The Function And Mechanism Of CD47and TSP-1in Traumatic Brain Injury In Mice

According to the World Health Organization, traumatic brain injury (TBI) will surpassmany diseases as the major cause of death and disability by the year2020. It is estimated that10million people are affected annually by TBI.. TBI causes brain damage after both theprimary mechanical impact and second degenerative responses that occur in the minutes todays following trauma The secondary injury cascade consists of complex neurochemical andphysiological events, including an acute inflammatory response with breakdown of theblood–brain barrier, edema formation, infiltration of peripheral immune cells, activation ofresident immunological cells and release of immune mediators including cytokines andchemokines, all of which may lead to acute and chronic cell death and contribute to functionalimpairment.CD47, also known as integrin-associated protein, is a member of immunoglobulinsuperfamily and widely expressed in most cells and tissues. CD47play an importantimmunoregulatory role in monocyte motility leukocyte adhesion and migration, phagocytosis,angiogenesis. Thrombospondin-1(TSP-1) is a large glycoprotein that synthesized andsecreted by many cell types in response to injury. CD47can be activated by its ligand TSP-1,changes the endothelial permeability, cell-mediated and cell-matrix interactions, and regulatedcell adhesion, motility, activation, and angiogenesis. Accumulating evidences havedemonstrated that CD47and TSP-1involved in brain injury in vitro and in vivo. But there isno study on the effect of CD47and TSP-1in traumatic brain injury in mice. In this study, weinvestigated the hypothesis that CD47and TSP-1may be involved in the pathophysiologicalcascade of brain damage after traumatic brain injury.Aims:(1) To investigate the effect of CD47in traumatic brain injury in mice;(2) Toinvestigate the effect of TSP-1in traumatic brain injury in mice.Methods:(1) We used ploymerase chain reaction to identify the CD47KO mice. Thenwe made mice traumatic brain injury model by CCI machine. Following TBI, the effect onneurological outcome, lestion volume, vescular density was measured on day21after TBI.BBB leakage, neutrophils infiltration were evaluated at24hours after TBI. Angiogenesismarker VEGF and Ang-1were evaluated on day0,1,7and21after TBI.(2) We usedploymerase chain reaction to identify the TSP-1KO mice. Then we made mice traumatic brain injury model by CCI machine. Following TBI, the effect on neurological outcome,lestion volume, vessel density was measured on day21after TBI. BBB leakage, neutrophilsinfiltration were evaluated at24hours after TBI. Time course of TSP-1expression in plasma,and time course of TSP-1mRNA and protein expression in brain tissue were measured afterTBI. BBB leakage, neutrophils infiltration were evaluated at24hours after TBI. Angiogenesismarker VEGF and Ang-1were evaluated on day0,1,7and21after TBI.Results:(1) Sensorimotor function and lesion volume were improved in CD47knockoutmice compared to WT mice after TBI3weeks. There was significant difference in theneutrophils infiltration and BBB leakage between WT and CD47KO mice at24h after TBI.CD47KO mice had more vescular density in pericontusinal cortex than WT after TBI3weeks. The VEGF protein level in pericontusinal cortex was significant higher in CD47KOmice than in WT mice after TBI7and14day.(2) Sensorimotor function was improved inTSP-1knockout mice compared to WT mice after TBI3weeks. No significant difference wasfound in lesion volume between WT mice and TSP-1KO mice. The TSP-1protein level inplasma significant increased after TBI and the peaking at3hours after TBI and quicklydecreased at24hours after TBI. The TSP-1mRNA and protein levels were significantincreased after TBI and decreasd at least2weeks after TBI. The neutrophils infiltration andBBB leakage was deleterious in TSP-1KO mice compared to WT mice at24h after TBI.TSP-1KO mice have more vescular density in pericontusinal cortex than WT after TBI3weeks. The VEGF protein level in pericontusinal cortex was significant higher in TSP-1KOmice than in WT mice after TBI7and14day.Conclusion: CD47and TSP-1are relatived to acute phase and long term recovery phaseafter traumatic brain injury. CD47and TSP-1knockout improved motor dysfunction afterTBI. CD47knockout decreased neutrophils infiltration in pericontusinal cortex at24h afterTBI, but TSP-1knockout increase neutrophils infiltration in pericontusinal cortex at24h afterTBI. These results suggested that the effect of CD47on neutrophils infiltration may dependon other pathway excluding TSP-1-CD47pathway. Also these results suggested that TSP-1can decrease inflammation at acute phase after TBI. The results of long term recovery showthat both CD47and TSP-1are related to the pathology after TBI. TSP-1-CD47pathwayinhibite VEGF-A expression and angiogenesis after TBI. The inhibition to TSP-1-CD47pathway at recovery phase maybe benefit to long term recovery.