Apolipoprotein J inhibits the migration, adhesion, and proliferation of vascular smooth muscle cells

Purpose: Apolipoprotein J (ApoJ) is expressed during tissue injury and remo deling and has been implicated in vascular smooth muscle cell (VSMC) differ entiation. Recently, the gene for ApoJ was identified as upregulated in dis tal anastomotic intimal hyperplasia after prosthetic arterial grafting. In this study we investigate the effect of ApoJ on VSMC migration, adhesion, p roliferation, and gene expression. Methods: To study the effect of ApoJ on cell migration, we used a microchem otaxis chamber with an intervening 8-mum pore semipermeable polycarbonate m embrane. Assays were performed with ApoJ alone (1-50 mug/mL) or in combinat ion with platelet-derived growth factor homodimer bb (PDGF-bb; 10 ng/mL) or 2% fetal bovine serum (FBS; n=8) in the lower wells. The influence of extr acellular matrix interactions on ApoJ and chemotaxis was studied in a simil ar way, except membranes were collagen coated. Furthermore, cells were expo sed to ApoJ 15 minutes before or after seeding on the coated membrane (n=10 ). The influence of ApoJ on cell adhesion to collagen was assessed with cel l exposure to ApoJ 15 minutes before or after seeding on a collagen-coated membrane (n=10). Migration and adhesion were quantified by counting the num ber of cells per three independent high-power fields with light microscopy. The effect of ApoJ in 0.4% FBS with or without PDGF-bb on VSMC proliferati on (n=12) was assessed by means of [Methyl-H-3] thymidine incorporation. Th e transcriptional profile of VSMCs in 2% FBS exposed to ApoJ and a control for 24 hours was analyzed with an oligonucleotide microarray containing 12, 560 genes. Results. ApoJ alone was not chemotactic for VSMCs. Without collagen, ApoJ d ecreased the migration of VSMCs toward 2% PBS by 96% or more starting at 10 mug/mL (P<.05) and toward PDGF-bb by 60.9% or more starting at 25 <mu>g/mL (P<.05) compared with the control. When collagen was introduced, ApoJ (25 <mu>g/mL) decreased migration toward 2% FBS by 64% (P<.01) and toward PDGF- bb by 67.5% (P<.01) and decreased adhesion by 26.8% (P<.01) only when VSMCs in solution were exposed to ApoJ before placement on collagen. ApoJ did no t induce VSMC proliferation. ApoJ alone decreased VSMC thymidine incorporat ion by 41.1% at 25 <mu>g/mL (P<.05). ApoJ decreased thymidine incorporation of PDGF-bb stimulated VSMCs by 42.8% at 50 <mu>g/mL (P<.05). Interleukin-8 and endothelin-1 were demonstrated by means of the microarray to be differ entially expressed more than twofold in VSMCs that were exposed to ApoJ. Conclusion: ApoJ is a potent inhibitor of VSMC migration, adhesion, and pro liferation. Its genetic targets are linked to cell senescence and different iation. Therefore, ApoJ may play a role, in part, in modulating the VSMC re sponse to injury.