Easter Elizabeth
Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, and North Carolina State University, Raleigh, North Carolina.
Proc Natl Conf Undergrad Res. 2017 Apr;2017:642-649.
Bone is a highly vascularized tissue that requires adequate blood perfusion to remodel in response to loading and heal after fracturing. Laser Doppler flowmetry (LDF) is a technique that has been validated to measure blood flow in mouse hindlimb bones , but to date it has only been used for measurements at a single timepoint, because the invasive surgery required to place the probe on the bone surface induced prolonged inflammation. The goal of this study was to determine if a modified, minimally invasive LDF technique could be performed repeatedly at the same bone site without altering gait patterns or causing substantial inflammation at the wound site, which would confound bone measurements in studies using exercise therapy. Twenty 14-week-old C57Bl/6J mice were divided into two activity groups and two LDF groups for 4 weeks prior to sacrifice. The exercise group performed daily treadmill exercise (30 min/day, 5 days/week), while the sedentary group spent a matched time on a stationary treadmill. Mice were further divided into either a repeated LDF group, which received an LDF procedure weekly (n=5 per activity group), or an endpoint LDF group, which underwent the LDF procedure only once (n=5 per activity group). LDF measurements were taken on the anteromedial surface of the right proximal tibial metaphysis. The effect of the LDF procedure was assessed with measures of blood perfusion, wound healing, and gait kinematics. Repeated LDF procedures did not alter blood perfusion measurements across weeks, either in the exercise or sedentary group. Wound area was measured from weekly photographs to determine the extent of inflammation. All wounds were fully closed within one week by the time of the next procedure. Changes in mouse gait kinematics were analyzed using weekly high-speed video of treadmill running. Duty cycle and phase dispersion remained constant from week to week with repeated LDF procedures. These results validated that the modified, minimally invasive LDF technique can be used for serial measurements of intraosseous blood perfusion without inducing potentially confounding effects of inflammation or altered gait or undesired changes in the perfusion itself. These findings will enable future longitudinal studies of bone perfusion with various pathologies, such as diabetes and stroke.
骨骼是一种血管高度丰富的组织，需要充足的血液灌注以响应负荷进行重塑，并在骨折后愈合。激光多普勒血流仪（LDF）是一种已被验证可用于测量小鼠后肢骨骼血流的技术，但迄今为止它仅用于单个时间点的测量，因为将探头放置在骨表面所需的侵入性手术会引发长时间的炎症。本研究的目的是确定一种改良的、微创的LDF技术是否可以在同一骨部位重复进行，而不改变步态模式或在伤口部位引起大量炎症，因为这会在使用运动疗法的研究中混淆骨测量结果。在处死前4周，将20只14周龄的C57Bl/6J小鼠分为两个活动组和两个LDF组。运动组每天进行跑步机运动（30分钟/天，5天/周），而久坐组在固定的跑步机上度过相同的时间。小鼠进一步分为重复LDF组，每周接受一次LDF操作（每个活动组n = 5），或终点LDF组，仅接受一次LDF操作（每个活动组n = 5）。在右胫骨近端干骺端的前内侧表面进行LDF测量。通过血液灌注、伤口愈合和步态运动学测量来评估LDF操作的效果。重复的LDF操作在数周内均未改变运动组或久坐组的血液灌注测量结果。通过每周的照片测量伤口面积以确定炎症程度。在下一次操作时，所有伤口在一周内完全愈合。使用跑步机跑步的每周高速视频分析小鼠步态运动学的变化。重复LDF操作时，占空比和相位离散度每周保持恒定。这些结果证实，改良的微创LDF技术可用于连续测量骨内血液灌注，而不会引起炎症的潜在混淆效应、步态改变或灌注本身的不良变化。这些发现将有助于未来对各种病理状态（如糖尿病和中风）下的骨灌注进行纵向研究。
