Cardiomyocytes derived from pluripotent stem cells: Progress and prospects from China

A new method for neonatal rat ventricular myocyte purification using superparamagnetic iron oxide particles

BACKGROUND

Neonatal rat ventricular myocytes (NRVMs) have proven to be an ideal research model for cardiac disease. However, the current methods to purify NRVMs have a limitation to obtain high purity. The purpose of this study was to develop a NRVM purification method by using superparamagnetic iron oxide particles (SIOP).

METHODS

NRVMs were purified by using SIOP (SIOP group). The differential attachment with or without bromodeoxyuridine (BrdU) treatment served as control and BrdU groups, respectively. The Percoll gradient (Percoll) and magnetic-activated cell sorting (MACS) methods were performed to compare the purity and viability of NRVMs with SIOP method.

RESULTS

The SIOP group enriched NRVMs up to 93.9 ± 2.0% purity determined by flow cytometry (FCM) and 95.6 ± 1.3% by immunofluorescence count (IF). In contrast, the control group gave purities of 71.9 ± 2.9% (by FCM) and 66.8 ± 8.9% (by IF), and the BrdU group obtained 82.0 ± 1.3% (by FCM) and 83.1 ± 2.4% (by IF). The purity of SIOP-isolated NRVMs was not different from that of Percoll and MACS groups. However, the cardiomyocytes separated by these methods, except SIOP protocol, were mixed with intrinsic cardiac adrenergic cells. NRVMs purified by SIOP shaped the similar three-dimensional morphology, with no difference in cell yield, viability and cytosolic Ca²⁺ homeostasis at 24 h after isolation compared with NRVMs in other groups. Furthermore, SIOP-purified NRVMs retained the responses to phenylephrine and lipopolysaccharide challenge.

CONCLUSION

We first reported an efficient and novel method to purify NRVMs using SIOP, which may help accelerate innovative research in the field of cardiomyocyte biology.

New easy-to-use hybrid system for extracellular potential and impedance recordings

The need for predictive, in vitro cardiac safety screening drives further development of automated, high-throughput-compatible drug evaluation based on cardiac cell preparations. Recently, pluripotent stem cells are evaluated as a new, more predictive model for cardiovascular risk assessment pertaining to in vitro assays. We present a new screening platform, the CardioExcyte 96, a hybrid instrument that combines impedance (cell contractility) with extracellular field potential (EFP) recordings. The electrophysiological measurements are noninvasive, label free and have a temporal resolution of 1 ms. This hybrid technology addresses the lack of easy-to-use high-throughput screening for in vitro assays and permits the reliable investigation of short- and long-term pharmacological effects. Several models of cardiomyocyte preparations were successfully validated for use with the CardioExcyte96. Furthermore, the pharmacological effects of a number of reference compounds were evaluated. Compound effects on cell monolayers of human-induced pluripotent stem cell-derived cardiomyocytes are evaluated using a quasi-simultaneous hybrid recording mode that combines impedance and EFP readouts. A specialized software package for rapid data handling and real-time analysis was developed, which allows for comprehensive investigation of the cellular beat signal. Combining impedance readouts of cell contractility and EFP (microelectrode array-like) recordings, the system opens up new possibilities in the field of in vitro cardiac safety assessment.