In Vivo Quantification of Vcam-1 Expression in Renal Ischemia Reperfusion Injury Using Non-Invasive Magnetic Resonance Molecular Imaging

Abstract

Rationale and ObjectiveVascular cell adhesion molecule-1 (VCAM-1) is upregulated in ischemia reperfusion injury (IRI), persisting after restoration of blood flow. We hypothesized that microparticles of iron oxide targeting VCAM-1 (VCAM-MPIO) would depict “ischemic memory” and enable in vivo assessment of VCAM-1 expression.Methodology and FindingsMice subject to unilateral, transient (30 minutes) renal ischemia and subsequent reperfusion received intravenous VCAM-MPIO (4.5 mg iron/kg body weight). Contrast agent bound rapidly (<30 minutes) in IRI-kidneys and appeared as intensely low signal areas by MRI in vivo. Automated segmentation and quantification yielded MPIO contrast volumes of 5991±354×106 µm3 in IRI vs. 87±7×106 µm3 in kidneys with no surgical intervention (P<0.001); 90±8×106 µm3 in IRI kidneys exposed to control (IgG-MPIO) and 625±80×106 µm3, in IRI kidneys pre-treated with a blocking dose of VCAM-1 antibody (P<0.001). In keeping with quantitative MRI data, VCAM-1 mRNA expression in IRI was 65-fold higher than in kidneys without surgical intervention (3.06±0.63 vs. 0.05±0.02, P<0.001). Indeed VCAM-1 mRNA expression and VCAM-MPIO contrast volume were highly correlated (R2 = 0.901, P<0.01), indicating that quantification of contrast volume reflected renal VCAM-1 transcription. Serial imaging showed VCAM-MPIO accumulation at target within 30 minutes, persisting for ≥90 minutes, while unbound VCAM-MPIO was cleared rapidly from blood, with sequestration by mac-3 positive Kupffer cells in the liver and monocyte/macrophages in the spleen.Conclusions(1) VCAM-MPIO detected VCAM-1 expression and defined its 3-dimensional distribution, revealing “ischemic memory” in renal IRI; (2) automated volumetric quantification of VCAM-MPIO accurately reflected tissue levels of VCAM-1 mRNA; and (3) VCAM-MPIO bound rapidly to target with active sequestration of unbound MPIO in the liver and spleen.

Molecular MRI enables early and sensitive detection of brain metastases

“…At the same time, considerably greater numbers of USPIO/SPIO are required to achieve the same contrast effect as for MPIO because of the markedly lower iron content and greatly reduced targeting valency of each particle [USPIO = 2.4-24 antibodies per particle (43) vs. VCAM-MPIO ∼ 25,000 antibodies per particle]. To date, no adverse events with the nonbiodegradable VCAM-MPIO have been observed in mice over 72 h after administration, and we have previously reported that, at both 30 min and 24 h after administration, antibody-conjugated 1-μm MPIO accumulate predominantly in the spleen and liver (24,44). We have now also assessed the possibility of systemic macrophage activation at the molecular level as a consequence of VCAM-MPIO administration, and we have found that an antiinflammatory rather than proinflammatory phenotype is induced in the liver (SI Text 2 and Fig.…”

“…This property has previously been used to track MPIO-labeled tumor cells in mouse models, thus enabling visualization of early metastasis distribution in the brain with sensitivity down to a single metastatic cell loaded with ∼50 pg iron at an imaging field strength of 1.5 T (17). Alternatively, conjugation of MPIO with targeting ligands enables their accumulation at sites where specific molecules are expressed (18)(19)(20)(21)(22)(23)(24)(25). Importantly, the targeted MPIO are not taken up by endothelial cells and do not enter the brain, thus providing an endovascular biomarker for pathology within the brain.…”

Erratum: Inflammatory processes in cardiovascular disease: a route to targeted therapies

“…For example, quantitative molecular imaging has been described for VCAM1 and P-selectin using 'leukocyte-mimetic' particles to examine extent and distribution of endothelial activation 102,103 , which has also been applied to measure the 'imprint' of previous ischaemia 104 . An alternative approach has been to image proteases that are critical in the pathogenesis of disease and has been applied to preclinical models 105 and humans after AMI 100 .…”

Integrin-Mediated Drug Delivery in Cancer and Cardiovascular Diseases with Peptide-Functionalized Nanoparticles

“…Substantially, the most relevant implications of integrins in pathology and therapy, already focused in therapeutic and diagnostic approaches [27][28][29], and currently also in the development of targeted NPs (although still limited to preclinical investigations) [30][31][32] are amenable to the role played by integrin α v β 3 in cancer angiogenesis [33][34][35], in cancer cell proliferation and metastatic diffusion [36][37][38][39], in angiogenesis in ischemic tissues, in atherosclerotic damage [29,40,41] and in vascular restenosis [42], as well as in osteoporosis [43], by integrin α 5 β 1 in angiogenetic processes [33,34,44], by integrin α IIb β 3 , mediating adhesion of platelets to fibrinogen, in thrombotic conditions [45,46], and by the leukocyte integrins α 4 β 1 , α 4 β 7 , α L β 2 and α M β 2 in inflammatory conditions and autoimmune diseases affecting various systems, e.g., multiple sclerosis, ulcerative colitis and Crohn's disease, asthma, psoriasis [29,[47][48][49], and in any way involving the adhesion and transmigrations of leukocytes across the vascular endothelium [50][51][52][53].…”

“…Up to now, the feasibility of targeting VCAM-1 with NPs has been explored only with antibodies, in vivo in atherosclerotic mice, and in murine models of renal and cerebral ischemia [52,53,256,264,266]. It can be noted that in the McAteer study [265], a particle dually labelled with P-selectin and VCAM-1 antibodies was also investigated.…”