The MET-FLAM Faculty

Susanne SATTLER

Scientific Interests:

Many cardiomyocyte-intrinsic as well as systemic processes are under investigation to identify targetable pathways. Increasing evidence suggests that immunopathology, encompassing both local myocardial inflammation and systemic anti-heart autoimmunity entwined in a persistent inflammatory-autoimmune loop, contributes to the development of heart failure.

We have previously contributed a significant body of evidence showing that not only acute innate inflammation but also the adaptive immune system is activated after MI and persistent autoimmunity contributes to the development of heart failure [4–8]. Indeed, the presence of auto-antibodies against cardiac epitopes during heart failure is a known clinical phenomenon [9], which we recently confirmed to be part of a fully established autoimmune syndrome. This includes activation and enlargement of the heart-draining lymph nodes, activated T and B cells and most importantly myocardial deposition of mature auto-antibodies and complement indicating pathological autoreactivity [6].

Autoimmunity is defined as immunological reactivity against self-antigens. It is induced under highly inflammatory conditions when peripheral tolerance mechanisms are overwhelmed. Dendritic cells (DC) are considered ‘professional’ antigen presenting cells, due to their ability to initiate T-cell activation from naïve state. DC are central in triggering autoimmunity as they determine the resulting T-cell functional phenotype depending on inflammatory context [10]. We have previously shown that they increase in numbers and upregulate their antigen-presentation capacity after MI (figure 1). In addition, the antigen-presentation machinery can be upregulated in tissue-resident cells under inflammatory conditions [11]. Importantly, aging and metabolic disease are associated with increased levels of systemic and tissue inflammation (inflammaging) [12], which has been suggested to affect antigen presentation pathways [13]. If increased antigen presentation due to metabolic disease and inflammaging has a role to play in immunopathology of the heart remains to be investigated.

Proposed Dissertation Topic:

Background: Systemic inflammation due to metabolic disease, including obesity, has been implicated in a range of cardiovascular conditions. Myocardial inflammation and an ensuing activation of adaptive immune responses and autoimmunity against cardiac antigens, is involved in the development of heart failure after a myocardial infarction (MI). Antigen-presentation by dendritic cells (DC) initiates autoimmunity, and tissue-resident mesenchymal and parenchymal cells can also contribute to antigen-presentation and may perpetuate local inflammation. The effect of obesity on antigen-presentation pathways, either through modified lipoproteins or inflammatory factors, leading to post-MI anti-heart autoimmunity and heart failure, remains to be investigated.

Hypothesis and objectives: We hypothesize that obesity increases the inflammatory self-antigen-presentation in DC as well as in heart-resident cells. This contributes to an adaptive immune response against cardiac antigens exacerbating adverse remodeling towards heart failure. The PhD candidate will (i) characterize the effect of obesity on the spatio-temporal dynamics of the DC population, (ii) analyze the antigen-presentation machinery in cardiac-resident cells, (iii) confirm functional relevance of antigen-presentation in obesity-induced cardiac remodeling, and (iv) analyze the respective effect of modified lipoproteins versus inflammation in in vitro DC cultures.

Methods and approaches: The PhD candidate will induce ischemic myocardial damage (type-2 myocardial infarction, T2MI) in high-fat diet (HFD)-fed mice (HFD-MI). He / she will confirm cardiac functional and structural impairment by echocardiography, and perform immunophenotyping with focus on the DC population, in the myocardium, heart-draining mediastinal lymph nodes, adipose tissue, blood and bone marrow before and after induction of T2MI. DC will be assessed for population changes, and their functional as well as metabolic phenotype. Measures of established autoimmune responses, including the presence of activated T cells and anti-heart auto-antibodies will be included. (1st and 2nd year). The PhD candidate will further isolate / differentiate DC from HFD-MI mice for in vitro functional assays to assess their ability to activate T cells against myocardial antigen. Besides DC, they will also isolate cardiac-resident cells including fibroblasts, endothelial cells and cardiomyocytes to assess their immunophenotype by immunostaining, flow cytometry and qPCR, as well as their potential antigen-presentation ability by in vitro co-culture assays. DC  from wild-type mice will be used in vitro to assess the effect of obesity-related modified lipoproteins and / or inflammatory factors on DC phenotype and function (2nd and 3rd year). Finally, the PhD candidate will treat HFD-MI mice with a pan-MHC-II inhibitor to block antigen presentation and assess their cardiac phenotype to evaluate functional relevance and potential therapeutic benefit (3rd and 4th year).

Pitfalls and alternative approaches: Obesity is a systemic condition affecting all organ systems and a wide range of pathways, hence several results obtained throughout this study will remain associative without showing direct causative effects. Causative effects are investigated through the included mechanistic in vitro studies (e. g. effect of modified lipoproteins on DC phenotype) and the therapeutic in vivo MHC-II blocking study. Therapeutic blockade using a pan-MHC-II inhibitor to block antigen presentation affects a wide range of cell types. The specific involvement of DC or cardiomyocyte MHC-II respectively, may be investigated using corresponding mouse lines with MHC-II specifically depleted in DC (Zbtb46-Cre / I-AB^flox/flox) or cardiomyocytes (MerCreMer / I-AB^flox/flox).

Involved Faculty members: Susanne Sattler (PI), Gunther Marsche (lipoprotein biology), Stefano Angiari (T-cell metabolism), Ákos Heinemann (endothelial cell assays), Michael Khalil (soluble markers of inflammation), Simon Sedej (in vivo cardiac phenotyping), Julia Kargl (immunophenotyping and DC metabolic pathways).

International Collaborations: Julia Gorelik, Tristan Rodríguez, Rasheda Chowdhury (Imperial College, London, UK), Gustavo Ramos (University of Würzburg, Germany), Florian Leuschner (University of Heidelberg, Germany), Sikander Hayat (University of Aachen, Germany), Nadia Rosenthal (The Jackson Laboratories, USA), Ebba Brakenhielm (University of Rouen, France), Pilar Martín Fernández (CNIC, Spain), Kory Lavine (Washington University, USA).

Facilities: Our lab is located in the Center for Medical Research (ZMF) within the campus of the Medical University of Graz. This location offers an excellent and stimulating scientific environment, formed through the local concentration of Medical University of Graz, University of Graz and Graz University of Technology. The local research group has strong expertise in the functional, structural, biochemical and molecular biological characterization of the cardiovascular system including in vivo cardiac profiling methods such as invasive haemodynamics, pre-clinical imaging equipment such as ultrahigh-resolution transthoracic echocardiography, non-invasive blood pressure measurements and set ups for metabolic experiments. Core facilities at the ZMF include state-of-the-art flow-cytometry equipment, laser-scanning confocal microscopy, an epi-fluorescent microscope combined with IonOptix Myocyte Contractility Recording System, a two-chamber oxygraph and a Seahorse assay system. Researchers at the Department of Cardiology have access to an extensive biobank of patient serum and myocardial biopsy samples obtained previously.

Preparatory Findings:

Figure 1. Dendritic cells in the post-MI heart.
(A) UMAP showing the DC clusters from a single cell sequencing data set of mouse cardiac ventricular tissue interstitial cells at homeostasis and over time post-MI [8]. (B) Quantification of the DC sub-population dynamics and relative frequency at homeostasis and different time points post-MI. (C) Quantification of the number of CD11c⁺MHCII⁺ cells / mg heart tissue at homeostasis and over time post-MI.

1. GBD 2015 Mortality and Causes of Death Collaborators: Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980–2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet, 2016; 388(10053):​1459–1544.
   
2. Bui AL, Horwich TB, Fonarow GC: Epidemiology and risk profile of heart failure. Nat Rev Cardiol, 2011; 8(1):​30–41.
   
3. Lawson CA, Solis-Trapala I, Dahlstrom U, Mamas M, Jaarsma T, Kadam UT, Stromberg A: Comorbidity health pathways in heart failure patients: A sequences-of-regressions analysis using cross-sectional data from 10,575 patients in the Swedish Heart Failure Registry. PLoS Med, 2018; 15:​e1002540.
   
4. Sattler S, Fairchild P, Watt FM, Rosenthal N, Harding SE: The adaptive immune response to cardiac injury — the true roadblock to effective regenerative therapies?. npj Regen Med, 2017; 2:19.
   
5. Panahi M, Papanikolaou A, Torabi A, Zhang J-G, Khan H, Vazir A, Hasham MG, Cleland JGF, Rosenthal NA, Harding SE, Sattler S: Immunomodulatory interventions in myocardial infarction and heart failure: a systematic review of clinical trials and meta-analysis of IL-1 inhibition. Cardiovasc Res, 2018; 114:​1445–1461.
   
6. Sintou A, Mansfield C, Iacob A, Chowdhury RA, Narodden S, Rothery SM, Podovei R, Sanchez-Alonso JL, Ferraro E, Swiatlowska P, Harding SE, Prasad S, Rosenthal N, Gorelik J, Sattler S: Mediastinal Lymphadenopathy, Class-Switched Auto-Antibodies and Myocardial Immune-Complexes During Heart Failure in Rodents and Humans. Front Cell Dev Biol, 2020; 8:​695.
   
7. Forte E, Perkins B, Sintou A, Kalkat HS, Papanikolaou A, Jenkins C, Alsubaie M, Chowdhury RA, Duffy TM, Skelly DA, Branca J, Bellahcene M, Schneider MD, Harding SE, Furtado MB, Ng FS, Hasham MG, Rosenthal N, Sattler S: Cross-Priming Dendritic Cells Exacerbate Immunopathology After Ischemic Tissue Damage in the Heart. Circulation, 2021; 143(8):​821–836.
   
8. Forte E, Panahi M, Ng FS, Boyle JJ, Branca J, Bedard O, Hasham MG, Benson L, Harding SE, Rosenthal N, Sattler S: Type 2 MI induced by a single high dose of isoproterenol in C57BL/6J mice triggers a persistent adaptive immune response against the heart. J Cell Mol Med, 2021; 25(1):​229–243.
   
9. Kaya Z, Leib C, Katus HA: Autoantibodies in Heart Failure and Cardiac Dysfunction. Circ Res, 2012; 110(1):​145–158.
   
10. Blanco P, Palucka AK, Pascual V, Banchereau J: Dendritic cells and cytokines in human inflammatory and autoimmune diseases. Cytokine Growth Factor Rev, 2008; 19(1):​41–52.
    
11. Harryvan TJ, de Lange S, Hawinkels LJAC, Verdegaal EME: The ABCs of Antigen Presentation by Stromal Non-Professional Antigen-Presenting Cells. Int J Mol Sci, 2021; 23(1):137.
    
12. Franceschi C, Garagnani P, Parini P, Giuliani C, Santoro A: Inflammaging: a new immune-metabolic viewpoint for age-related diseases. Nat Rev Endocrinol, 2018; 14(10):​576–590.
    
13. Thelemann C, Eren RO, Coutaz M, Brasseit J, Bouzourene H, Rosa M, Duval A, Lavanchy C, Mack V, Mueller C, Reith W, Acha-Orbea H: Interferon-γ Induces Expression of MHC Class II on Intestinal Epithelial Cells and Protects Mice from Colitis. PLoS One, 2014; 9(1):​e86844.