McMaster researchers zone in on 'best performing' bone marrow stem cells

Mick Bhatia, in true Canadian sprit, uses a hockey analogy to describe his new findings in blood stem cell regeneration that could make bone marrow transplants happen more frequently and more effective.

"Stem cells are absolute professionals, they're NHL players, all of them regenerate," Bhatia, professor and scientific director of the McMaster Stem Cell and Cancer Research Institute, said. "But in certain arenas, when you have home ice advantage or whatever it is, they perform better."

Translate his hockey scenario to real life and Bhatia's research shows is that blood stem cells at the end of the bone perform better because of their environment, not because of how they are trained — the cells they are nestled up against are sending them a signal to perform better.

Published Thursday in the journal Cell Stem Cell, the results, Bhatia said, show "we can take something that works and make it better, so it can be applied and used for more patients."

Bone marrow transplants have been happening for over 50 years, Bhatia said, as a life-saving treatment for cancers, leukemia, anemia and immune disorders. But the number of stem cells in bone marrow taken from donors is limited, restricting the number of recipients who can go through a treatment.

"Physicians know how they send home so many patients," Bhatia said. "But they were shocked when we posed the question... they said, 'no, we don't know that.' "

Bhatia said he and his team decided to start looking, taking pictures of bones with sophisticated imaging software trying to find where stem cells are situated. These cells are always around other cell types (bone-making, vascular cells). The ends of the bones (the bumpy end opposed to the long shaft, he said) contained the best blood stem cells.

"Up until now, bone marrow transplants are done as if everything in the bone is pretty much the same," he said. "As if there is no difference between the middle and the end of the bone."

But stem cells from different parts of the bone perform at the same level, the team discovered. Bhatia said there are stem cells that regenerate the blood system by producing maybe a million or two million cells over the course of three months, and then stop. A better performing cell, he said, could produce 20 million cells over a period of about three years. The "best performing" cells are the ones located in the bone ends.

Here is how current bone marrow transplants work:The number of cells needed for a successful transplant is based on body weight.

"If a doctor doesn't have enough cells, they won't do the transplant," he said. Right now, Bhatia said, it isn't documented how many transplant candidates are turned away. But he does know this: According to the Canadian Bone Marrow Transplant website, of the 3,000 Canadians who were diagnosed with acute leukemia in 2010, only 50 to 60 received transplants.  

"I don't want to extrapolate too much, but I would have to believe a lot of people would have benefited [from a bone marrow transplant]," Bhatia said.

If doctors knew the stem cells would "pack more punch," they would need less and be able to do more transplants, he said.

Bhatia and his team are planning further research to find out where blood stem cells go — to the end of the bone or the shaft — once transplanted to test whether their hypothesis is correct.

"We want to make it better for more patients," he said. "That's the goal."