Molecular imaging of alpha v beta3 integrin expression in atherosclerotic plaques with a mimetic of RGD peptide grafted to Gd-DTPA.
OBJECTIVE
The integrin alpha v beta3 is highly expressed in atherosclerotic plaques by medial and intimal smooth muscle cells and by endothelial cells of angiogenic microvessels. In this study, we have assessed non-invasive molecular magnetic resonance imaging (MRI) of plaque-associated alpha v beta3 integrin expression on transgenic ApoE-/- mice with a low molecular weight peptidomimetic of Arg-Gly-Asp (mimRGD) grafted to gadolinium diethylenetriaminepentaacetate (Gd-DTPA-g-mimRGD). The analogous compound Eu-DTPA-g-mimRGD was employed for an in vivo competition experiment and to confirm the molecular targeting. The specific interaction of mimRGD conjugated to Gd-DTPA or to 99mTc-DTPA with alpha v beta3 integrin was furthermore confirmed on Jurkat T lymphocytes.


RESULTS
The mimRGD was synthesized and conjugated to DTPA. DTPA-g-mimRGD was complexed with GdCl3.6H2O, EuCl3.6H2O, or with [99mTc(CO)3(H2O)3]+. MRI evaluation was performed on a 4.7 T Bruker imaging system. Blood pharmacokinetics of Gd-DTPA-g-mimRGD were assessed in Wistar rats and in c57bl/6j mice. The presence of angiogenic blood vessels and the expression of alpha v beta3 integrin were confirmed in aorta specimens by immunohistochemistry. Gd-DTPA-g-mimRGD produced a strong enhancement of the external structures of the aortic wall and of the more profound layers (possibly tunica media and intima). The aortic lumen seemed to be restrained and distorted. Pre-injection of Eu-DTPA-g-mimRGD diminished the Gd-DTPA-g-mimRGD binding to atherosclerotic plaque and confirmed the specific molecular targeting. A slower blood clearance was observed for Gd-DTPA-g-mimRGD, as indicated by a prolonged elimination half-life and a diminished total clearance.


CONCLUSIONS
The new compound is potentially useful for the diagnosis of vulnerable atherosclerotic plaques and of other pathologies characterized by alpha v beta3 integrin expression, such as cancer and inflammation. The delayed blood clearance, the significant enhancement of the signal-to-noise ratio, and the low immunogenicity of the mimetic molecule highlight its potential for an industrial and clinical implementation.
Burtea
Carmen
C
Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons-Hainaut, 24, Avenue du Champ de Mars, B-7000 Mons, Belgium.
Laurent
Sophie
S
Murariu
Oltea
O
Rattat
Dirk
D
Toubeau
Gérard
G
Verbruggen
Alfons
A
Vansthertem
David
D
Vander Elst
Luce
L
Muller
Robert N
RN
D000818:Animals; D001011:Aorta / Q000378:metabolism* / Q000473:pathology; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism; D050197:Atherosclerosis / Q000378:metabolism* / Q000473:pathology; D001667:Binding, Competitive; D003287:Contrast Media / Q000378:metabolism* / Q000493:pharmacokinetics; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D019169:Jurkat Cells; D018810:Magnetic Resonance Angiography / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009942:Organometallic Compounds / Q000378:metabolism* / Q000493:pharmacokinetics; D004369:Pentetic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012815:Signal Processing, Computer-Assisted; D016284:Technetium Tc 99m Pentetate / Q000378:metabolism
D001057:Apolipoproteins E; D003287:Contrast Media; D039302:Integrin alphaVbeta3; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; C531177:gadolinium-DTPA-g-mimRGD; D004369:Pentetic Acid; D016284:Technetium Tc 99m Pentetate