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Abstract
Therapies for cardiac arrhythmias could greatly benefit from approaches to enhance electrical excitability and action potential conduction in the heart by stably overexpressing mammalian voltage-gated sodium channels. However, the large size of these channels precludes their incorporation into therapeutic viral vectors. Here, we report a platform utilizing small-size, codon-optimized engineered prokaryotic sodium channels (BacNav) driven by muscle-specific promoters that significantly enhance excitability and conduction in rat and human cardiomyocytes in vitro and adult cardiac tissues from multiple species in silico. We also show that the expression of BacNav significantly reduces occurrence of conduction block and reentrant arrhythmias in fibrotic cardiac cultures. Moreover, functional BacNav channels are stably expressed in healthy mouse hearts six weeks following intravenous injection of self-complementary adeno-associated virus (scAAV) without causing any adverse effects on cardiac electrophysiology. The large diversity of prokaryotic sodium channels and experimental-computational platform reported in this study should facilitate the development and evaluation of BacNav-based gene therapies for cardiac conduction disorders.
Highlights
Therapies for cardiac arrhythmias could greatly benefit from approaches to enhance electrical excitability and action potential conduction in the heart by stably overexpressing mammalian voltage-gated sodium channels
In addition to mutations that directly alter voltage-gated sodium channels (VGSCs), reduced-sodium current density and slow action potential conduction can arise from the altered extracellular environment, cell morphology, or channel regulation that occur in acquired pathological conditions, such as cardiac ischemia, infarction, and failure[2,3,4]
We demonstrate that optimized viral expression of BacNav significantly improves excitability and velocity of action potential conduction in rat and human cardiomyocyte cultures without altering endogenous ion currents and greatly decreases the incidence of reentrant arrhythmias in an in vitro model of fibrotic cardiac tissue
Summary
Therapies for cardiac arrhythmias could greatly benefit from approaches to enhance electrical excitability and action potential conduction in the heart by stably overexpressing mammalian voltage-gated sodium channels. Channel to generate electrically excitable and actively conducting somatic cells[12,13] capable of functionally bridging large conduction gaps in excitable tissues[12] In this current report, we sought to further explore the therapeutic suitability of engineered BacNav channels for gene therapy applications by optimizing their membrane expression and investigating their effects on the excitability and conduction in cardiac tissues from different species, in vitro, in silico, and in vivo. Stable virally induced expression of an optimized version of NavSheP D60A variant (h2SheP) and its effects on cardiac electrophysiology are demonstrated in mouse hearts in vivo These results warrant the future development of the BacNav gene therapy platform towards cardiac arrhythmia applications. These results demonstrated significant improvement in the expression level of functional NavSheP D60A channels via codon optimization, using the ATUM algorithm, and h2SheP was selected for all subsequent studies
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