By far the predominant stem cell therapy today is a bone marrow transplant. The 60,000 people who receive a transplant this year have Nobel Laureate E. Donnall Thomas to thank for the treatment.
Thomas, who died this week, began working on bone marrow transplants back in the 1950s, when the prevailing wisdom held that no human organs could be transplanted, much less bone marrow. An obituary in the Seattle Times quoted Thomas:
“In the 1960s in particular and even into the 1970s, there were very responsible physicians who said this would never work. Some suggested it shouldn’t go on as an experimental thing.”
When the millionth person receives a transplant this year, I’m sure that person will be grateful that Thomas ignored the conventional wisdom and continued those experiments.
A bone marrow transplant works because blood-forming stem cells in the bone marrow, taken from either from a donor or from the patient, are transferred to someone with leukemia or other blood diseases, and those stem cells replace the person’s diseased blood system with a healthy one. Since the 1970s, when the first transplant between unrelated people was successful, scientists have incrementally improved the risky technique and expanded its range of use.
CIRM is part of that expansion. Our grantees are developing new ways of genetically engineering the blood-forming stem cells before transplantation to fix genetic diseases like sickle cell disease or to make cells resistant to HIV. Other scientists are working with cord blood cells, which contain the blood-forming stem cells taken from a baby’s umbilical cord at birth. These cells, like adult blood-forming stem cells, have proven widely useful in treating a range of diseases.
Today, diverse stem cell types are now beginning to enter clinical trials. Neural stem cells from the brain, mesenchymal stem cells from bone marrow or fat, and cells generated from embryonic stem cells and reprogrammed iPS cells are among those that are either in or nearing clinical trials.
When Thomas’ work entered clinical trials in the 1950s and 1960s, nobody knew how many lives that controversial therapy would save. Fifty years from now, I wonder which of today’s prospective therapies will be as commonplace. We won’t know until stem cell scientists do as Thomas did: keep trying.