Table 1.

Key characteristics of iPSC-CM maturation and related recommended measurements to asses these characteristics

Characteristics	Recommended measurement
Cardiomyocyte-specific gene expression	Transcriptome analysis
	Methylation patterns
Structural features	Sarcomere number, density, and organization
	Length, shape, and % binucleated
	Mitochondrial volume and morphology
Electrophysiological phenotypes	Action potential profile
	Ion current densities and gating properties
	Cardiomyocyte subtype determination
Calcium handling and contractility	Ability to contract; spontaneous vs. stimulation
	Calcium transients, sparks, and waves
	Contractile force
Metabolic profile	Lipid oxidation vs. glycolysis
	Oxygen consumption and maximum respiration
Response to sympathetic stimulation	Positive inotropic, chronotropic, and lusitropic effects
Electrical coupling	Gap junction localization, density, and composition Conduction velocity