Expression of Slit and Robo during remodeling of corticospinal tract in cervical spinal cord in middle cerebral artery occlusion rats.

Zhenhao Ying,Guoli Zhang,Xueyun Pang,Wei Liu,Weiming Zhu,Xin Li,Wenjun Jiang,Junxuan Wu

doi:10.1007/s11033-021-06803-1

Abstract

Slits and Robos were associated with the generation of axons of corticospinal tract during the corticospinal tract (CST) remodeling after the cerebral ischemic stroke (CIS). However, little is known about the mechanism of CST remodeling. In this study, we detected the expression of Slits and Robos in middle cerebral artery occlusion (MCAO) rats to investigate the roles of Slits and Robos in the CIS. MCAO model was established using modified Zea Longa method. Beam walking test (BWT) was conducted to evaluate the motor function. The images of the track of cortical spinal cord beam on day 7, 14 and 21 were observed by anterograde CST tracing. Biopinylated dextan amine (BDA) was used to mark CST anterogradely. Expression of GAP-43 mRNA and GAP-43 protein in cervical spinal cord was detected by Real-Time PCR and Western blot analysis, respectively. The expression of Slit1, Slit2 and Robo1 in cervical spinal cord was detected by immunofluorescence staining. The scores in the model group were significantly reduced compared to sham-operation group on day 7 (P < 0.001), 14 (P < 0.001) and 21 (P < 0.001), respectively. There was no significant difference in the score on day 7, 14 and 21 of the sham-operation groups (P > 0.05). In contrast, significant increase was noticed in the scores in model group, presenting a time-dependent manner. More CST staining fibers could be observed at the degenerative side in the model group compared with that of the sham-operation group on day 21. GAP-43 mRNA expression in the model group showed significant increase compared to that of sham-operation group on day 14 (P = 0.015) and 21days (P = 0.002). The expression of GAP-43 protein in model group showed significant increase compared to that of sham-operation group on day 14 (P = 0.022) and day 21 (P = 0.008), respectively. The expression of Slit1 and Slit2 showed increase on day 14 and day 21, while the expression of Robo1 showed significant decrease in MCAO rats. Up-regulation of Slit1 and Slit2 and the downregulation of Robo1 may be related to the axons of CST midline crossing in spinal cord of MCAO rat during the spontaneous recovery of impaired motor function.

Highlights

Slits and Robos were associated with the generation of axons of corticospinal tract during the corticospinal tract (CST) remodeling after the cerebral ischemic stroke (CIS)
This implied that motor function in middle cerebral artery occlusion (MCAO) rats showed significant reduction after surgery compared to that of sham-operation group
These tests indicated that the motor function of MCAO rats could spontaneously recovered to some extent

Summary

Introduction

Slits and Robos were associated with the generation of axons of corticospinal tract during the corticospinal tract (CST) remodeling after the cerebral ischemic stroke (CIS). We detected the expression of Slits and Robos in middle cerebral artery occlusion (MCAO) rats to investigate the roles of Slits and Robos in the CIS. Slits (i.e. Slit 1-3) and Robo receptors (i.e. Robo1-4) are crucial for the passing of axons through the midline of spinal cord that is closely related to the CST. In focal cerebral infarction rats, electroacupuncture intervention significantly improved the neurological function and obviously upregulated the expression of cerebral Slit 2 and Robo 1 proteins [5]. The roles of Slit-Robo signaling pathway in the focal cerebral infarction are still not well defined

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