Kvanta A
Department of Ophthalmology, St Erik's Eye Hospital, Stockholm, Sweden.
Curr Eye Res. 1995 Nov;14(11):1015-20. doi: 10.3109/02713689508998523.
Subretinal neovascularization is a severe sight-threatening complication into age-related macular degeneration. Previous immunohistochemical studies on surgically removed neovascular membranes have revealed that these membranes, in addition to the neovascular stroma, are comprised of several different cell types such as retinal pigment epithelial (RPE) cells, choroidal fibroblasts and vascular endothelial cells. Since vascular endothelial growth factor (VEGF) potently and specifically induces angiogenesis it was investigated whether VEGF is expressed and/or inducible in choroidal fibroblasts and RPE cells. Choroidal fibroblasts and RPE cells were isolated from human adult post-mortem eyes and expression of VEGF mRNA and protein was measured. By using Northern blotting, both choroidal fibroblasts and RPE cells were found to express VEGF mRNA at low levels. In order to examine whether this VEGF expression was further inducible, the intracellular effector enzyme protein kinase C was activated by phorbol esters. This activation resulted in a prominent increase in VEGF mRNA in choroidal fibroblasts, but not in RPE cells, with a maximal increase detected after 6 h. Elevation of intracellular cyclic AMP levels by forskolin had no clear effect on VEGF mRNA in either cell type. Stimulation with interleukin-1, transforming growth factor beta, tumour necrosis factor alpha and platelet derived growth factor was tested to see if VEGF expression is cytokine inducible. Both interleukin-1 and transforming growth factor beta induced VEGF expression in choroidal fibroblasts although with different time courses. Whereas the transforming growth factor beta effect was transient the interleukin-1 effect was sustained for at least 48 h. None of the cytokines tested affected VEGF expression in RPE cells. By using Western blotting, it was further found that stimulation with interleukin-1 induced VEGF protein expression in choroidal fibroblasts but not in RPE cells. In conclusion, choroidal fibroblasts respond by elevated VEGF mRNA levels after phorbol ester, interleukin-1 and transforming growth factor beta stimulation and elevated VEGF protein levels after phorbol ester and interleukin-1 stimulation suggesting that choroidal fibroblasts may be target cells for increased VEGF synthesis secondary to paracrine cytokine production.
视网膜下新生血管形成是年龄相关性黄斑变性中一种严重的威胁视力的并发症。以往对手术切除的新生血管膜进行的免疫组织化学研究表明，除了新生血管基质外，这些膜还由几种不同的细胞类型组成，如视网膜色素上皮（RPE）细胞、脉络膜成纤维细胞和血管内皮细胞。由于血管内皮生长因子（VEGF）能有效且特异性地诱导血管生成，因此研究了VEGF在脉络膜成纤维细胞和RPE细胞中是否表达和/或可诱导。从成年人类死后的眼睛中分离出脉络膜成纤维细胞和RPE细胞，并检测VEGF mRNA和蛋白的表达。通过Northern印迹法发现，脉络膜成纤维细胞和RPE细胞均低水平表达VEGF mRNA。为了研究这种VEGF表达是否进一步可诱导，用佛波酯激活细胞内效应酶蛋白激酶C。这种激活导致脉络膜成纤维细胞中VEGF mRNA显著增加，但RPE细胞中未增加，6小时后检测到最大增加。用福斯高林提高细胞内环磷酸腺苷水平对两种细胞类型中的VEGF mRNA均无明显影响。测试了白细胞介素-1、转化生长因子β、肿瘤坏死因子α和血小板衍生生长因子的刺激，以观察VEGF表达是否受细胞因子诱导。白细胞介素-1和转化生长因子β均诱导脉络膜成纤维细胞中VEGF表达，尽管时间进程不同。转化生长因子β的作用是短暂的，而白细胞介素-1的作用持续至少48小时。所测试的细胞因子均未影响RPE细胞中VEGF的表达。通过Western印迹法进一步发现，白细胞介素-1刺激诱导脉络膜成纤维细胞中VEGF蛋白表达，但RPE细胞中未诱导。总之，脉络膜成纤维细胞在佛波酯、白细胞介素-1和转化生长因子β刺激后VEGF mRNA水平升高，在佛波酯和白细胞介素-1刺激后VEGF蛋白水平升高，表明脉络膜成纤维细胞可能是旁分泌细胞因子产生继发的VEGF合成增加的靶细胞。
