Stem cells: Growing mouse kidneys in rats

Fully developed kidneys formed from mouse pluripotent stem cells (PSCs) have been generated in rats genetically modified to develop no kidneys of their own, reports a study in Nature Communications. The PSCs were injected into embryonic rats, which were transferred to surrogate rats to develop.

Growing human kidneys in animals may one day have the potential to mitigate the shortage of donor organs available for transplantation. However, at present, the problem of how to cross the species barrier has not been resolved.

Using the same approach they had used previously to generate a mouse-derived pancreas in rats, Masumi Hirabayashi and colleagues injected mouse PSCs into early embryo structures, called blastocysts. These blastocysts had been collected from rats that had been genetically modified so that they could not form kidneys of their own. The blastocysts were then transferred into a host rat to develop. Although the mutation caused the rats to die shortly after birth, which limits the functional analysis that could take place, the authors found that the mouse-derived kidneys generated had the same number of glomeruli as normal mouse kidneys, and possessed fully formed ureter-bladder junctions.

Full characterisation of kidney function and architecture is needed before this method could potentially be considered for use with human PSCs. However, issues concerning crossing a larger species barrier, the chimeric nature of the organs produced, and ethical considerations regarding their development will also need to be addressed.