ScienceDaily reports on progress in growing functioning kidneys from specialized embryonic cell clusters. Researchers are still working on animal models, but this looks very much like the promising early work on heart transplants in the 1950s. The scientist in charge of this work predicts that "therapies based on growing new organs will be part of mainstream medical practice by the middle of the 21st century." This sort of therapy, if coupled with reliable approaches to curing cancer and neurodegenerative diseases such as Alzheimer's, will enable medical science to greatly extend the healthy human life span. The body is simply a complex machine, and we need these better tools for repair and maintenance.
Link: http://www.sciencedaily.com/releases/2004/06/040622014422.htm