AimsDiseased atria are characterized by functional and structural heterogeneities, adding to abnormal impulse generation and propagation. These heterogeneities are thought to lie at the origin of... Show moreAimsDiseased atria are characterized by functional and structural heterogeneities, adding to abnormal impulse generation and propagation. These heterogeneities are thought to lie at the origin of fractionated electrograms recorded during sinus rhythm (SR) in atrial fibrillation (AF) patients and are assumed to be involved in the onset and perpetuation (e.g. by re-entry) of this disorder. The underlying mechanisms, however, remain incompletely understood. Here, we tested whether regions of dense fibrosis could create an electrically isolated conduction pathway (EICP) in which re-entry could be established via ectopy and local block to become ‘trapped’. We also investigated whether this could generate local fractionated electrograms and whether the re-entrant wave could ‘escape’ and cause a global tachyarrhythmia due to dynamic changes at a connecting isthmus.Methods and resultsTo precisely control and explore the geometrical properties of EICPs, we used light-gated depolarizing ion channels and patterned illumination for creating specific non-conducting regions in silico and in vitro. Insight from these studies was used for complementary investigations in virtual human atria with localized fibrosis. We demonstrated that a re-entrant tachyarrhythmia can exist locally within an EICP with SR prevailing in the surrounding tissue and identified conditions under which re-entry could escape from the EICP, thereby converting a local latent arrhythmic source into an active driver with global impact on the heart. In a realistic three-dimensional model of human atria, unipolar epicardial pseudo-electrograms showed fractionation at the site of ‘trapped re-entry’ in coexistence with regular SR electrograms elsewhere in the atria. Upon escape of the re-entrant wave, acute arrhythmia onset was observed.ConclusionsTrapped re-entry as a latent source of arrhythmogenesis can explain the sudden onset of focal arrhythmias, which are able to transgress into AF. Our study might help to improve the effectiveness of ablation of aberrant cardiac electrical signals in clinical practice. Show less
Gartner, T.C.L.B.; Wang, Y.; Leiteris, L.; Adrichem, I. van; Marsman, J.; Goumans, M.J.; ... ; Hjortnaes, J. 2023
In cardiac fibrosis, in response to stress or injury, cardiac fibroblasts deposit excessive amounts of collagens which contribute to the development of heart failure. The biochemical stimuli in... Show moreIn cardiac fibrosis, in response to stress or injury, cardiac fibroblasts deposit excessive amounts of collagens which contribute to the development of heart failure. The biochemical stimuli in this process have been extensively studied, but the influence of cyclic deformation on the fibrogenic behavior of cardiac fibroblasts in the ever-beating heart is not fully understood. In fact, most investigated mechanotransduction pathways in cardiac fibroblasts seem to ultimately have profibrotic effects, which leaves an important question in cardiac fibrosis research unanswered: how do cardiac fibroblasts stay quiescent in the ever-beating human heart? In this study, we developed a human cardiac fibrosis-on-a-chip platform and utilized it to investigate if and how cyclic strain affects fibrogenic signaling. The pneumatically actuated platform can expose engineered tissues to controlled strain magnitudes of 0–25% – which covers the entire physiological and pathological strain range in the human heart – and to biochemical stimuli and enables high-throughput screening of multiple samples. Microtissues of human fetal cardiac fibroblasts (hfCF) embedded in gelatin methacryloyl (GelMA) were 3D-cultured on this platform and exposed to strain conditions which mimic the healthy human heart. The results provide evidence of an antifibrotic effect of the applied strain conditions on cardiac fibroblast behavior, emphasizing the influence of biomechanical stimuli on the fibrogenic process and giving a detailed overview of the mechanosensitive pathways and genes involved, which can be used in the development of novel therapies against cardiac fibrosis. Show less
Aim This study explores the relationship between in vivo 4D flow cardiovascular magnetic resonance (CMR) derived blood flow energetics in the total cavopulmonary connection (TCPC), exercise... Show moreAim This study explores the relationship between in vivo 4D flow cardiovascular magnetic resonance (CMR) derived blood flow energetics in the total cavopulmonary connection (TCPC), exercise capacity and CMR-derived liver fibrosis/congestion. Background The Fontan circulation, in which both caval veins are directly connected with the pulmonary arteries (i.e. the TCPC) is the palliative approach for single ventricle patients. Blood flow efficiency in the TCPC has been associated with exercise capacity and liver fibrosis using computational fluid dynamic modelling. 4D flow CMR allows for assessment of in vivo blood flow energetics, including kinetic energy (KE) and viscous energy loss rate (EL). Methods Fontan patients were prospectively evaluated between 2018 and 2021 using a comprehensive cardiovascular and liver CMR protocol, including 4D flow imaging of the TCPC. Peak oxygen consumption (VO2) was determined using cardiopulmonary exercise testing (CPET). Iron-corrected whole liver T1 (cT1) mapping was performed as a marker of liver fibrosis/congestion. KE and EL in the TCPC were computed from 4D flow CMR and normalized for inflow. Furthermore, blood flow energetics were compared between standardized segments of the TCPC. Results Sixty-two Fontan patients were included (53% male, 17.3 +/- 5.1 years). Maximal effort CPET was obtained in 50 patients (peak VO2 27.1 +/- 6.2 ml/kg/min, 56 +/- 12% of predicted). Both KE and EL in the entire TCPC (n = 28) were significantly correlated with cT1 (r = 0.50, p = 0.006 and r = 0.39, p = 0.04, respectively), peak VO2 (r = - 0.61, p = 0.003 and r = - 0.54, p = 0.009, respectively) and % predicted peak VO2 (r = - 0.44, p = 0.04 and r = - 0.46, p = 0.03, respectively). Segmental analysis indicated that the most adverse flow energetics were found in the Fontan tunnel and left pulmonary artery. Conclusions Adverse 4D flow CMR derived KE and EL in the TCPC correlate with decreased exercise capacity and increased levels of liver fibrosis/congestion. 4D flow CMR is promising as a non-invasive screening tool for identification of patients with adverse TCPC flow efficiency. Show less
The objectives of this thesis were to elucidate the pathogenesis of metabolic heart disease, evaluate the associated changes in myocardial structure and contractile function, and determine the long... Show moreThe objectives of this thesis were to elucidate the pathogenesis of metabolic heart disease, evaluate the associated changes in myocardial structure and contractile function, and determine the long-term prognostic implications of subclinical myocardial dysfunction on all-cause mortality. Show less
This thesis describes the possible applicability of mesenchymal stromal cells (MSCs) in the treatment of liver fibrosis. In CCL4 induced animal models for liver fibrosis, we showed that local... Show moreThis thesis describes the possible applicability of mesenchymal stromal cells (MSCs) in the treatment of liver fibrosis. In CCL4 induced animal models for liver fibrosis, we showed that local administration of MSCs after partial hepatectomy, results in a dose‐dependent on‐site amelioration of fibrosis. Furthermore, we compared the pro-regenerative and anti-fibrotic effects of four different subpopulations of MSCs, categorized on Endoglin (CD105) and VCAM (CD106) membrane expression. Our results showed that VCAM-positive subpopulations of MSCs are superior compared to VCAM-negative subpopulations in relation to their anti-fibrotic and pro-regenerative properties. In another study we showed that TAA induce liver fibrogenesis in zebrafish embryos through mechanisms similar to man and mice. In addition, we found that MSCs ameliorate fibrogenesis in this model.CRIPTO-1 is an (onco)foetal protein and is correlated to poor prognosis in HCC. The observations of our HCC study are suggestive for the existence of a more aggressive subgroup of HCCs recognized by their high CRIPTO-1 expression which also seems to be resistant to Sorafenib treatment. Cell survival and cell proliferation are some of the processes stimulated by CRIPTO-1, which are also known to be important during liver regeneration and fibrogenesis. We identified that multiple species show enhanced CRIPTO-1 during fibrogenesis and that elevated CRIPTO-1 plasma levels in humans with cirrhosis normalize after liver transplantation. Show less
The major hallmark of Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the formation of many fluid-filled cysts in the kidneys, which ultimately impairs the normal renal structure and... Show moreThe major hallmark of Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the formation of many fluid-filled cysts in the kidneys, which ultimately impairs the normal renal structure and function, leading to end-stage renal disease (ESRD). A large body of evidence suggests that injury-repair mechanisms are part of ADPKD progression. Once cysts have been formed, proliferation and fluid secretion contribute to the cyst size increase, which eventually causes stress on the surrounding tissue resulting in local injury and fibrosis. In addition, renal injury can cause or accelerate cyst formation.In this review, we will describe the various mechanisms activated during renal injury and tissue repair and show how they largely overlap with the molecular mechanisms activated during PKD progression. In particular, we will discuss molecular mechanisms such as proliferation, inflammation, cell differentiation, cytokines and growth factors secretion, which are activated following the renal injury to allow the remodelling of the tissue and a proper organ repair. We will also underline how, in a context of PKD-related gene mutations, aberrant or chronic activation of these developmental pathways and repair/remodelling mechanisms results in exacerbation of the disease. Show less
Sramko, M.; Hoogendoorn, J.C.; Glashan, C.A.; Zeppenfeld, K. 2019
Over the last decades, substrate-based approaches to ventricular tachycardia (VT) ablation have evolved into an important therapeutic option for patients with various structural heart diseases (SHD... Show moreOver the last decades, substrate-based approaches to ventricular tachycardia (VT) ablation have evolved into an important therapeutic option for patients with various structural heart diseases (SHD) and unmappable VT. The well-recognized limitations of conventional electroanatomical mapping (EAM) to delineate the complex 3D architecture of scar, and the potential capability of advanced cardiac imaging technologies to provide adjunctive information, have stimulated electrophysiologists to evaluate the role of imaging to improve safety and efficacy of catheter ablation. In this review, we summarize the histological differences between SHD aetiologies related to monomorphic sustained VT and the currently available data on the histological validation of cardiac imaging modalities and EAM to delineate scar and the arrhythmogenic substrate. We review the current evidence of the value provided by cardiac imaging to facilitate VT ablation and to ultimately improve outcome. Show less
Within this thesis, several diseases central in the field of cardiovascular disease will be outlined. First, the central dogma of molecular biology, RNA biology in general, RNA (alternative... Show moreWithin this thesis, several diseases central in the field of cardiovascular disease will be outlined. First, the central dogma of molecular biology, RNA biology in general, RNA (alternative)splicing and the role of RNA-binding proteins within these processes will be discussed to enhance the accessibility to non-molecular biologists. Subsequently, the current literature and insights into the RNA-binding protein Quaking will be outlined. Thereafter, a brief summary of the role of many distinct RNA-binding proteins (RBPs) in the cardiovascular system is provided, detailing their importance in the heart and cells of the blood vessels. This review provides some historical and biological perspectives, while simultaneously highlighting many recent advances in our understanding of RBP function in cardiovascular health and disease. By harnessing established and novel techniques, including RNA-sequencing, this thesis will describe the role of Quaking in vascular stenosis, atherosclerosis, inflammation and endothelial barrier function. Collectively, Quaking can be described as a genome-wide governor of RNA-processing that results in the proper translation into functional proteins. This thesis describes which RNA transcripts are under control of Quaking, which alternative transcripts are being generated through modulation by Quaking, while also describing the unique role for this protein in health and cardiovascular and renal disease. Show less
Thomsen, L.H.; Fog-Tonnesen, M.; Fink, L.N.; Norlin, J.; Vinuesa, A.G. de; Hansen, T.K.; ... ; Rosendahl, A. 2017
Bronchopulmonary dysplasia is the most common complication when premature birth occurs at less than 28 weeks gestational age. The general aim of this thesis is to explore the therapeutic... Show moreBronchopulmonary dysplasia is the most common complication when premature birth occurs at less than 28 weeks gestational age. The general aim of this thesis is to explore the therapeutic potential of interventions in signaling pathways, involved in lung development and oxidative stress-induced lung injury, to prevent or attenuate BPD in a neonatal rat model, in which experimental BPD is induced by exposure to hyperoxia. The therapeutic potential of the targeting compounds of signaling pathways was investigated by studying their beneficial effects on contributing factors to severe experimental BPD pathology, including aberrant alveolar and vascular development, inflammation, fibrosis, coagulation, vascular remodeling, pulmonary arterial hypertension and right ventricular hypertrophy. We found ⑴angiotensin II type 2 receptor ligand PD123319 attenuates hyperoxia-induced lung and heart injury at a low dose in newborn rats; ⑵ Metformin attenuates hyperoxia-induced lung injury in neonatal rats by reducing the inflammatory response; ⑶ Deficiency or inhibition of lysophosphatidic acid receptor 1 protects against hyperoxia-induced lung injury in neonatal rats; ⑷Adult lysophosphatidic acid receptor 1-deficient rats with hyperoxia-induced neonatal chronic lung disease are protected against lipopolysaccharide-induced acute lung injury; ⑸ Bone morphogenetic protein 9 protects against neonatal hyperoxia-induced impairment of alveolarization and pulmonary inflammation. Show less
Cancer and fibrosis are devastating diseases of high mortality rate and with limited curative therapies available. A better understanding of the biological drivers of these diseases is fundamental... Show moreCancer and fibrosis are devastating diseases of high mortality rate and with limited curative therapies available. A better understanding of the biological drivers of these diseases is fundamental in order to develop effective therapeutics. At the molecular level, signaling pathways control cell growth, differentiation or apoptosis during development and adult life of the organism ensuring homeostasis. Paradoxically, the same signals are often implicated or even drive disease progression. One of the signaling pathways with key regulatory functions in homeostasis, tissue fibrosis and cancer in many organs is the TGFβ/BMP pathway. In this thesis we addressed the role and therapeutic potential of TGFβ/BMP pathway inhibition using different drug compounds that are currently towards the clinic or being tested in clinical trials. Three distinct types of inhibitors were used; small molecule inhibitors of the ALK4, 5 and 7 TGFβ receptor kinases, an antisense oligonucleotide interfering with ALK5 mRNA splicing and an ALK1 ligand trap; a peptide that contains the extracellular domain of ALK1 fused to Fc and sequesters BMP9 and BMP10. These inhibitors were used in an ex vivo human fibrosis model and in vivo mouse models of various human diseases (acute liver failure/ liver regeneration, Dupuytren's fibrosis) and cancer (prostate, liver). Show less
Piers, S.R.D.; Everaerts, K.; Geest, R.J. van der; Hazebroek, M.R.; Siebelink, H.M.; Pison, L.A.F.G.; ... ; Zeppenfeld, K. 2015
Overload of nutrients can lead to diet-induced inflammation, also called metabolic inflammation, which is thought to play an important role in many metabolic diseases, including the development of... Show moreOverload of nutrients can lead to diet-induced inflammation, also called metabolic inflammation, which is thought to play an important role in many metabolic diseases, including the development of nonalcoholic fatty liver disease (NAFLD). NAFLD encompasses a spectrum of pathologies that range from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH) and fibrosis. The pathogenesis of NAFLD, including the sequence of events in time and the underlying mechanisms that initiate the transition from a fatty liver to NASH and fibrosis, remain poorly understood. Effective and reliable therapeutic approaches that are based on the understanding of the pathogenesis of NASH are therefore still lacking. In order to gain more insight into the mechanisms of NASH pathogenesis, we started with comparison of human NASH and experimental NASH. Subsequently, we provided evidence that activation of AP-1 and associated neutrophil infiltration is important for NAFL progression towards NASH and this can be induced experimentally by __metabolic__ dietary triggers of inflammation.Furthermore, we explored novel nutritional and pharmacological agents as potential strategies to combat NASH. Finally, we investigated the effects of high fat diet-induced metabolic overload on the liver in relation to inflammation in white adipose tissue and kidney, and the dysfunction of these tissues. Show less
Reinders, M.E.J.; Bank, J.R.; Dreyer, G.J.; Roelofs, H.; Heidt, S.; Roelen, D.L.; ... ; Fijter, J.W. de 2014
