Histologic evidence ofHistologic evidence of
SPIO accumulation inSPIO accumulation in
vulnerable plaquesvulnerable plaques
Silvio Litovsky, MDSilvio Litovsky, MD
June 7, 2002June 7, 2002
In-vitro Study of Macrophage
In a series of in-vitro studies we have tested
the rate of SPIO uptake by human activated
monocytes in different conditions regarding
incubation time and concentration of SPIO.
SPIO particles were labeled by a fluorescent
FL-labeled SPIO Incubated Macrophages after 24hr
Double DAPI Staining with Fluorescence-labeled SPIO Macrophages
after 24hr Incubation
Macrophages labeled with
fluorescent microspheres adhere
to atherosclerotic plaques.
In-vivo distribution of SPIO in ApoE
deficient and wild type mice:
•For the initial study, we use the mouse model of
•ApoE deficient mouse has similar atherosclerotic
lesions to human and the lesions are more common in
the aortic arch and thoracic aorta.
• We used ApoE deficient mice and normal variant
(C57BL mice) as control.
•Animals were sacrificed on day 3 and 5 after injection.
•Tissues from different organs including liver,
kidneys, lung, heart, spleen and aorta
(including valve region, ascending, descending
and abdominal) were obtained and stained.
• We used Hematoxyline and Eosin (H&E), Iron,
CD68 and Movat staining.
• After Iron staining, aortic walls of the ApoE
deficient mice and normal variant were
compared based on the number of Iron
ApoE k/o Mouse 5 Days AfterApoE k/o Mouse 5 Days After
Injection- LiverInjection- Liver
Histopathologic Study of the Mice Injected
with SPIO (Aortic Root)
ApoE K/O mouse, Movat staining, aortic root
Histopathologic study of ApoE K/O Mouse injected
With SPIO (Aortic Root)
Iron Staining (aortic plaque) Iron Staining (coronary section)
Iron particles Iron particles
Histopathologic Study of Wild Type Mouse
Injected with SPIO (Thoracic Aorta)
CD68 stainingIron staining
Comparison of the Number of the Iron Particles (per
HPF) in ApoE K/O Mice Plaque vs. Normal Wall
number of iron
Histopathologic studies of Thoracic aorta in Watanabe
Hereditary Hypercholesterolemic rabbit after SPIO injection
Macrophage staining Iron staining
Hypercholesterolemic Rabbit, Aorta, 4 days after
Perls’ Staining H&E Staining
Electron Microscopy Evidence of Intracellular
SPIO in the Rabbit Aorta
Endothelial cell, x7500 Foamy cell, x4000
0 10 20 30 40 50 60 70
macrophage (foam cell) density
Correlation Between Iron Positive Cells in Iron
Staining and Foam Cell Density in H&E Staining in Rabbit
Plaque Iron in ApoE k/o mousePlaque Iron in ApoE k/o mouse
after SPIOafter SPIO
H&E IRON STAIN
Plaque Iron in Cytokine-TreatedPlaque Iron in Cytokine-Treated
Mice after SPIOMice after SPIO
H&E stain Iron stain
Plaque Iron in Cytokine–Treated MicePlaque Iron in Cytokine–Treated Mice
after SPIOafter SPIO
Overlying plaques Plaque-free area
1) SPIO nanoparticles actively accumulate in
areas of atherosclerotic lesions in rabbits and mice.
2) There is a strong correlation between areas of foamy
cells infiltration and SPIO uptake in mice and rabbit
3) Cytokines markedly increase the SPIO uptake by
atherosclerotic plaques, thus providing a method for
quantifying recruitment of monocytes.
4) MRI has the potential for non-invasively assessing
monocyte homing into atherosclerotic plaque.
Center for Vulnerable Plaque ResearchCenter for Vulnerable Plaque Research
Houston, TexasHouston, Texas