Somatostatin receptor 2A expression in choroidal neovascularization secondary to age-related macular degeneration

PURPOSE. The growth of ocular neovascularization is regulated by a balance between stimulating and inhibiting growth factors. Somatostatin affects ang iogenesis by inhibiting the growth hormone-insulin-like growth factor axis and also has a direct antiproliferative effect on human retinal endothelial cells. The purpose of our study is to investigate the expression of somato statin receptor (sst) subtypes and particularly sst subtype 2A (sst(2A)) in normal human macula, and to study sst(2A) in different stages of age-relat ed maculopathy (ARM), because of the potential anti-angiogenic effect of so matostatin analogues. METHODS. Sixteen eyes (10 enucleated eyes, 4 donor eyes, and 2 surgically r emoved choroidal neovascular [CNV] membranes) of 15 patients with eyes at d ifferent stages of ARM were used for immunohistochemistry. Formaldehyde-fix ed paraffin-embedded slides were incubated with a polyclonal anti-human sst (2A) antibody. mRNA expression of five ssts and somatostatin was determined in the posterior pole of three normal human eyes by reverse transcriptase- polymerase chain reaction. RESULTS. The immunohistochemical expression of sst(2A) in newly formed endo thelial cells and fibroblast-like cells was strong in fibrovascular CNV mem branes. mRNA of sst subtypes 1, 2A, and 3, as well as somatostatin, was pre sent in the normal posterior pole; sst subtypes 4 and 5 were not detectable . CONCLUSIONS. Most early-formed CNV in ARM express sst(2A). The presence of mRNA of sst subtype 2A was observed in normal human macula, and subtypes 1 and 3 and somatostatin are also present. sst(2A) receptors bind potential a nti-angiogenic somatostatin analogues such as octreotide. Therefore, somato statin analogues may be an effective therapy in early stages of CNV in ARM.