Differential expression levels of CD151 enable enrichment of atrial cardiomyocytes derived from human induced-pluripotent stem cell
Authors: Koakutsu M , Miki K , Naka Y , Sasaki M , Napier S , Nishimoto T , Yoshida Y 
Published: November 2020

Abstract

Introduction
Human iPSCs-derived cardiomyocytes (hiPSCs-CMs) are heterogeneous populations that contain ventricular-like CMs (VCMs), atrial-like CMs (ACMs) and pacemaker cells. Isolation of pure populations of each hiPSCs-CM subtype corresponding to the target regions of the heart enables effective drug screening process and stable engraftment of hiPSCs-CMs (e.g. ventricular cardiomyocytes without impurities).

Purpose
Atrial and ventricular cardiomyocytes develop from distinct mesoderm populations, and many of different genes are expressed between two subtypes. Since our method of cardiomyocytes differentiation from hiPSCs mimics in vivo cardiomyocytes development, we hypothesized that two subtypes could be separated by differentially expressed genes in hiPSCs-CMs differentiation process. In this study, we focused cell surface genes which are useful for analysis by flow cytometry, and then identified cell surface marker that can distinguish atrial and ventricular cardiomyocytes from hiPSCs-CMs.

Methods
We performed an antibody-based screening using hiPSCs-CMs induced under atrial induction condition (AIC) and ventricular induction condition (VIC) by flow cytometry. To identify cell surface markers which enable discrimination of cardiac subtypes, we isolated the cell populations using the antibodies against the cell surface markers. Quantitative PCR was performed to analyze expression levels of subtype-specific genes in sorted cells. We confirmed subtype classification of cells using patch-clamp method.

Results
We identified CD151 as a novel candidate of atrial/ventricular selectable marker. The expression level of CD151 was low in most hiPSCs-CMs under AIC. In these cells, CD151-low cells highly expressed atrial genes compared to CD151-high cells. In contrast, the expression level of CD151 was high in most hiPSCs-CMs under VIC. In these cells, CD151-high cells highly expressed ventricular genes compared to CD151-low cells. Furthermore, we investigated the electrophysiological properties of CD151-high and -low cells using patch-clamp experiments. As expected, the cells showing atrial type action potential were enriched in AIC with low expression of CD151 (n=17). On the other hand, CD151-high cells (n=16) contained no atrial CMs, but mostly nodal like cells. In addition, CD151-low cells in AIC were affected with action potential duration by exposure of atrial specific channel blocker (4-aminopyridine) and activator (carbachol). In VIC, CD151-high cells (n=16) demonstrated ventricular type action potential property compared to CD151-low cells (n=21).

Conclusion
These results suggest that CD151 is a useful marker which can enrich ACMs from hiPSCs-CMs. Because these enriched ACMs are uniform population, it may be appropriate for atrial-selective drug screening. Additionally, this marker can reduce contaminated ACMs from hiPSCs-CMs cultured in VIC.
Action potential of CD151-high/low CMs

Funding Acknowledgement
Type of funding source: Other. Main funding source(s): Takeda pharmaceutical company limited, Japan society for the promotion of science(JSPS) KAKENHI