Micro-PET study of 68Ga-HZ20 in the
rhACE2-intraperitoneal spleen model
RhACE2 was injected in situ into the spleen of KM mice, and PET
imaging showed significant aggregation of the68Ga-HZ20 probe in the 0.4 nmol rhACE2 injection group
(Fig. 5A, Fig. S7). Comparing SUVmax
in PET images revealed that the difference in probe uptake in the spleen
between the 0.2 nmol rhACE2 injection group and the control group was
small, while that in the 0.4 nmol rhACE2 injection group was
significantly higher than that of the other two groups, and the SUVmax
at 15 min after probe injection was 0.28± 0.03, 0.28±0.01 and 0.58±0.01,
respectively (Fig. 5B). Similarly,
the splenic muscle target ratio was significantly higher in the 0.4 nmol
rhACE2 injection group than in the 0.2 nmol and control groups, with 60
min ratios of 1.25±0.20, 1.30±0.14 and 4.13±0.05, respectively (Fig.
5C). After 60 min of probe injection, the spleen was sampled forex vivo imaging, and PET showed that the probe had a high uptake
in the spleen in the 0.4 nmol group and a small amount of uptake in the
0.2 nmol group, especially at the injection site of rhACE2 (Fig. 5D).
After ex vivo imaging, the
spleen tissue was measured by a γ counter to analyze probe uptake more
accurately, and the results showed that the % ID/g in the rhACE2
injection group was significantly higher than that in the control group,
which was 0.41±0.01, 0.53±0.01 and 0.86±0.03, respectively (Fig. 5E).
The correlation analysis between rhACE2 and SUVmax showed the highest
correlation 45 min after probe injection, and the R2was 0.9095 (Fig. 5F). Similarly, there was almost no expression of ACE2
in the spleen, and rhACE2 aggregation in the spleen tissue was observed
in the injection group, but the rhACE2 content was significantly lower
than that of other model groups with the same dose, although the
analysis results may be due to the small volume of the spleen and the
leakage of rhACE2 during surgery (Fig. 5G).