Ah, yes, you knew this would happen. At least if you truly thought about it.
Japanese scientists have cloned stem cells to produce viable kidneys. Ok, in rats. But still! This is the sort of research that our country feels is in contravention to some religious morality. (Why not just let those folks NOT perform the research themselves. We have many others who want to help our sick citizens!)
Drs. S. Yokote, S. Yamanaka, K. Matsumoto, E. Fujimoto, T. Yokoo (all from Jikei University School of Medicine, Tokyo; Yokoo is the senior author), H. Nagashima , H. Matsunari, A. Uchikura (these three from Meiji University, Kawasaki) S. Iwai (Kitasato University, Towada) , and E. Kobayashi (Keio School of Medicine, Shijuku-ku) published their findings in the Proceedings of the National Academy of Science of the United States (PNAS). (Yes, a US publication for stem cell research!) Their paper, Urine excretion strategy for stem cell-generated embryonic kidneys, highlights the key difference this development has offered to the science- urine production from the nephron. (Their research has been funded by the Otsuka Pharmaceutical Factory, Inc.)
Part of the reason their stem-cell produced kidney has been able to produce urine is because the researchers did not just use stem cells and grow the kidney- they created special urine excretion pathways in the kidney, and attached them to bladders and then to ureters. These pathways are called cloacae, orifices (openings) that exist in the urinary (such openings are also found in the intestines and reproductive organs) tract for various animals. This drainage canal and bladder were the critical keys to the success of this concept. (The researchers have termed this improvement a “stepwise peristaltic ureter” [SWPU].) Also, the stem cells, once the nephrons and cloaca were distinct, did not complete their growth cycle in vitro (under glass), but within the animal species itself.
The produced urine from the kidney enters the new cloacae, whihc then traverses to the produced bladders, and then finally to the host animal’s actual bladder. Another key factor: these stem cell kidneys had been functioning for at least 8 weeks.
Not content to leave the test just with rats, the researchers repeated the process with a larger animal- a mammal, a pig. And, it worked, too.
It seems clear that their concept- the need for additional pathways to discharge the urine- could be the vital conceptual improvement that will let us progress to a human cloned kidney that works.
NOTE: THIS MOVIE FROM THE PNAS SITE WILL NOT WORK IN CHROME BROWSERS. GOOGLE HAS DISABLED THIS SORT OF EMBED. SORRY.
