Journal
CIRCULATION JOURNAL
Volume 77, Issue 5, Pages 1307-1314Publisher
JAPANESE CIRCULATION SOC
DOI: 10.1253/circj.CJ-12-0987
Keywords
Cardiomyocytes; Induced pluripotent stem cells; Ultrastructure
Categories
Funding
- Ministry of Educadon, Culture, Science, and Technology of Japan
- Suzuken Memorial Foundation
- Fujiwara Memorial Foundation
- Uehara Memorial Foundation
- health science research grants from the Ministry of Health, Labor and Welfare of Japan for Clinical Research on Measures for Intractable Diseases
- Grants-in-Aid for Scientific Research [24790277, 23390209, 24591575] Funding Source: KAKEN
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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. Methods and 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. (Circ J 2013; 77: 1307-1314)
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