Abstract T MP111: Gpr124 Regulates Post-Stroke Cerebrovascular Integrity

Introduction: GPR124/TEM5 is an orphan G-protein coupled receptor (GPCR) with a large extracellular domain. We and others have previously demonstrated that GPR124 exerts CNS-specific angiogenesis regulation with knockout mice exhibiting embryonic lethality from hemorrhagic glomeruloid vascular malformations in forebrain and neural tube (c.f. Kuhnert et al., Science , Nov 12;330(6006):985-9 . (2010)). Hypothesis: GPR124 regulates adult angiogenesis and blood-brain barrier (BBB) integrity during homeostasis or after stroke. Methods: To bypass GPR124 embryonic lethality, we generated GPR124 conditional knockout (cko) mice allowing temporally-regulated deletion. Tamoxifen treatment of GPR124flox/-; ROSA-CreER mice versus GPR124flox/+; ROSA-CreER littermate controls allowed GPR124 cko versus heterozygosity, respectively, in adult mice. GPR124 deletion was followed by analyses of microvascular structure and patterning and blood-brain barrier (BBB) integrity). GPR124 cko mice versus controls were also subjected to 60 minute middle cerebral artery occlusion (MCAO) and effects on stroke volume, survival and microvascular structure assessed. Results: GPR124 deletion in neonatal or adult mice was well-tolerated without impairment of postnatal vascular patterning, BBB maturation or BBB integrity. However, GPR124 cko mice subjected to the middle cerebral artery occlusion (MCAO) stroke model exhibited impaired survival and a profound microvascular hemorrhagic transformation that was confined to the infarct region relative to wild-type controls. GPR124 cko stroke vasculature also exhibited numerous cellular and architectural defects relative to controls that will be discussed. Conclusions: GPR124 deletion is well tolerated in adult mice but results in marked hemorrhagic transformation in the MCAO stroke model. GPR124 represents a novel receptor whose function is essential for cerebrovascular integrity in the post-stroke setting, with attendant therapeutic implications.