Magnetic resonance imaging tracking and assessing repair function of the bone marrow mesenchymal stem cells transplantation in a rat model of spinal cord injury.

The transplantation of bone marrow mesenchymal stem cells (BMSCs) to repair spinal cord injury (SCI) has become a promising therapy. However, there is still a lack of visual evidence directly implicating the transplanted cells as the source of the improvement of spinal cord function. In this study, BMSCs were labeled with NF-200 promoter and lipase-activated gadolinium-containing nanoparticles (Gd-DTPA-FA). Double labeled BMSCs were implanted into spinal cord transaction injury in rat models in situ, the function recovery was evaluated on 1st, 7th, 14th, 28 th days by MRI, Diffusion Tensor Imaing, CT imaging and post-processing, and histological observations. BBB scores were used for assessing function recovery. After transplantation of BMSCs, the hypersignal emerged in spinal cord in T1WI starting at day 7 that was focused at the injection site, which then increased and extended until day 14. Subsequently, the increased signal intensity area rapidly spread from the injection site to entire injured segment lasting four weeks. The diffusion tensor tractography and histological analysis both showed the nerve fibre from dividing to connecting partly. Immunofluorescence showed higher expression of NF-200 in Repaired group than Injury group. Electron microscopy showed detachment and loose of myelin lamellar getting better in Repaired group compared with the Injury group. BBB scores in Repaired group were significantly higher than those of injury animals. Our study suggests that the migration and distribution of Gd-DTPA-FA labeled BMSCs can be tracked using MRI. Transplantation of BMSCs represents a promising potential strategy for the repair of SCI.