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.