Dynamic Change About Apolipoprotein E Synthetic And The Mechanism Of ApoE On Astrocytes After Spinal Cord Injury

Objectives:The study aimed to explore the effect of ApoE on motor function restoration and state of Astrocytes in wild type and ApoE knockout mice with SCI.The study purpose also encompasses the investigation of its pathophysiological mechanism,to provide a theoretical basis for the effect of ApoE in the CNS.Method:Using the brain stalk device,it produced the animal model with SCI in C57/BL6 mice.Three study groups were devised to investigate the effect of ApoE:Sham operation group(simple laminectomy,absent SCI),wild-type group(present SCI)and ApoE-/-group with SCI.Determined by Western blotting and reverse transcription-PCR in wild-type mice,the level of gene expression of ApoE protein and mRNA during the recovery was quantitatively recorded.BBB function scores were also performed daily until the experiment terminated to monitor its motor function recovery status.Hematoxylin-eosin staining(H&E)indicated the areas of SCI to observe its oedema and inflammatory responses.Lastly,the changes in the expression of the glial fibrillary acidic protein,the marker of Astrocytes,were analysed by Western blotting and Immunofluorescence technique;ultimately observing the growth of nerve fibres.Results:1.The level of gene expression of ApoE protein and mRNA in wild-type C57/BL6 mice increased from the third day onwards,especially between days 7 and 14 with the Sham group(P<0.01).The concentration of ApoE mRNA peaked on the 7th day,with the highest level of ApoE protein on the 14th day.Despite the decreased levels of ApoE on the 28th day,it was nevertheless superior to that on the first day after injury in the Sham operation group(P<0.05).2.The BBB score showed favourable results towards the wild-type mice over the ApoE-/-mice on the 7th day after injury.There was a significant difference on the 14th day,which narrowed on the 28th day(P<0.05).This development indicated a faster recovery rate of hind limb function in wild-type mice than in ApoE-/-mice.3.In comparison to ApoE-/-mice,the structure of the injured spinal cord in wild-type mice was more restored.Evidently,the wild-type mice showed lighter nuclear pyknosis,and the presence of visible,clear and relatively regular-shaped cytoplasmic nucleus.Meanwhile,the tissue structure of ApoE-/-mice showed a lack of organisation;accompanied with extensive oedema,severely condensed and dissipated nucleus,and an increased inflammatory cell infiltration,4.The Western Blot showed elevated gene expression of GFAP protein in all study groups after injury.The expression of GFAP in ApoE-/-mice was significantly higher than the wild-type mice on the 7th day,14th day and 28th day.5.The Immunofluorescence technique showed a surpassing level of GFAP-positive cells in ApoE-/-mice than in wild-type mice.Similarly,the ApoE-/-group demonstrated stronger Astrogliosis with a greater number of axons.Thus,the ApoE-/-mice had a higher capacity for activating Astrocytes than wild-type mice.Conclusion:1.The significant elevation was found in gene expression of ApoE in C57/BL6 mice with the progression of the injury.2.The BBB score indicated the therapeutic potential of ApoE on nerve damage repair from SCI.Compared with the wild-type mice,a slower recovery rate of hind limb motor function and an increase in the inflammatory response were observed in ApoE-/-group.3.There is a possible correlation between the repair of SCI with ApoE and the reduction of Astrocyte reactivity.Hence,the profound association between ApoE and Astrocytes may be a valuable therapeutic target for developing an improved SCI therapy.