Ottawa rehabilitation researchers find simulated space travel increases bone marrow fat

November 12, 2009

As a specialist at The Ottawa Hospital Rehabilitation Centre, Dr. Guy Trudel has always been interested in improving how patients recover from long term injuries and immobility, so when an opportunity arose to study a similar problem in the unique context of space travel, he jumped at the chance. His results, published in the Journal of Applied Physiology, suggest that simulated space travel may accelerate the accumulation of fat in the bone marrow and this could affect the production of blood cells.

The research was part of the Women International Space Simulation for Exploration (WISE) study, which was funded by space agencies around the world, including the Canadian Space Agency, as well as the Canadian Institutes of Health Research. The study took place in France in 2005, with 24 healthy female participants lying in beds at a slight head-down angle for 60 days. This position was chosen because it simulates some of the effects of lack of gravity, including the shift of body fluids into the upper part of the body. Scientists from around the world submitted research proposals for the WISE project and the Trudel laboratory’s proposal to study fat accumulation in the bone marrow was selected.

Dr. Trudel’s results show that the fraction of fat in the women’s bone marrow increased by an average of nine per cent over the course of the study, and it was still significantly elevated a year after the immobilization ended. Although no non-immobilized controls were included in the study, previous research suggests that the rate of bone marrow fat accumulation seen in this study was 25 times greater than the normal level. Looking at it another way, 60 days of bed rest resulted in the women’s bone marrow aging the equivalent of four years. This occurred despite a decrease in the women’s overall body fat during the study.

“Our results suggest that situations of long term immobilization may irreversibly increase the amount of fat in the bone marrow,” said Dr. Trudel, who is also a clinical investigator at the Ottawa Hospital Research Institute and a Professor of Medicine at the University of Ottawa. “This was a small study, but it is very intriguing, so we need to conduct further research in various settings including in space to confirm the findings.”

Dr. Trudel also examined the levels of various blood components in the volunteers, since bone marrow is the primary site where new blood cells are produced. He found that the concentration of red blood cells went up initially during bed rest, but returned to normal levels a year later. The overall concentration of white blood cells did not change during the course of the study, but it went up after the study ended and stayed up for at least a year.

“One plausible explanation for our results is that a factor in bone marrow fat may stimulate the production of blood cells, but we will need to do more research to investigate this,” said Dr. Trudel. “Eventually, we hope that our findings will help us develop better strategies to help people recover from both long term immobilizing injuries and space travel.”

“This is an interesting and potentially very important study,” said Dr. Jane Aubin, Scientific Director of the Canadian Institutes of Health Research's Institute of Musculoskeletal Health and Arthritis. “While the mechanism is not well understood, we know that bone marrow fat increases in bone diseases such as osteoporosis and in response to treatments that reduce bone density such as chronic glucocorticoid therapy. By reinforcing our understanding of the complex relationship between bone, bone marrow and blood cell production, Dr. Trudel's work may help develop new treatments for bone diseases.”

About the Ottawa Hospital Research Institute
The Ottawa Hospital Research Institute (OHRI) is the research arm of The Ottawa Hospital and is an affiliated institute of the University of Ottawa, closely associated with the University’s Faculties of Medicine and Health Sciences. The OHRI includes more than 1,500 scientists, clinical investigators, graduate students, postdoctoral fellows and staff conducting research to improve the understanding, prevention, diagnosis and treatment of human disease.

About the Canadian Institutes of Health Research
The Canadian Institutes of Health Research (CIHR) is the Government of Canada’s agency for health research. CIHR’s mission is to create new scientific knowledge and to enable its translation into improved health, more effective health services and products, and a strengthened Canadian health-care system. Composed of 13 Institutes, CIHR provides leadership and support to nearly 12,000 health researchers and trainees across Canada.

Media contacts
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David Coulombe, CIHR Media Relations