title: Ultrastructural maturation of human-induced pluripotent stem cell-derived cardiomyocytes in a long-term culture.
abstract: BACKGROUND
  In the short- to mid-term, cardiomyocytes generated from human-induced pluripotent stem cells (hiPSC-CMs) have been reported to be less mature than those of adult hearts. However, the maturation process in a long-term culture remains unknown.
  
  
  RESULTS
  A hiPSC clone generated from a healthy control was differentiated into CMs through embryoid body (EB) formation. The ultrastructural characteristics and gene expressions of spontaneously contracting EBs were analyzed through 1-year of culture after cardiac differentiation was initiated. The 14-day-old EBs contained a low number of myofibrils, which lacked alignment, and immature high-density Z-bands lacking A-, H-, I-, and M-bands. Through the long-term culture up to 180 days, the myofibrils became more tightly packed and formed parallel arrays accompanied by the appearance of mature Z-, A-, H-, and I-bands, but not M-bands. Notably, M-bands were finally detected in 360-day-old EBs. The expression levels of the M-band-specific genes in hiPSC-CMs remained lower in comparison with those in the adult heart. Immunocytochemistry indicated increasing number of MLC2v-positive/MLC2a-negative cells with decreasing number of MLC2v/MLC2a double-positive cells, indicating maturing of ventricular-type CMs.
  
  
  CONCLUSIONS
  The structural maturation process of hiPSC-CMs through 1-year of culture revealed ultrastructural sarcomeric changes accompanied by delayed formation of M-bands. Our study provides new insight into the maturation process of hiPSC-CMs.
authors: Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors: Tsukasa
authors: T
authors: Kamakura
authors: Takeru
authors: T
authors: Makiyama
authors: Kenichi
authors: K
authors: Sasaki
authors: Yoshinori
authors: Y
authors: Yoshida
authors: Yimin
authors: Y
authors: Wuriyanghai
authors: Jiarong
authors: J
authors: Chen
authors: Tetsuhisa
authors: T
authors: Hattori
authors: Seiko
authors: S
authors: Ohno
authors: Toru
authors: T
authors: Kita
authors: Minoru
authors: M
authors: Horie
authors: Shinya
authors: S
authors: Yamanaka
authors: Takeshi
authors: T
authors: Kimura
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D019070:Cell Lineage; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000648:ultrastructure*; D012518:Sarcomeres / Q000000981:diagnostic imaging* / Q000378:metabolism; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D015415:Biomarkers; D009124:Muscle Proteins