Stimulation of endothelial cell proliferation by microvesicles. A) Gel electrophoresis of amplified microvesicular M-phase-related transcripts. Presence of CENPE, KIF15, CEP55, CCNA2, NEK2, PBK and CDK8 were confirmed using RT-PCR. B) Immunofluorescence of HUVECs treated with microvesicles labeled with PKH26 (red). Cells were stained with anti-calnexin antibody, an endoplasmic reticulum marker protein (green). C-E) Immunostaining of HUVECs with anti-phospho-histone H3 (green) and anti-α-tubulin antibodies (red). After 12 hours, microvesicle-treated endothelial cells were at metaphase (D) and cytokinesis with mitotic spindle formation (E). None of the untreated control endothelial cells were in metaphase or cytokinesis stages. Scale bars represent 10 μm (B, D, E) and 40 μm (C). The symbol of PH3 represents phospho-histone H3.