Magnetic resonance diffusion tensor imaging evaluation of electroacupuncture and stem cell therapy for acute peripheral nerve injury in rats
Objective: To evaluate the therapeutic effect of electroacupuncture and stem cell transplantation on acute peripheral nerve injury by magnetic resonance diffusion tensor imaging (DTI). Materials and Methods: A total of 48 adult SD rats with successful modeling were randomly divided into an electroacupuncture (EA) group, a stem cell group and a control group, 16 rats in each group. The rats in the EA group were treated with EA at Huantiao (GB 30) and Zusanli (ST 36). Rats in the stem cell group were microinjected with 3μL saline suspension containing about 5×105 bone marrow mesenchymal stem cells under the epineurium at the injury site. The control group was microinjected with the same volume of saline. Multi-parametric magnetic resonance imaging [DTI and T2-weighted fat saturation (T2WI-FS)], histological evaluation and immunohistochemical analysis were used to monitor the changes of nerve structure (including nerve diameter, myelin sheath thickness and morphological changes, axonal continuity recovery). Somatic functional index (SFI) and gait trajectory analysis were used to evaluate the motor function of sciatic nerve. The differences of T2 value, DTI parameters [fractional anisotropy (FA), radial diffusivity (RD)] and SFI values among different experimental groups were analyzed by repeated measures one-way ANOVA. Bonferroni test was used to correct the threshold results of multiple testing at different time points. Results: At the first week after acute peripheral nerve injury, the FA value of all groups decreased significantly, and then gradually increased, and returned to the normal level at the fourth week. The mean value of RD increased significantly within 1 week after surgery, then gradually decreased, and returned to the normal level at the 4th week. The recovery of rats in the EA group and the stem cell group was better than that in the control group at different time points (2-4 weeks) after operation, and the recovery in the EA group was the most significant (P<0.001). T2WI-FS showed that at 1, 2, and 4 weeks after operation, the EA group and the stem cell group had significant differences in the speed of nerve edema regression compared with the control group (P<0.001). The nerve diameter and T2 value increased significantly in the first week after operation, then gradually decreased, and returned to the normal level in the fourth week. Toluidine blue staining and SPRR1A axonal staining indicated that the nerve fiber continuity in the EA group recovered most rapidly, followed by the stem cell group. Conclusions: The therapeutic effect of electroacupuncture on acute peripheral nerve injury is similar to that of stem cell transplantation, and it has great advantages in reducing edema and inflammatory response. DTI parameters FA and RD values are imaging markers of myelin integrity.
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