Prof. Yair Reisner's latest achievement is growing tiny, functional kidneys in mice out of human stem cells. The trick to growing the kidneys is timing: too early, and the implanted cells grow into a mass of mixed tissue cells; too late, and the body rejects the kidney...If organs could be grown on demand from stem cells, rejection would be a thing of the past...
For people suffering from fatal diseases, such as leukemia or kidney failure, the scarcity of available transplants is often the cause of feelings of hopelessness. Thousands of people in the U.S. alone languish on waiting lists, tied to dialysis tubing, hoping for the transplant that may save their lives.
But if there were a way to make transplants immediately and widely available to all who need them, suddenly, it would be something everyone could afford, and something that would be accessible to all.
This is what Prof. Yair Reisner is trying to achieve. Having recently garnered international attention for growing functional kidneys in mice out of human stem cells, Prof. Reisner has long been finding ways to foil the human immune system into accepting transplants that it would otherwise reject.
Prof. Reisner began his long career by researching alternatives to bone marrow transplants. Since bone marrow harbors immune cells, bone marrow transplants are exceptionally tricky. Not only can the immune system attack the foreign marrow—known as graft rejection—but in some cases, immune cells in the marrow actually attack the patient, causing a sometimes-fatal condition called Graft Versus Host Disease (GVHD). Four out of 10 patients needing a marrow transplant cannot find a matching donor, putting them at risk for either never receiving a transplant, facing devastating complications, or GVHD from a poorly matched donor.
Prof. Reisner tackled this problem by using a hormone to mobilize the patient's bone marrow cells, instead of the traditional method of attempting to kill them with radiation. He then used a special filter to remove every last one of the cells to prepare the patient for the new marrow. By following this procedure with a "megadose" transplant that infuses up to a liter of donated marrow—a quantity large enough to overcome the body's rejection mechanism—he substantially reduced the rejection rate of transplants. Not only did the patients go into remission, but further studies show that they continue to do well. This method saved the lives of leukemia patients and "bubble" children and is now in clinical trials in Europe. At a recent lecture at ACWIS headquarters, Prof. Reisner was pleased to report on clinical success. "Now we have experience to show the patients survived. The rest is up to the clinicians."
Not satisfied with that major advance, Prof. Reisner continues to pursue his interest in circumventing the human immune system to allow it to accept transplants. His latest achievement is growing tiny, functional kidneys in mice out of human stem cells. The trick to growing the kidneys is timing. Implant too early and the implanted cells grow into a mass of mixed tissue cells; too late, and the body rejects the kidney. Prof. Reisner and his team discovered a window of opportunity during which the transplant can occur. The cells already know how to become kidney cells, but are not so developed that the body will recognize and reject them.
If organs could be grown on demand from stem cells, rejection would be a thing of the past, and transplants could be done quickly, safely, and less expensively than now. Over 50,000 people in the U.S. are on the kidney transplant waiting list, and more than 2,000 die annually waiting for a match. Prof. Reisner hopes that eventually organs can be grown to supplement damaged or diseased organs, such as a pancreas that would produce insulin for diabetics. The procedure he developed is now in the pre-clinical study stage. If all goes well, new treatments may ensue in the near future.
Prof. Yair Reisner is the incumbent of the Henry Drake Chair of Immunology.
