Determination of appropriate stage of human-induced pluripotent stem cell-derived cardiomyocytes for drug screening and pharmacological evaluation in vitro.

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) at different stages (approximate days 30, 60, and 90) were used to determine the appropriate stage for functional and morphological assessment of drug effects in vitro. The hiPS-CMs had spontaneous beating activity, and β-adrenergic function was comparable in all stages of differentiation. Microelectrode array analyses using ion channel blockers indicated that the electrophysiological properties of these ion channels were comparable at all differentiation stages. Ultrastructural analysis using electron microscopy showed that myofibrillar structures at days 60 and 90 were similarly distributed and more mature than that at day 30. Analysis of motion vectors in contracting cells showed that the velocity of contraction was the highest at day 90 and was the most mature among the three stages. Gene expression analysis demonstrated that expression of some genes related to myofilament and sarcoplasmic reticulum increased with maturation of morphological and contractile properties. In conclusion, day 30 cardiomyocytes are useful for basic screening such as the assessment of electrophysiological properties, and days 60 and 90 are the appropriate differentiation stage for morphological assays. For the assay of contractile function associated with subcellular components such as sarcoplasmic reticulum, day 90 cardiomyocytes are the most suitable.