#4708 RENAL ORGANOID FROM URINE-DERIVED HUMAN ADULT RENAL PROGENITOR CELLS CAN SPONTANEOUSLY GENERATE LONG RENAL TUBULES
Authors: Sallustio Fabio , Giannuzzi Francesca , Picerno Angela , Montenegro Francesca , Maiullari Silvia , Cicirielli Antonella , Stasi Alessandra , Pertosa Giovanni , Gesualdo Loreto 
Published: June 2023

Abstract

Background and Aims
Organoids are self-organizing 3D aggregations of cells that represent the structure and function of organs. Kidney organoids have the potential to advance the field of nephrology by providing a tool for the study of human kidney development and disease, by providing a tool for in vitro drug screening, and ultimately, for regenerative therapy. They can be derived from embryonic stem cells or induced pluripotent stem cells. We aimed to explore for the first time, the potentiality of human adult renal progenitor cells (ARPCs), isolated from urine of healthy subjects and patients, to generate spheroids and organoids for regenerative purpose.

Method
ARPCs were isolated from urine by immunolabeling. Optical microscopy, immunofluorescence experiments and cytofluorimetric analysis were used to characterize spheroids and organoids. CD133, NANOG, SSA4, OCT 3-4 and GATA-3, SOX2 stemness marker antibodies were used to study spheroids and CD13, Lotus tetragonolobus lectin, ZO-1, uromodulin, and aminopeptidase antibodies were used to investigate renal tubular markers. PKH26 was used to study cell migration from organoids to tubules. Real-time PCR was used to generate gene expression data of aquaporin profile in renal tubules. Chick embryo chorioallantoic membrane (CAM) assays were used as in vivo model for angiogenesis.

Results
We isolated ARPCs from urine of healthy subjects or CKD patients. Usually, organoids were generated using complicate induction protocols with several chemical factors. However, for the first time we generated renal spheroids and organoids under 3D culture conditions without any stimulation, such as chemokines or growth factors, starting from ARPCs isolated from subject urine. We showed that the spheroids express high levels of stem cell markers as CD133 and NANOG, functional and constitutional marker of ARPCs, and high levels of stem cell markers that normally are low or not at all expressed in ARPCs and are typical of embryonic stem cells: GATA-3, SSEA4, and Sox2. Moreover, the spheroids were able to induce angiogenesis when implanted in chick embryo chorioallantoic membrane. The urine-derived CD133+ organoids can spontaneously generate long renal tubules in 6–12 days, as showed by PKH26 tagging. The renal tubules were positive for the proximal tubule cell markers CD13 (aminopeptidase N), Lotus tetragonolobus lectin and ZO-1. Moreover, renal tubules expressed the aminopeptidase A (CD249) that is normally present in proximal tubules and glomeruli of the kidneys and that catalyzed the conversion of the Angiotensin II in Angiotensin III witch is important in the local regulation of blood pressure. Also uromodulin was expressed by tubules. It is normally present in epithelial cells of the thick ascending limb of Henle's loop, and after proteolytical cleavage, is secreted into urine. In addition, the renal tubules express several genes typical of renal tubules as AQP1 channel protein that facilitates the flow of water molecules into the cells of the proximal tubule and descending limb of the loop of Henle; γGlut enzyme used for the transport of amino acids across cell membranes; Na/H exchanger 1 (SLC9A1), transporter involved in the regulation of pH homeostasis, cell migration and cell volume; Na/Gluc-1 co-transporter SGLUT1, which promotes the passage of glucose across the membrane in renal tubular cells. In some cases, tubule structures were similar to that found in nephrons, including proximal convoluted tubule, Loop of Henle, Distal Convoluted tubule and collecting duct, as shown by optical microscopy.

Conclusion
For the first time we demonstrated that kidney organoids can be generated starting by urine-derived human adult renal progenitor cells from patients and for the first time we showed that these organoids can generate, spontaneously, without specific stimulation, long portions of renal tubules. These results open new perspectives in the field of the regenerative medicine as ARPCs can be isolated from urine of patients and used to generate spheroids for the study of human kidney development and disease, for in vitro drug screening, and ultimately, for regenerative therapy.