Atherosclerosis and matrix metalloproteinases: experimental molecular MR imaging in vivo.
OBJECTIVE
To evaluate the capability of P947, a magnetic resonance (MR) imaging contrast agent that molecularly targets matrix metalloproteinases (MMPs), to aid detection and imaging of MMPs in atherosclerotic lesions in vivo; its specificity compared with that of P1135; expression and distribution of MMPs in atherosclerotic vessels; and in vivo distribution and molecular localization of fluorescent europium (Eu) P947.


METHODS
The Animal Care and Use Committee approved all experiments. P947 was synthesized by attaching a gadolinium chelate (1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid) to a peptide that specifically binds MMPs. Scrambled form of P947 (P1135) was synthesized by replacing the targeting moiety of P947 with a scrambled peptide lacking the ability to bind MMPs. P947, P1135, and gadoterate meglumine were injected into atherosclerotic apolipoprotein E-deficient and wild-type mice. The aortic MR imaging enhancement produced by the contrast agents was measured at different times and was compared by using one-way analysis of variance. MMP expression was investigated in the aortas by using MMP immunostaining and in situ MMP zymography. A fluorescent form of P947 (Eu-P947) was synthesized to compare the in vivo distribution of the contrast agent (Eu-P947) with specific MMP immunofluorescent staining.


RESULTS
MMP-targeted P947 facilitated a 93% increase (P < .001) in MR image signal intensity (contrast-to-noise ratio [CNR], 17.7 compared with 7.7; P < .001) of atherosclerotic lesions in vivo. Nontargeted P1135 (scrambled P947) provided 33% MR image enhancement (CNR, 10.8), whereas gadoterate meglumine provided 5% (CNR, 6.9). Confocal laser scanning microscopy demonstrated colocalization between fluorescent Eu-P947 and MMPs in atherosclerotic plaques. Eu-P947 was particularly present in the fibrous cap region of plaques.


CONCLUSIONS
P947 improved MR imaging for atherosclerosis through MMP-specific targeting. The results were validated and provide support for further assessment of P947 as a potential tool for the identification of unstable atherosclerosis.
Amirbekian
Vardan
V
Translational and Molecular Imaging Institute, Department of Radiology, Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai Schoolof Medicine, New York, NY 10029, USA.
Aguinaldo
Juan Gilberto S
JG
Amirbekian
Smbat
S
Hyafil
Fabien
F
Vucic
Esad
E
Sirol
Marc
M
Weinreb
David B
DB
Le Greneur
Soizic
S
Lancelot
Eric
E
Corot
Claire
C
Fisher
Edward A
EA
Galis
Zorina S
ZS
Fayad
Zahi A
ZA
D000818:Animals; D050197:Atherosclerosis / Q000175:diagnosis* / Q000378:metabolism*; D002614:Chelating Agents / Q000493:pharmacokinetics; D005682:Gadolinium / Q000493:pharmacokinetics*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015336:Molecular Probe Techniques; D025941:Protein Interaction Mapping / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D002614:Chelating Agents; D005682:Gadolinium; D020782:Matrix Metalloproteinases