Validation of a neuropathology score using quantitative methods to evaluate brain injury in a pig model of hypoxia ischaemia

Background: Neuropathological examination is the classic outcome measure in experimental studies of newborn brain injury to evaluate novel therapies. We have used a graded neuropathology score in an established global model of perinatal hypoxic-ischaemic (HI) injury. We wished to validate the score using cell counting in our model. New method: 32 newborn pigs underwent a 45 min global HI insult then maintained at normothermia (NT, rectal temperature, T-rectal 38.5 degrees C) for 72 h or mild total body hypothermia (HT, T-rectal 37.0 degrees C) combined with selective head cooling for 48 hand subsequently maintained at NT for 24 h before brain perfusion fixation. A perinatal pathologist scored haematoxylin and eosin stained 6 mu m histological sections for injury in the hippocampus and basal ganglia on a 9-step scale (0.0 = no injury, 4.0 = >75% injury). We counted the number of healthy neurons in the hippocampus CA1 region and putamen using morphological criteria in eight random, non-overlapping fields from representative sections. Results: Healthy neuronal cell density correlated with neuropathology score in the hippocampus CA1 (r=-0.74) and in the putamen (r=-0.75) and both measures detected a difference between groups. The correlation coefficients were better for the NT compared to the HT group in both the hippocampus (r=-0.87 vs. -0.53) and putamen (r=-0.77 vs. -0.54). Comparison with existing method: We have validated a histological neuropathological scoring system in our model of perinatal HI by showing correlation between neuronal cell count and estimated injury. Conclusions: Our neuropathology score is a valid method to assess brain injury with good reproducibility and sensitivity. (C) 2014 Elsevier B.V. All rights reserved.