Semiquantitative Evaluation of Muscle Repair by Diffusion Tensor Imaging in Mice.

Muscle injury is one of the most common traumas in orthopedic and sports medicine. However, there are only a few treatment options with marginal clinical benefits for this condition. Muscle repair after injury involves multiple and complex processes, such as the inflammation phase, regeneration phase, and remodeling phase. To develop a treatment modality and to examine the efficacy of novel interventions and agents for patients with muscle injuries, it is essential to establish a reliable and sensitive method to monitor the changes in muscle structure and status during muscle repair. Diffusion-weighted magnetic resonance imaging has been widely used to assess the diffusivity of water molecules in tissue. When it is used in combination with diffusion tensor imaging (DTI), the microstructure of muscle tissue can be indirectly depicted. In the present study, we evaluated the time-course changes in the diffusivity and anisotropy in muscles by DTI and histology after injury in mice. We found that the diffusivity and anisotropy exhibit distinct kinetics during muscle repair and that these kinetics were significantly altered in mutant mice with a defect in muscle regeneration. Our data show that muscle repair processes can be readily evaluated and monitored by DTI technique and suggest that DTI can be clinically applied for assessing muscle injury and repair in humans. © 2018 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.