Background

Hyaluronan is a biologically active polymer, which can be formulated into nanoparticles. In our study, we aimed to probe atherosclerosis-associated inflammation by using hyaluronan nanoparticles and to determine whether they can ameliorate atherosclerosis. Hyaluronan nanoparticles (HA-NPs) were prepared by reacting amine-functionalized oligomeric hyaluronan (HA) with cholanic ester and labeled with a fluorescent or radioactive label. HA-NPs were characterized in vitro by several advanced microscopy methods. The targeting properties and biodistribution of HA-NPs were studied in apoe–/– mice, which received either fluorescent or radiolabeled HA-NPs and were examined ex vivo by flow cytometry or nuclear techniques. Furthermore, three atherosclerotic rabbits received 89Zr-HA-NPs and were imaged by PET/MRI. The therapeutic effects of HA-NPs were studied in apoe–/– mice, which received weekly doses of 50 mg/kg HA-NPs during a 12-week high-fat diet feeding period. Hydrated HA-NPs were ca. 90 nm in diameter and displayed very stable morphology under hydrolysis conditions. Flow cytometry revealed a 6- to 40-fold higher uptake of Cy7-HA-NPs by aortic macrophages compared to normal tissue macrophages. Interestingly, both local and systemic HA-NP–immune cell interactions significantly decreased over the disease progression. 89Zr-HA-NPs-induced radioactivity in atherosclerotic aortas was 30% higher than in wild-type controls. PET imaging of rabbits revealed 6-fold higher standardized uptake values compared to the muscle. The plaques of HA-NP-treated mice contained 30% fewer macrophages compared to control and free HA-treated group. In conclusion, we show favorable targeting properties of HA-NPs, which can be exploited for PET imaging of atherosclerosis-associated inflammation. Furthermore, we demonstrate the anti-inflammatory effects of HA-NPs in atherosclerosis.

Abstract-The cardiovascular effect of estrogen is currently under intense investigation, but the role of androgens in vascular biology has attracted little attention. Because endothelial repair and vascular smooth muscle cell (VSMC) proliferation affect atherogenesis, we analyzed the effects of 17␤-estradiol (E 2 ), dihydrotestosterone (DHT), and sex hormone antagonists on DNA synthesis in human umbilical VSMCs and in E304 cells (a human umbilical endothelial cell line). In VSMCs, both E 2 and DHT had a biphasic effect on [ 3 H]thymidine incorporation into DNA: low concentrations (0.3 nmol/L for E 2 , 3 nmol/L for DHT) stimulated [ 3 H]thymidine incorporation (ϩ35% and ϩ41%, respectively), whereas high concentrations (30 nmol/L for E 2 , 300 nmol/L for DHT) inhibited [ 3 H]thymidine incorporation (Ϫ40%). In contrast, E 2 (0.3 to 300 nmol/L) and DHT (3 to 3000 nmol/L) dose-dependently enhanced [ 3 H]thymidine incorporation in E304 cells (peak, ϩ85% for both). In VSMCs, high concentrations of E 2 and DHT inhibited platelet-derived growth factor (PDGF)-or insulin-like growth factor (IGF-1)-induced DNA synthesis (Ϫ50% to 80%), whereas PDGF-or IGF-1-dependent DNA synthesis in E304 cells was further increased by E 2 . The antiestrogens tamoxifen and raloxifene mimicked the effects of E 2 on DNA synthesis in both VSMCs and E304 cells. However, when coincubated with a stimulatory concentration of E 2 (0.3 nmol/L), tamoxifen and raloxifene blocked E 2 -induced