Journal of Cytology & Histology

Digital Image Processing Assessment of the Differential in vitro Antiangiogenic Effects of Dimeric and Monomeric Beta2-Glycoprotein I

Abstract

Camila Machado, Miriela Escobedo Nicot, Carolina Nigro Stella, Sara Vaz, Cassia Prado, Durvanei Augusto Maria, Francisco Palacios Fernandez and Ligia Ferreira Gomes

The β2 -glycoprotein I (β2GPI) is an endothelial cell ligand, accessible for systemic, autocrine and paracrine signaling. In vivo, β2GPI is immobilized by binding, mainly to the endothelial cell membrane heparan sulfate but also to anionic phospholipids, and functional receptors. The β2GPI was attributed antiangiogenic properties both in vitro and in vivo. This work was designed to evaluate the antiangiogenic effects of native, monomeric, and dimeric β2GPI. Monomeric as well as dimeric forms were purified from human plasma, and the native protein was obtained as a balanced mixture of both components present in human plasma. The proliferation, migration, and differentiation of Human Umbilical Vascular Endothelial Cells (HUVEC) were considered in an in vitro angiogenesis model based on tridimensional cultures and quantitative digital image processing techniques. The early events of the in vitro HUVEC growth and differentiation in the tridimensional cultures microenvironment were addressed by the morphological analysis. The morphological aspects were correlated to the cell growth, oxidative balance outcome and mitochondrial toxicity assays, leading to the evidence that non-confluent HUVEC cultures temporarily stop growing in the presence of the native protein, but remain competent to proliferate. The β2GPI monomer allowed the in vitro differentiation of the HUVECs into typical trabeculæ and incomplete capillary-like tubes, along with lowering the available proliferation fraction. In opposition, the dimer rich purification fraction exposure halted cell elongation and migration, and prevented the organization of the tubular structures in tridimensional cultures, maintaining cell growth. The morphological approach was useful to attribute to β2GPI dimerization the cell migration inhibition modulation, which potentially leads to overcome the diminished sprouting antiangiogenic effect of the monomer fraction of the native protein.