Advances in Technologies Guiding Human Pluripotent Stem Cell Differentiation

Human pluripotent stem cells (hPSCs), derived from both human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs), are unique in vitro models for studying human development and have enormous potential for regenerative medicine, disease modeling, and drug discovery. Nevertheless, differentiation of hPSCs into specific lineages in an efficient and reproducible manner is still a limitation. This review provides an overview of the major methods and progress of directed differentiation in recent years. First, it presents the CRISPR/Cas9 gene editing tools, such as inducible CRISPR interference (CRISPRi) and activation (CRISPRa) approaches, for the discovery of causative transcription factors and signal pathways of differentiation. Secondly, it highlights small molecule regulatory strategies to induce lineages at low cost and high efficiency under chemically defined conditions, including the Wnt pathway (CHIR99021 and IWP2). Third, it discusses three-dimensional culture systems (organoids and organ-on-a-chip) more closely recapitulating tissue structure and physical microenvironment and applied to microcephaly and heart disease modeling. Overall, these improvements provide not only a better understanding of the differentiation route of hPSCs but also bring the field closer to clinically applicable personalized regenerative medicine.