Objective: Bone marrow mesenchymal stem cells (BMSCs) play an important role in repairing nerve injury, meanwhile external temperature has significant effect on BMSCs transplantation, proliferation, and differentiation. To investigate the effect of BMSCs transplantation and mild hypothermia on repair of rat spinal cord injury (SCI).
Methods: Forty-five female adult SD rats (weighing 200-250 g) were made the models of hemitransection SCI and divided randomly into 3 groups according to different treatments: group A (SCI group), group B (BMSCs transplantation group), and group C [BMSCs transplantation combined with mild hypothermia (33-35 degrees C) group]. At 1, 2, 4, 6, and 8 weeks after injury, the function of hind limb was evaluated with Basso Beattie and Bresnahan (BBB) score and inclined plane test. At 4 weeks after injury, histopathology and BrdU immunohistochemistry staining were performed. At 8 weeks after injury, horseradish peroxidase (HRP) retrograde nerve trace and transmission electron microscope (TEM) testing were performed to observe the regeneration of axon.
Results: After 4 weeks, the function of hind limb obviously recovered in groups B and C, there were significant differences in BBB score between groups B, C and group A (P < 0.05), between group B and group C (P < 0.05). There was no significant difference (P > 0.05) in tilt angle among 3 groups after 1 and 2 weeks, and there were significant differences (P < 0.05) among 3 groups after 4 weeks. HE staining showed that significant cavity could be seen in group A, little in group B, and no cavity in group C. BrdU immunohistochemistry staining showed that the number of positive cells was 0, 90.54 +/- 6.23, and 121.22 +/- 7.54 in groups A, B, and C, respectively; showing significant differences (P < 0.01) among 3 groups. HRP retrograde neural tracing observation showed that the number of HRP positive nerve fibers was 10.35 +/- 1.72, 43.25 +/- 2.65, and 84.37 +/- 4.59 in groups A, B, and C, respectively, showing significant differences (P < 0.01) among 3 groups. TEM observation showed that a great amount of unmyelinated nerve fibers and myelinated nerve fibers were found in central transverse plane in group C.
Conclusion: The BMSCs transplantation play an important role in promotion of recovering the function of hind limb after SCI, and mild hypothermia has synergism effects.