SHAPE Society

1. Histopathologic Study ofHistopathologic Study of
SPIO Distribution in MouseSPIO Distribution in Mouse
Introducing our MethodIntroducing our Method

2. Endocytosis and Particle Size
Endocytosis Particle diameter
Phagocytosis 0.1-10µm
Pinocytosis 0.5-100nm

3. ♦ Both phagocytosis and pinocytosis occur in
macrophages
♦ Although internalization of particles less
than 1 µm showed characteristics of both
receptor mediated endocytosis and
phagocytosis, increasing particle size
increases the probability of phagocytosis of
readily phagocytosed particles

4. ♦Macrophages are sensitive
to composition, size, and
concentration of the
challenging particles.
phagocytosis.

6. ♦ Particles with surface associated
ligands (such as antibody or
complement) that specifically bind a cell
membrane are more readily
phagocytosed than those without
surface receptors. Strong binding
between receptors and ligands can lead
to fusion if the phagocytosed body is a
liposome, virus, or bacterium.

7. ♦ Average diameter of low density
lipoprotein (LDL) is 24.4 nm to more
than 26 nm
♦ Receptor mediated endocytosis is
responsible for the internalization of low
density lipoproteins and for uptake of many
substances

8. Oxidized LDL are recognized
and taken up by:
♦ Common receptor for acetyl LDL (scavenger
receptor)
♦ Specific receptor for oxidized LDL
♦ Mouse peritoneal macrophages selectively or
preferentially ingest aggregated oxidized
LDL, but not native oxidized LDL

9. Macrophages may take up
Oxidized LDL according to its
degree of aggregation
♦ Small aggregated molecules generated
under a mild oxidative condition are
recognized via scavenger receptor
♦ Large aggregated particles are taken up by
phagocytosis.

10.
SPIO Endocytosis
♦ Fluid phase endocytosis for tumor cells
♦ Receptor mediated endocytosis
(phagocytosis) for macrophages
♦ The later pathway can be dramatically
enhanced by opsonization of particles with
plasma protein (Schulze )

11. ♦Macrophagesand macrophage-like cell
lines had thehighest uptake. Tumor
cells, however, also showed
considerableuptake, ranging from 11.9
to 118 ng of iron per million
cells(Moore)
♦ With the introduction of smaller and
long-circulatingiron oxides, this
distribution was shown to be different,
withless uptake in liver and spleen and
concomitantly more uptakein lymph
nodes (Weissleder )

12. ♦After introduction of long-circulating
particles tumoral uptake also increased
particularly whit higher doses
♦The faster the growth rate,the greater
the Iron oxide uptake, this may be
relatedto the higher endocytosis rate in
the faster-proliferating cells

13. LCDIO Distribution into Tumor Compartments as
Determined with Fluorescence Microscopy and
Immunohistochemistry Tumor Compartment
LCDIO Distribution (%)
Extracellular
Vascular volume fraction 4.5 ± 0.8
Interstitial fraction 19.0 ± 1.8
Intracellular
Glioma tumor cells 49.0 ± 4.6
Tumor-associated macrophages 21.0 ± 3.1
Tumor vascular endothelium 6.5 ± 1.4

14. Endothelial cells also show iron oxide
uptake; however, it is unclearwhether
the relatively high uptake is related to
cellular proliferation

15. Which Dose Is Better
♦ 3mmolFe/kg is the maximum safe dose?
♦ 1mmolFe/kg is the dose that Reuhem used
for his study
♦ 0.01mmolFe/kg is the human dose of
Feridex

16. ♦ No acute or sub-acute toxic effects were
seen in rats or dogs who received a total of
3000µmolFe/kg,150 times the dose
proposed for MR imaging of the liver
♦ In human and animals it has been shown
that these iron particles enter the usual iron
metabolism pathway in body

17. When We Have The Highest
Concentration of These Particles
in Atherosclerotic Plaque?

18. Particle Core Size ParticleSize Blood
(nm) (nm) half life
Combidex 5-6 20-30 8h
Feridex 4-6 35-50 2.4±0.2h
MION 4-6 17

19. Biodistribution 24 Hours after IV Administration of 125
I-labeled LCDIO into Four Rats with 9L-GFP Brain Tumor
Injected dose per gram of tissue mean ± SD
Blood
0.5 ± 0.2
Brain
0.01 ± 0.01
Bone
0.1 ± 0.1
Heart
0.2 ± 0.1
Intestine
0.1 ± 0.1
Lymph node
25.0 ± 3.2
Kidney
0.8 ± 0.1
Liver
1.9 ± 0.3
Lung
0.2 ± 0.1
Muscle
0.1 ± 0.1
Spleen
9.8 ± 0.8
Tumor 0.1 ± 0.1

20. What we are going to do
♦We are going to study the
distribution of these particles over
time in 2 extreme doses, in normal
and Apo E deficient mice

21. Method and Material
♦ 20 Apo E-deficient mice >20 months,and 4
normal same age mice
♦ Group 1: 10 Apo-E deficient mice and 2
normal mice,3mmol Fe/kg
♦ Group 2:10 Apo-E deficient mice and 2
normal mice, 0.01mmol Fe/kg

22. S a m p les fro m h ea rt, lu n g , liver,sp leen , k id n ey,
eso p h a g u s a n d 5 p a rts o f a o rta
fo r H & E ,P ea rl,M a cro p h a g e S ta in in g
In jectio n o f F erid ex 3 m m o l F e/k g
S a m p les fro m h ea rt, lu n g , liver,sp leen ,k id n ey,
eso p h a g u s a n d 5 p a rts o f a o rta
fo r H & E ,P ea rl,M a cro p h a g e S ta in in g
In jectio n o f F erid ex 0 .0 1 m m o l F e/k g
2 0 A p o E d eficien t M ice