Katharina Schimmel

All Publications

• Increased BMP-Responsive Transcription Factors in Distinct Endothelial and Mesenchymal Cells in PAH. American journal of respiratory and critical care medicine Andruska, A. M., Cantu Valadez, R., Ichimura, K., Chu, P., Zhang, T., Schimmel, K., Wang, L., Cao, A., Aldred, M. A., Spiekerkoetter, E. 2024

  View details for DOI 10.1164/rccm.202405-1039LE

  View details for PubMedID 39499865

• Somatic mutations in arteriovenous malformations in hereditary hemorrhagic telangiectasia support a bi-allelic two-hit mutation mechanism of pathogenesis. American journal of human genetics DeBose-Scarlett, E., Ressler, A. K., Gallione, C. J., Sapisochin Cantis, G., Friday, C., Weinsheimer, S., Schimmel, K., Spiekerkoetter, E., Kim, H., Gossage, J. R., Faughnan, M. E., Marchuk, D. A. 2024

  Abstract

  Hereditary hemorrhagic telangiectasia (HHT) is an inherited disorder of vascular malformations characterized by mucocutaneous telangiectases and arteriovenous malformations (AVMs) in internal organs. HHT is caused by inheritance of a loss of function mutation in one of three genes. Although individuals with HHT are haploinsufficient for one of these genes throughout their entire body, rather than exhibiting a systemic vascular phenotype, vascular malformations occur as focal lesions in discrete anatomic locations. The inconsistency between genotype and phenotype has provoked debate over whether haploinsufficiency or a different mechanism gives rise to the vascular malformations. We previously showed that HHT-associated skin telangiectases develop by a two-hit mutation mechanism in an HHT gene. However, somatic mutations were identified in only half of the telangiectases, raising the question whether a second-hit somatic mutation is a necessary (required) event in HHT pathogenesis. Here, we show that another mechanism for the second hit is loss of heterozygosity across the chromosome bearing the germline mutation. Secondly, we investigate the two-hit mutation mechanism for internal organ AVMs, the source of much of the morbidity of HHT. Here, we identified somatic molecular genetic events in eight liver telangiectases, including point mutations and a loss of heterozygosity event. We also identified somatic mutations in one pulmonary AVM and two brain AVMs, confirming that mucocutaneous and internal organ vascular malformations undergo the same molecular mechanisms. Together, these data argue that bi-allelic loss of function in an HHT gene is a required event in the pathogenesis of HHT-associated vascular malformations.

  View details for DOI 10.1016/j.ajhg.2024.08.020

  View details for PubMedID 39299239

• 3D Imaging Reveals Complex Microvascular Remodeling in the Right Ventricle in Pulmonary Hypertension. Circulation research Ichimura, K., Boehm, M., Andruska, A. M., Zhang, F., Schimmel, K., Bonham, S., Kabiri, A., Kheyfets, V. O., Ichimura, S., Reddy, S., Mao, Y., Zhang, T., Wang, G., Santana, E. J., Tian, X., Essafri, I., Vinh, R., Tian, W., Nicolls, M. R., Yajima, S., Shudo, Y., MacArthur, J. W., Woo, Y. J., Metzger, R. J., Spiekerkoetter, E. 2024

  Abstract

  Pathogenic concepts of right ventricular (RV) failure in pulmonary arterial hypertension focus on a critical loss of microvasculature. However, the methods underpinning prior studies did not take into account the 3-dimensional (3D) aspects of cardiac tissue, making accurate quantification difficult. We applied deep-tissue imaging to the pressure-overloaded RV to uncover the 3D properties of the microvascular network and determine whether deficient microvascular adaptation contributes to RV failure.Heart sections measuring 250-µm-thick were obtained from mice after pulmonary artery banding (PAB) or debanding PAB surgery and properties of the RV microvascular network were assessed using 3D imaging and quantification. Human heart tissues harvested at the time of transplantation from pulmonary arterial hypertension cases were compared with tissues from control cases with normal RV function.Longitudinal 3D assessment of PAB mouse hearts uncovered complex microvascular remodeling characterized by tortuous, shorter, thicker, highly branched vessels, and overall preserved microvascular density. This remodeling process was reversible in debanding PAB mice in which the RV function recovers over time. The remodeled microvasculature tightly wrapped around the hypertrophied cardiomyocytes to maintain a stable contact surface to cardiomyocytes as an adaptation to RV pressure overload, even in end-stage RV failure. However, microvasculature-cardiomyocyte contact was impaired in areas with interstitial fibrosis where cardiomyocytes displayed signs of hypoxia. Similar to PAB animals, microvascular density in the RV was preserved in patients with end-stage pulmonary arterial hypertension, and microvascular architectural changes appeared to vary by etiology, with patients with pulmonary veno-occlusive disease displaying a lack of microvascular complexity with uniformly short segments.3D deep tissue imaging of the failing RV in PAB mice, pulmonary hypertension rats, and patients with pulmonary arterial hypertension reveals complex microvascular changes to preserve the microvascular density and maintain a stable microvascular-cardiomyocyte contact. Our studies provide a novel framework to understand microvascular adaptation in the pressure-overloaded RV that focuses on cell-cell interaction and goes beyond the concept of capillary rarefaction.

  View details for DOI 10.1161/CIRCRESAHA.123.323546

  View details for PubMedID 38770652

• Rat microbial biogeography and age-dependent lactic acid bacteria in healthy lungs. Lab animal Zhao, L., Cunningham, C. M., Andruska, A. M., Schimmel, K., Ali, M. K., Kim, D., Gu, S., Chang, J. L., Spiekerkoetter, E., Nicolls, M. R. 2024; 53 (2): 43-55

  Abstract

  The laboratory rat emerges as a useful tool for studying the interaction between the host and its microbiome. To advance principles relevant to the human microbiome, we systematically investigated and defined the multitissue microbial biogeography of healthy Fischer 344 rats across their lifespan. Microbial community profiling data were extracted and integrated with host transcriptomic data from the Sequencing Quality Control consortium. Unsupervised machine learning, correlation, taxonomic diversity and abundance analyses were performed to determine and characterize the rat microbial biogeography and identify four intertissue microbial heterogeneity patterns (P1-P4). We found that the 11 body habitats harbored a greater diversity of microbes than previously suspected. Lactic acid bacteria (LAB) abundance progressively declined in lungs from breastfed newborn to adolescence/adult, and was below detectable levels in elderly rats. Bioinformatics analyses indicate that the abundance of LAB may be modulated by the lung-immune axis. The presence and levels of LAB in lungs were further evaluated by PCR in two validation datasets. The lung, testes, thymus, kidney, adrenal and muscle niches were found to have age-dependent alterations in microbial abundance. The 357 microbial signatures were positively correlated with host genes in cell proliferation (P1), DNA damage repair (P2) and DNA transcription (P3). Our study established a link between the metabolic properties of LAB with lung microbiota maturation and development. Breastfeeding and environmental exposure influence microbiome composition and host health and longevity. The inferred rat microbial biogeography and pattern-specific microbial signatures could be useful for microbiome therapeutic approaches to human health and life quality enhancement.

  View details for DOI 10.1038/s41684-023-01322-x

  View details for PubMedID 38297075

  View details for PubMedCentralID PMC10834367

• PTPN1 Deficiency Modulates BMPR2 Signaling and Induces Endothelial Dysfunction in Pulmonary Arterial Hypertension. Cells Ali, M. K., Tian, X., Zhao, L., Schimmel, K., Rhodes, C. J., Wilkins, M. R., Nicolls, M. R., Spiekerkoetter, E. F. 2023; 12 (2)

  Abstract

  Bone morphogenic protein receptor 2 (BMPR2) expression and signaling are impaired in pulmonary arterial hypertension (PAH). How BMPR2 signaling is decreased in PAH is poorly understood. Protein tyrosine phosphatases (PTPs) play important roles in vascular remodeling in PAH. To identify whether PTPs modify BMPR2 signaling, we used a siRNA-mediated high-throughput screening of 22,124 murine genes in mouse myoblastoma reporter cells using ID1 expression as readout for BMPR2 signaling. We further experimentally validated the top hit, PTPN1 (PTP1B), in healthy human pulmonary arterial endothelial cells (PAECs) either silenced by siRNA or exposed to hypoxia and confirmed its relevance to PAH by measuring PTPN1 levels in blood and PAECs collected from PAH patients. We identified PTPN1 as a novel regulator of BMPR2 signaling in PAECs, which is downregulated in the blood of PAH patients, and documented that downregulation of PTPN1 is linked to endothelial dysfunction in PAECs. These findings point to a potential involvement for PTPN1 in PAH and will aid in our understanding of the molecular mechanisms involved in the disease.

  View details for DOI 10.3390/cells12020316

  View details for PubMedID 36672250

• Early Right Ventricular Snail Expression is a Druggable Target to Improve Right Ventricular Function in Pressure-Overloaded Right Heart Failure Ichimura, K., Mao, Y., Boehm, M., Ali, K., Andruska, A., Schimmel, K., Zhang, F., Reddy, S., Spiekerkoetter, E. 2023

  View details for DOI 10.1161/circ.148.suppl_1.14585

• A Novel Mouse Model Replicates Pulmonary Arteriovenous Malformations in Hereditary Hemorrhagic Telangiectasia Schimmel, K., Ichimura, K., Andruska, A., Spiekerkoetter, E. 2023

  View details for DOI 10.1161/circ.148.suppl_1.12567

• The role of circular RNAs in pulmonary hypertension. The European respiratory journal Ali, M. K., Schimmel, K., Zhao, L., Chen, C. K., Dua, K., Nicolls, M. R., Spiekerkoetter, E. 2022

  Abstract

  Circular RNAs (CircRNAs) are endogenous, covalently circularized, non-protein-coding RNAs generated from back splicing. Most circRNAs are very stable, highly conserved, and expressed in a tissue-, cell- and developmental stage-specific manner. CircRNAs play a significant role in various biological processes, such as regulation of gene expression and protein translation via sponging of microRNAs and binding with RNA binding proteins. CircRNAs have become a topic of great interest in research due to their close link with the development of various diseases. Their high stability, conservation, and abundance in body fluids make them promising biomarkers for many diseases. A growing body of evidence suggests that aberrant expression of circRNAs and their targets plays a crucial role in pulmonary vascular remodeling and Group 1 pulmonary arterial hypertension (PAH) as well as other forms of pulmonary hypertension (PH) (Group 3 and 4). Here we discuss the roles and molecular mechanisms of circRNAs in the pathogenesis of pulmonary vascular remodeling and PH. We also highlight the therapeutic and biomarker potential of circRNAs in PH.

  View details for DOI 10.1183/13993003.00012-2022

  View details for PubMedID 35680145

• Cardiac Fibrosis in the Pressure Overloaded Left and Right Ventricle as a Therapeutic Target. Frontiers in cardiovascular medicine Schimmel, K., Ichimura, K., Reddy, S., Haddad, F., Spiekerkoetter, E. 2022; 9: 886553

  Abstract

  Myocardial fibrosis is a remodeling process of the extracellular matrix (ECM) following cardiac stress. "Replacement fibrosis" is a term used to describe wound healing in the acute phase of an injury, such as myocardial infarction. In striking contrast, ECM remodeling following chronic pressure overload insidiously develops over time as "reactive fibrosis" leading to diffuse interstitial and perivascular collagen deposition that continuously perturbs the function of the left (L) or the right ventricle (RV). Examples for pressure-overload conditions resulting in reactive fibrosis in the LV are systemic hypertension or aortic stenosis, whereas pulmonary arterial hypertension (PAH) or congenital heart disease with right sided obstructive lesions such as pulmonary stenosis result in RV reactive fibrosis. In-depth phenotyping of cardiac fibrosis has made it increasingly clear that both forms, replacement and reactive fibrosis co-exist in various etiologies of heart failure. While the role of fibrosis in the pathogenesis of RV heart failure needs further assessment, reactive fibrosis in the LV is a pathological hallmark of adverse cardiac remodeling that is correlated with or potentially might even drive both development and progression of heart failure (HF). Further, LV reactive fibrosis predicts adverse outcome in various myocardial diseases and contributes to arrhythmias. The ability to effectively block pathological ECM remodeling of the LV is therefore an important medical need. At a cellular level, the cardiac fibroblast takes center stage in reactive fibrotic remodeling of the heart. Activation and proliferation of endogenous fibroblast populations are the major source of synthesis, secretion, and deposition of collagens in response to a variety of stimuli. Enzymes residing in the ECM are responsible for collagen maturation and cross-linking. Highly cross-linked type I collagen stiffens the ventricles and predominates over more elastic type III collagen in pressure-overloaded conditions. Research has attempted to identify pro-fibrotic drivers causing fibrotic remodeling. Single key factors such as Transforming Growth Factor β (TGFβ) have been described and subsequently targeted to test their usefulness in inhibiting fibrosis in cultured fibroblasts of the ventricles, and in animal models of cardiac fibrosis. More recently, modulation of phenotypic behaviors like inhibition of proliferating fibroblasts has emerged as a strategy to reduce pathogenic cardiac fibroblast numbers in the heart. Some studies targeting LV reactive fibrosis as outlined above have successfully led to improvements of cardiac structure and function in relevant animal models. For the RV, fibrosis research is needed to better understand the evolution and roles of fibrosis in RV failure. RV fibrosis is seen as an integral part of RV remodeling and presents at varying degrees in patients with PAH and animal models replicating the disease of RV afterload. The extent to which ECM remodeling impacts RV function and thus patient survival is less clear. In this review, we describe differences as well as common characteristics and key players in ECM remodeling of the LV vs. the RV in response to pressure overload. We review pre-clinical studies assessing the effect of anti-fibrotic drug candidates on LV and RV function and their premise for clinical testing. Finally, we discuss the mode of action, safety and efficacy of anti-fibrotic drugs currently tested for the treatment of left HF in clinical trials, which might guide development of new approaches to target right heart failure. We touch upon important considerations and knowledge gaps to be addressed for future clinical testing of anti-fibrotic cardiac therapies.

  View details for DOI 10.3389/fcvm.2022.886553

  View details for PubMedID 35600469

  View details for PubMedCentralID PMC9120363

• Arteriovenous Malformations-Current Understanding of the Pathogenesis with Implications for Treatment. International journal of molecular sciences Schimmel, K., Ali, M. K., Tan, S. Y., Teng, J., Do, H. M., Steinberg, G. K., Stevenson, D. A., Spiekerkoetter, E. 2021; 22 (16)

  Abstract

  Arteriovenous malformations are a vascular anomaly typically present at birth, characterized by an abnormal connection between an artery and a vein (bypassing the capillaries). These high flow lesions can vary in size and location. Therapeutic approaches are limited, and AVMs can cause significant morbidity and mortality. Here, we describe our current understanding of the pathogenesis of arteriovenous malformations based on preclinical and clinical findings. We discuss past and present accomplishments and challenges in the field and identify research gaps that need to be filled for the successful development of therapeutic strategies in the future.

  View details for DOI 10.3390/ijms22169037

  View details for PubMedID 34445743

• High-Frequency Ultrasound Echocardiography to Assess Zebrafish Cardiac Function. Journal of visualized experiments : JoVE Evangelisti, A., Schimmel, K., Joshi, S., Shah, K., Fisch, S., Alexander, K. M., Liao, R., Morgado, I. 2020

  Abstract

  The zebrafish (Danio rerio) has become a very popular model organism in cardiovascular research, including human cardiac diseases, largely due to its embryonic transparency, genetic tractability, and amenity to rapid, high-throughput studies. However, the loss of transparency limits heart function analysis at the adult stage, which complicates modeling of age-related heart conditions. To overcome such limitations, high-frequency ultrasound echocardiography in zebrafish is emerging as a viable option. Here, we present a detailed protocol to assess cardiac function in adult zebrafish by non-invasive echocardiography using high-frequency ultrasound. The method allows visualization and analysis of zebrafish heart dimension and quantification of important functional parameters, including heart rate, stroke volume, cardiac output, and ejection fraction. In this method, the fish are anesthetized and kept underwater and can be recovered after the procedure. Although high-frequency ultrasound is an expensive technology, the same imaging platform can be used for different species (e.g., murine and zebrafish) by adapting different transducers. Zebrafish echocardiography is a robust method for cardiac phenotyping, useful in the validation and characterization of disease models, particularly late-onset diseases; drug screens; and studies of heart injury, recovery, and regenerative capacity.

  View details for DOI 10.3791/60976

  View details for PubMedID 32225163

• Natural Compound Library Screening Identifies New Molecules for the Treatment of Cardiac Fibrosis and Diastolic Dysfunction. Circulation Schimmel, K. n., Jung, M. n., Foinquinos, A. n., San José, G. n., Beaumont, J. n., Bock, K. n., Grote-Levi, L. n., Xiao, K. n., Bär, C. n., Pfanne, A. n., Just, A. n., Zimmer, K. n., Ngoy, S. n., López, B. n., Ravassa, S. n., Samolovac, S. n., Janssen-Peters, H. n., Remke, J. n., Scherf, K. n., Dangwal, S. n., Piccoli, M. T., Kleemiss, F. n., Kreutzer, F. P., Kenneweg, F. n., Leonardy, J. n., Hobuß, L. n., Santer, L. n., Do, Q. T., Geffers, R. n., Braesen, J. H., Schmitz, J. n., Brandenberger, C. n., Müller, D. N., Wilck, N. n., Kaever, V. n., Bähre, H. n., Batkai, S. n., Fiedler, J. n., Alexander, K. M., Wertheim, B. M., Fisch, S. n., Liao, R. n., Diez, J. n., González, A. n., Thum, T. n. 2020

  Abstract

  Background: Myocardial fibrosis is a hallmark of cardiac remodeling and functionally involved in heart failure (HF) development, a leading cause of deaths worldwide. Clinically there is no therapeutic strategy available that specifically attenuates maladaptive responses of cardiac fibroblasts, the effector cells of fibrosis in the heart. Therefore, we aimed at the development of novel anti-fibrotic therapeutics based on natural-derived substance library screens for the treatment of cardiac fibrosis. Methods: Anti-fibrotic drug candidates were identified by functional screening of 480 chemically diverse natural compounds in primary human cardiac fibroblasts (HCFs), subsequent validation and mechanistic in vitro and in vivo studies. Hits were analyzed for dose-dependent inhibition of proliferation of HCFs, for modulation of apoptosis and extracellular matrix expression. In vitro findings were confirmed in vivo, using an angiotensin II (Ang II)-mediated murine model of cardiac fibrosis in both preventive and therapeutic settings, as well as in the Dahl salt sensitive rat model. To investigate the mechanism underlying the anti-fibrotic potential of the lead compounds, treatment-dependent changes in the noncoding RNAome in primary HCFs were analyzed by RNA-deep sequencing. Results: High-throughput natural compound library screening identified 15 substances with antiproliferative effects in HCFs. Using multiple in vitro fibrosis assays and stringent selection algorithms we identified the steroid bufalin (from Chinese toad venom) and the alkaloid lycorine (from Amaryllidaceae species) to be effective anti-fibrotic molecules both in vitro and in vivo leading to improvement in diastolic function in two hypertension-dependent rodent models of cardiac fibrosis. Administration at effective doses did not change plasma damage markers nor the morphology of kidney and liver, providing first toxicological safety data. By next-generation sequencing we identified the conserved microRNA (miR) miR-671-5p and downstream the antifibrotic selenoprotein P1 (SEPP1) as common effectors of the anti-fibrotic compounds. Conclusions: We identified the molecules bufalin and lycorine as drug candidates for therapeutic applications in cardiac fibrosis and diastolic dysfunction.

  View details for DOI 10.1161/CIRCULATIONAHA.119.042559

  View details for PubMedID 31948273

• Combined high-throughput library screening and next generation RNA sequencing uncover microRNAs controlling human cardiac fibroblast biology. Journal of molecular and cellular cardiology Schimmel, K. n., Stojanović, S. D., Huang, C. K., Jung, M. n., Meyer, M. H., Xiao, K. n., Grote-Levi, L. n., Bär, C. n., Pfanne, A. n., Mitzka, S. n., Just, A. n., Geffers, R. n., Bock, K. n., Kenneweg, F. n., Kleemiß, F. n., Falk, C. S., Fiedler, J. n., Thum, T. n. 2020

  Abstract

  Myocardial fibrosis is a hallmark of the failing heart, contributing to the most common causes of deaths worldwide. Several microRNAs (miRNAs, miRs) controlling cardiac fibrosis were identified in recent years; however, a more global approach to identify miRNAs involved in fibrosis is missing.Functional miRNA mimic library screens were applied in human cardiac fibroblasts (HCFs) to identify annotated miRNAs inducing proliferation. In parallel, miRNA deep sequencing was performed after subjecting HCFs to proliferating and resting stimuli, additionally enabling discovery of novel miRNAs. In-depth in vitro analysis confirmed the pro-fibrotic nature of selected, highly conserved miRNAs miR-20a-5p and miR-132-3p. To determine downstream cellular pathways and their role in the fibrotic response, targets of the annotated miRNA candidates were modulated by synthetic siRNA. We here provide evidence that repression of autophagy and detoxification of reactive oxygen species by miR-20a-5p and miR-132-3p explain some of their pro-fibrotic nature on a mechanistic level.We here identified both miR-20a-5p and miR-132-3p as crucial regulators of fibrotic pathways in an in vitro model of human cardiac fibroblast biology.

  View details for DOI 10.1016/j.yjmcc.2020.10.008

  View details for PubMedID 33127387

• Long Noncoding RNA-Enriched Vesicles Secreted by Hypoxic Cardiomyocytes Drive Cardiac Fibrosis MOLECULAR THERAPY-NUCLEIC ACIDS Kenneweg, F., Bang, C., Xiao, K., Boulanger, C. M., Loyer, X., Mazlan, S., Schroen, B., Hermans-Beijnsberger, S., Foinquinos, A., Hirt, M. N., Eschenhagen, T., Funcke, S., Stojanovic, S., Genschel, C., Schimmel, K., Just, A., Pfanne, A., Scherf, K., Dehmel, S., Raemon-Buettner, S. M., Fiedler, J., Thum, T. 2019; 18: 363–74

  Abstract

  Long non-coding RNAs (lncRNAs) have potential as novel therapeutic targets in cardiovascular diseases, but detailed information about the intercellular lncRNA shuttling mechanisms in the heart is lacking. Here, we report an important novel crosstalk between cardiomyocytes and fibroblasts mediated by the transfer of lncRNA-enriched extracellular vesicles (EVs) in the context of cardiac ischemia. lncRNA profiling identified two hypoxia-sensitive lncRNAs: ENSMUST00000122745 was predominantly found in small EVs, whereas lncRNA Neat1 was enriched in large EVs in vitro and in vivo. Vesicles were taken up by fibroblasts, triggering expression of profibrotic genes. In addition, lncRNA Neat1 was transcriptionally regulated by P53 under basal conditions and by HIF2A during hypoxia. The function of Neat1 was further elucidated in vitro and in vivo. Silencing of Neat1 in vitro revealed that Neat1 was indispensable for fibroblast and cardiomyocyte survival and affected fibroblast functions (reduced migration capacity, stalled cell cycle, and decreased expression of fibrotic genes). Of translational importance, genetic loss of Neat1 in vivo resulted in an impaired heart function after myocardial infarction highlighting its translational relevance.

  View details for DOI 10.1016/j.omtn.2019.09.003

  View details for Web of Science ID 000500716400034

  View details for PubMedID 31634682

  View details for PubMedCentralID PMC6807307

• Gene Signatures to Distinguish Amyloid Cardiomyopathy Risk in Multiple Myeloma Patients Jha, A., Morgado, I., Lee, D. J., Alexander, K., Tsai, C., Schimmel, K., Ward, J., Witteles, R., Liedtke, M., Liao, R., Dangwal, S. LIPPINCOTT WILLIAMS & WILKINS. 2019

  View details for Web of Science ID 000511467800441

• Prenatal Exposure of Cigarette Smoke Impacts Cardiac Regeneration Schimmel, K., Morgado, I., Tsai, C., Evangelisti, A., Fisch, S., Ngoy, S., Lee, D., Dangwal, S., Alexander, K., Ward, J. E., Liao, R. LIPPINCOTT WILLIAMS & WILKINS. 2019

  View details for Web of Science ID 000511467800423

• Blood-based microRNA profiling in patients with cardiac amyloidosis PLOS ONE Derda, A. A., Pfanne, A., Baer, C., Schimmel, K., Kennel, P. J., Xiao, K., Schulze, P., Bauersachs, J., Thum, T. 2018; 13 (10): e0204235

  Abstract

  Amyloidosis is caused by dysregulation of protein folding resulting in systemic or organ specific amyloid aggregation. When affecting the heart, amyloidosis can cause severe heart failure, which is associated with a high morbidity and mortality. Different subtypes of cardiac amyloidosis exist e.g. transthyretin cardiac amyloidosis and senile cardiac amyloidosis. Today, diagnostics is primarily based on cardiac biopsies and no clinically used circulating blood-based biomarkers existing. Therefore, our aim was to identify circulating microRNAs in patients with different forms of amyloidosis.Blood was collected from healthy subjects (n = 10), patients with reduced ejection fraction (EF < 35%; n = 10), patients affected by transthyretin cardiac amyloidosis (n = 13) as well as senile cardiac amyloidosis (n = 11). After performing TaqMan array profiling, promising candidates, in particular miR-99a-5p, miR-122-5p, miR-27a-3p, miR-221-3p, miR-1180-3p, miR-155-5p, miR-339-3p, miR-574-3p, miR-342-3p and miR-329-3p were validated via quantitative real time PCR.The validation experiments revealed a significant upregulation of miR-339-3p in patients affected with senile cardiac amyloidosis compared to controls. This corresponded to the array profiling results. In contrast, there was no deregulation in the other patient groups.MiR-339-3p was increased in blood of patients with senile cardiac amyloidosis. Therefore, miR-339-3p is a potential candidate as biomarker for senile cardiac amyloidosis in future studies. Larger patient cohorts should be investigated.

  View details for DOI 10.1371/journal.pone.0204235

  View details for Web of Science ID 000447638200011

  View details for PubMedID 30332417

  View details for PubMedCentralID PMC6192556

• A large shRNA library approach identifies lncRNA Ntep as an essential regulator of cell proliferation. Cell death and differentiation Beermann, J. n., Kirste, D. n., Iwanov, K. n., Lu, D. n., Kleemiß, F. n., Kumarswamy, R. n., Schimmel, K. n., Bär, C. n., Thum, T. n. 2018; 25 (2): 307–18

  Abstract

  The mammalian cell cycle is a complex and tightly controlled event. Myriads of different control mechanisms are involved in its regulation. Long non-coding RNAs (lncRNA) have emerged as important regulators of many cellular processes including cellular proliferation. However, a more global and unbiased approach to identify lncRNAs with importance for cell proliferation is missing. Here, we present a lentiviral shRNA library-based approach for functional lncRNA profiling. We validated our library approach in NIH3T3 (3T3) fibroblasts by identifying lncRNAs critically involved in cell proliferation. Using stringent selection criteria we identified lncRNA NR_015491.1 out of 3842 different RNA targets represented in our library. We termed this transcript Ntep (non-coding transcript essential for proliferation), as a bona fide lncRNA essential for cell cycle progression. Inhibition of Ntep in 3T3 and primary fibroblasts prevented normal cell growth and expression of key fibroblast markers. Mechanistically, we discovered that Ntep is important to activate P53 concomitant with increased apoptosis and cell cycle blockade in late G2/M. Our findings suggest Ntep to serve as an important regulator of fibroblast proliferation and function. In summary, our study demonstrates the applicability of an innovative shRNA library approach to identify long non-coding RNA functions in a massive parallel approach.

  View details for DOI 10.1038/cdd.2017.158

  View details for PubMedID 29099486

  View details for PubMedCentralID PMC5762845

• Leukocyte telomere length correlates with hypertrophic cardiomyopathy severity. Scientific reports Chatterjee, S. n., de Gonzalo-Calvo, D. n., Derda, A. A., Schimmel, K. n., Sonnenschein, K. n., Bavendiek, U. n., Bauersachs, J. n., Bär, C. n., Thum, T. n. 2018; 8 (1): 11227

  Abstract

  Telomere length is a marker of biological aging. Short leukocyte telomere length has been associated with various conditions including cardiovascular disorders. Here, we evaluated if patients with hypertrophic cardiomyopathy have altered leukocyte telomere length and whether this is associated with disease severity. A quantitative polymerase chain reaction-based method was used to measure peripheral blood leukocyte telomere length in 59 healthy control subjects and a well-characterized cohort of 88 patients diagnosed with hypertrophic cardiomyopathy: 32 patients with non-obstructive cardiomyopathy (HNCM) and 56 patients with obstructive cardiomyopathy (HOCM). We observed shorter leukocyte telomeres in both HNCM and HOCM patients compared to healthy controls. Furthermore, leukocyte telomere length was inversely associated with HCM even after adjusting for age and sex. Telomere length of HOCM patients was also inversely correlated with left ventricular outflow tract obstruction. Therefore, HOCM patients were categorized by tertiles of telomere length. Patients in the first tertile (shortest telomeres) had a significantly increased left ventricular posterior wall thickness at end-diastole and higher left ventricular outflow tract gradients, whereas the left ventricular end-diastolic diameter was lower compared with patients in the second and third tertile. In summary, telomere length is associated with the severity of the disease in the HOCM subtype.

  View details for DOI 10.1038/s41598-018-29072-8

  View details for PubMedID 30046139

  View details for PubMedCentralID PMC6060137

• Mitochondrial energy metabolism is required for lifespan extension by the spastic paraplegia-associated protein spartin MICROBIAL CELL Ring, J., Rockenfeller, P., Abraham, C., Tadic, J., Poglitsch, M., Schimmel, K., Westermayer, J., Schauer, S., Achleitner, B., Schimpel, C., Moitzi, B., Rechberger, G. N., Sigrist, S. J., Carmona-Gutierrez, D., Kroemer, G., Buettner, S., Eisenberg, T., Madeo, F. 2017; 4 (12): 411–22

  View details for DOI 10.15698/mic2017.12.603

  View details for Web of Science ID 000417023400003

• Noncoding RNAs in Heart Failure HEART FAILURE Dangwal, S., Schimmel, K., Foinquinos, A., Xiao, K., Thum, T., Bauersachs, J., Butler, J., Sandner, P. 2017; 243: 423–45

  Abstract

  Heart failure is a major contributor to the healthcare burden and mortality worldwide. Current treatment strategies are able to slow down the transition of healthy heart into the failing one; nevertheless better understanding of the complex genetic regulation of maladaptive remodeling in the failing heart is essential for new drug discovery. Noncoding RNAs are key epigenetic regulators of cardiac gene expression and thus significantly influence cardiac homeostasis and functions.In this chapter we will discuss characteristics of noncoding RNAs, especially miRNAs, long noncoding RNAs, and circular RNAs, and review recent evidences proving their profound involvement during different stages of heart failure progression. Several open questions still prevent the extensive use of noncoding RNA-modulating therapies in clinics; yet they are becoming an attractive target to define novel regulatory mechanisms in the heart. In-depth study of their interaction with gene networks will refine our current view of heart failure and revolutionize the drug development in coming years.

  View details for DOI 10.1007/164_2016_99

  View details for Web of Science ID 000456448800020

  View details for PubMedID 27995387

• MicroRNA-Based Therapy of GATA2-Deficient Vascular Disease. Circulation Hartmann, D. n., Fiedler, J. n., Sonnenschein, K. n., Just, A. n., Pfanne, A. n., Zimmer, K. n., Remke, J. n., Foinquinos, A. n., Butzlaff, M. n., Schimmel, K. n., Maegdefessel, L. n., Hilfiker-Kleiner, D. n., Lachmann, N. n., Schober, A. n., Froese, N. n., Heineke, J. n., Bauersachs, J. n., Batkai, S. n., Thum, T. n. 2016; 134 (24): 1973–90

  Abstract

  The transcription factor GATA2 orchestrates the expression of many endothelial-specific genes, illustrating its crucial importance for endothelial cell function. The capacity of this transcription factor in orchestrating endothelial-important microRNAs (miRNAs/miR) is unknown.Endothelial GATA2 was functionally analyzed in human endothelial cells in vitro. Endogenous short interfering RNA-mediated knockdown and lentiviral-based overexpression were applied to decipher the capacity of GATA2 in regulating cell viability and capillary formation. Next, the GATA2-dependent miR transcriptome was identified by using a profiling approach on the basis of quantitative real-time polymerase chain reaction. Transcriptional control of miR promoters was assessed via chromatin immunoprecipitation, luciferase promoter assays, and bisulfite sequencing analysis of sites in proximity. Selected miRs were modulated in combination with GATA2 to identify signaling pathways at the angiogenic cytokine level via proteome profiler and enzyme-linked immunosorbent assays. Downstream miR targets were identified via bioinformatic target prediction and luciferase reporter gene assays. In vitro findings were translated to a mouse model of carotid injury in an endothelial GATA2 knockout background. Nanoparticle-mediated delivery of proangiogenic miR-126 was tested in the reendothelialization model.GATA2 gain- and loss-of-function experiments in human umbilical vein endothelial cells identified a key role of GATA2 as master regulator of multiple endothelial functions via miRNA-dependent mechanisms. Global miRNAnome-screening identified several GATA2-regulated miRNAs including miR-126 and miR-221. Specifically, proangiogenic miR-126 was regulated by GATA2 transcriptionally and targeted antiangiogenic SPRED1 and FOXO3a contributing to GATA2-mediated formation of normal vascular structures, whereas GATA2 deficiency led to vascular abnormalities. In contrast to GATA2 deficiency, supplementation with miR-126 normalized vascular function and expression profiles of cytokines contributing to proangiogenic paracrine effects. GATA2 silencing resulted in endothelial DNA hypomethylation leading to induced expression of antiangiogenic miR-221 by GATA2-dependent demethylation of a putative CpG island in the miR-221 promoter. Mechanistically, a reverted GATA2 phenotype by endogenous suppression of miR-221 was mediated through direct proangiogenic miR-221 target genes ICAM1 and ETS1. In a mouse model of carotid injury, GATA2 was reduced, and systemic supplementation of miR-126-coupled nanoparticles enhanced miR-126 availability in the carotid artery and improved reendothelialization of injured carotid arteries in vivo.GATA2-mediated regulation of miR-126 and miR-221 has an important impact on endothelial biology. Hence, modulation of GATA2 and its targets miR-126 and miR-221 is a promising therapeutic strategy for treatment of many vascular diseases.

  View details for DOI 10.1161/CIRCULATIONAHA.116.022478

  View details for PubMedID 27780851

• Nucleocytosolic Depletion of the Energy Metabolite Acetyl-Coenzyme A Stimulates Autophagy and Prolongs Lifespan CELL METABOLISM Eisenberg, T., Schroeder, S., Andryushkova, A., Pendl, T., Kuettner, V., Bhukel, A., Marino, G., Pietrocola, F., Harger, A., Zimmermann, A., Moustafa, T., Sprenger, A., Jany, E., Buettner, S., Carmona-Gutierrez, D., Ruckenstuhl, C., Ring, J., Reichelt, W., Schimmel, K., Leeb, T., Moser, C., Schatz, S., Kamolz, L., Magnes, C., Sinner, F., Sedej, S., Froehlich, K., Juhasz, G., Pieber, T. R., Dengjel, J., Sigrist, S. J., Kroemer, G., Madeo, F. 2014; 19 (3): 431–44

  Abstract

  Healthy aging depends on removal of damaged cellular material that is in part mediated by autophagy. The nutritional status of cells affects both aging and autophagy through as-yet-elusive metabolic circuitries. Here, we show that nucleocytosolic acetyl-coenzyme A (AcCoA) production is a metabolic repressor of autophagy during aging in yeast. Blocking the mitochondrial route to AcCoA by deletion of the CoA-transferase ACH1 caused cytosolic accumulation of the AcCoA precursor acetate. This led to hyperactivation of nucleocytosolic AcCoA-synthetase Acs2p, triggering histone acetylation, repression of autophagy genes, and an age-dependent defect in autophagic flux, culminating in a reduced lifespan. Inhibition of nutrient signaling failed to restore, while simultaneous knockdown of ACS2 reinstated, autophagy and survival of ach1 mutant. Brain-specific knockdown of Drosophila AcCoA synthetase was sufficient to enhance autophagic protein clearance and prolong lifespan. Since AcCoA integrates various nutrition pathways, our findings may explain diet-dependent lifespan and autophagy regulation.

  View details for DOI 10.1016/j.cmet.2014.02.010

  View details for Web of Science ID 000332395500013

  View details for PubMedID 24606900

  View details for PubMedCentralID PMC3988959