cNGR: a novel homing sequence for CD13/APN targeted molecular imaging of murine cardiac angiogenesis in vivo.
OBJECTIVE
Previously, the peptide sequence cNGR has been shown to home specifically to CD13/APN (aminopeptidase N) on tumor endothelium. Here, we investigated the feasibility of selective imaging of cardiac angiogenesis using the cNGR-CD13/APN system.


RESULTS
CD13/APN induction and cNGR homing were studied in the murine myocardial infarction (MI) model. By real-time polymerase chain reaction (PCR) at 7 days after MI, CD13/APN expression was 10- to 20-fold higher in the angiogenic infarct border zone and the MI area than in non-MI areas. In vivo fluorescence microscopy confirmed specific homing of fluorophore-tagged cNGR to the border zone and MI territory at 4 and 7 days after MI with a local advantage of 2.3, but not at 1 or 14 days after MI. Tissue residence half-life was 9.1+/-0.3 hours, whereas the half-life in plasma was 15.4+/-3.4 minutes. Pulse chase experiments confirmed reversible binding of cNGR in the infarct area. Fluorescent labeled cNGR conjugates or antibodies were injected in vivo, and their distribution was studied ex vivo by 2-photon laser scanning microscopy (TPLSM). cNGR co-localized exclusively with CD13/APN and the endothelial marker CD31 on vessels.


CONCLUSIONS
In cardiac angiogenesis endothelial CD13/APN is upregulated. It can be targeted specifically with cNGR conjugates. In the heart cNGR binds its endothelial target only in angiogenic areas.
Buehler
Alexandra
A
CARIM, University of Maastricht, Maastricht, The Netherlands. abuehler@prdbe.jnj.com
van Zandvoort
Marc A M J
MA
Stelt
Bram J
BJ
Hackeng
Tilman M
TM
Schrans-Stassen
Bianca H G J
BH
Bennaghmouch
Abdelkader
A
Hofstra
Leo
L
Cleutjens
Jack P M
JP
Duijvestijn
Adriaan
A
Smeets
Mirjam B
MB
de Kleijn
Dominique P V
DP
Post
Mark J
MJ
de Muinck
Ebo D
ED
D000818:Animals; D018826:CD13 Antigens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology; D008297:Male; D051379:Mice; D008856:Microscopy, Fluorescence / Q000379:methods; D009203:Myocardial Infarction / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053758:Nanoparticles; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D021382:Protein Sorting Signals
D019408:Platelet Endothelial Cell Adhesion Molecule-1; D021382:Protein Sorting Signals; D018826:CD13 Antigens