SHAPE Society

1. The Fat-Fed Apolipoprotein E
Knockout Mouse
Chris Jackson
Bristol Heart Institute, University of Bristol, UK
Emerging Animal Models of
Vulnerable Plaque

2. Animals
• Closed outbred colony of
C57:129 homozygous apoE
knockout mice
• Diet supplemented with 21%
lard, 0.15% cholesterol
• Age at start of study was 6 to 8
weeks

3. Study Design
• 98 animals (51 male) were put on
study
• 34 animals: scheduled termination
• Pressure perfusion fixed (10% formalin) at
a constant pressure of 100mmHg
• 64 animals: sudden death
• Not pressure perfusion fixed

4. Sudden Deaths
60565248444036322824201612840
0
10
20
30
40
50
60
70
80
90
100
Time (weeks)
Survival (%)

5. Brachiocephalic Artery

6. Parameters Measured
• Presence or absence of rupture
• Plaque cross-sectional area
• Media cross-sectional area
• Plaque/media area ratio
• % Lumenal occlusion
• Cap thickness
• Number of previous ruptures
• Lipid burden

7. Incidence of Rupture
• 64 sudden deaths
• 35 ruptured brachiocephalics
• 34 scheduled terminations
• 16 ruptured brachiocephalics

8. Time Course of Rupture
605550454035302520151050
0
5
10
15
20
25
30
35
Time (Weeks)
Cumulative Ruptures

9. Plaque Characterisation
• Acutely ruptured (“ruptured”)
• Visible tear or discontinuity in the cap
• Blood-derived components within the
lesion
• Healed previous rupture (“intact”)
• Buried fibrous cap

10. Vessel Dimensions
Intact Ruptured
0
25000
50000
75000
100000
125000
150000
175000
200000
225000
Media Area
Plaque Area
Area (sq µm)
NS
p=0.0015

11. Expansive Remodelling
36322824201612840
0
50000
100000
150000
200000
250000
300000
350000
400000
450000
500000
550000
600000
Media
Plaque
Lumen
Total
Time (Weeks)
Area (sq µm)

12. Lumenal Occlusion
Intact Ruptured
0
10
20
30
40
50
60
Occlusion (%)
p<0.0001

13. Cap Thickness
Intact Ruptured
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Cap Thickness (um)
p=0.0004

14. Previous Healed Ruptures
Intact Ruptured
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Buried Caps
p<0.0001

15. Lipid Burden
Intact Ruptured
0
5
10
15
20
25
30
35
40
45
50
55
Lipid Content (%)
p=0.0019

16. Summary
• Ruptured plaques:
• Are 56% bigger
• Are 52% more occlusive
• Have caps that are 57% thinner
• Have 151% more previous ruptures
• Have a 36% greater lipid burden

17. Intervention Study Design
• To detect ∆(rupture, intact) with 80% power:
• Cap thickness: 17 mice
• Lipid content: 22 mice
• Lumenal occlusion: 24 mice
• Rupture frequency: 33 mice
• Plaque area: 53 mice

18. Late-Breaking News
• Earliest ruptures are seen after 7 weeks
of high-fat diet
• 75% of males have ruptures after 8 weeks
• Pravastatin significantly reduces the
incidence of sudden death
• PAI-1-/-
/apoE-/-
double knockouts have
significantly more plaque ruptures than
apoE-/-
single knockouts

19. Acknowledgments
• Helen Williams, PhD
• Jason Johnson, MSc
• Kevin Carson, MB ChB
• Ray Bush, PhD
• Deb Watkins, BSc
• British Heart Foundation
• Organon Laboratories
• Pfizer
• AstraZeneca