McMaster researchers have found one more reason to exercise: working out triggers
influential stem cells to become bone instead of fat, improving overall health by
boosting the body's capacity to make blood.

The body's mesenchymal stem cells are most likely to become fat or bone, depending
on which path they follow.

Using treadmill-conditioned mice, a team led by the Department of Kinesiology's Gianni
Parise has shown that aerobic exercise triggers those cells to become bone more often
than fat.

The exercising mice ran less than an hour, three times a week, enough time to have a
significant impact on their blood production, said Parise, an associate professor.

In sedentary mice, the same stem cells were more likely to become fat, impairing blood
production in the marrow cavities of bones.

The research appears in a new paper published by the Journal of the Federation of
American Societies for Experimental Biology.

“The interesting thing was that a modest exercise program was able to significantly
increase blood cells in the marrow and in circulation,” said Parise. “What we're
suggesting is that exercise is a potent stimulus – enough of a stimulus to actually
trigger a switch in these mesenchymal stem cells.”

The composition of cells in the bone marrow cavity has an important influence on the
productivity of blood stem cells.

In ideal conditions, blood stem cells create healthy blood that boosts the immune
system, permits the efficient uptake of oxygen, and improves the ability to clot wounds.
Bone cells improve the climate for blood stem cells to make blood.

But when fat cells start to fill the bone marrow cavity — a common symptom of
sedentary behavior — blood stem cells become less productive, and conditions such as
anemia can result.

The findings add to the growing list of established benefits of exercise, Parise said, and
suggest that novel non-medicinal treatments for blood-related disorders may be in the
future.

“Some of the impact of exercise is comparable to what we see with pharmaceutical
intervention,” he said. “Exercise has the ability to impact stem cell biology. It has the
ability to influence how they differentiate.”