A SUBPOPULATION OF INTERNEURONS AND CAJAL-RETZIUS CELLS EXPRESS CD200 DURING DEVELOPMENT AND FOLLOWING HYPOXIA/ISCHEMIA IN C57BL/6 MICE BRAIN.

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

Congreso; The 24th Biennial Joint Meeting of the International Sociey for Neurochemistry and American Society of Neurochemistry; 2013

ISN-ASN

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. However, 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. The calcium-binding protein calretinin (CR) on the other hand is shown to express on a subset of cortical interneurons. The role of CR in other intracellular calcium sensitive processes and in neuroprotection is still unclear and remains to be defined. Previous studies from our group have described the expression of CD200-CD200R in brain during development. CD200 expression showed a distinct pattern of expression in layer I of cortex and in the hippocampus. Hence, the aim of this study was to characterize the expression pattern of CD200 expressing cells using the marker for interneurons, CR by immunofluorescence, during development and following Hypoxic/Ischemic (H/I) injury in 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. Results: In control neonatal brains, CD200 was expressed on neurons, blood vessels and some astrocytes, while CR was expressed only on neurons. Most CR+ neurons were CD200+ especially on interneurons in the innermolecular layer of hippocampus, Layer I of the neocortex and the hilus at most age groups studied. After H/I, CD200-CR immunolabeling was increased in the hippocampal fissure until 7 days post-lesion. Characterization of CD200+ cells by double immunofluorescence showed that most CD200+ neurons expressed CR, characteristic of interneurons or the cajal retzius cells. This followed a change in CD200R+ microglial cells done previously. Conclusion: CD200-CR+ cells are involved in neuronal and microglial response following neonatal H/I injury.