulmonary Fibrosis (PF) is a life-threatening illness that is characterized by progressive scarring in the lung interstitium. There is an urgent need for new PF therapies because current treatments only slow down the progression of fibrosis and the median life expectancy post-diagnosis is only 4 to 6 years. Since PF patients frequently exhibit telomere attrition, overexpressing telomerase, the enzyme responsible for synthesizing telomeres represents a compelling therapeutic option. In this study, we in vitro transcribed human telomerase reverse transcriptase (hTERT) mRNA using modified nucleosides (modRNA). ModRNA hTERT treatment led to transient activation of telomerase activity in a dose-dependent manner in MRC-5 cells and, importantly, in primary human alveolar type II pneumocytes (ATII cells). Consequently, the proliferative capacity was increased, concomitant with reduced DNA damage and elongated telomere length. Notably, induction of cellular immune response was only detectable at the highest modRNA concentration, and returned to normal levels within 48 hours. Next, we demonstrated that circularized, exonuclease-resistant modRNA hTERT extended the transient expression profile which may be clinically advantageous. Finally, we provided therapeutic proof of concept in organotypic 3D ex vivo human precision-cut lung slices derived from end-stage PF patients. Intriguingly, a single modRNA hTERT treatment inhibited senescence as indicated by significantly lower levels of senescence-associated {beta}-galactosidase, and pro-inflammatory IL6 and IL8. Concurrently, the key fibrosis mediators TGF{beta} and COL1A1 were markedly reduced. In conclusion, the data presented herein provide initial evidence for the potential of RNA-based hTERT therapy for treating human lung fibrosis.

molecular biology↗

bioRxiv2024

The long non-coding RNA NEAT1 regulates the transcriptional landscape of cardiomyocytes

Long non-coding RNAs (lncRNAs) play a crucial role in fine-tuning the gene expression. In the present study, we identified that the lncRNA NEAT1 is upregulated in failing murine hearts and in human hypertrophic cardiomyopathies. Further investigations demonstrated that NEAT1 expression is regulated by calcium dependent NFAT (nuclear factor of activated T cells). Overexpression of NEAT1 led to increased cardiomyocyte size and elevated expression of cardiac stress markers while its depletion had the opposite effect. Through transcriptomic analysis in NEAT1-KO cells, we demonstrated the cis-regulatory role of NEAT1, wherein it maintains the transcription of neighboring genes by interacting with the coactivator p300. Additionally, NEAT1 depletion resulted in decreased expression of GRK2 (G protein-coupled receptor kinase 2), a key player in the development of cardiac hypertrophy, suggesting that NEAT1 contributes to the development of cardiac hypertrophy by regulating GRK2 expression. Consistent with this, Neat1-/- mice are resistant to {beta}-adrenergic stimulation. Overall, our study provides enough evidence that NEAT1 is a calcium-regulated, pro-hypertrophic lncRNA that exerts significant control over the transcriptional landscape of cardiomyocytes during heart failure.

cell biology↗

bioRxiv2023

SGLT2 inhibitors attenuate endothelial to mesenchymal transition and cardiac fibroblast activation

Beneficial effects of sodium glucose co-transporter 2 inhibitors (SGLT2is) in cardiovascular diseases have been extensively reported leading to the inclusion of these drugs in the treatment guidelines for heart failure. However, molecular actions especially on non-myocyte cells remain uncertain. We observed dose-dependent inhibitory effects of two SGLT2is, dapagliflozin (DAPA) and empagliflozin (EMPA), on inflammatory signaling in human umbilical vein endothelial cells (HUVECs). Proteomics analyses and subsequent enrichment analyses discovered profound effects of these SGLT2is on proteins involved in mitochondrial respiration and actin cytoskeleton. Validation in functional oxygen consumption measurements as well as tube formation and migration assays revealed strong impacts of DAPA. Considering that most influenced parameters played central roles in endothelial to mesenchymal transition (EndMT), we performed in vitro EndMT assays and identified substantial reduction of mesenchymal and fibrosis marker expression as well as changes in cellular morphology upon treatment with SGLT2is. In line, human cardiac fibroblasts (HCFs) exposed to DAPA showed less proliferation, reduced ATP production, and decelerated migration capacity while less extensive impacts were observed upon EMPA. Mechanistically, sodium proton exchanger 1 (NHE1) as well as sodium-myoinositol cotransporter (SMIT) and sodium-multivitamin cotransporter (SMVT) could be identified as relevant targets of SGLT2is in non-myocyte cardiovascular cells as validated by individual siRNA-knockdown experiments. In summary, we found comprehensive beneficial effects of SGLT2is on human endothelial cells and cardiac fibroblasts. The results of this study therefore support a distinct effect of selected SGLT2i on non-myocyte cardiovascular cells and grant further insights into potential molecular mode of action of these drugs.

pharmacology and toxicology↗

bioRxiv2023

Musashi-2 causes cardiac hypertrophy and heart failure by inducing mitochondrial dysfunction through destabilizing Cluh and Smyd1 mRNA

Regulation of RNA stability and translation by RNA-binding proteins (RBPs) is a crucial process altering gene expression. Musashi family of RBPs comprising Msi1 and Msi2 are known to control RNA stability and translation. However, despite the presence of MSI2 in the heart, its function remains entirely unknown. Here, we aim to explore the cardiac functions of MSI2. We confirmed the presence of MSI2 in the adult mouse, rat heart, and neonatal rat cardiomyocytes. Furthermore, Msi2 was significantly enriched in the hearts cardiomyocyte fraction. Next, using RNA-seq data and isoform-specific PCR primers, we identified, Msi2 isoforms 1, 4, and 5 and two novel putative isoforms labeled as Msi2 isoforms 6 and 7 to be expressed in the heart. Overexpression of Msi2 isoforms led to cardiac hypertrophy in cultured cardiomyocytes. Additionally, Msi2 was also found to be significantly increased in a pressure-overload model of cardiac hypertrophy. To validate the hypertrophic effects, we selected isoforms 4 and 7 due to their unique alternative splicing patterns. AAV9-mediated overexpression of Msi2 isoforms 4 and 7 in murine hearts led to cardiac hypertrophy, dilation, heart failure, and eventually early death, confirming a pathological function for Msi2. Using global proteomics, gene ontology, transmission electron microscopy, and transmembrane potential measurement assays increased MSI2 was found to cause mitochondrial dysfunction in the heart. Mechanistically, we identified Cluh and Smyd1 as direct downstream targets of Msi2. Overexpression of Cluh or Smyd1 inhibited Msi2-induced hypertrophy and mitochondrial dysfunction in cardiomyocytes. Collectively, we show that Msi2 induces hypertrophy, mitochondrial dysfunction, and heart failure.

cell biology↗

bioRxiv2021

Long-term ecosystem nitrogen limitation from foliar δ15N data and a land surface model

The effect of nutrient availability on plant growth and the terrestrial carbon sink under climate change and elevated CO2 remains one of the main uncertainties of the terrestrial carbon cycle. This is partially due to the difficulty of assessing nutrient limitation at large scales over long periods of time. Consistent declines in leaf nitrogen (N) content and leaf {delta}15N have been used to suggest that nitrogen limitation has increased in recent decades, most likely due to the concurrent increase in atmospheric CO2. However, such datasets are often not straightforward to interpret due to the complex factors that contribute to the spatial and temporal variation in leaf N and isotope concentration. We use the land surface model QUINCY, which has the unique capacity to represent N isotopic processes, in conjunction with two large datasets of foliar N and N isotope content. We run the model with different scenarios to test whether foliar {delta}15N isotopic data can be used to infer large scale nitrogen limitation and if the observed trends are caused by increasing atmospheric CO2, changes in climate or changes in sources of anthropogenic N deposition. We show that while the model can capture the observed change in leaf N content and predicts widespread increases in N limitation, it does not capture the pronounced, but very spatially heterogeneous, decrease in foliar {delta}15N observed in the data across the globe. The addition of an observed temporal trend in isotopic composition of N deposition leads to a more pronounced decrease in simulated leaf {delta}15N. Our results show that leaf {delta}15N observations should not, on their own, be used to assess global scale N limitation and that using such a dataset in conjunction with a land surface model can reveal the drivers behind the observed patterns.

ecology↗

bioRxiv2019

Whole-plant optimality predicts changes in leaf nitrogen under variable CO2 and nutrient availability

O_LIVegetation nutrient limitation is essential for understanding ecosystem responses to global change. In particular, leaf nitrogen (N) is known to be plastic under changed nutrient limitation. However, models can often not capture these observed changes, leading to erroneous predictions of whole-ecosystem stocks and fluxes.\nC_LIO_LIWe hypothesise that an optimality approach can improve representation of leaf N content compared to existing empirical approaches. Unlike previous optimality-based approaches, which adjust foliar N concentrations based on canopy carbon export, we use a maximisation criteria based on whole-plant growth and allow for a lagged response of foliar N to this maximisation criterion to account for the limited plasticity of this plant trait. We test these model variants at a range of Free-Air CO2 Enrichment (FACE) and N fertilisation experimental sites.\nC_LIO_LIWe show a model solely based on canopy carbon export fails to reproduce observed patterns and predicts decreasing leaf N content with increased N availability. However, an optimal model which maximises total plant growth can correctly reproduce the observed patterns.\nC_LIO_LIThe optimality model we present here is a whole-plant approach which reproduces biologically realistic changes in leaf N and can thereby improve ecosystem-level predictions under transient conditions.\nC_LI

ecology↗