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Effects of Cyclic Strain and Growth Factors on
Vascular Smooth Muscle Cells
Seth R. Hills, Hemang Patel, Dr. Kytai T. Nguyen
BIE Department, Utah State University, Logan, UT 84322
Introduction
Cardiovascular disease (CVD) is the leading cause of
mortality in the U.S. More than 61 million Americans
(25% of the population) have some form of CVD.
Associated medical treatment costs in 2004 are
estimated to be more than $350 billion. Our research
is primarily concerned with atherosclerosis (figure 1.b):
the progressive narrowing and hardening of the
arteries over time due to smooth muscle cell (SMC)
proliferation and migration underneath and through the
endothelial layer.[1]
d) Significance:
This research will reveal the
combination of cyclic strain and
growth factors that affects certain
gene expressions.
This research will also help in
understanding the mechanism of
atherosclerosis.
Materials and Methods
Materials:
Biochemical Factors-Growth Factors (GFs):
PDGF (AA, AB, BB) (Platelet Derived
Growth Factor)
TGFβ (Transforming Growth Factor
Beta)
FGF (Fibroblast Growth Factor)
Figure 5 - Substrate Cell Growth
Biomechanical Factors-Cyclic Strain
SMCs experience mostly cyclic strain
Figure 1- a) Trilamellar Artery, b) Atherosclerosis [2]
Background
Arteries are trilamellar (figure 1.a)
Figure 6 - Concentration Study of Platelet
Derived Growth Factor
• The inner or intimal (EC, red) layer is a single
layer of endothelial cells that serves as a barrier.
• The intermediate or medial layer is composed of
SMCs (light blue) and extracellular matrix
components such as collagen, elastin, and
proteoglycans. The medial layer contributes the
most to the mechanical strength of the vessel as
well as its native ability to contract or relax in
response to external stimuli.
Figure 2 - Cyclic Strain System: Vacuum provides
stretch induced biochemical changes.[3]
• The outer adventitial layer, composed primarily of
fibroblasts (tan) and extracellular matrix (ECM),
harbors the microscopic blood supply of the artery
as well as its nerve supply.
Our goal
Figure 3 - SMCs at 40x
Investigate the effects of bio-mechanical
(cyclic strain) and -chemical factors (growth
factors, GFs) on SMC proliferation.
Methods:
Our Hypothesis
Cyclic strain might act synergistically with GFs
to alter SMC functions including proliferation.
Our Strategy
Effects of bio-mechanical –chemical factors:
a) Preliminary Studies
DNA studies of cell DNA vs. Cell
number
Study of Substrates to get
maximum cell growth
Study of optimal GF concentration
b) Studies:
Expose SMCs to bio-mechanical
(cyclic strain) and -chemical factors
(growth factors)
Cell proliferation using DNA assays
Gene expression profiles using
cDNA microarrays
c) Assays:
DNA assays (PicoGreen) will reveal
the combination of substrate, GF
concentration and mechanical
factors, that yields highest SMC
growth.
cDNA microarrays will help to learn
which genes are affected by the
corresponding condition in each
process.
Figure 7 - Concentration Study of Fibroblast
Growth Factor
Cell Number vs. Cell DNA (Figure 4)
Day 1: Seed cells at different Densities
in 24 well plates
Day 2: Lyse cells and perform DNA assay
Substrate Study (Figure 5)
Day 1: Seed at 96,000 cells/well in BioFlex™
plates of different substrate along with
a control.
Day 2: After cells are confluent, lyse the cells
and perform DNA assays.
GF Concentration Study (Figure 6-8)
Day 1: Seed cells in tissue culture plates.
Day 2: Feed cells with quiescent media.
Day 3: Begin feeding cells with different GF
concentrations, including a quiescent
control. After cell confluence in any
concentration, lyse cells and perform
DNA assay.
Figure 8 - Concentration Study of Transforming
Growth Factor Beta
Future Work
-
Results
-
The effects of cyclic strain, compared
to static controls, on SMCs with and
without GFs, combination studies.
• DNA assays
• cDNA microarrays (in process)
Factorial designs (in process)
Pulsatile flow studies
References
Figure 4 - Cell Number and DNA Content Correlation
1. Preventing Heart Disease and Stroke, in
Chronic Disease Prevention. 2004,
Centers for Disease Control and
Prevention: Web article.
2. Cytokine & Growth Factor Reviews, 15
PDGF and cardiovascular disease, Elaine
W. Raines
3. FlexCell Corporation