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X. Zhang, M. C. Gillies; Expression of the Two Isoforms of Flk-1 Transcripts in Early Diabetic Rat Retinas. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5089.
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Aims: Previous studies have shown that two alternative spliced functional isoforms of vascular endothelial factor receptor 2(VEGFR2, Flk-1) are present in normal rat retinas. However the functions of the two isoforms have not been fully understood in diabetic retinopathy. To evaluate the functions of the two isoforms and to further investigate the potential mechanisms of intravitreal injection of triamcinolone acetonide (IVTA) on the expression of rat Flk-1 gene, we investigated the regulation of the gene expression of the two isoforms in rat retinas.
Three pairs of PCR primers were designed to specifically amplify the total, long and truncated isoforms of rat Flk-1 mRNA. Gene transcriptional levels of the two isoforms were evaluated in the streptozotozine (STZ)-induced diabetic with /without IVTA- treated retinas, using quantitative polymerase chain reaction (real time RT-PCR). To detect the gene activities, standard efficiency standard curves were set up for each of the candidate isoforms.
The mRNA expression level of the long form Flk-1 gene was 10 times more abundant than short form in normal rat retinas. The expression of the total, long and short form of Flk-1 was up regulated by 1.5, 1.8 and 0.7 fold respectively in sham-treated diabetic retinas compared to the sham-treated non-diabetic retinas. IVTA inhibited the expression of the total, long and short forms of Flk-1by 1.2, 2.0 and 0.3 fold respectively in the IVTA-treated diabetic compared to sham-treated retinas. There was no statistical significance in the expression of the total and short form of Flk-1 between the four groups.
The long form of Flk-1 is the predominant mediator of VEGF-A in the pathogenesis of DR, and can be significantly inhibited by IVTA treatment. The short form may also contribute to the pathogenesis of DR.
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