• 
• 
• 
• 
• 

Nephron progenitors in the embryonic kidney propagate while generating differentiated nephrons. However, in mice, the progenitors terminally differentiate shortly after birth. Here, we report a method to selectively expand nephron progenitors in vitro in an undifferentiated state. Combinatorial and concentration-dependent stimulation with LIF, FGF2/9, BMP7, and a WNT agonist is critical for expansion. The purified progenitors proliferated beyond the physiological limits observed in vivo, both for cell numbers and lifespan. Neonatal progenitors were maintained for a week, while progenitors from embryonic day 11.5 expanded 1800-fold for nearly 20 days and still reconstituted three-dimensional nephrons containing glomeruli and renal tubules. Furthermore, progenitors generated from mouse embryonic stem cells and human induced pluripotent cells could be expanded with retained nephron-forming potential. Thus, we have established in vitro conditions to promote propagation of nephron progenitors, which will be essential for dissecting the mechanisms of kidney organogenesis and for regenerative medicine.

 

 

 

Figure 1. Schematic of the culture method for nephron progenitors.
Nephron progenitors from embryos or pluripotent stem cells are propagated in the presence of LIF, FGF, WNT, and BMP in the serum-free media. Expanded cells retain the competence to form glomeruli and renal tubules.

 

 

 

Figure 2. Reconstitution of nephron structures by propagated nephron progenitors derived from human iPS cells.
Yellow arrowheads: glomeruli, Black arrowheads: renal tubules. Scale bar: 20 µm