Generation of renal spheroids and tubule-like structures from ARPCs. (A) ARPCs formed spheroids after 2 days in 3D culture conditions. Each circle in the image represents the microcavity of the 3D plates containing a spheroid. (B) Primary and (C) immortalized RPTECs cannot form spheroids in 3D plates, and they appear to break up and disperse in the microcavities. Both tARPC (D) and gARPC (E) were able to form spheroids. (F) Spheroids derived from the mixed-cell population of uARPCs/CD133^- cells cultured in normal plates for 30-45 days without changing their morphology. (G) Spheroids from gARPCs formed circular protrusions similar to those of podocyte cell bodies connected by primary processes. (H-I) Spheroids derived from the mixed-cell population of uARPCs/CD133^- cells spontaneously generated tubular-like structures starting from one or both poles. (J-M) Tubule-like structures spontaneously generated by the uARPCs/CD133^- mixed cell population showing many similarities with the nephron unit of the kidney. (J) Image of a tubule-like structure acquired with a stereomicroscope. (M) Images acquired by a phase contrast microscope of the same tubule-like structure observed in (J) via a stereomicroscope. The scale bars represent 100 μm.