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Real-Time Measurements of Calcium and Contractility Parameters in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes
Published on: May 26, 2023
Calcium homeostasis in human induced pluripotent stem cell-derived cardiomyocytes
Yee-Ki Lee1, Kwong-Man Ng, Wing-Hon Lai
1Cardiology Division, Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong, China.
Insights
Human induced pluripotent stem cell-derived cardiomyocytes show immature calcium handling compared to human embryonic stem cell counterparts, impacting their potential for regenerative medicine. Further research is needed to optimize these cells for cardiac repair.
Area of Science:
- Stem cell biology
- Cardiovascular research
- Regenerative medicine
Background:
- Human induced pluripotent stem cells (hiPSCs) offer promise for cardiomyocyte replacement in regenerative medicine.
- Understanding calcium homeostasis in hiPSC-derived cardiomyocytes is crucial for excitation-contraction coupling, yet remains largely unknown.
Purpose of the Study:
- To investigate and compare the calcium handling properties of hiPSC-derived cardiomyocytes with those derived from human embryonic stem cells (hESCs).
Main Methods:
- Cardiomyocytes were differentiated from hiPSCs (IMR90, KS1) and hESCs (H7, HES3).
- Cardiac-specific marker expression was confirmed via RT-PCR.
- Calcium handling properties were assessed using fluorescence confocal microscopy and line-scan imaging in 20-day-old cells.
Main Results:
- hiPSC-derived cardiomyocytes exhibited smaller amplitude and slower upstroke velocity of spontaneous calcium transients compared to hESC-derived cardiomyocytes.
- hESC-derived cardiomyocytes showed enhanced calcium handling kinetics and higher sarcoplasmic reticulum calcium stores.
- Key calcium-handling protein expression (RyR2, SERCA, Jun, TRDN) was significantly lower in hiPSC-derived cardiomyocytes.
- Spatial inhomogeneity in calcium transient properties was more pronounced in hiPSC-derived cardiomyocytes.
Conclusions:
- hiPSC-derived cardiomyocytes display relatively immature calcium handling properties compared to hESC-derived cardiomyocytes.
- These findings highlight developmental immaturity as a potential limitation for the use of hiPSC-derived cardiomyocytes in cardiac regeneration.
Rationale:
Cardiomyocytes generated from human induced pluripotent stem cells (hiPSCs) are suggested as the most promising candidate to replenish cardiomyocyte loss in regenerative medicine. Little is known about their calcium homeostasis, the key process underlying excitation-contraction coupling.
Objective:
We investigated the calcium handling properties of hiPSC-derived cardiomyocytes and compared with those from human embryonic stem cells (hESCs).
Methods And Results:
We differentiated cardiomyocytes from hiPSCs (IMR90 and KS1) and hESCs (H7 and HES3) with established protocols. Beating outgrowths from embryoid bodies were typically observed 2 weeks after induction. Cells in these outgrowths were stained positively for tropomyosin and sarcomeric alpha-actinin. Reverse-transcription polymerase chain reaction studies demonstrated the expressions of cardiac-specific markers in both hiPSC- and hESC-derived cardiomyocytes. Calcium handling properties of 20-day-old hiPSC- and hESC-derived cardiomyocytes were investigated using fluorescence confocal microscopy. Compared with hESC-derived cardiomyocytes, spontaneous calcium transients from both lines of hiPSC-derived cardiomyocytes were of significantly smaller amplitude and with slower maximal upstroke velocity. Better caffeine-induced calcium handling kinetics in hESC-CMs indicates a higher sacroplasmic recticulum calcium store. Furthermore, in contrast with hESC-derived cardiomyocytes, ryanodine did not reduce the amplitudes, maximal upstroke and decay velocity of calcium transients of hiPSC-derived cardiomyocytes. In addition, spatial inhomogeneity in temporal properties of calcium transients across the width of cardiomyocytes was more pronounced in hiPSC-derived cardiomyocytes than their hESC counterpart as revealed line-scan calcium imaging. Expressions of the key calcium-handling proteins including ryanodine recptor-2 (RyR2), sacroplasmic recticulum calcium-ATPase (SERCA), junction (Jun) and triadin (TRDN), were significantly lower in hiPSC than in hESCs.
Conclusions:
The results indicate the calcium handling properties of hiPSC-derived cardiomyocytes are relatively immature to hESC counterparts.
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