PPARD and age-related macular degeneration: With regard to AMD biology, PPARβ/δ is expressed in both RPE and choroidal endothelial cells [28], and aged PPARβ/δ−/− mice have been shown to develop several features of early dry AMD, including thin continuous sub-RPE deposits, Bruch’s membrane thickening, RPE pigmentary changes, and disorganized basal infoldings in RPE cells, suggesting an essential role of PPARβ/δ in RPE cell health [28].