Many blood disorders, immune disorders and metabolic disorders can be cured with a transplant of hematopoietic (blood-forming) stem cells, also known as bone marrow transplant. But patients must first receive high-dose, whole-body chemotherapy and/or radiation to deplete their own defective stem cells, providing space for the donor cells to engraft. These “conditioning” regimens are highly toxic: they wipe out the immune system, raising infection risk, and can cause anemia, infertility, other organ damage and cancers. And when the donor isn’t an exact match, patients’ immune systems must be suppressed for prolonged periods to prevent rejection.
As a result, most patients either don’t receive a transplant
or must endure serious side effects. But if two new studies bear out in
clinical trials, a far gentler conditioning treatment could enable stem-cell
transplants for a much wider range of disorders, even possibly from unmatched
Since the late 1970s, biologists have known that blood develops in a specific body location. But they’ve wondered why different creatures house their blood stem cells in different places. In humans and other mammals, they’re in the bone. In fish, they’re in the kidney. Why?
Type 1 diabetes is caused by an immune attack on the pancreatic beta cells that produce insulin. To curb the attack, some researchers have tried rebooting patients’ immune systems with an autologous bone-marrow transplant, infusing them with their own blood stem cells. But this method has had only partial success.
“We found that in diabetes, blood stem cells are defective, promoting inflammation and possibly leading to the onset of disease,” says Paolo Fiorina, MD, PhD, of Boston Children’s Hospital, senior investigator on the study.
But they also found that the defect can be fixed — by pre-treating the blood stem cells with small molecules or with gene therapy, to get them to make more of a protein called PD-L1.
In experiments, the treated stem cells homed to the pancreas and reversed hyperglycemia in diabetic mice, curing almost all of them of diabetes in the short term. One third maintained normal blood sugar levels for the duration of their lives. …
When Emily Coughlin complained of a sore knee in May 2009, doctors initially suspected Lyme disease. After antibiotics failed to relieve the pain, Emily was diagnosed with neuroblastoma, a cancer that begins in nerve cells outside the brain, just shy of her fourth birthday. Though neuroblastomia is rare — about 700 new cases occur annually in the United States — it is the most common cancer in infants and toddlers.
Bone marrow transplantation, a.k.a. stem cell transplantation, can offer a cure for certain cancers, blood disorders, immune deficiencies and even metabolic disorders. But it’s a highly toxic procedure, especially when a closely matched marrow donor can’t be found. Using stem cells from umbilical cord blood banked after childbirth could open up many more matching possibilities, making transplantation safer.
But what if the blood stem cells in those units could be supercharged to engraft more efficiently in the bone marrow and grow their numbers faster? That’s been the quest of the Zon lab for the past seven years, in partnership with a see-through zebrafish called Casper. …
A:SCID is a group of disorders that compromise the blood’s T cells, a key component of the immune system that helps the body fight common viral infections, other opportunistic infections and fungal infections. T-cells are also important for the development of antibody responses to bacteria and other microorganisms. A baby born with SCID appears healthy at birth, but once the maternal antibodies that the baby is born with start to wane, the infant is at risk for life-threatening infections. Unless diagnosed and treated—with a stem cell transplant from a healthy donor or a more experimental therapy like gene therapy—babies with SCID typically die before their first birthday. …
For years, the lab of Leonard Zon, MD, director of the Stem Cell Research Program at Boston Children’s Hospital, has sought ways to enhance bone marrow transplants for patients with cancer, serious immune deficiencies and blood disorders. Using zebrafish as a drug-screening platform, the lab has found a number of promising compounds, including one called ProHema that is now in clinical trials.
But truthfully, until now, Zon and his colleagues have largely been flying blind.
“Stem cell and bone marrow transplants are still very much a black box: cells are introduced into a patient and later on we can measure recovery of their blood system, but what happens in between can’t be seen,” says Owen Tamplin, PhD, in the Zon Lab. “Now we have a system where we can actually watch that middle step.” …
As a hematologist, I see all too many children battling blood disorders that are essentially untreatable. Babies with immune deficiencies living life in a virtual bubble, hospitalized again and again for infections their bodies can’t fight. Children disabled by strokes caused by sickle cell disease, or suffering through sickle cell crises that drug treatments can’t completely prevent. Children whose only recourse is to risk a bone marrow transplant—if a suitably matched donor can even be found.
Over the past 20 years, my lab and that of George Daley, MD, PhD, at Boston Children’s Hospital have worked hard to give these children a one-time, potentially curative option—a treatment that begins with patients’ own cells and doesn’t require finding a match. …
One thing that most people don’t realize about stem cell transplants (also called bone marrow or hematopoietic stem cell transplants) is that for patients, the transplant itself is probably the easiest part of the process. The grueling part is the preparation for a transplant, called conditioning.