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Circulation. 2012 Jul 31;126(5):528-36. doi: 10.1161/CIRCULATIONAHA.111.083584. Epub 2012 Jun 29.

Ca(2+)-stimulated adenylyl cyclase AC1 generates efficient biological pacing as single gene therapy and in combination with HCN2.

Author information

1
Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, NY 10032, USA.

Abstract

BACKGROUND:

Biological pacing performed solely via HCN2 gene transfer in vivo results in relatively slow idioventricular rates and only moderate autonomic responsiveness. We induced biological pacing using the Ca(2+)-stimulated adenylyl cyclase AC1 gene expressed alone or in combination with HCN2 and compared outcomes with those with single-gene HCN2 transfer.

METHODS AND RESULTS:

We implanted adenoviral HCN2, AC1, or HCN2/AC1 constructs into the left bundle branches of atrioventricular-blocked dogs. During steady-state gene expression (days 5-7), differences between AC1, HCN2/AC1, and HCN2 alone were evident in basal beating rate, escape time, and dependence on electronic backup pacing. In HCN2, AC1, and HCN2/AC1, these parameters were as follows: basal beating rate: 50±1.5, 60±5.0, and 129±28.9 bpm (P<0.05 for HCN2/AC1 versus HCN2 or AC1 alone), respectively; escape time: 2.4±0.2, 1.3±0.2, and 1.1±.0.4 seconds (P<0.05 for AC1 and HCN2/AC1 versus HCN2); and percent electronic beats: 34±8%, 2±1%, and 6±2% (P<0.05 for AC1 and HCN2/AC1 versus HCN2). Instantaneous (SD1) and long-term (SD2) heart rate variability and circadian rhythm analyzed via 24-hour Holter recordings showed a shift toward greater sensitivity to parasympathetic modulation in animals injected with AC1 and a high degree of sympathetic modulation in animals injected with HCN2/AC1.

CONCLUSION:

AC1 or HCN2/AC1 overexpression in left bundle branches provides highly efficient biological pacing and greater sensitivity to autonomic modulation than HCN2 alone.

PMID:
22753192
PMCID:
PMC3418050
DOI:
10.1161/CIRCULATIONAHA.111.083584
[Indexed for MEDLINE]
Free PMC Article

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