Ten years later he isolated the same cell from the bone marrow of people.
Twenty five years later, that single cell Weissman isolated—called a blood-forming stem cell or, if you want to get technical, a hematopoietic stem cell—is the basis for stem cell transplants to treat cancer and is being tested for a range of other diseases.
Weissman wasn't the first to show that the cells exist. That honor goes to James Till and Ernest McCulloch of the Ontario Cancer Institute. But Weissman was the first to learn how to isolate the cells in the lab.
Ruthann Richter at Stanford wrote an excellent profile about Weissman's discoveries for their magazine. In it, she writes:
While Weissman was busy at Stanford as a medical student, the Toronto researchers – James Till, PhD, and Ernest McCulloch, MD – were searching for a remedy for the radiation effects observed in post-war Japan. In doing so, the researchers delivered lethal radiation doses to laboratory mice and were able to rescue them with injections of fresh bone marrow, which completely rebuilt the animals’ stores of red and white blood cells. When the scientists used genetic markers to track the origins of the new blood cells, they found that all the cells emanated from a single source; this, they knew, had to be a stem cell.Having laid hands on that elusive cell, scientists could then use them to replace the bone marrow in patients after cancer treatment. Recently, scientists have begun testing ways of removing the blood-forming stem cells from people with diseases like HIV/AIDS or sickle cell disease, making changes to those cells then returning them to the patient where the cells will be able to fight the disease.
This rare, blood-forming cell had another distinguishing quality, the researchers found: It had the ability to renew itself, thus serving as a constant source of replenishment for the blood. They now had indirect proof that this type of cell existed and they estimated it comprised one of every 2,000 cells in the bone marrow. But they could not lay their hands on the cell itself.
Weissman now has several awards from CIRM developing approaches to treating disease that all came out of that initial discovery 25 years ago.