Cxcl12 Gene Engineered Endothelial Progenitor Cells Further Improve The Functions Of Oligodendrocyte Precursor Cells

Ischemic stroke could cause injuries not only to the gray matter but also to the white matter of the brain.New oligodendrocytes are needed for the brain repair process.Cerebral ischemia induces the proliferation and differentiation of oligodendrocyte progenitor cells(OPCs)to a limited extent.Studies revealed that chemokine CXCL12 and endothelial progenitor cells(EPCs)both could promoteremyelination by recruiting OPCs to the demyelinatedregion or promoting OPCs proliferation and differentiation tooligodendrocytes.We hypothesized that the beneficial effects of EPCs and CXCL12 can be harnessed to synergistically improve thefunction of OPCs.In this work,EPCs were genetically engineered via lentivirus mediated cxcl12 gene transfer to generate CXCL12-EPC.CXCL12-EPC conditioned media(CM)was used to treat OPCs.Effects of the CM on OPCs proliferation,migration,differentiation and survival were examined.The expression levels of downstream effectors such as PDGFR?,bFGF,MBP,CXCR4 and CXCR7 were evaluated.HUVEC,un-modified EPC and GFP-EPC were used as controls.To explore the signaling pathway of CXCL12 in OPCs,we blocked or knocked-down the two known receptors of CXCL12,CXCR4 and CXCR7,respectively,and investigated their impact on OPCs properties.Results demonstrated that CXCL12-EPC CM further promoted OPCs proliferation and migration(p<0.05),and attenuated cell death during oxygen-glucose deprivation(p<0.05),compared to un-modified EPC and GFP-EPC controls.CXCL12-EPC CM promoted the differentiation of late OPCs and up-regulated the expression of PDGFR?,bFGF,CXCR4 and CXCR7 in OPCs,albeit following different time course.Subsequent experiments revealed that blocking CXCR4 with antagonist AMD3100 or knocking down CXCR4 with siCXCR4 both diminished the beneficial effect of CXCL12-EPC on OPCs proliferation and migration(p<0.05),while knocking-down CXCR7 with siCXCR7 inhibited OPCs differentiation.Ourresults supported that cxcl12 gene modification of EPC further promoted EPCs' ability in augmenting the oligogenesis properties of OPCs,suggesting that CXCL12-EPCs holds great potential in white matter repair after ischemic injury.