A critical role of retinoic acid concentration for the induction of a fully human-like atrial action potential phenotype in hiPSC-CM
Carl Schulz, Muhammed Sönmez, Julia Krause, Edzard Schwedhelm, Bangfen Pan, Dzenefa Alihodzic, Arne Hansen, Thomas Eschenhagen, Torsten Christ
Abstract
Retinoic acid (RA) induces an atrial phenotype in human induced pluripotent stem cells (hiPSCs), but expression of atrium-selective currents such as the ultrarapid (I Kur ) and acetylcholine-stimulated K + current is variable and less than in the adult human atrium. We suspected methodological issues and systematically investigated the concentration dependency of RA. RA treatment increased I Kur concentration dependently from 1.1 ± 0.54 pA/pF (0 RA) to 3.8 ± 1.1, 5.8 ± 2.5, and 12.2 ± 4.3 at 0.01, 0.1, and 1 μM, respectively. Only 1 μM RA induced enough I Kur to fully reproduce human atrial action potential (AP) shape and a robust shortening of APs upon carbachol. We found that sterile filtration caused substantial loss of RA. We conclude that 1 μM RA seems to be necessary and sufficient to induce a full atrial AP shape in hiPSC-CM in EHT format. RA concentrations are prone to methodological issues and may profoundly impact the success of atrial differentiation.