The retinal pigment epithelium (RPE) maintains the choriocapillaris (CC) in the normal eye and is involved in the pathogenesis of choroidal neovascularization in age-related macular degeneration. Vascular endothelial growth factor-A (VEGF) is produced by differentiated human RPE cells in vitro and in vivo and may be involved in paracrine signaling between the RPE and the CC. We investigated whether there is a polarized secretion of VEGF by RPE cells in vitro. Also, the localization of VEGF receptors in the human retina was investigated. We observed that highly differentiated human RPE cells, cultured on transwell filters in normoxic conditions, produced two- to sevenfold more VEGF toward their basolateral side as compared to the apical side. In hypoxic conditions, VEGF-A secretion increased to the basal side only, resulting in a three- to 10-fold higher basolateral secretion. By immunohistochemistry in 30 human eyes and in two cynomolgus monkey eyes, KDR (VEGFR-2) and flt-4 (VEGFR-3) were preferentially localized at the side of the CC endothelium facing the RPE cell layer, whereas flt-1 (VEGFR-1) was found on the inner CC and on other choroidal vessels. Our results indicate that RPE secretes VEGF toward its basal side where its receptor KDR is located on the adjacent CC endothelium, suggesting a role of VEGF in a paracrine relation, possibly in cooperation with flt-4 and its ligand. This can explain the known trophic function of the RPE in the maintenance of the CC and its fenestrated permeable phenotype and points to a role for VEGF in normal eye functioning. Up-regulated basolateral VEGF secretion by RPE in hypoxia or loss of polarity of VEGF production may play a role in the pathogenesis of choroidal neovascularization.

%Purpose. Pseudomonas aeruginosa is the most im portant cause of contact lens-associated ulcera tive keratitis, especially for those who use extended-wear lenses. U ntil now, the presence of specific anti-P. aeruginosa im m unoglobulin A (IgA) antibodies in the tears of contact lens wearers has n o t been investigated an d is the purpose of the current study. M ethods.T h e levels o f specific IgA antibodies against P. aeruginosa and total secretory IgA (sIgA) concentrations were m easured in tears o f various groups o f contact lens and non-contact lens wearers using enzyme-linked im m unosorbent assays. Contact lens groups were divided into the following categories: daily-wear rigid gas-permeable lenses (n = 23), daily-wear soft lenses (n = 22), extended-wear soft lenses (n = 17), and non-contact lens wearers (n = 23). As a positive control group, we tested tears obtained from patients with cystic fibrosis (n = 5) because the respiratory tract of these persons often are colonized by P. aeruginosa.Results. T he percentage o f nonresponders (< 1 5 U /m l) varied between 9% in daily-wear rigid gas-perm eable contact lens users to 23% in daily-wear soft contact lens users. T he percentage o f n o n resp o n d ers in controls was 13%. The frequency o f nonresponders was n o t significandy different am ong the different groups tested. All patients with cystic fibrosis showed a very high anti-P. aeruginosa IgA response in their tears. W hen analyzing the m ean anti-P. aeruginosa IgA response, a significandy lower level was fo u n d in extended-wear contact lens users (38 U /m l) com pared to non-contact lens wearers (82 U /m l), Total s-IgA levels in the tears of the various groups tested were n o t significandy different. Conclusions.A substantial n u m b er of persons in the population of contact lens wearers tested lack detectable IgA antibodies against P. aeruginosa in their tears and may be susceptible to P. aeruginosa keratitis if the physiological condition of their cornea is compromised. Invest O p h th alm o l Vis