2018 - Introducing simulated IK1 into human iPSC-cardiomyocytes using dynamic clamp on an automated patch clamp setup
Patchliner poster, Biophysics Annual Meeting 2018 (1.0 MB)
Dynamic clamp is a powerful tool involving injection of real-time simulated membrane currents into patch clamped cells. This technique has been employed in conventional patch clamp electrophysiology to introduce inward rectifier IK1 current into human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). IK1 is expressed at low levels in these cells. For this reason, hiPSC-CMs display a more depolarized membrane potential than adult cardiomyocytes, limiting their use in safety pharmacology. Therefore, introducing simulated IK1 into hiPSCCMs may improve maturity of these cells and ensure that they represent a viable alternative to the scarcely available dissociated adult human cardiomyocytes. Indeed, they are attractive cells types because of their unlimited availability and human origin.
In this study, we combined dynamic clamp with an automated patch clamp platform to demonstrate that IK1 conductance can be added to hiPSC-CMs on this platform. Our results
show that IK1 can be successfully added to hiPSC-CMs to up to 4 cells simultaneously and that this results in a more stabilized and hyperpolarized resting membrane potential. Action potential (AP) shape also changes when IK1 is added. We have used with different amounts of IK1 (100-2000 pS/pF) and show that increasing IK1 results in AP shortening and an acceleration of the upstroke. We could measure native Ba2+-sensitive IK1 in voltage clamp mode in approximately 50% of these cells, but IK1 was small, on average 1.98±0.42 pA/pF (mean ± SEM). Adding a Ca2+ channel activator (BayK 8644), or blocker (nifedipine) caused an increase and decrease of the AP duration, respectively. In conclusion, combining dynamic clamp with automated patch clamping results in an enhanced, medium-throughput platform for safety pharmacology.