Keiko Tsuchiya, Presenter: Nothing to Disclose

Norihisa Nitta MD, Abstract Co-Author: Nothing to Disclose

Masashi Shiomi PhD, Abstract Co-Author: Nothing to Disclose

Satoshi Nohara, Abstract Co-Author: Nothing to Disclose

Akinaga Sonoda MD, Abstract Co-Author: Nothing to Disclose

Kiyoshi Murata MD, Abstract Co-Author: Nothing to Disclose

Ayumi Seko MD, Abstract Co-Author: Nothing to Disclose

Shinichi Ohta, Abstract Co-Author: Nothing to Disclose

Yasuhiko Tabata, Abstract Co-Author: Nothing to Disclose

Masashi Takahashi MD, Abstract Co-Author: Nothing to Disclose

We made a comparative study of mannan-coated USPIO(M-USPIO), USPIO, mannan-coated SPIO(M-SPIO), and SPIO in the uptake by the atherosclerotic wall using MRI and histology. We posited that the expression of the mannose receptor of M2 macrophages in atherosclerotic lesions may facilitate their uptake of M-USPIO and M-SPIO.  

We used 14 Watanabe hereditary atherosclerotic rabbits (WHHL) 9 to 12 months of age, all of which except 2 (control) were intravenously injected with 4 types of superparamagnetic iron oxides (M-USPIO, USPIO, M-SPIO,SPIO) into 3 rabbits each at a dosage of 0.8 mmol Fe/kg. The animals were painlessly sacrificed at 5 days after administration of 4 types of contrast agents and the aortae were removed and followed by in vitro MRI. Animals underwent in vivo contrast-enhanced MRA before and at 5 days after administration of contrast agents. For both the in vivo and vitro studies, the vessel wall signal intensities were assessed as the same ROI and SNRs were calculated. Histological assessment was made by measurement of iron-positive regions in Berlin blue-stained specimens. The uptake levels of 4 types of superparamagnetic iron oxide by cultured murine macrophages (J774.1) were compared by means of quantifying phagocytized iron using atomic absorptometry.  

We observed significant differences regarding the iron-positive regions. (M-USPIO > USPIO, M-SPIO > SPIO, USPIO>SPIO: p<0.05). However there was no significant difference between M-USPIO and M-SPIO.  For in vivo MRA, the SNR was significantly reduced after administration of contrast agents was compared to pre-contrast. The signals reduced more in M-USPIO and M-SPIO than USPIO and SPIO (p<0.05). The SNR in vitro MRI showed a tendency to be lower in M-USPIO and M-SPIO than USPIO and SPIO(P<0.1). The iron amount of phagocytosized cultured cells was higher in M-USPIO, M-SPIO, SPIO than USPIO.

Both M-USPIO and M-SPIO were trapped inside the atherosclerotic wall, being verified by a remarkable reduction of the SNR. Histological and imaging analysis revealed a tendency that mannan-coated superparamagnetic iron oxides were taken up more by the atherosclerotic wall than non-mannan coated ones.

We think mannan-coated superparamagnetic iron oxides have a new possibility to improve the detectability of atherosclerotic lesions and its therapeutic response using lipidemic-lowering drugs on MRI.

Tsuchiya, K, Nitta, N, Shiomi, M, Nohara, S, Sonoda, A, Murata, K, Seko, A, Ohta, S, Tabata, Y, Takahashi, M, Atherosclerotic Imaging Using 4 Types of Superparamagnetic Iron Oxides: New Possibilities Using Mannan-coated Particles.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11007912.html