Inhibitors of DNA (Id) proteins have been implicated in cell growth, cell cycle control, apoptosis and angiogenesis. Studies reveal that Id1 and Id3 may be required for angiogenesis in adult tissues. This work aimed at investigating the consequences of loss-of-function of Id protein on growth and apoptosis in an in vitro model using Human Umbilical Vein Endothelial Cells (HUVECs). Using automated image analysis software (CellProfiler Analyst), cell cycle profiles of cell populations following siRNA down-regulation of Id proteins were investigated. Also, cell viability analysis with 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was evaluated. The study also employed flow cytometry using mitochondrial membrane-potential marker (3, 3-Dihexyloxacarbocyanine Iodide) (DiOC6) and Propidium Iodide (PI) as a marker of non-viable necrotic cells. Down-regulation of Id1 and Id3 reduced viable HUVECs populations. In addition, knock down of Id1 and Id3 showed cell cycle arrest. Furthermore, cell death analysis following the silencing of Id1 and Id3 induced apoptosis. These findings suggest that the inhibition of Id1 and Id3 may impair endothelial cell activation and angiogenesis and may also provide an attractive target for the development of new therapies for angiogenic disorders.
Key words: Apoptosis, Angiogenesis, S-phase, Down-regulation, Human umbilical vein endothelial cells, Knock-down
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