Liver dysplasia: US molecular imaging with targeted contrast agent enables early assessment.
OBJECTIVE
To investigate the ability of vascular endothelial growth factor receptor type 2 (VEGFR2)-targeted ultrasonographic (US) microbubbles for the assessment of liver dysplasia in transgenic mice.


METHODS
Animal experiments were approved by the governmental review committee. Nuclear factor-κB essential modulator knock-out mice with liver dysplasia and wild-type mice underwent liver imaging by using a clinical US system. Two types of contrast agents were investigated: nontargeted, commercially available, second-generation microbubbles (SonoVue) and clinically translatable PEGylated VEGFR2-targeted microbubbles (BR55). Microbubble kinetics was investigated over the course of 4 minutes. Targeted contrast material-enhanced US signal was quantified 5 minutes after injection. Competitive in vivo binding experiments with BR55 were performed in knock-out mice. Immunohistochemical and hematoxylin-eosin staining of liver sections was performed to validate the in vivo US results. Groups were compared by using the Mann-Whitney test.


RESULTS
Peak enhancement after injection of SonoVue and BR55 did not differ in healthy and dysplastic livers (SonoVue, P = .46; BR55, P = .43). Accordingly, immunohistochemical findings revealed comparable vessel densities in both groups. The specificity of BR55 to VEGFR2 was proved by in vivo competition (P = .0262). While the SonoVue signal decreased similarly in healthy and dysplastic livers during the 4 minutes, there was an accumulation of BR55 in dysplastic livers compared with healthy ones. Furthermore, targeted contrast-enhanced US signal indicated a significantly higher site-specific binding of BR55 in dysplastic than healthy livers (P = .005). Quantitative immunohistologic findings confirmed significantly higher VEGFR2 levels in dysplastic livers (P = .02).


CONCLUSIONS
BR55 enables the distinction of early stages of liver dysplasia from normal liver.
Department of Experimental Molecular Imaging, Internal Medicine III, and Nuclear Medicine, RWTH-Aachen University, Pauwelsstrasse 30, 52074 Aachen, Germany.
Christoph
C
Grouls
Maximillian
M
Hatting
Anne
A
Rix
Sibylle
S
Pochon
Wiltrud
W
Lederle
Isabelle
I
Tardy
Christiane K
CK
Kuhl
Christian
C
Trautwein
Fabian
F
Kiessling
Moritz
M
Palmowski
D000818:Animals; D003287:Contrast Media; D008099:Liver / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D057054:Molecular Imaging; D010743:Phospholipids; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013459:Sulfur Hexafluoride; D014463:Ultrasonography; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D040301:Vascular Endothelial Growth Factor Receptor-2; D013459:Sulfur Hexafluoride