4th vulnerable plaque symposium
TRANSCRIPT
Plaque temperature heterogeneity is associated with
macrophage accumulation and metalloproteinase activity
R. Krams, LCA van Damme
Dept. Experimental Cardiology, Thoraxcenter, Rotterdam, The Netherlands
Background
• Plaque rupture has been related to a high MMP activity and macrophage (Mø) accumulation
Galis et al, J. Clin. Invest. 1994
• Recently, regional temperature heterogeneity has been observed in atherosclerotic plaques in vivo
Verheye et al, Circulation 2002
Aim of this study
• To test the hypothesis that temperature heterogeneity is associated not only with macrophage accumulation but also with MMP-activity in atherosclerotic plaques in vivo.
MethodsIn 6 NZW rabbits:• Endothelium was removed (denudation) of the infra renal aorta
• 2 months 2% cholesterol diet
• Temperature measurement after 2 months of follow up
• Immunohistochemistry for the detection of mø (RAM11, Dako), smooth muscle cells (1A4), histology for collagen amount (picro-serious red) and lipid contents (oil red o) and MMP activity in a zymogram
start
end
3F Fogarty
50 mm
Infra renalaorta
Renal artery
Denudation area
Thermography
• Intravascular thermography
• Catheter: Thermocore Medical Systems
• Accuracy: ± 0.01 °C
• Pullback speed: 0.2 mm/sec
• Measurement of temperature difference from a reference area
Analysis I
•Thermography with / without blood flow-pull back over 6 cm-mean of 4 thermistors-mean of 2 pull backs-reference area set at 0 °C
Analysis II• Histological analysis:
-Mø % of plaque area-Lipid % of plaque
area-Collagen % of plaque
area-Smooth Muscle
Cell(SMC) % of plaque area
• Vulnerability Index (VI-index):
VI = Mø% + Lipid% Collagen% + SMC%
Shiomi et al, Atherosclerosis 2001
Analysis III• MMP activity in a zymogram
-SDS PAGE gel electroforese
-separation on molecular weight
-substrate: gelatin
ProtocolInducing atherosclerosis
Perform thermography after 2 months
Hot Cold
Isolate area Isolate area
MMP-activity / cel distribution MMP-activity / cel distribution
Compare
Distance (mm) from renal artery
0 5 10 15 20 25 30 35 40 45 50 55
T (°
C) f
rom
refe
renc
e
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
T (°
C) f
rom
refe
renc
e
-0.2
-0.1
0.0
0.1
length (mm) vs Mean without blood flowlength (mm) vs Mean with blood flow
Results IThermograph (with and without blood flow)
Hot spot 1
Hot spot 2Cold area
Example 1
Length from renal artery (mm)
0 5 10 15 20 25 30 35 40 45 50 55
T (°
C) f
rom
refe
renc
e ar
ea
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
T (°
C) f
rom
refe
renc
e ar
ea
-0.01
0.00
0.01
0.02
0.03
length (mm) vs Mean without blood flowlength (mm) vs Mean with blood flow
Example 2
Results IThermograph (with and without blood flow)
T (°C) from reference
0.1 0.2 0.3 0.4 0.5 0.6 0.7
VI-i
ndex
0
1
2
3
VI-indexRegression between VI-index and T R=0.8, p=0.013
Results II
Results II
T (°C) from reference
0.1 0.2 0.3 0.4 0.5 0.6 0.7
Mø
(%) i
n th
e pl
aque
0
5
10
15
20
25
30
møRegression between mø(%) and T (°C), R = 0.7 p = 0.020
Results IIIMMP-9
Pro-MMP-2
MMP-2 active
MMP-9
Pro-MMP-2
MMP-2 active
MMP-9
Pro-MMP-2
MMP-2 active
Length (mm) from renal artery0 10 20 30 40 50 60
T (°
C) f
rom
refe
renc
e
0.00
0.25
0.50
0.75
MMP2activeproMMP2 MMP9
MM
P a
ctiv
ity (p
ixel
s/m
m2 )
0
5000
10000
Hot regionsReference rgeions
*
*
* p<0.05
Results III
Summary
• We found that temperature has a positive correlation between mø% and VI-index
• We found more pro-MMP2 and active MMP2 inside the hot area’s compared to the cold area’s
•We found almost no rise in temperature in presence of blood flow
Conclusion I
• Temperature heterogeneity is associated with a VI-index
• The underlying mechanism of this association is mø accumulation
• The high MMP-activity suggests that active mø are detected by temperature changes
Conclusion II• We have seen in our model that it is almost impossible to measure temperature differences in presence of blood flow
Discussion
• Blood has a cooling effect on the vessel wall, and blood flow is high in the rabbit’s abdominal aorta (twice human coronary flow).
• Therefore to exclude a dominant flow effect on our measurements, we stopped the flow with a balloon
Co-operation
• Catherization laboratoryProf. Dr. PW SerruysDr. W. van der Giessen
• Experimental Cardiology Rotterdam L.C.A van Damme
C. van PeltB. Mousavi GourabiW. MaatD. SegersC. ChengDr. R. KramsDr. D.J. Duncker
• Experimental Cardiology UtrechtDr. G. PasterkampC. SnijderA. Schoneveld
• Thermocore Medical SystemsDr. G. Van LangenhoveDr. T. FlintDr. Y. Yianni
• Middelheim Hospital AntwerpenS. Verheye
M. KockxM. Knaapen