36-OR: ENDOTHELIAL CELL GENE EXPRESSION PROFILE IN RESPONSE TO EXPOSURE WITH ENDOTHELIAL CELL ANTIBODIES

Aim To determine the changes in gene expression in Endothelial Precursor Cells (EPC) exposed to Anti Endothelial Cell Antibodies (AECA) that are Non-HLA-specific. Methods Magnetic-bead column isolation followed by XM-One crossmatch procedure using reagents from Absorber Inc. was employed to identify serum samples with non-HLA AECA. For Gene expression assays, EPCs were obtained from T and B cell depleted PBL using reagents from Absorber Inc. The endothelial cell gene expression was performed on total RNA using Real-Time RT-PCR profiler reagents from QIAGEN Inc. Results EPCs exposed to a combination of IgM and IgG AECAs, affected the expression of more endothelial cell genes than EPCs exposed to IgM or IgG alone. Exposure of EPCs to IgM AECA alone caused changes in a few genes while exposure to IgG AECA alone did not significantly alter expression of any endothelial cell genes. In all, the genes which were up-regulated (ANXA5; APOE; BAX; BCL2L1; CALCA; CFLAR; COL18A1; EDN1; EDN2; EDNRA; FLT1; HIF1A; HMOX1; ICAM1; ITGAV; ITGB1; KDR; OCLN; PF4; SELE; THBS1) were those associated with pro-apoptotic, thrombocytic and or hemolytic events. One of the highly down-regulated genes was the Tissue inhibitor of Matrix Metalloproteinase (TIMP) that inhibit the matrix metalloproteinases which leads to increased extracellular protein deposition resulting in excessive extracellular connective tissue deposition, which is a hallmark of fibrosis which in turn is associated with chronic allograft rejection. Conclusions Human EPCs seem to respond to non-HLA antibodies by altering the gene expressions of endothelial cell biology which might be associated with events leading to allograft injury in a complement independent way. More detailed gene expression studies with organ specific endothelial cells and IgM/IgG specific non-HLA endothelial cell antibodies are needed to assess the full significance of AECA in allograft rejection.