Abstract P2164: Expression Of Engineered Bacterial Sodium Channel Improves Cardiomyocyte Contractility
Wu, T; Li, B; Koconis, J; Bhattacharjee, A; Ye, L; Bursac, N
Published in: Circulation Research
Our recent studies in non-human primates have demonstrated adeno-associated virus (AAV) delivery of prokaryotic sodium channel (BacNa
) can improve the contractile function of infarcted hearts. We hypothesized that BacNa
expression increases cardiomyocyte (CM) contractile function by indirectly augmenting Ca
transient amplitude via increase in sarcoplasmic reticulum (SR) Ca
stores.
We developed an
model of ischemia-reperfusion (I/R) injury in engineered heart tissues (cardiopatches) made from human iPSC-derived CMs (hiPSC-CMs). Prior to formation, tissues were transduced with lentivirus conferring a doxycycline (Dox)-inducible expression of BacNa
. Upon I/R injury, the tissues were treated with either vehicle or Dox for 48h followed by force testing and Ca
imaging. The effect of BacNa
expression on Ca
handling was additionally studied using neonatal rat ventricular myocytes (NRVMs).
The tissue injury from I/R was evident from increases in cleaved-caspase 3 area (0.25% vs 1.53%), ROS generation (1.2 fold), LDH release (4.1 fold), and percent dead cells (0.97% vs 4.67%). Immediately following the I/R injury, tissues showed decrease in contractile force (2.78mN vs 0.74mN) and conduction velocity (20.7cm/s vs 7.9cm/s). At 72hr post-injury, BacNa
-expressing tissues exhibited significantly higher contractile force (1.67mN vs 1.32mN) and Ca
transient (1.8 fold) amplitudes compared to the vehicle control. Furthermore, in uninjured NRVM monolayers, BacNa
expression resulted in higher Ca
transient amplitude (1.31 fold), as well as increased SR calcium stores (1.3 fold) and slower sodium/calcium exchanger (NCX) extrusion rate (1.03s
vs 0.82s
) in the presence of caffeine. Blocking NCX with 10M ORM-10962 eliminated the difference in Ca
transient amplitude between BacNa
-expressing and control CMs.
Our results suggest BacNa
expression augments CM contractility and Ca
transient amplitude, at least in part through the suppression of Ca
efflux mode of the NCX. In addition to its antiarrhythmic effects, BacNa
gene delivery may represent an effective therapeutic strategy to improve cardiac contractility in congestive heart failure.
