A semi-permeable insert culture model for the distal part of the nephron with human and mouse tubuloid epithelial cells.

Tubuloids are advanced in vitro models obtained from adult human or mouse kidney cells with great potential for modelling kidney function in health and disease. Here, we developed a polarized human and mouse tubuloid epithelium on cell culture inserts, namely Transwell™ filters, as a model of the distal nephron with an accessible apical and basolateral side that allow for characterization of epithelial properties such as leak-tightness and epithelial resistance. Tubuloids formed a leak-tight and confluent epithelium on Transwells™ and the human tubuloids were differentiated towards the distal part of the nephron. Differentiation induced a significant upregulation of mRNA and protein expression of crucial segment transporters/channels NKCC2 (thick ascending limb of the loop of Henle), NCC (distal convoluted tubule), AQP2 (connecting tubule and collecting duct) and Na⁺/K⁺-ATPase (all segments) in a polarized fashion. In conclusion, this study illustrates the potential of human and mouse tubuloid epithelium on Transwells™ for studies of tubuloid epithelium formation and tubuloid differentiation towards the distal nephron. This approach holds great promise for assisting future research towards kidney (patho)physiology and transport function.