Abstract
OBJECTIVE: Manganese (Mn2+)-enhanced magnetic resonance imaging (MEMRI) is a potentially important tool for assessing neural tissue regeneration after spinal cord injury (SCI). We evaluated the relation between Mn2+ and T1-weighted magnetic resonance (MR) signals in an SCI rat model.
METHODS: Rats were divided into 4 groups with or without SCI (T9-level transection) and with or without Mn2+ injection. Two microliters of 0.2 mol/L MnCl2 was injected into the lateral ventricles. Magnetic resonance imaging (MRI) was performed 60 hours after injection. Signal intensities at cervical, thoracic, and lumbar levels were measured and normalized to the intensity of perivertebral muscles. Spinal cord sections were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for total Mn2+ content. The results of ICP-MS were compared with MR signal intensity.
RESULTS:T1-weighted MR signal intensity and ICP-MS-measured Mn2+ were significantly decreased below the SCI injury site in Mn2+-injected groups with or without SCI, and were similar to intensity and Mn2+ levels of noninjected animals. Signal intensity and Mn2+ concentration tended to decrease from cervical to lumbar spinal levels in the control rats. ICPMS data correlated with MRI results.
CONCLUSION:The results confirmed Mn2+ uptake in the spinal cord after intraventricular injection. T1-weighted MR signal intensity correlates with spinal Mn2+ concentration as measured with ICP-MS. This work establishes the repeatability of MEMRI of the injured spinal cord and makes it possible to compare changes in axonal transport rates through the spinal cord after neuronal regeneration in vivo at different stages. MEMRI in animal models may improve understanding of the factors required to promote spinal cord regeneration.