Purpose Based on multimodal imaging combined with a variety of histological techniques,to visually evaluate the changes of rats brain metabolic microenvironment after cerebral hypoxia and ischemia of prematurity,and to discuss the effects of abnormal lactate metabolism in the brain on oligodendrocyte precursor cells,so as to provide a basis for the early diagnosis and treatment of premature white matter injury(PWMI).Materials and Methods A total of 36 SPF-grade healthy 3-day-old Sprague-Dawley neonatal rats were randomly assigned to the sham surgery(Sham)group and the model(PWMI)group using a random number table method,with 18 rats in each group.A neonatal rat PWMI model was established by hypoxia-ischemia method.Twenty-four hours after modeling,laser speckle imaging was used to monitor cerebral blood flow and blood oxygen changes.Multimodal imaging was used to observe the changes in brain tissue microstructure and metabolism after PWMI.HE staining was used to observe the morphological changes of nerve cells in the white matter of the brain.Enzyme-linked immunosorbent assay was used to detect the changes of lactate content and lactate dehydrogenase activity in the white matter region of the brain after PWMI in neonatal rats.PDGFR-α immunofluorescence staining was used to observe the dynamic changes of the number of oligodendrocyte precursor cells in the subependymal zone after PWMI in neonatal rats.Results Twenty-four hours after modeling,the multimodal imaging results showed that the T2WI and diffusion-weighted imaging on the injured side of the PWMI group showed high intensity,and the relative cerebral blood flow,relative oxygen saturation,relative apparent diffusion coefficient and amide proton transfer(APT)Lorentzian difference value were lower than those in the Sham group(t=29.466,23.522,59.006,54.778,10.263,all P<0.001),and the lactate content was higher than that in the Sham group(t=-7.521,P<0.001).The results of HE staining and enzyme-linked immunosorbent assay showed that the arrangement of nerve cells in the white matter area of the injured side of the brain in the PWMI group was loose and disordered.The lactate content and lactate dehydrogenase activity were higher than those in the Sham group(t=-6.079,-10.548,both P<0.001).The results of immunofluorescence staining showed that the number of PDGFR-α+cells in the subependymal zone of the damaged side of the PWMI group was higher than that of the Sham group at 24 hours after modeling,and lower than that in the Sham group at 11 days after modeling(t=-8.386,6.676,both P<0.001).The correlation analysis between the lactate content and APT Lorentzian difference value in the brain and the number of oligodendrocyte precursor cells in the brain 11 days after modeling showed that the number of oligodendrocyte precursor cells in the subependymal zone was positively correlated with the APT Lorentzian difference value(r=0.821,P=0.001 1),and negatively correlated with the lactate content in the brain(r=-0.880,P=0.000 2).Conclusion Multimodal imaging can monitor the early brain metabolism changes of PWMI in neonatal rats,especially the changes of lactate,and provide a visual basis for their early diagnosis.The level of lactate in the brain increases after cerebral hypoxia and ischemia in prematurity,and oligodendrocyte precursor cells increase transiently and then decrease,resulting in PWMI.

Purpose Based on multimodal imaging combined with a variety of histological techniques,to visually evaluate the changes of rats brain metabolic microenvironment after cerebral hypoxia and ischemia of prematurity,and to discuss the effects of abnormal lactate metabolism in the brain on oligodendrocyte precursor cells,so as to provide a basis for the early diagnosis and treatment of premature white matter injury(PWMI).Materials and Methods A total of 36 SPF-grade healthy 3-day-old Sprague-Dawley neonatal rats were randomly assigned to the sham surgery(Sham)group and the model(PWMI)group using a random number table method,with 18 rats in each group.A neonatal rat PWMI model was established by hypoxia-ischemia method.Twenty-four hours after modeling,laser speckle imaging was used to monitor cerebral blood flow and blood oxygen changes.Multimodal imaging was used to observe the changes in brain tissue microstructure and metabolism after PWMI.HE staining was used to observe the morphological changes of nerve cells in the white matter of the brain.Enzyme-linked immunosorbent assay was used to detect the changes of lactate content and lactate dehydrogenase activity in the white matter region of the brain after PWMI in neonatal rats.PDGFR-α immunofluorescence staining was used to observe the dynamic changes of the number of oligodendrocyte precursor cells in the subependymal zone after PWMI in neonatal rats.Results Twenty-four hours after modeling,the multimodal imaging results showed that the T2WI and diffusion-weighted imaging on the injured side of the PWMI group showed high intensity,and the relative cerebral blood flow,relative oxygen saturation,relative apparent diffusion coefficient and amide proton transfer(APT)Lorentzian difference value were lower than those in the Sham group(t=29.466,23.522,59.006,54.778,10.263,all P<0.001),and the lactate content was higher than that in the Sham group(t=-7.521,P<0.001).The results of HE staining and enzyme-linked immunosorbent assay showed that the arrangement of nerve cells in the white matter area of the injured side of the brain in the PWMI group was loose and disordered.The lactate content and lactate dehydrogenase activity were higher than those in the Sham group(t=-6.079,-10.548,both P<0.001).The results of immunofluorescence staining showed that the number of PDGFR-α+cells in the subependymal zone of the damaged side of the PWMI group was higher than that of the Sham group at 24 hours after modeling,and lower than that in the Sham group at 11 days after modeling(t=-8.386,6.676,both P<0.001).The correlation analysis between the lactate content and APT Lorentzian difference value in the brain and the number of oligodendrocyte precursor cells in the brain 11 days after modeling showed that the number of oligodendrocyte precursor cells in the subependymal zone was positively correlated with the APT Lorentzian difference value(r=0.821,P=0.001 1),and negatively correlated with the lactate content in the brain(r=-0.880,P=0.000 2).Conclusion Multimodal imaging can monitor the early brain metabolism changes of PWMI in neonatal rats,especially the changes of lactate,and provide a visual basis for their early diagnosis.The level of lactate in the brain increases after cerebral hypoxia and ischemia in prematurity,and oligodendrocyte precursor cells increase transiently and then decrease,resulting in PWMI.