Graph analysis of cell clusters forming vascular networks.

A P Alves,J Gómez-Gardeñes,O N Mesquita,U Agero

doi:10.1098/rsos.171592

Abstract

This manuscript describes the experimental observation of vasculogenesis in chick embryos by means of network analysis. The formation of the vascular network was observed in the area opaca of embryos from 40 to 55 h of development. In the area opaca endothelial cell clusters self-organize as a primitive and approximately regular network of capillaries. The process was observed by bright-field microscopy in control embryos and in embryos treated with Bevacizumab (Avastin®), an antibody that inhibits the signalling of the vascular endothelial growth factor (VEGF). The sequence of images of the vascular growth were thresholded, and used to quantify the forming network in control and Avastin-treated embryos. This characterization is made by measuring vessels density, number of cell clusters and the largest cluster density. From the original images, the topology of the vascular network was extracted and characterized by means of the usual network metrics such as: the degree distribution, average clustering coefficient, average short path length and assortativity, among others. This analysis allows to monitor how the largest connected cluster of the vascular network evolves in time and provides with quantitative evidence of the disruptive effects that Avastin has on the tree structure of vascular networks.

Highlights

Vasculogenesis is the process of de novo blood vessel formation [1,2]
It has been shown that a low dose of Bevacizumab (Avastin R ) administered in tumour regions induces the renormalization of the vascular network, improving the oxygenation and drug penetration into tumours
We proceed to show the main results that characterize the spatio-temporal self-organization of endothelial cells (ECs) clusters forming the vascular network in both groups of control and Avastin-treated chick embryos

Summary

Introduction

Vasculogenesis is the process of de novo blood vessel formation [1,2]. At early stages of development, a forming vascular network involves several processes such as migration, proliferation and aggregation of endothelial cells (ECs) [1,3]. The mechanisms involved in vasculogenesis have been largely studied using EC assembly [7,8,9,10,13], we still lack quantitative analysis to understand how a vascular network is formed in a more complex system [14,15]. In this regard, the development of new visualization techniques has allowed to monitor the vasculogenesis process on a whole embryo [2,15,16]. The anti-angiogenic factor slows down the tumour dissemination and enhances the effectiveness of chemo- and radiotherapies [19]

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