In situ Hybridization of miRNAs in Human Embryonic Kidney and Human Pluripotent Stem Cell-derived Kidney Organoids.

MicroRNAs are small RNAs that negatively regulate gene expression and play an important role in fine-tuning molecular pathways during development. There is increasing interest in studying their function in the kidney, but the majority of studies to date use kidney cell lines and assess the total amounts of miRNAs of interest either by qPCR or by high-throughput methods such as next generation sequencing. However, this provides little information as to the distribution of the miRNAs in the developing kidney, which is crucial in deciphering their role, especially as there are multiple kidney cell types, each with its own specific transcriptome. Thus, we present a protocol for obtaining spatial information for miRNA expression during kidney development by in situ hybridization (ISH) of anti-miRNA, digoxigenin-labelled (DIG), Locked Nucleic Acid (LNA®) probes on (i) native human embryonic tissue and (ii) human pluripotent stem cell (hPSC)-derived 3D kidney organoids that model kidney development. We found that the method reveals the precise localization of miRNA in specific anatomical structures and/or cell types and confirms their absence from others, thus informing as to their specific role during development.