The Influence of Physical Forces on Progenitor Cell Migration, Proliferation and Differentiation in Fracture Repair PRINCIPAL INVESTIGATOR:

The local mechanical environment and the availability of mesenchymal stem cells (MSCs)have both been shown to be important factors in bone fracture healing. This study was designed toinvestigate how the timing of an applied axial displacement across a healing fracture affects callusproperties as well as the migration of systemically introduced MSCs. Bilateral osteotomies werecreated in male, Sprague-Dawley rats. Exogenous MSCs were injected via the tail vein, and acontrolled micro-motion was applied to one defect starting 0, 3, 10, or 24 days after surgery. Theresults showed that fractures stimulated 10 days after surgery had more mineral, less cartilage, andgreater mechanical properties at 48 days than other groups. Populations of MSCs were found inosteotomies 48 days after surgery, with the exception of the group that was stimulated 10 daysafter surgery. These results demonstrate that the timing of mechanical stimulation affects thephysical properties of the callus and the migration of MSCs to the fracture site. Suggested Reviewers: Cato Laurencin M.D., Ph.D.