Abstract
Purpose:
Toll-like receptor 9 agonist, CpG-rich oligodeoxynucleotides (CpG-ODNs), differentially regulate angiogenesis, dependent upon CpG backbone. Here our aim was to understand how Class C CpG-ODN2395 regulates activity of vascular endothelial cells.
Methods:
Utilising mouse corneal sutured-angiogenesis model, Class C TLR9 Agonist (CpG-ODN2395) was administered sub-conjunctivally to determine regulation of angiogenesis. The length and volume of corneal neo-vessels were quantified after 7 days post-treatment. In addition, mouse choroidal and aortic ring assays were used in matrigel or collagen, respectively, and the sprouting area or sprouting numbers were quantified. Further, human umbilical vein endothelial cells (HUVECs) were stimulated with CpG-ODN2395) after culture either on matrigel or in cell culture inserts to observe ODN2395 regulation of endothelial tube formation, cell migration and cell phenotype (CD31, CD34, Flk1 and Tie2 expression). Cell viability assay was used to determine cytotoxicity. To determine influence on vascular support via human primary pericytes, cells were treated with HUVECs ODN2395-conditioned culture medium in a transwell assay and then quantifying the number of migrated pericytes.
Results:
Sub-conjunctional injection of CpG-ODN2395 suppressed both length and volume of corneal neo-vessels compared to vehicle control. CpG-ODN2395 suppressed choroidal and aortic ring sprouts as well as HUVECs tube formation in a dose-dependent manner. CpG-ODN2395 not only delayed HUVECs migration process, but also prevented differentiation into CD34+ tip cells. CpG-ODN2395 treated HUVECs reduced pericytes migration compared to control.
Conclusions:
The data supports the notion that Class C CpG-ODN2395 suppresses angiogenesis by restraining endothelial migration, inhibiting tip cell formation and thus maintaining a steady state of endothelial activity resulting indirectly in reduced capacity for pericytes migration.