Epigenetic cues regulating airway development in human lung organoids: Polycomb repressive complex 2 and altered chromatin accessibility determine cell fate.

Today, human organoids are becoming an integrated part of genomics and epigenomics, as they provide a platform that can be used for the definite study of molecular and cellular mechanisms occurring at different stages of development, particularly organogenesis, within the human body. Airway development is a complex process heavily influenced by epigenetic regulatory mechanisms in response to environmental changes, and as such, human lung organoids are an indispensable asset for further exploration of these mechanisms as a mode of transition from human in vitro to human ex vivo studies. Cultured primarily in compounds mimicking the extracellular matrix, such as Matrigel, these lung organoids have helped us to come to a better understanding of the role of polycomb repressive complex 2 (PRC2) and enhancer of zeste homolog 2 (EZH2) in lung epithelial cell differentiation and airway development, which was first reported in the FASEB journal in 2019. The following is an extended account of how the histone methylation-regulating PRC2 comes to play in the molding of the human bronchial tree, along with further epigenetic insights based on more recently developed human lung organoids.