The future of organ transplantation.

No challenge in medicine can be more urgent than the devising of new strategies for replacing organs. The need for organ replacement not only exceeds by far the supply of organs available for transplantation, the need is likely to increase dramatically. The induction of tolerance to spare transplanted organs and the use of animal organs, i.e. xenotransplantation, could help address this problem but neither appears close to application. Here we discuss a strategy involving the sequential generation of pleuripotent stem cells, formation of human organs in an adoptive xenogeneic host, the harvesting of human cells, tissues or organs from that host and implantation into the individual from whom the stem cells were obtained as one potential way to generate histocompatible organs. We discuss as well the promise, limitations and uncertainties of these steps. This approach, while speculative and perhaps unlikely, may lead to development of further new technologies and insights, the pursuit of which could provide new approaches to replacing organ function.