Regulation of cardiomyocyte maturation during critical perinatal window

Abstract

A primary limitation in the use of pluripotent stem cell-derived cardiomyocytes (PSC-CMs) for both patient health and scientific investigation is the failure of these cells to achieve full functional maturity. In vivo, cardiomyocytes undergo numerous adaptive structural, functional and metabolic changes during maturation. By contrast, PSC-CMs fail to fully undergo these developmental processes, instead remaining arrested at an embryonic stage of maturation. There is thus a significant need to understand the biological processes underlying proper CM maturation in vivo. Here, we discuss what is known regarding the initiation and coordination of CM maturation. We postulate that there is a critical perinatal window, ranging from embryonic day 18.5 to postnatal day 14 in mice, in which the maturation process is exquisitely sensitive to perturbation. While the initiation mechanisms of this process are unknown, it is increasingly clear that maturation proceeds through interconnected regulatory circuits that feed into one another to coordinate concomitant structural, functional and metabolic CM maturation. We highlight PGC1α, SRF and the MEF2 family as transcription factors that may potentially mediate this cross-talk. We lastly discuss several emerging technologies that will facilitate future studies into the mechanisms of CM maturation. Further study will not only produce a better understanding of its key processes, but provide practical insights into developing a robust strategy to produce mature PSC-CMs.

Keywords: cardiac; cardiomyocyte; disease modeling; maturation; pluripotent stem cells; regenerative medicine.

Figure 1.. Summary of transplantation experiments for PSC-CM maturation

When early PSC-CMs are transplanted in vivo during the perinatal period, they achieve full structural, functional and transcriptomic maturity. However, when either late PSC-CMs are transplanted or an older host is used, only partial maturation occurs. These results support the existence of a critical window for CM maturation both in vitro and in vivo.

Figure 2.. Cross-talk between processes involved in CM maturation

During maturation, CMs undergo significant changes in structure, function, metabolism and cell cycle, among other processes. Evidence from various in vitro studies suggests that these processes may function in an interdependent manner, allowing for coordinated CM maturation.

Figure 3.. scRNA-seq enables improved understanding of CM maturation

A, scRNA-seq data of CMs at various stages of development reveals that while maturation proceeds in a stage-specific manner, individual CMs proceed heterogeneously across the maturation trajectory before converging on the final mature phenotype. B, scRNA-seq profiles may enable more precise benchmarking of PSC-CM maturation. By comparing individual PSC-CMs to in vivo CM data, their position along the maturation trajectory can be ascertained and used to quantify a maturation score for single cells. This approach has enabled us to identify, for example, that PSC-CMs transplanted in vivo achieve a maturation score greater than those cultured in vitro and comparable with adult CMs (authors’ unpublished data).