Validating Laser Doppler Flowmetry for In Vivo Longitudinal Measurements of Bone Blood Perfusion

Elizabeth Easter

Abstract


Bone is a highly vascularized tissue that requires adequate blood perfusion to maintain structural integrity, remodel in response to loading, and heal after fractures. Some pathologies associated with vascular dysfunction are also associated with bone loss, such as atherosclerosis. Exercise is an important stimulator of bone remodeling and angiogenesis, indicating that it may have therapeutic potential in patients suffering from cardiovascular disease related bone loss. Laser Doppler flowmetry (LDF) has been used to measure blood flow in mouse bones in vivo but the surgery was invasive and non-repeatable. Our goal is to determine if our minimally invasive LDF technique can be used to measure changes in blood perfusion. Twenty 14-week-old C57Bl/6J mice were divided into two activity groups, subjected either to an active treadmill at 12 m/min (Exercise, n=10) or a stationary treadmill (Sedentary, n=10) for 4 weeks (30 min/day, 5 days/week). Mice were further divided into two surgical groups, receiving an LDF procedure either weekly for 4 weeks (Repeated LDF, n=5 per activity group) or only once at the endpoint (Endpoint LDF, n=5 per activity group). LDF measurements were taken on the anteromedial surface of the left tibial metaphysis, a superficial site with active bone metabolism. The effect of the LDF procedure is being assessed with measures of inflammation, wound healing, and gait kinematics. Serum levels of a pro-inflammatory marker (interleukin 6) will be quantified using blood samples collected from all groups on LDF protocol days following the procedure. Wound area will be measured from weekly photographs to determine the extent of inflammation and healing progression. Limping and changes in mouse gait kinematics will be analyzed using weekly high-speed video of treadmill running. If confounding effects are not found, the LDF procedure will be used in future research to assess the effect of pathologies on longitudinal osteovascular blood perfusion.

Keywords


Blood flow; Bone; laser Doppler flowmetry

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