Abstract
Purpose:
As the origin of choroidal neovascularisation (CNV) and the role of pericytes (pc) in wet age-related macular degeneration (AMD) pathogenesis are yet not completely understood, this work aimed in investigating the number of pericytes in choroidal, choriocapillaris (CC) and CNV blood vessels of 17 AMD donor eye tissues, and seven age-matched controls.<br />
Methods:
Perimacular sections of eight late wet AMD donor eyes (mean age 81±11 years), three dry AMD donor eyes (89±5 years), seven age-matched control donor eyes (74±9 years) and six CNV explants (age unknown) were investigated with light and electron microscopy. The ultrastructures and lumen areas of aged choroidal, CC and new built CNV vessels were investigated with respect to the number of accompanying pericytes. Pericyte-like cells were counted if they were included in the same basal membrane as the vessels and at least 0.4 µm high and maximum 0.8 µm away from the endothelium. If more than one pericyte layer was present, only the inner one was counted. Statistics were performed using the Wilcoxon test.
Results:
Control CC showed about one pericyte per CC vessel (pc/CC), while the number was doubled in the AMD donors (p<0.001). The number of pcs per area of CC was also significantly higher (p=0.02) in AMD.<br /> If investigated according to AMD type it was found that wet AMD CC showed more pericytes per vessel than controls (p<0.001 for pc/v; p=0.01 for pc/area) and CC of dry AMD donors. However, the latter difference not being statistically significant.<br /> CNV explants showed also about two pc/v, as it was found in wet AMD CC (p=0.002 to control). The number of vessels with at least one pericyte was as follows: control (26.4 %) < dry AMD (37.2 %) < AMD mean (52.3 %) < wet AMD (58 %) < CNV (59.3 %).<br /> Pericytes in vessels of the choroid were also counted in five vessels of four wet AMD eyes and three controls. They were ~six times more abundant than in CC, but not different between controls and AMD samples if investigated per area (p>0.05).
Conclusions:
This study shows for the first time that pericytes in the CC of AMD donor eyes, especially those with wet AMD, become enriched as compared to age-matched controls. In the choroid, the number of pericytes does not change. This indicates an activating role of pericytes in wet AMD pathogenesis with subsequent neovascularisation originating from the CC.