PURPOSE: The growth of ocular neovascularization is regulated by a balance
between stimulating and inhibiting growth factors. Somatostatin affects
angiogenesis 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 somatostatin receptor (sst) subtypes and particularly sst
subtype 2A (sst2A) in normal human macula, and to study sst2A in different
stages of age-related maculopathy (ARM), because of the potential
anti-angiogenic effect of somatostatin analogues. METHODS: Sixteen eyes
(10 enucleated eyes, 4 donor eyes, and 2 surgically removed choroidal
neovascular [CNV] membranes) of 15 patients with eyes at different stages
of ARM were used for immunohistochemistry. Formaldehyde-fixed
paraffin-embedded slides were incubated with a polyclonal anti-human sst2A
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 sstA in newly formed endothelial cells and fibroblast-like
cells was strong in fibrovascular CNV membranes. mRNA of sst subtypes 1,
2A, and 3, as well as somatostatin, was present in the normal posterior
pole; sst subtypes 4 and 5 were not detectable. CONCLUSIONS: Most
early-formed CNV in ARM express sst2A. The presence of mRNA of sst subtype
2A was observed in normal human macula, and subtypes 1 and 3 and
somatostatin are also present. sst2A receptors bind potential
anti-angiogenic somatostatin analogues such as octreotide. Therefore,
somatostatin analogues may be an effective therapy in early stages of CNV
in ARM
