DEVELOPMENT OF NOVEL CELL THERAPIES USING FUNCTIONALLY ENHANCED HUMAN iPS CELL-DERIVED NEPHRON PROGENITOR CELLS FOR AKI AND CKD

With a 10–15% mortality rate and 20–30% of cases progressing to chronic kidney disease (CKD), acute kidney injury (AKI) affects an estimated 13.3 million people worldwide annually. In turn, CKD affects about 850 million people and is expected to become the fifth leading cause of death globally by 2030. With kidney transplantation as the only curative therapy, a growing dependency on dialysis has arisen due to donor shortages and limited treatments for AKI and CKD, which also raise the risk of cardiovascular and cerebrovascular diseases. Regenerative medicine in the form of cell therapies has emerged as a promising approach to address these challenges. While mesenchymal stromal cells (MSCs) have been widely tested, clinical benefit remains limited, and adverse events, such as MSC differentiation into adipose tissue within the glomeruli, have been reported. Therefore, there is an urgent need to establish novel therapeutic strategies using human iPS cell-derived nephron progenitor cells (iNPCs) that differentiate specifically into kidney tissues. Clinical application remains unrealized, despite recent reports of therapeutic benefits of iNPCs in AKI. Conversely, evidence for iNPC efficacy in CKD, especially advanced cases, remains sparse. The characteristics of iNPCs vary among iPS cell lines and experimental batches. Thus, while uniform large-scale production of iNPCs is essential for cell therapy, efficient methods remain undeveloped and represent a major translational bottleneck.

To establish high-efficiency iNPC expansion, we screened multiple low-molecular-weight compounds and growth factors on iNPC-derived aggregates. Expanded iNPCs were transplanted into the renal subcapsules of cisplatin-induced AKI (cis-AKI) and aristolochic acid-induced CKD (AA-CKD) mouse models, with kidney function and histology assessed. Conditioned medium (CM) from expanded iNPCs was administered intraperitoneally in parallel to cis-AKI mice to assess paracrine effects, and CM and iNPCs underwent mass spectrometry and RNA sequencing analyses, respectively. We generated and evaluated iNPCs functionally enhanced with reno-protective factors.

We developed the CFY (CHIR99021, FGF9, Y-27632) medium to enable iNPC expansion over 100-fold within two passages while maintaining NPC marker expression and renal differentiation potential in multiple iPS cell lines. Expanded iNPCs attenuated kidney injury and improved survival in cis-AKI model mice and prevented renal dysfunction, interstitial fibrosis, and senescence in AA-CKD mice. c-MET was identified as a specific surface marker, and purified c-MET⁺ iNPCs exhibited therapeutic efficacy in both AKI and CKD. Contralateral kidneys of transplanted mice also improved, suggesting reno-protective paracrine effects. Intraperitoneal CM administration preserved renal function and survival, as analysis identified multiple secreted factors, including vascular endothelial growth factor (VEGF)-A. Furthermore, we demonstrated that iNPCs with enhanced reno-protective effects are therapeutically more effective than conventional iNPCs.

While expanded iNPCs show great promise as a cell-based therapy for AKI and CKD, functionally enhanced iNPCs may present as even stronger candidates. Developing such advanced therapies opens new avenues for treating kidney diseases.