Abstract
Purpose :
The early stage of age-related macular degeneration (AMD) is marked by loss of choriocapillaris and choroidal vessels, which leads to outer retinal hypoxia and subsequent pathological choroidal neovascularization (wet AMD). In health, endothelial cells (ECs) efficiently form new vessels to replace those lost to injury. Thus, here we investigated whether choroidal ECs from early AMD eyes lose their neovascularization potential and, if so, what potential mechanisms might underlie this impaired functional response.
Methods :
Choroidal ECs were isolated from young normal (YN; 6 yrs old), old normal (ON; 20 yrs old), and old-drusen-laden (AMD; 19 yrs old) eyes of rhesus monkeys and plated at 20,000 cells/cm2 on the surface of regular or type 2 (higher stiffness) Cultrex® basement membrane (10 mg/mL) in starvation medium composed of basal medium supplemented with 0.5% fetal bovine serum and antibiotics. Further, choroidal ECs isolated from the peripheral regions of AMD eyes were also compared with their corresponding macular counterparts. Images of capillary-like structures were obtained at 12h using a Zeiss Axio Observer 7 epifluorescence microscope, and total chord length per unit area was quantified using ImageJ.
Results :
Our findings revealed that, of the three groups of choroidal ECs, those from AMD eyes exhibited the lowest neovascularization potential, which was 15% (P<0.05) or 48% (P<0.05) lower than their YN or age-matched ON counterparts, respectively. Notably, peripheral ECs from AMD eyes formed significantly (~1.6-fold; P<0.05) longer chord structures than their macular counterparts. Interestingly, the superior chord formation ability of YN ECs was substantially reduced on basement membrane of lower stiffness.
Conclusions :
These studies show that choroidal ECs from early AMD eyes, and specifically those from the macula, exhibit poor neovascularization potential, which may explain their inability to replace the degenerating choroidal vessels in early AMD. Further, the observation that chord formation was impaired on softer basement membrane indicates a potential role of mechanotransduction in the observed differences in chord formation. Ongoing studies are aimed at further elucidating the molecular mechanisms underlying these spatial (macular vs peripheral) and temporal (young vs AMD) differences in neovascularization potential.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.