Expression of RGMb in brain tissue of MCAO rats and its relationship with axonal regeneration.

OBJECTIVE: To investigate the changes in the expression of repulsive guidance molecule b (RGMb) in brain tissue of rats with ischemic cerebral infarction and determine its relationship with axonal regeneration, synapse remodeling and magnetic resonance imaging (MRI) parameters with magnetic resonance diffusion tensor imaging as the dynamic continuous monitoring method in vivo, so as to explore the pathophysiological mechanism of the occurrence, development and prognosis of cerebral infarction.

METHODS: Ninety Sprague-Dawley (SD) rats were randomly divided into six groups, namely control group, middle cerebral artery occlusion (MCAO) 12-h group, MCAO 24-h group, MCAO 48-h group, MCAO 7-day group and MCAO 10-day group, each of 15 animals. Rats were examined by head MRI at corresponding time points, followed by measurement of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values. Subsequently, brain tissues were taken to detect the expression of RGMb, axonal regeneration and synapse remodeling.

RESULTS: After infarction, ADC and FA values of the infarcted core area were lower in rats of each group compared to those in rats of normal group (P<0.05), which was lowest at 12h. The positive expressions of RGMb and synaptophysin were continuously increased from the 12th hour after operation, which reached a peak at 48h; while axonas was gradually reduced after operation in each group, which revealed the most obvious damage in the MCAO 24-h group. The protein expression of RGMb was negatively correlated with MRI parameters and axon growth.

CONCLUSION: After supratentorial cerebral infarction, the expressions of RGMb and synaptophysin were up-regulated in rats, neurofilament protein (NF-200) expression was decreased, and MRI parameters (ADC and FA values) were reduced, indicating that RGMb protein may be involved in the regeneration and remodeling of axons and synapses, and exert an important role in pathophysiological processes such as nerve regeneration disturbance and neuron apoptosis after cerebral ischemia injury. In vivo MRI can be a noninvasive technique to monitor the areas of cerebral infarction and the recovery of neurological function.