Center of Excellence: Microcirculation

Main pathologies:
Ischemia-reperfusion injury; inflammation; obesity-induced
vascular dysfunction; vascular permeability and edema; endothelial dysfunction; obstructive (atherosclerotic) microvascular disease

Unique research expertise:

  • Live cell confocal microscopy and image analysis
  • Analysis of angiogenesis/vascular sprouting in 3D
  • Endothelial cell culture under hyper/hypoxic conditions
  • Ex vivo analysis of (insulin-mediated) vascular function
  • Ultrasound-mediated analysis of tissue perfusion
  • Biochemical analysis of protein activation, ubiquitylation and degradation
  • Intracoronary flow and pressure measurements to assess microvascular function
  • Identification and prognostic implications of coronary vasospasms

The endothelium is the largest and at the same time most diffuse organ in the human body. Endothelial cells (EC) control oxygenation, organ function and -perfusion and mediate the communication between blood and tissue. Because EC line all vessels, they are exposed to systemic soluble and mechanical factors including cytokines and growth factors, blood composition as well as microvesicles and hemodynamic force. Conversely, the endothelium reflects the tissues’ condition to circulating cells and plasma and communicates with downstream sections of the vasculature and -tissues, through (i) the release of microvesicles; (ii) the expression and shedding of surface molecules or (iii) the secretion of cytokines. Obstructive artery disease and Dysfunctional endothelial behavior of the coronary microcirculation has fundamental implications on the origin of ischemic heart disease and is frequently overlooked in contemporary guidelines on treatment of myocardial ischemia.

The Research Cluster Microvascular Disease aims to aggregate excellent research on the microvascular endothelium, focusing on the cell biology, physiology and mechano-biology which drives vessel formation, integrity and perfusion. Balanced, bi-directional communication between clinicians and fundamental researchers to develop relevant research programs will be a key feature. This RC will combine molecular, mechanistic studies with advanced research technology and with ex vivo and in vivo approaches. Emphasis will be on disease-driven, translational research which is aimed at (1) increasing mechanistic insight; (2) developing specific diagnostic tools aimed at (non-)invasive assessment of microvascular health in different tissues; (3) developing of patient-tailored identification of ischemic heart disease; (4) developing patient-tailored prevention together with patient-tailored improved treatment strategies;

Left: Monolayer of human endothelial cells (White, VE-cadherin; red, F-actin; blue, nuclei).
Right: zoomed image detailing F-actin in red, VE-cadherin in white and focal adhesions in green. Nuclei in blue.

Research topics

Oxygenation and perfusion
Throughout the body, the vasculature, and in particular the endothelium is exposed to different levels of oxygen. A lack or excess of oxygen can have damaging effects on endothelial cells.  Vascular occlusion, for example after a thrombotic event, will lead to hypo-perfusion and ischemia, followed, upon treatment, by reperfusion. This reperfusion induces endothelial activation, production of ROS, endothelial damage and increased vascular leak.
Obesity, insulin resistance and diabetes are closely related to cardiovascular diseases such as atherosclerosis, hypertension and heart failure. Microvascular functions such as control of blood flow and inflammation contribute to heart failure with preserved ejection fraction (HFpEF), but also to failure of other organs such as the brain, muscles and kidneys. In our group, we study the role of fat tissue around blood vessels (perivascular adipose tissue, PVAT) in these cardiovascular diseases. For this purpose, we combine molecular phenotyping of human and mouse PVAT with targeted interventions in PVAT as well as its effector molecules in endothelium.

Human PVAT (peri-vascular adipose tissue)

Inflammation and permeability
Endothelial dysfunction is commonly associated with inflammation. We study various aspects of inflammatory responses, including the analysis of endothelial permeability, upregulation of inflammatory markers such as leukocyte adhesion receptors and expression of specific regulatory proteins. These all affect cell-cell interactions between endothelial cells, the mechanistic basis of which is also of key interest. Vascular-Endothelial cadherin is a central adhesion molecule linking endothelial cells, and its regulation by phosphorylation as well as actin dynamics is a one of our main interests. The consequent interactions of leukocytes and platelets with the activated endothelium is directly relevant for local inflammation, edema and tissue damage. This topic is studied in vitro using primary human endothelium and we recently started using zebrafish embryos for analysis of vascular permeability.

Zebrafish blood vessels

Mechano-biology and ageing
The effects of local forces, induced by flow, on the endothelium has direct and significant impact on vascular permeability, inflammation and perfusion. These forces are dependent on flow patterns, are altered by ischemia-reperfusion, but also modulated by systemic disease associated with hypertension. Local changes in flow may result in increased vascular stiffness, which is pro-inflammatory. We study the role of biomechanics at the vascular, cellular and molecular level in relation to reactivity and permeability. Altered vascular stiffness is also relevant for development of aneurysms and in we therefore also study vascular smooth muscle cell phenotype and contractility.
Another independent risk factor for cardiovascular disease is aging. Endothelial function declines with aging and we aim to unravel the molecular mechanisms contributing to this. Since it has become clear that the majority of RNA is not translated into protein, our focus lies on non-coding RNAs. In particular we study long non-coding RNAs that control aging-related processes in endothelial cells.

Inflammatory response following ischaemia/reperfusion injury.
Following acute myocardial infarction (AMI), an adequate healing response is crucial for preserving left ventricular (LV) function and geometry, and thus preventing adverse LV remodelling in patients. Infarct healing is a complex and dynamic process, consisting of removing necrotic myocardium to replace this with scar tissue. During this process, a wide range of inflammatory cells dominate and monocytes in particular have recently drawn considerable attention as a target to improve healing following AMI. The cardiology department of the AMC collaborates for this project with the pathology department of the VUmc to evaluate the infiltration of the wide range of inflammatory cells in myocardial tissue specimens of AMI patients. Additionally, we focus on determining clinical characteristics of inflammatory cells in the peripheral blood of AMI patients to predict the development of adverse LV remodelling.         

Microvascular involvement in ischemic heart disease
Since the introduction of the coronary angiogram, the identification and treatment of ischemic heart disease has been dominated by epicardial approaches. Accumulating evidence suggest involvement of the coronary microcirculation in the manifestation of ischemic heart disease, which is frequently being overlooked in contemporary guidelines of myocardial ischemia. With the use of combined intra-coronary pressure (FFR) and flow measurements (CFR), we aim to study the
respective contribution of coronary and microvascular involvement in ischemic heart disease, the magnitude of microvascular resistance in the setting of NST-ACS and aim to investigate the independent prognostic value of combined FFR and CFR measurement in order to develop and implement tailored treatment strategies for patients with stable heart disease.

Coronary vasospasm (endothelial dysfunction)
A substantial number of patients with angina symptoms display no obstructive coronary artery disease on the diagnostic coronary angiogram. Vascular smooth muscle hyper-activity is considered one of the primary causes of endothelial-dependent dysfunction, which is associated with temporal epicardial and microvascular spastic vasomotion. Being frequently overlooked in the diagnosis of ischemic heart disease, patients with endothelial-dysfunction show persistent misunderstood angina and associated with a poor quality of life and profound healthcare costs. We study the application the acetylcholine provocation test to identify spontaneous coronary vasomotion and study the prognostic long-term implications of patients with a positive acetylcholine provocation test demonstrating coronary epicardial or microvascular endothelial dysfunction.