A critical role of retinoic acid concentration for the induction of a fully human-like atrial action potential phenotype in hiPSC-CM

• Published in: Stem cell reports 2023-11, Vol.18 (11), p.2096-2107
• Main Authors: Schulz, Carl, Sönmez, Muhammed, Krause, Julia, Schwedhelm, Edzard, Bangfen, Pan, Alihodzic, Dzenefa, Hansen, Arne, Eschenhagen, Thomas, Christ, Torsten
• Format: Article
• Language: English
• Subjects: action potential; Action Potentials; atrial differentiation; Atrial Fibrillation - metabolism; atrial hiPSC-CM; electrophysiology; engineered heart tissue; Heart Atria; Humans; IKUR; Induced Pluripotent Stem Cells - metabolism; Myocytes, Cardiac; Phenotype; retinoid acid; Tretinoin - metabolism; Tretinoin - pharmacology; ultrarapid repolarizing current
• ISSN: 2213-6711; 2213-6711
• DOI: 10.1016/j.stemcr.2023.10.006

Retinoic acid (RA) induces an atrial phenotype in human induced pluripotent stem cells (hiPSCs), but expression of atrium-selective currents such as the ultrarapid (IKur) 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 IKur 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 IKur 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. •A concentration of unfiltered 1 μM RA is sufficient and necessary to induce a fully human-like atrial AP phenotype in hiPSC-CM•Sterile filtration of RA can lead to a relevant loss of RA preventing the induction of an adult atrial AP phenotype•APD90 shortening upon IKur block by 4-aminopyridine is present in human adult atrial tissue and atrial EHT•Sharp microelectrode measurements in intact tissues (EHT) remain the gold standard In this article, Carl Schulz and colleagues show that unfiltered RA is sufficient and necessary to induce a fully human-like atrial AP phenotype in hiPSC-CM in the EHT format. However, sterile filtration of RA can lead to a relevant loss of RA, preventing the induction of the human adult-like atrial AP phenotype.