Changes in MRI and AQP4 expression in the early stage of hypoxic ischemic brain edema in neonatal pigs

Objective To investigate MRI changes in the early stage of hypoxic ischemic brain edema,and to study Aquaporin-4(AQP4) expression and their correlation.Methods Fourteen neonatal pigs were randomly divided into two groups:operation group(n=8)and pseudo-operation group(n=6,as control group).MRI were done at a different interval of time 0 h,1.5 h,3 h,4.5 h and 6 h after hypoxic ischemic brain damage.Immunohistochemical investigation of AQP4 expression was followed by MRI at 6 h after hypoxic ischemic brain damage.Results We observed a significantly decreased apparent diffusion coefficients(ADC)and an increased diffusion weighted imaging(DWI)within injured cortical and hippocampus regions.There was a significant increase in AQP4 expression[(15.0±4.0)%vs(5.1±2.9)%]in the iniured tissues(t=3.09,P＜0.01),and its correlation with regional MR changes was significant(r=0.846,P＜0.01).Conclusion ADC and DWI play an important role in detection of earlier brain edema.AQP4 may be involved in edema formation,and the changes of ADC and DWI may reflect the level of AQP4 expression. Key words: Brain edema; Magnetic resonance imaging; Aquaporin-4