PHENOTYPIC CHARACTERIZATION OF CD200R+ MICROGLIA/ MACROPHAGES AND CD200+ NEURONAL CELLS IN NEONATAL C57BL/6 MICE BRAIN FOLLOWING HYPOXIA/ISCHEMIA

SHRIVASTAVA KALPANA; CHERTOFF, MARIELA; GIMENEZ LLORT LYDIA; GONZALEZ BERTA

Congreso; EUROGLIA; 2013

Introduction: CD200 & CD200R are immune inhibitory molecules that have been shown to be involved in inducing immune tolerance and in contributing to immune privileged status of the CNS. The developing brain exhibits distinct morphological as well as physiological characteristics determining a peculiar response to injury showing an aggravated susceptibility to excitotoxicity and pro-inflammatory cytokines, along with an exacerbated inflammatory response. Previous studies from our group have described the expression of CD200-CD200R in brain during development showing a distinct pattern of expression in the cortex and the hippocampus. Hence, the aim of this study is phenotypic characterization of CD200R+ microglia/macrophages and CD200+ neuronal cells following hypoxia/ischemia (H/I) in neonatal mice brain. Methods: Wild-type C57/BL6 mice postnatal (P) day 1,3,5,7,10,14,21 and adult were used for developmental studies. P7 mice was used for H/I injury that was administered using Vannucci model modified for neonatal mice (8% O2, 55 min) and samples were collected 3h, 12h, 24h, 48h, 72h & 7 days after hypoxia for immunofluorescence staining. Results: Phenotypic characterization of CD200R+ microglia/macrophages showed them to express markers of pro- or anti-inflammatory phenotype in a temporal fashion post lesion. They expressed M2 phenotype as observed by colocalization with CD206+ cells throughout the time points studied but a subpopulation of CD200R+ cells exhibited M1 phenotype as exhibited by MHCII+, CD86+ cells from 24-48 hrs post lesion. Calretinin (CR) used for the characterization of CD200+ neurons showed that most CR+ neurons were CD200+ especially the interneurons in the innermolecular layer of hippocampus, Layer I of the neocortex and the hilus at most age groups studied. After H/I, CD200 immunolabeling was increased in the hippocampal fissure until 7 days post-lesion. This followed a change in CD200R+ microglial cells described above. To conclude, a balance between M1/M2 phenotype of CD200R+ microglia/macrophages and expression of CD200 by CR+ cells are involved in evolution of H/I induced brain injury in neonatal mice.