Chronic and sustained amplification of ACE2 activity in vivo has required the development of
transgenic mice or the use of viral vectors. Minicircle is a new gene delivery technology
which is resistant to gene silencing, and therefore represents an attractive
platform for gene replacement strategies in vivo. Here we cloned cDNA of
soluble mouse ACE2 into a circular expression cassette and the resulting ACE2
minicircle (MC) was injected to female FVB
mice using iv. hydrodynamic approach (10ug or 30ug/mouse). At 3-7d after MC
administration, serum ACE2 activity in mice that received 10ug ACE2MC (n=9) was
over 100-fold higher than in controls (n=9) (138±48 vs 0.7±0.2 RFU/uL/hr) and in
ACE2MC mice (30ug) (n=8) was almost 1000-fold higher than in controls (n=14) (480
±153 vs 0.5±0.1 RFU/uL/hr, respectively). Mice that received 10 ug ACE2MC were
followed for consecutive serum ACE2 activity monitoring, BP measurements and
plasma Ang levels. The increase in serum ACE2 activity was sustained until the
end of the study (up to 82 days) (Figure).
Despite such a marked increase in serum ACE2 activity in ACE2MC mice, conscious
SBP was not different from controls (137±8 vs 138±7 mmHg, respectively). At the
end of the study, when Ang II was infused acutely (0.2 ug/kg BW i.p.), the
increase in plasma Ang II in ACE2MC mice was significantly reduced compared to
control mice (915±154 vs 1420±131 fmoL/mL, p<0.05).
Mini-circle delivery of ACE2 results in a dose-dependent and sustained long-term
increase in serum ACE2 that efficiently degrades plasma Ang II. Extremely high
increases in serum ACE2 activity do not reduce BP probably due to activation of
non-ACE2 dependent compensatory Ang-hydrolyzing pathways.