Abstract
Purpose :
The majority of AMD-related severe vision loss occurs in patients with the wet form of the disease. It is characterized by pathological neovascularization from the choriocapillaris. Given only a fraction of AMD patients demonstrate benefit with the current anti-VEGF therapies, it is crucial to identify other pathogenic mechanisms involved in neovascularization. PPARs are members of a family of lipid activated nuclear receptors. Since the PPARβ/δ isoform has been shown to regulate angiogenesis and inflammation, we investigated its role in wet AMD.
Methods :
Cell migration and tube formation in RF/6A (macaque choroidal endothelial) cells were analyzed after PPARβ/δ knockdown, ligand (agonist or antagonist) treatment, and incubation with conditioned media (CM) from ARPE19 (human retinal pigment epithelium) cells treated with PPARβ/δ ligands. The choroid was examined in eyes from aged Pparβ/δ-/- and Pparβ/δ+/+ mice by electron microscopy. The effect of PPARβ/δ expression (Pparβ/δ-/- and Pparβ/δ+/+) and pharmacological modulation [vehicle control, PPARβ/δ antagonist (GSK0660) or PPARβ/δ agonist (GW0742)] on choroidal neovascular (CNV) lesion severity was examined in isolectin-IB4 stained flatmounts of mouse eyes following laser induced CNV. Cryosections from Pparβ/δ-/- and Pparβ/δ+/+ eyes were probed with antibodies to Iba1 and F4/80, to evaluate microglial localization within the CNV lesions.
Results :
Knocking down PPARβ/δ expression with siRNA or antagonizing PPARβ/δ function decreased bFGF-induced cell migration and tube formation. Additionally, treatment of ARPE19 CM with a PPARβ/δ antagonist was able to reverse CM-induced migration of RF/6A cells. While ultrastructural images displayed no differences in the choroid between Pparβ/δ-/- and Pparβ/δ+/+controls, Pparβ/δ-/- mice exhibited decreased volume and size of CNV lesions and a 2-fold higher localization of Iba1+ and F4/80+ microglia as compared to age-matched controls.
Conclusions :
These results support our previous findings that PPARβ/δ regulates AMD pathobiology in a cell-specific manner. While PPARβ/δ antagonism may have therapeutic benefit in the context of the choroid and wet-AMD, RPE cells might benefit from ligand activation of PPARβ/δ to treat sub-RPE deposit formation. Finally, the increase in microglial cells within smaller CNV lesions may be indicative of macrophage polarization regulated by PPARβ/δ.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.