Micro-PET study of 68Ga-HZ20 in the
rhACE2-intraperitoneal brain model
PET imaging showed slight uptake of the probe in the brains of control
mice, while significant aggregation was observed in the rhACE2 injection
group (Fig. 6A, Fig. S9). SUVmax
showed that within 120 min after probe injection, there were significant
differences between the rhACE2 injection group and the control group,
and at 15 min after probe injection, the uptake values were 0.42± 0.01,
0.44±0.01, 0.56±0.02 and 0.72±0.01, respectively (Fig. 6B).
The target ratio of brain to muscle
also showed consistent results, with 2.23±0.10, 2.85±0.06, 3.34±0.12,
and 4.23±0.12 at 120 min, respectively (Fig. 6C). After 120 min, brain
tissue ex vivo imaging was performed, and the results were
consistent with the results of in vivo PET. There was almost no
probe uptake in the brains of mice that were not injected with rhACE2,
while the uptake of probe in brain tissue was observed in the injection
group, especially in the 0.8 nmol rhACE2 group (Fig. 6D). This result
also showed that the 68Ga-HZ20 probe can be applied to
the quantitative monitoring of rhACE2 in brain tissue.
Brain tissue % ID/g also showed that
the rhACE2 injection group was significantly higher than that of the
noninjection group, with the highest in the 0.8 nmol group, which was
0.004±0.001, 0.024±0.001, 0.048±0.001 and 0.123±0.002, respectively
(Fig. 6E). The correlation analysis between rhACE2 and SUVmax showed the
highest correlation 30 min after probe injection, and the
R2 was 0.9913 (Fig. 6F). The content of rhACE2 in
brain tissue was detected by western blot, and the results showed that
there was a small amount of ACE2 expression in the brain tissue itself,
and obvious bands and gradient relationships were visible in the
injection group, indicating that rhACE2 maintained stability in
structure and quantity in the brain within 120 min (Fig. 6G).