Behavioral, histological, and ex vivo magnetic resonance imaging assessment of graded contusion spinal cord injury in mice

Abstract

This study characterized the Infinite Horizon (IH) Impactor for use in mouse models of contusion spinal cord injury (SCI), and investigated the feasibility and reliability of using magnetic resonance imaging (MRI) as a method to accurately measure lesion volume after mouse contusion SCI. Eight-week-old female C57Bl/6 mice received a mild (30 kilodyne), moderate (50 kilodyne), or severe (70 kilodyne) contusion injury at the T9 vertebral level. Uninjured control mice received a T9 laminectomy only. Functional recovery was assessed using the Basso, Beattie, Bresnahan (BBB) and Basso Mouse Scale (BMS) open-field locomotor rating scales. Next, 4% paraformaldehyde-perfused spinal cords were collected between the T6 and T12 spinal roots, and stored in phosphate-buffered saline (PBS) at 4 degrees C until MRI analysis. MRI lesion volumes were determined using T1-weighted images on a 7-Tesla MRI. Histology was performed on 20-microm polyester wax-embedded sections processed from the same spinal cords for stereological determination of fibronectin lesion volume and myelin basic protein spared white matter volume. Area of spared white matter at the epicenter was also analyzed. The results demonstrated that the IH Impactor produced precise, graded contusion SCI in mice. Lesion volumes were positively correlated with force of impact, and negatively correlated with spared white matter and functional recovery. Additionally, similar lesion volumes were detected using fibronectin staining and MRI analysis, although MRI may be more sensitive for milder injuries. These results give researchers more options in how to analyze spinal cord injuries in animal models.