Lecture series Atherosclerosis 2324
HC 1 Atherosclerosis introduction (06/11/23) ........................................................................................ 1
HC 2 Experimental models of Atherosclerosis (06/11/23) ...................................................................... 3
HC 3 The immune system in atherosclerosis (06/11/23) ...................................................................... 10
HC 4 Macrophages in atherosclerosis (07/11/23) ................................................................................. 15
HC 5 Noncoding RNAs in atherosclerosis (07/11/23) ............................................................................ 19
HC 6 CD8+ T cells in atherosclerosis (09/11/23) ................................................................................... 22
HC 7 Immunomodulation and therapy (09/11/23) ............................................................................... 28
HC 8 Single-cell sequencing in atherosclerosis research (14/11/23) .................................................... 31
HC 9 Age-associated immunity in atherosclerosis (14/11/23) .............................................................. 35
HC 10 Mechanisms of plaque destabilization (16/11/23) ..................................................................... 42
HC 11 The vulnerable patient (16/11/23) ............................................................................................. 48
HC 1 Atherosclerosis introduction (06/11/23)
Cardiovascular disease (CVD) is the main cause of
death worldwide, so there is a need to target this
disease. There are many CVD types; aortic
aneurysms, inflammation around the heart sack
(pericarditis) etc. The occlusion of vessels caused by
plaques include peripheral vascular disease and
coronary heart disease eventually leading to heart
failure. Multiple risk factors, including genetics, play
a role in the susceptibility of these diseases.
Atherosclerosis is a chronic inflammatory disease
resulted from multiple events. Damage of the
endothelial wall leads to the accumulation of lipids
and immune cells in the arterial wall. The
development of atherosclerosis eventually
leads to the narrowing of the blood vessel.
Various immune cells are involved in this
development.
Development of atherosclerosis is mostly
found in the artery system with bifurcations
or branches. For example, in the neck in the
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,carotid artery. Also in the aortic arch and the coronary arteries of the heart atherosclerotic
formations can be found.
In figure (a) you can see a healthy artery. The first layer is the so-called intima layer which is in direct
contact with the blood and covered with a layer of endothelial cells and under some smooth muscle
cells (SMCs). There under lays the media with a lot of SMCs which are embedded in some
extracellular matrix. The last layer is the adventitia which contains the micro vessels, the nerve
endings, but also mast cells which can act when needed. (b) When irregular processes occur, such as
high blood pressure, the endothelial cells are activated and can upregulate adhesion molecules which
allows other immune cells to bind and integrate into the intima. When monocytes are integrated into
the intima, they differentiate into macrophages and can take up lipids, forming foam cells. The uptake
of an abundance of lipids leads to the formation of a fatty streak, which is the first phase of
atherosclerotic development. (c) As atherosclerosis further progresses you can see that for instance
SMCs migrate to the intima layer and form a fibrous cap, preventing rupture. Under this cap an
accumulation of foam cells can be seen. Some foam cells undergo apoptosis and thereby release their
contents, leading to the formation of the necrotic core. (d) Further advancement involves the rupture
of the plaque leading to thrombus formation eventually resulting in disease.
Complete occlusion of a blood vessel can lead to an acute cardiovascular event, such as a myocardial
infarction or a stroke. Current treatment include statins, which can lower lipid levels, betablockers,
but also surgeries and lifestyle changes. But because lipids are not the only key mediator, it is
believed that the immune system also plays a very important role.
The focus of BioTherapeutics research:
• Elucidate the mechanism underlying the development and progression of atherosclerosis;
mainly focusing on the interplay between lipids and immune cells.
• Identify novel therapeutic targets to combat atherosclerosis.
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,Research approaches include analyzing human plaque material obtained after surgery and examining
the present cells. However, to really mimic the development, mouse models are implemented to
investigate specific research targets.
Both lipids and immune response lead to the development of atherosclerosis. The innate and
adaptive immune response play a role, including a subset of immune cells, the CD8+ T cells.
A plaque is somewhat stable, however after some time, degradation of the fibrous cap leads to the
rupture of the plaque. Multiple immune cells, such as macrophages, mast cells and neutrophils play a
role in this process. Moreover, aging is the main risk factor for atherosclerosis, and other risk factors
include gender, smoking, stress and genetics. Lastly, the use of single-cell proteomics is used to
investigate the present cell subsets in atherosclerosis.
HC 2 Experimental models of Atherosclerosis (06/11/23)
The development of atherosclerosis: endothelial damage, leading to the
accumulation of cholesterol/lipids and immune cells in the arterial wall, resulting
in atherosclerotic plaque formation. Atherosclerosis involves a lot of cell types,
including cells from the immune system.
Experimental models of atherosclerosis are needed to investigate the underlying mechanisms of
atherosclerosis and to also test the efficacy of novel drug candidates. These models include, in vitro
(cell culture), in vivo (animal models) and ex vivo/in vivo (human tissue)
In vitro models, such as cell culture systems are ideal for studies on one single cell type. However, the
information is limited as for example the interaction between these cell types cannot be studied.
Endothelial SMCs Macrophages T cells
cells
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, Therefore, in vivo models are used. In general, mice cannot develop atherosclerosis as the majority
of cholesterol is transported by the atheroprotective HDL and mice largely lack the typical pro-
atherogenic lipoprotein, LDL. To develop atherosclerosis, LDL is believed to be one of the first triggers.
There are different lipoprotein classes and they can transport triglycerides and cholesterol through
the bloodstream. Chylomicrons are the biggest particles and contain a lot of triglycerides and some
cholesterol. VLDL also contains a lot of triglycerides. LDL contains lots of cholesterol. HDL particles
transports cholesterol from the circulation to the liver out of the body; so this is the “good”
cholesterol. These lipoproteins are measured based on size using fast-performance liquid
chromatography (FPLC). After injection of the sample onto the column, the particles are then eluted
based on their size. The larger particles will be eluted first, the smaller last. This is due to the column,
containing pores. Smaller particles can go through these pores and therefore stay longer in the
column.
Wild-type (WT) mice, so mice with no atherosclerosis or hyperlipemia, have higher levels of HDL
where most of the cholesterol can be found. Compared to humans, cholesterol can be mainly found
in LDL and somewhat in HDL particles. So it may seem that using mouse models are not a good model
to study atherosclerosis. However, more atherosclerosis studies have been done using mice models.
WT mice can develop atherosclerosis after inducing the Paigen diet. Due to the turbulence of the
blood flow, atherosclerotic development is usually found in the aortic root/arch of the mice, in the
innominate artery. Another location is by the kidney, where there are also many branches. Not all WT
mice strain can develop atherosclerosis, only the C57Bl/6J strain. However, the developed lesions
were quite small.
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