Abstract 627: Human Osteopontin Isoforms Differentially Promote Neovascularization in Response to Ischemia via Macrophage Recruitment and Survival

Background: Coronary and peripheral artery diseases result in vessel occlusion and ischemia, initiating neovascularization to restore blood flow and preserve function. We previously established that osteopontin (OPN), a matricellular cytokine, is critical to ischemia-induced neovascularization. Unlike rodents, humans express 3 OPN isoforms (a, b, and c); however, the roles of these isoforms in neovascularization and cell migration remain undefined.

Methods and Results: Using a murine model of hindlimb ischemia in OPN -/- mice and 1.5x10 6 lentivirus particles expressing OPNa, OPNb or OPNc delivered IM, we found that OPN isoforms have different effects on functional perfusion recovery in vivo . OPNa increased limb perfusion 30.4%±0.8 and OPNc by 70.9%±6.3, as measured by laser Doppler perfusion imaging (d14; p<0.001 vs. LVGFP). Increases in perfusion translated to significant increases in functional limb use in OPNa and OPNc treated animals (61.1%±8.2; 76.2%±9.7; p<0.05), as assessed by voluntary running wheel use, and was not due to isoform expression differences (ELISA, n=6, p=ns). While OPN isoforms did not differentially affect angiogenesis, OPNa and OPNc significantly increased arteriogenesis (enlargement of arterioles), as measured by the increase in SM α-actin positive vessels in the small (200 - 700 μm 2 ; 47.2%±6.1; 55.9%±6.7) and large artery (1000 - 2500 μm 2 ; 54.2%±6.1; 76.5%±10.9) ranges in vivo (n=9; p<0.001 vs. OPNb). We hypothesized that OPN isoform-dependent effects on arteriogenesis are due to differential effects on macrophage function. OPN isoforms did not differentially affect macrophage polarization and all 3 isoforms increased macrophage survival (64.9%±1.1 - 78.6%±1.9 vs. control; p<0.0001). However, OPNa and OPNc both increased macrophage migration, where OPNc was the more potent migratory stimulus (n=4, p<0.001 vs. no trx, OPNa, OPNb).

Conclusion: In conclusion, human OPN isoforms exert divergent effects on neovascularization through differential effects on arteriogenesis and macrophage migration and survival. Altogether, these data support that human OPN isoforms may represent novel therapeutic targets to improve neovascualrization and preserve tissue function in obstructive artery disease patients.

Abstract 11: The Role of Human Osteopontin Isoforms in Post-Ischemic Neovascularization

Coronary and peripheral artery diseases lead to ischemia, initiating processes that promote neovascularization to restore blood flow and preserve tissue function. We demonstrated previously that osteopontin (OPN), a matricellular cytokine, is critical to ischemia-induced neovascularization. Unlike rodents, humans express 3 OPN isoforms (a, b, and c); however, the roles of these isoforms in neovascularization and cell migration remain undefined. To assess how human OPN isoforms affect neovascularization, OPN -/- mice underwent hind limb ischemia surgery. At the time of surgery, 1.5x10 6 lentivirus particles expressing human OPNa, OPNb or OPNc were delivered by intramuscular injection. While OPNa improved limb perfusion 30.4%±0.8 in OPN -/- mice, OPNc improved perfusion by 70.9%±6.3 (d14; p<0.001 vs. LVGFP), as measured by laser Doppler perfusion imaging. Importantly, both OPNa and OPNc isoforms significantly rescued neovascularization better than OPNb (n=6, p<0.05). Isoform effects on vascular volume, density, connectivity and diameter were further assessed using Micro-CT angiograms. OPNa and OPNc rescued limb function compared to control and OPNb treated animals (61.1%±8.2; 76.2%±9.7; p<0.05), as assessed by voluntary running wheel use. To verify the differences in neovascularization were due to divergent effects on receptor binding and/or signaling and not variations in isoform expression, we confirmed similar OPN isoform expression levels by ELISA (n=6, p=ns) and immunofluorescence. OPN isoforms a and c both increased macrophage infiltration 2.5 fold, as assessed by mRNA (d7; p<0.05) and histology, leading to increases in vascular smooth muscle cell (VSMC) infiltration (d7; p<0.05). Several pro-arteriogenic factors were also significantly increased at the mRNA level. Finally, we confirmed in vitro that OPNa and OPNc significantly increased VSMC migration compared to OPN b and control (49.8%±3.1; 75.2%±6.3; p<0.05). In conclusion, human OPN isoforms may exhert divergent effects on neovascularization through varried effects on macrophage and VSMC recruitment. Human OPN isoforms may represent potential new therapeutic targets to promote neovascularization and preserve function in patients with peripheral artery disease.

Global microRNA expression profiling: curcumin (diferuloylmethane) alters oxidative stress-responsive microRNAs in human ARPE-19 cells

PURPOSE

In recent years, microRNAs (miRNAs) have been reported to play important roles in a broad range of biologic processes, including oxidative stress-mediated ocular diseases. In addition, the polyphenolic compound curcumin has been shown to possess anti-inflammatory, antioxidant, anticancer, antiproliferative, and proapoptotic activities. The aim of this study was to investigate the impact of curcumin on the expression profiles of miRNAs in ARPE-19 cells exposed to oxidative stress.

METHODS

MiRNA expression profiles were measured in ARPE-19 cells treated with 20 μΜ curcumin and 200 μΜ H₂O₂. PCR array analysis was performed using web-based software from SABiosciences. The cytotoxicity of ARPE-19 cells was determined with the CellTiter-Blue cell viability assay. The effects of curcumin on potential miRNA targets were analyzed with quantitative real-time PCR and western blotting.

RESULTS

Curcumin treatment alone for 6 h had no effect on ARPE-19 cell viability. Incubation with H₂O₂ (200 µM) alone for 18 h decreased cell viability by 12.5%. Curcumin alone downregulated 20 miRNAs and upregulated nine miRNAs compared with controls. H₂O₂ downregulated 18 miRNAs and upregulated 29 miRNAs. Furthermore, curcumin pretreatment in cells exposed to H₂O₂ significantly reduced the H₂O₂-induced expression of 17 miRNAs. As determined with quantitative real-time PCR and western blotting, curcumin increased the expression of antioxidant genes and reduced angiotensin II type 1 receptor, nuclear factor-kappa B, and vascular endothelial growth factor expression at the messenger RNA and protein levels.

CONCLUSIONS

The results demonstrated that curcumin alters the expression of H₂O₂-modulated miRNAs that are putative regulators of antioxidant defense and renin-angiotensin systems, which have been reported to be linked to ocular diseases.