Retinoic acid signaling activation in early intermediate mesoderm differentiation promotes dual lineage of intermediate mesoderm specification and enhances full-segment kidney organoid generation

During kidney development, an intermediate mesoderm (IM) give rise to distinct structures: the ureteric bud (UB) and the metanephric mesenchyme (MM). These structures differentiate further into the collecting duct and nephron, forming a mature kidney. Generating functional kidney organoids has been challenging due to incomplete development of the UB. Researchers have overcome this limitation by differentiating UB and MM separately and co-culturing them to generate kidney organoids. However, this study developed a co-culture-free method using retinoic acid (RA), plays important role in the anterior IM differentiation and BMP7 secreted by UB in vivo development. This protocol provided not only simplifies the complexity of kidney organoid generation but also advances our understanding of the crucial signaling pathways involved in kidney development. Overall design: Pluripotent stem cells were cultured with 10 uM CHIR99021 for 4 days for inducing premitive streak differentiation. And then cells were exposed 0.1uM retinoic acid for 2 days with 100ng/ml FGF9 and withdrawn the retinoic acid for 1 day for inducing intermediate mesoderm cells.