Biomedical Engineering Reference
In-Depth Information
aetiology of AAA and other vascular diseases. Moreover, it has immediate
application to tissue engineering, e.g., aiding the design and optimisation of tissue
engineered vascular constructs.
1 Introduction
Tissue engineering offers the possibility of developing a biological substitute
material in vitro with the inherent mechanical, chemical, biological, and
morphological properties required in vivo, on an individual patient basis [
1
].
Computational modelling has an integral role to play in these ambitions. However,
for in-silico modelling to realise its potential, i.e. to guide the design and opti-
misation of tissue engineered constructs, it must accurately represent the under-
lying mechanobiology. Whilst early modelling attempts are characterised by a
substantial distance between computer and bench, the integration of biological
experiments and simulation efforts are increasing [
2
].
The need for improved mechanobiological modelling is not restricted to the
domain of tissue engineering, such research is necessary to guide our under-
standing of human physiological and pathophysiology, e.g. the evolution of
vascular diseases. In this chapter, we illustrate a computational model for the
evolution of abdominal aortic aneurysm (AAA). It combines a realistic micro-
structural model of the arterial wall with computational fluid dynamics and
structural analyses to quantify the mechanical environment that acts on the
vascular cells. Growth and remodelling algorithms simulate the cells responding to
mechanical stimuli and adapting the tissue structure. The model simulates a
fusiform abdominal aortic aneurysm that evolves with similar mechanical, bio-
logical and morphological properties with those observed in vivo. Whilst in need
of further sophistications to more accurately reflect the mechanobiology of the
arterial wall, it should be readily recognisable to the reader that this computational
framework has substantial potential to be applied to aid the design and optimi-
sation of tissue engineered vascular constructs.
Abdominal Aortic Aneurysm (AAA) is characterised by a bulge in the
abdominal aorta. Development is associated with dilation of the arterial wall and
the possibility of rupture [
3
]. Prevalence rates are estimated between 1.3 and 8.9 %
in men and between 1.0 and 2.2 % in women [
4
]. They are more common in
subjects who smoke [
5
] and suffer from hypertension [
6
]. Between 80 and 90 % of
ruptured AAAs will result in death [
7
]; rupture is responsible for 1-2 % of all
deaths in the UK each year [
8
]. Surgery to repair the AAA is an option; however, it
is a high-risk procedure with a 5 % mortality rate [
9
]. Intervention is recommended
when the risk of rupture exceeds the risk of surgery. Statistically, this occurs when
the diameter exceeds 5.5 cm [
10
]. However, such a criterion fails to identify small
AAAs with high risk of rupture [
11
] and large AAAs with low risk [
12
]. Thus there
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