| Objective A gradual improvement in neonatal intensive care, resulting in increased survival rates of preterm infants, has been achieved. However, preterm infants exposure to the extrauterine environment negatively affects the brains’ developmental trajectory. It found that infection was an important risk factor for white matter damage in preterm infants, which resulted in poor prognosis of nervous system. So far, most studies have either used conventional T1-weighted or T2-weighted imaging to study white matter damage. With the rapid development of the level of medical imaging technology, diffusion weighted imaging has been unisersally acknowledged in the diagnosis of the acute brain lessions. In this study, we developed a 3-day-old rat model of infection using lipopolysaccharide to obervation effects of infection on myelin associated glycoprotein(MAG) and nuclear transcription factor-kappa B(NF-КB) in the SD rat brain and to explore the pathogenesis of white matter lesions in the perinatal period and clarify the diagnostic value of DWI.Methods The 3-day-old SD rat pups(provided by the experimental animal center of Henan province), regardless of male and female were randomly divided into experimental group(50) and control group(50). An i.p. injection of LPS(2mg/kg) was administered to 3-day-old(P3) Sprague-Dawley rat pups.The control rats were injected with the same volume of saline. Then,two groups of SD rat pups were given magnetic resonance imaging at 6h(after intraperitoneal injection of drugs), 1d, 3d, 7d, 12 d and taken the brain tissue. Application of hematoxylin eosin stain and immunohistochemical method to research the pathological changes of all ages newborn rat pups about brain white matter, and expression charactertics of MAG and NF-КB, as well as conventional MRI and DWI detection.Additional, collected 56 preterm infants with WMD from our hospital’s neonatal ward and 12 normal full-term infants, both of them underwent T2 WI and DWI examination. At the 40 weeks corrected gestational age, the conventional MRI in brain, to evaluate the brain development and follow-up examinations in preterm infants with cerebral white matter damage by total maturation scores.Results1. The pathological change in different groups of SD rat brain tissuesIn the control group, SD rat in the white matter areas of the brain showed that structure closely, glial cells arranged in neat, large nucleus, small cytoplasm. 6h, 1d experimental group offspring of white matter changes in the organizational structure is not obvious; the experimental group of 3d visible swelling of the cell body, cell sparse, disorganized, unclear structure; the experimental group of 7d and 12 d obviously sparse white matter structures, nerve fibers toward disorder, uneven thickness, visible cytoplasm loose,large pathchy necrosis.2. Expression of MAG and NF-КB of brain tissue of SD rats in each groupCompared with control group:the expression of MAG and NF-КB increased obviously in each group, the difference has statistic significance(P <0.05). The expression of MAG reached a peak at 7d, the expression of 12 d was lower than 7d, there was statistical significance(P <0.05), the expression of NF-КB at 3d reached a peak, the experimental group of 7d and 12 d were decreased, the difference has statistic significance(P <0.05).3. The study of DWI in SD ratsConventional MRI examination in the control group and the experimental group, there were not markedly abnormal in the T2 WI. Experimental group of 6h, 1d, 3d, 7d group on DWI images: the areas of paraventricular, hippocampus, and corpus callosum showed these high signal varied in shapes and size, each time’s control group didn’t seen obviously and unusually change. Using independent sample t test, 6h, 1d, 3d, 7d group compared with the control group, measured ADC values were statistically significant(P <0.05). There was no significant difference bettween the experimental group of 12 d and the control group(P >0.05). Different parts of the experimental and control groups were compared using ANOVA, the difference was statistically significant(P <0.05). 4. The study of DWI in preterm infants with white matter injuryThe imaging of 56 preterm infants, 26 cases were found the focal WMD on DWI, 21 cases showed the wide WMD on DWI, 9 cases showed the diffuse WMD on DWI. TMS of infants with white matter damage were significantly lower than normal full term newborns, these infants developed retardation in myelination and the cortical maturation, there was no significant difference in germinal matrix and bands of migrating glial cell migration.Conclusions1.To successful estabish brain lesion of SD rats by intraperitoneal injection with lipopolysaccharide, pathological changes in brain tissue were observed with microscope.2.Compared with routine MRI, DWI could be early found white matter damage, it was very useful method in the diagnosis of SD rats and preterm infants.3.Comared with absence of brain lesion group, TMS is signifantly lower in the cerebral white matter damage group. |
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