Localisation of SDF-1 and its receptor CXCR4 in retina and choroid of aged human eyes and in eyes with age related macular degeneration

Aim: To examine the immunolocalisation of stromal cell derived factor 1 (SDF-1) and its receptor CXCR4 in aged control human donor eyes and eyes with age related macular degeneration (AMD). Methods: Postmortem eyes from eight aged control donors (mean age 79.8 years) and from 12 donors with AMD (mean age 83.9 years) were cryopreserved and sectioned through the macular region. SDF-1 and CXCR4 were localised using streptavidin alkaline phosphatase immunohistochemistry and then sections were bleached. Three independent masked observers scored the immunohistochemical reaction product. Results: In aged control retinas, SDF-1 immunoreactivity was most intense in inner photoreceptor matrix (IPM). CXCR4 showed a similar pattern of immunostaining, but was more prominent in inner segments of photoreceptors. In aged control and AMD choroid, SDF-1 and CXCR4 localisations were most prominent in retinal pigment epithelial (RPE) cells and choroidal stroma. However, the intensity for SDF-1 was significantly reduced in RPE (p < 0.0001) and choroidal stroma (p < 0.05) in late AMD eyes. SDF-1 and CXCR4 immunoreactivities were weak or nearly absent in disciform scars with choroidal neovascularisation (CNV). Circulating cells, presumably leucocytes, were most intensely positive for CXCR4. Conclusions: These results show that changes in distribution and relative levels of SDF-1/CXCR4 were not evident in early AMD. This suggests that SDF-1/CXCR4 may not contribute to the formation of CNV in AMD, in that CXCR4+ cells were not incorporated into neovascularisation. However, the examples of CNV studied were within disciform scars, so the authors cannot comment on the role of SDF-1/CXCR4 in the early stages of CNV formation.