Significance StatementThe ability to differentiate human induced pluripotent stem cells to kidney organoids in vitro holds promise for disease modeling, drug discovery, and clinical application.... Show moreSignificance StatementThe ability to differentiate human induced pluripotent stem cells to kidney organoids in vitro holds promise for disease modeling, drug discovery, and clinical application. The authors differentiated such cells to kidney tissue comprising glomerular, proximal, and distal tubular structures. Earlier research demonstrated that these structures become vascularized upon transplantation in mice and show advanced maturation. To investigate whether human induced pluripotent stem cell?derived kidney organoids can also become functional in vivo, they applied high-resolution intravital multiphoton imaging through a titanium imaging window. They demonstrated in vivo glomerular filtration and size-selective glomerular barrier function in the transplanted organoids. This technique can be instrumental for further developing stem cell?derived organoids toward clinical applications. BackgroundThe utility of kidney organoids in regenerative medicine will rely on the functionality of the glomerular and tubular structures in these tissues. Recent studies have demonstrated the vascularization and subsequent maturation of human pluripotent stem cell?derived kidney organoids after renal subcapsular transplantation. This raises the question of whether the glomeruli also become functional upon transplantation.MethodsWe transplanted kidney organoids under the renal capsule of the left kidney in immunodeficient mice followed by the implantation of a titanium imaging window on top of the kidney organoid. To assess glomerular function in the transplanted human pluripotent stem cell?derived kidney tissue 1, 2, and 3 weeks after transplantation, we applied high-resolution intravital multiphoton imaging through the imaging window during intravenous infusion of fluorescently labeled low and high molecular mass dextran molecules or albumin.ResultsAfter vascularization, glomerular structures in the organoid displayed dextran and albumin size selectivity across their glomerular filtration barrier. We also observed evidence of proximal tubular dextran reuptake.ConclusionsOur results demonstrate that human pluripotent stem cell?derived glomeruli can develop an appropriate barrier function and discriminate between molecules of varying size. These characteristics together with tubular presence of low molecular mass dextran provide clear evidence of functional filtration. This approach to visualizing glomerular filtration function will be instrumental for translation of organoid technology for clinical applications as well as for disease modeling. Show less
