validate new imaging technology 15m Robert L Wilensky, M.D. - - PowerPoint PPT Presentation

Atherosclerotic animal models: a way to validate new imaging technology 15m Robert L Wilensky, M.D. University of Pennsylvania

Is there a suitable animal model of human atherosclerosis and vulnerable plaque?

• Human atherosclerosis develops over

decades while we use a model that develops over weeks to months.

• Incidence of coronary artery disease is

variable despite similar risk factors.

• Do we fully understand the process

leading from vulnerable plaque to plaque rupture?

The ideal animal model for vulnerable plaque assessment

• Similar morphology and physiological

characteristics to human disease.

• High percentage of high-risk coronary

artery lesions.

• Variable lesion development.
• The lesion phenotype can be modified.

Advantages of porcine models

• Aged pigs develop atherosclerosis.
• Serial intraluminal evaluations of

atherosclerotic lesions are possible.

• Lesions are similar to human lesions.
• Have been used in diagnostic,

pharmacologic and interventional studies

Porcine models of accelerated coronary atherosclerosis

Model Advantages Limitations

Diabetes/ hypercholesterolemic

Well characterized. Reproducible human like atherosclerosis. Results obtained from diagnostic and pharmacologic treatment studies corroborate data obtained in humans. Complex lesions detectable as early as 6 months after induction. Type I diabetic model. Variable development of atherosclerosis. Expensive

Rapacz familial hypercholesterolemic

Well characterized Models a known human disease state. Long induction period for atherosclerosis. Large size of animals (although genetic modified mini-pig has been developed). Expensive

PCSK9 gain of function

Small size. Models a known human disease state Reproducible lesions. Limited commercial availability. Relatively long term induction period (12 months)

Ossabaw

Only model of metabolic syndrome induced atherosclerosis. Small size. Relatively short induction period after a high fat diet regimen. Limited commercial availability. Questionable development of severe lesions.

Hamamdzic & Wilensky. J Diabetes Res 2013:761415

Thin cap Large plaque burden Large necrotic core Expansive remodelling Inflammation of the fibrous cap

Schaar JA et al. Eur Heart J 2004;25:1077

Rapacz mini-pig: Coronary artery at 13 months

Courtesy of E. Falk in J Diabetes Res 2013:761415

PSCK-9-transgenic Yucatan mini-pig: Coronary artery at13 months of atherogenic diet

Courtesy of E. Falk in J Diabetes Res 2013:761415

Ossabaw feral pigs

Diffuse atherosclerosis in Ossabaw pigs

Neeb ZP et al. Comp Med 2010;60:300

Coronary artery from Ossabaw pig

Courtesy of M Sturek in J Diabetes Res 2013:761415

DM/HC causes increased coronary artery lesion complexity

Wilensky et al Nat Med 2008;14:1059

Proximal LAD lesions: 7 months

Higher lipid content is associated with coronary events.

• Culprit lesions in ACS are more likely to

have a high lipid core than non-culprit lesions by NIRS (84.4% vs 52.8%) Circ

Cardiovasc Intervent 2012;5:55.

• Non-culprit lesions in ACS have a

higher lipid core than patients with stable angina by NIRS Circ Cardiovasc Intervent

2012;5:55

• Culprit lesions in STEMI have higher

lipid core burden index compared to non-culprit lesions by NIRS Arterioscler Thromb

Vasc Biol 2016;36:1010 d

TCFA present TCFA absent

LCBI: 16 LCBI: 5

3 months 6 months 9 months

300 µm 300 µm

LCBI: 45 LCBI: 306

300 µm

Figure 3:

Increased early lipid deposition in arteries developing a TCFA

Saybolt et al Euro Invent 2016;11:1612

LCBI

P=0.04

LCBI

P=0.97

Arteries containing TCFA Arteries containing no TCFAs Saybolt et al Euro Invent 2016;11:1612

DM/HC porcine model: The vulnerable artery

TCFA ThCFA PIT Normal/IH

3 mth NEG POS NEG POS 6 mth NEG NEG POS POS

10 20 30 40 50 60 70 80 90 100

152 32 38 16 Number of histology sections % of histology sections

Early NIRS+ predicts future TCFA and fibroatheroma development by histology (9 months).

TCFAs

+ at 3-m or 6-m P=0.007 + 6-m only P=0.004 + at 3-m & 6-m P=0.03

Fibroatheromas

+ at 3-m or 6-m P=0.0001 + 6-m only P=0.0001 + at 3-m & 6-m P=0.0004

Patel et al ATVB 2013;33:346

NIRS positivity is associated with increased inflammation

NIRS+ NIRS-

Patel et al. ATVB 2013;33:346

NIRS+ TCFA NIRS- ThCFA

Cat S Cat S TUNEL TUNEL Ki-67 Ki-67 Patel et al ATVB 2013;33:346 Movat’s Movat’s Cat S Cat S P-S red P-S red

1 4 2 3 1 4 2 3 1 4 2 3 1 4 2 3 1 4 2 3 3-m 6-m 9-m

Progression of IVUS/NIRS results over time

Patel et al. ATVB 2013;33:346

Sudden death due to ACS in pig 4 months after DM/HC induction

AtheroRemo:Time-to-event for all-cause mortality or non-fatal ACS

Oemrawsingh RM et al JACC 2014;64:2510

Median LCBI 43

DM/HC pigs demonstrate increased plaque burden, lipid content and inflammation in lesions exhibiting very low endothelial shear stress.

Chatzizisis YS et al. Circulation 2008;117:993

PREDICTION: Large plaque burden and low endothelial shear stress predict progression of lesions (6-10 months).

Stone PH et al. Circulation 2012;126:172

PREDICTION: Large plaque burden and low endothelial shear stress independently predict progression of plaque burden.

Stone PH et al. Circulation 2012;126:172

Induction of DM/HC causes more severe and less variable atherosclerosis in the abdominal aortae compared to the coronary arteries

Coronary Artery Abdominal Aorta

Thin fibrous cap Medial destruction Calcification Intra-plaque hemorrhage

100 um 500 um

1

100 um

2

100 um

3

100 um

4

25 um 200 um 500 um

Coronary Artery Abdominal Aorta

Fenning RS et al JAHA 2015;4:e001477

In DM/HC pigs, abdominal aortic disease severity correlates with glucose and cholesterol levels while coronary artery disease severity does not.

P = 0.0014 10 20 30 40 50 60 70

400 500 600 700 800 900 1000 1100

AA Mean Lesion Size (mm^2) Total Plasma Cholesterol Levels (mg/dL)

Control Darapladib Treated

P = 0.0043

10 20 30 40 50 60 70

200 250 300 350 400 450 500

AA Mean Lesion Size (mm^2) Total Plasma Glucose Levels (mg/dL)

Control Darapladib Treated

P = 0.579

0,5 1 1,5 2 2,5 3 3,5

400 500 600 700 800 900 1000 1100

Coronary Mean Leion Size (mm^2) Total Plasma Cholesterol Levels (mg/dL)

Control Darapladib Treated

P = 0.843

0,5 1 1,5 2 2,5 3 3,5

200 250 300 350 400 450 500

Coronary Mean Leion Size (mm^2) Total Plasma Glucose Levels (mg/dL)

Control Darapladib Treated

Coronary arteries Abdominal aortae

• 2 worst proximal LAD lesions

Control Treated

Darapladib reduces coronary artery lesion complexity compared to control

Wilensky et al Nat Med 2008;14:1059

Kaplan–Meier curves for the primary end point of death from cardiovascular causes, myocardial infarction, or stroke.

• STABILITY. N Engl J Med 2014;370:1702

STABILITY: Randomization and follow-up.

• STABILITY. N Engl J Med 2014;370:1702

7924 patients in treatment group were included in the analysis, however, only 5322 were taking darapladib (67.2%) The majority of patients were being treated with 4 cardiac medications

STABILITY: Primary and secondary efficacy end points.

• STABILITY. N Engl J Med 2014;370:1702

Selective inhibition of Lp-PLA2 does not reduce development of AA atherosclerosis

DM/HC control DM/HC darapladib

Fenning RS et al JAHA 2015;4:e001477

Summary

• Animal models are not perfect replications of

human disease.

• Pre-clinical testing of the vulnerable plaque

should make use of coronary arteries as the atherosclerotic process may differ in other arterial beds.

• Surrogate markers should include necrotic

core size, fibrous cap thickness, and vascular inflammation (genes and/or cells). Serial imaging may be of particular importance.