No abstract

Octreotide has inhibitory properties after activation of BCEC with growth factors under normoxic and hypoxic conditions in vitro. Since activation of these cells is a crucial event in the development and progression of AMD, octreotide may be a potential drug for treatment of choroidal neovascularization in these patients.

Ocular diseases such as proliferative diabetic retinopathy are the major cause of blindness in industrialized countries. The main pathologic features of these diseases are hypoxia and overproduction of growth factors resulting in pathologic proliferation of endothelial cells and new vessel formation. Particularly, hypoxia and growth factors, such as VEGF, IGF-1, bFGF and TGF 2 , show a complex interaction in the onset and progression of the diseases. Therefore, to date, most therapeutic strategies for proliferative retinopathies have targeted proliferation of endothelial cells evoked by growth factors. Recently, a synthetic analog of somatostatin, octreotide, has been shown to inhibit the proliferation of various cells in vitro, including endothelial cells. In this study, we have investigated the proliferative response of bovine retinal endothelial cells (BREC) to growth factors under hypoxic conditions and the modulation by octreotide. We found a dose-dependent increase of cell proliferation with VEGF, IGF-1 and bFGF, and inhibition of hypoxia-induced cell proliferation with TGF 2 . Moreover, growth factorinduced, but not hypoxia-induced, cell proliferation was attenuated in the presence of octreotide. In contrast, TGF 2 abolished hypoxia-induced BREC proliferation. Similar to octreotide BIM23027, a somatastatin receptor subtype 2 (SSTR2) receptor agonist was able to attenuate the growth factor-induced proliferation of BREC expressing mRNA and protein for SSTR2. Therefore, we postulate that octreotide exerts its effects mainly through binding to the SSTR2. Taken together, our findings point to octreotide as a promising candidate for the treatment of eye disorders involving growth factor-dependent proliferation of endothelial cells.

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The data showed that bFGF and TGFbeta2 are strong mitogens for HLEC. The HLEC-SRA 01/04 cell line derived from HLEC reacted to growth factors, with cell proliferation only to a lesser extent. Such quiescence of these cells, when compared with cells in primary culture, cannot be explained by the lack of respective receptors for growth factors. Further investigation of growth factor-induced responses of both cell types will provide new insight into the proliferative processes involved in postoperative secondary cataract formation.