Effects of intravenously injected tanshinone IIA on neurological function recovery of adult rat after spinal cord injury

YANG Yong-dong; YU Xing; GAO Yu-shan

doi:10.3969/j.issn.2095-252X.2016.06.003

Abstract：Objective To determine the impact of tanshinone IIA ( TIIA ) on the recovery of hindlimb neurological disorders and to explore the possible mechanisms. Methods Adult female Sprague-Dawley rats ( n = 45 ) were randomly divided into 4 groups: Sham group ( laminectomy only ), SCI group ( T9 spinal cord contusive injury ), SCI / TIIA group ( SCI with intravenous injection of TIIA [ 20 mg / kg ] from 1 to 7 days post-injury at the same time ), SCI / MP group ( SCI with intravenous injection of methylprednisolone [ 30 mg / kg ] once post-injury ). SCI was generated by using NYU injury device with a 10-g weight dropped from a height of 25 mm. Sham group and SCI group were treated with intravenous injection of 1 ml normal saline from 1 to 7 days post-injury at the same time. ( 1 ) Spontaneous locomotion and sensory function of all animals were assessed by the Basso, Beattie, and Bresnahan ( BBB ) open field locomotor test and hot plate test. Transcardiac perfusion fixation were done at 1, 4 and 8 weeks post-SCI. Sections of T9 spinal cord were collected. Then the T9 spinal cord tissue stained with Cresyl Violet for Nissl staining and stained with hematoxylin and eosin for HE staining. Microglia in the injured spinal cord were marked by immunohistochemistry at 7 days and 8 weeks post-SCI. Results ( 1 ) Hindlimb motor function of TIIA group ( 1.91 ± 0.31 ) and MP group ( 3.10 ± 0.41 ) was significantly improved 3 days post-surgery, but MP group was more effective ( P < 0.05 ); at 8 weeks post-surgery, hindlimb motor function of MP group ( 17.00 ± 0.41 ) was still more effective than in TIIA group ( 15.50 ± 0.43 ) ( P < 0.05 ). ( 2 ) Sensory function of MP group ( 4.06 ± 0.26 ) recovered faster than TIIA group ( 4.59 ± 0.71 ) 3 days post-surgery, and the difference was statistically significant ( P < 0.05 ). But TIIA group ( 3.06 ± 0.13 ) showed a trend that sensory function recovers faster than MP group ( 3.14 ± 0.13 ) at 2 weeks post-surgery, almost reached statistical significance ( P > 0.05 ). ( 3 ) In each group, except sham group, microglia contract their processes and transformed from a ramified to an ameboid morphology at 7 days post-surgery. Changes of morphology in TIIA group and MP group were relatively smaller, but the integrated optical density ( IOD ) of macrophage / microglia in TIIA group ( 11.61 ± 2.64 ) and MP group ( 11.88 ± 1.47 ) was reduced significantly compared with SCI group ( 27.22 ± 3.04 ), and the difference was statistically significant ( P < 0.05 ). ( 4 ) In each group, except sham group, microglia transformed from an ameboid to a ramified morphology at 8 weeks post-surgery. The IOD of macrophage / microglia increased in TIIA group ( 2.89 ± 0.12 ) and MP group ( 2.93 ± 0.15 ) compared with SCI group ( 1.58 ± 0.20 ), and the difference was statistically significant ( P < 0.05 ). Conclusions ( 1 ) TIIA possibly promotes the recovery of motor and sensory function of hindlimb in rats after SCI. ( 2 ) TIIA plays a positive role in the recovery of neurological disorder by influencing the macrophage / microglia.