Human iPSC-derived renal collecting duct organoid model cystogenesis in ADPKD.

In autosomal dominant polycystic kidney disease (ADPKD), renal cyst lesions predominantly arise from collecting ducts (CDs). However, relevant CD cyst models using human cells are lacking. Although previous reports have generated in vitro renal tubule cyst models from human induced pluripotent stem cells (hiPSCs), therapeutic drug candidates for ADPKD have not been identified. Here, by establishing expansion cultures of hiPSC-derived ureteric bud tip cells, an embryonic precursor that gives rise to CDs, we succeed in advancing the developmental stage of CD organoids and show that all CD organoids derived from PKD1-/- hiPSCs spontaneously develop multiple cysts, clarifying the initiation mechanisms of cystogenesis. Moreover, we identify retinoic acid receptor (RAR) agonists as candidate drugs that suppress in vitro cystogenesis and confirm the therapeutic effects on an ADPKD mouse model in vivo. Therefore, our in vitro CD cyst model contributes to understanding disease mechanisms and drug discovery for ADPKD.

In vitro methods to ensure absence of residual undifferentiated human induced pluripotent stem cells intermingled in induced nephron progenitor cells.

Cell therapies using human induced pluripotent stem cell (hiPSC)-derived nephron progenitor cells (NPCs) are expected to ameliorate acute kidney injury (AKI). However, using hiPSC-derived NPCs clinically is a challenge because hiPSCs themselves are tumorigenic. LIN28A, ESRG, CNMD and SFRP2 transcripts have been used as a marker of residual hiPSCs for a variety of cell types undergoing clinical trials. In this study, by reanalyzing public databases, we found a baseline expression of LIN28A, ESRG, CNMD and SFRP2 in hiPSC-derived NPCs and several other cell types, suggesting LIN28A, ESRG, CNMD and SFRP2 are not always reliable markers for iPSC detection. As an alternative, we discovered a lncRNA marker gene, MIR302CHG, among many known and unknown iPSC markers, as highly differentially expressed between hiPSCs and NPCs, by RNA sequencing and quantitative RT-PCR (qRT-PCR) analyses. Using MIR302CHG as an hiPSC marker, we constructed two assay methods, a combination of magnetic bead-based enrichment and qRT-PCR and digital droplet PCR alone, to detect a small number of residual hiPSCs in NPC populations. The use of these in vitro assays could contribute to patient safety in treatments using hiPSC-derived cells.

Protocol for the generation and expansion of human iPS cell-derived ureteric bud organoids.

The ureteric bud (UB) is a kidney precursor tissue that repeats branching morphogenesis and gives rise to the collecting ducts (CDs) and lower urinary tract. Here, we describe protocols to generate iUB organoids from human iPSCs; iUB organoids repeat branching morphogenesis. We describe how to expand iUB-organoid-derived tip colonies and how to induce CD progenitors from iUB organoids. These organoids can be used to study CD development and potentially as a model of kidney and urinary tract diseases. For complete details on the use and execution of this protocol, please refer to Mae et al. (2020).

Expansion of Human iPSC-Derived Ureteric Bud Organoids with Repeated Branching Potential.

Ureteric bud (UB) is the embryonic kidney progenitor tissue that gives rise to the collecting duct and lower urinary tract. UB-like structures generated from human pluripotent stem cells by previously reported methods show limited developmental ability and limited branching. Here we report a method to generate UB organoids that possess epithelial polarity and tubular lumen and repeat branching morphogenesis. We also succeed in monitoring UB tip cells by utilizing the ability of tip cells to uptake very-low-density lipoprotein, cryopreserving UB progenitor cells, and expanding UB tip cells that can reconstitute the organoids and differentiate into collecting duct progenitors. Moreover, we successfully reproduce some phenotypes of multicystic dysplastic kidney (MCDK) using the UB organoids. These methods will help elucidate the developmental mechanisms of UB branching and develop a selective differentiation method for collecting duct cells, contributing to the creation of disease models for congenital renal abnormalities.

A Modular Differentiation System Maps Multiple Human Kidney Lineages from Pluripotent Stem Cells.

Recent studies using human pluripotent stem cells (hPSCs) have developed protocols to induce kidney-lineage cells and reconstruct kidney organoids. However, the separate generation of metanephric nephron progenitors (NPs), mesonephric NPs, and ureteric bud (UB) cells, which constitute embryonic kidneys, in in vitro differentiation culture systems has not been fully investigated. Here, we create a culture system in which these mesoderm-like cell types and paraxial and lateral plate mesoderm-like cells are separately generated from hPSCs. We recapitulate nephrogenic niches from separately induced metanephric NP-like and UB-like cells, which are subsequently differentiated into glomeruli, renal tubules, and collecting ducts in vitro and further vascularized in vivo. Our selective differentiation protocols should contribute to understanding the mechanisms underlying human kidney development and disease and also supply cell sources for regenerative therapies.

Protocol to Generate Ureteric Bud Structures from Human iPS Cells.

The generation of ureteric bud (UB), which is the renal progenitor that gives rise to renal collecting ducts and lower urinary tract, from human-induced pluripotent stem cells (hiPSCs) provides a cell source for studying the development of UB and kidney disease. Here we describe a stepwise and efficient two-dimensional differentiation method of hiPSCs into Wolffian duct (WD) cells. We also describe how to generate three-dimensional WD epithelial structures that can differentiate into UB-like structures.

Generation of branching ureteric bud tissues from human pluripotent stem cells.

Recent progress in kidney regeneration research is noteworthy. However, the selective and robust differentiation of the ureteric bud (UB), an embryonic renal progenitor, from human pluripotent stem cells (hPSCs) remains to be established. The present study aimed to establish a robust induction method for branching UB tissue from hPSCs towards the creation of renal disease models. Here, we found that anterior intermediate mesoderm (IM) differentiates from anterior primitive streak, which allowed us to successfully develop an efficient two-dimensional differentiation method of hPSCs into Wolffian duct (WD) cells. We also established a simplified procedure to generate three-dimensional WD epithelial structures that can form branching UB tissues. This system may contribute to hPSC-based regenerative therapies and disease models for intractable disorders arising in the kidney and lower urinary tract.

Solid-type RCC originating from native kidneys in renal transplant recipients should be monitored cautiously.

Incidental hemodialysis-related renal cell carcinoma (id-RCC) has been reported to have a good prognosis. However, we have observed rapid progression of id-RCC in some renal transplant patients. Operative indications for id-RCC detected via computed tomography (CT) immediately before renal transplantation (RTx) remain unclear. The purpose of this study was to examine the effects of immunosuppression on the progression of solid-type RCC (s-RCC) and cystic-type RCC (c-RCC). We divided 202 patients with id-RCC into four groups as follows: Group 1, s-RCC with RTx (n = 17); Group 2, c-RCC with RTx (n = 27); Group 3, s-RCC without RTx (n = 53); and Group 4, c-RCC without RTx (n = 105). Five-year cancer specific survival (CSS) rates were significantly worse in Group 1 than Group 3 (79.6% and 100%, respectively, P = 0.012), as were non-recurrence rates (NRRs) (59.2 and 100%, respectively, P < 0.001). In contrast, 5-year CSS rates were similar in Group 2 and Group 4 (100% and 95.7%, respectively, P = 0.295) as were NRR (100% and 98.7%, respectively, P = 0.230). Solid-type RCC should be removed immediately after RTx, and more carefully monitored for recurrence during follow-up.

Successful Kidney Transplantation for End-Stage Renal Disease in Marfan's Syndrome.

Marfan's syndrome is a systemic disorder of the connective tissue caused by mutations in the extracellular matrix protein fibrillin-1, with aortic dissection and aneurysm being its most life-threatening manifestations. Kidney transplantation for end-stage renal disease (ESRD) in patients with Marfan's syndrome has not been reported in the literature, and the rate of the incidence of dissection or aneurysm in the iliac artery is unknown. Here, we present a patient with Marfan's syndrome with ESRD due to severe renal ischemia caused by massive bleeding from thoracoabdominal aortic dissection leading to transplant surgery of a living kidney procured from the patient's mother. After kidney transplantation, the renal function normalized without vascular complications, and stable graft function along with negative results for both microhematuria and proteinuria continued for two years. Also, vascular complication such as aneurysm or dissection of the iliac artery was not observed using ultrasonography during the follow-up period. ESRD patients with Marfan's syndrome might be suitable for kidney transplantation, but long-term and careful observations are needed.