Experimental study of magnetic resonance targeted myelin probe Gd-DTDAS in multiple sclerotic rat myelin injury model
Objective:To investigate the application value of MRI contrast agent Gd-DTDAS in multiple sclerosis(MS)rat myelin injury model.Materials and Methods:In cell experiments,oligodendrocyte precursor cells(OLN-93)were randomly divided into control group 2(n=3)and lysophosphatidylcholine(LPC)group(n=3),and the cells of LPC group were incubated with 1 mL of 800 μM LPC in a sterile confocal dish for 30 min.Cytotoxicity was evaluated by methyl thiazolyl tetrazolium(MTT),and the absorbance and survival rate of OLN-93 after incubation with Gd-DTDAS for 24 h were calculated.In the uptake experiment,the control group 2 and the LPC group were compared to quantify the uptake value of Gd-DTDAS and the corresponding fluorescence intensity of the two groups.In animal experiments,6-8 week-old SD rats were randomly divided into control group(n=12)and experimental group(n=18),and the left corpus callosum of rats in the experimental group was injected with 1%LPC solution(1%LPC dissolved in PBS).After molding,behavioral observation was performed(1,3,7 d),and T1WI and T2WI sequence scanning were performed 7 d after injecting.Gd-DTDAS staining(n=6)and soaking(n=6)of rat brain tissue were performed according to the MRI abnormal signal site to evaluate the binding of Gd-DTDAS to the myelin site.Among them,the staining experiment was named as control group 3 and experimental group 3,while the soaking experiment group was named as control group 4 and experimental group 4.Gd-DTDAS was injected by tail vein,MRI assessed cerebral myelin sheath changes before and after Gd-DTDAS injection in the experiment group(n=6).Results:In the cytotoxicity experiment,when the concentration of Gd-DTDAS increased to 400 μM,the survival rate of OLN-93 cells was about 95%,and there was no significant difference in cell survival between concentrations(t=4.20,P>0.05).In the cell uptake experiment,both groups of cells could uptake Gd-DTDAS,and the uptake of LPC group was significantly lower than that of the control group 2,and the difference was statistically significant(t=31.75,P<0.01).In vitro experiments,compared with the control group 3,the fluorescence intensity of brain tissue sections in the experiment 3 group stained with Gd-DTDAS decreased significantly,and the difference was statistically significant(U=9,P<0.01).After immersion of brain tissue slices in Gd-DTDAS,the MRI resolution significantly increased in both the control group 4(n=3)and the experiment group 4(n=6),with statistically significant differences(control group 4,t =8.76,P<0.01;experiment group 4,t =2.89,P<0.01).In vivo experiments,MRI T1maps relaxation in the medullary region was significantly reduced after injection compared with before tail vein injection(t =14.46,P<0.01).Conclusions:The myelin probe Gd-DTDAS can better bind to myelin-rich regions,and the myelin sheath can be better targeted for MRI,and can specifically show the damage site of myelin sheath in multiple sclerosis.
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