Ex Vivo Expanded 3D Human Kidney Spheres Engraft Long Term and Repair Chronic Renal Injury in Mice

Summary: End-stage renal disease is a worldwide epidemic requiring renal replacement therapy. Harvesting tissue from failing kidneys and autotransplantation of tissue progenitors could theoretically delay the need for dialysis. Here we use healthy and end-stage human adult kidneys to robustly expand proliferative kidney epithelial cells and establish 3D kidney epithelial cultures termed “nephrospheres.” Formation of nephrospheres reestablishes renal identity and function in primary cultures. Transplantation into NOD/SCID mice shows that nephrospheres restore self-organogenetic properties lost in monolayer cultures, allowing long-term engraftment as tubular structures, potentially adding nephron segments and demonstrating self-organization as critical to survival. Furthermore, long-term tubular engraftment of nephrospheres is functionally beneficial in murine models of chronic kidney disease. Remarkably, nephrospheres inhibit pro-fibrotic collagen production in cultured fibroblasts via paracrine modulation, while transplanted nephrospheres induce transcriptional signatures of proliferation and release from quiescence, suggesting re-activation of endogenous repair. These data support the use of human nephrospheres for renal cell therapy. : Human kidney cells quickly degenerate in culture, precluding them as a source for cell therapy for chronic kidney disease (CKD). Herein, Harari-Steinberg et al. show that upon culturing as 3D nephrospheres, human kidney cells regain their epithelial phenotype and acquire in vivo tissue-forming and reparative properties in a CKD mouse model. Keywords: nephrospheres, kidney regeneration, 3D culture, kidney stem cells, in vivo differentiation, renal epithelial differentiation, mouse CKD model, 5/6 nephrectomy, autologous treatment, antifibrotic effect