Research Article Behaviour of Endothelial Cells in a Tridimensional In Vitro Environment Raif Eren Ayata, 1,2,3 Stéphane Chabaud, 1,2 Michèle Auger, 4 and Roxane Pouliot 1,2,3 1 Centre de Recherche en Organog´ en` ese Exp´ erimentale de l’Universit´ e Laval/ LOEX, Qu´ ebec, QC, Canada G1J 1Z4 2 Division of Regenerative Medicine, CHU de Qu´ ebec Research Centre, Quebec, QC, Canada G1J 1Z4 3 Facult´ e de Pharmacie, Universit´ e Laval, Qu´ ebec, QC, Canada G1V 0A6 4 D´ epartement de Chimie, PROTEO, CERMA, Universit´ e Laval, Qu´ ebec, QC, Canada G1V 0A6 Correspondence should be addressed to Roxane Pouliot; roxane.pouliot@pha.ulaval.ca Received 8 October 2014; Revised 25 January 2015; Accepted 25 January 2015 Academic Editor: Hannes Stockinger Copyright © 2015 Raif Eren Ayata et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Angiogenesis is a fundamental process in healing, tumor growth, and a variety of medical conditions. For this reason, in vitro angiogenesis is an area of interest for researchers. Additionally, in vitro angiogenesis is important for the survival of prevascularized tissue-engineering models. he aim of this study was to observe the self-tubular organization behaviour of endothelial cells in the self-assembly method. In this study, bilayered and dermal substitutes were prepared using the self-assembly method. Histological, immunostaining, and biochemical tests were performed. he behavioural dynamics of endothelial cells in this biological environment of supportive cells were observed, as were the steps of the in vitro angiogenic cascade with self-organizing capillary-like structures formation. he epidermal component of the substitutes was seen to promote network expansion and density. It also increased the quantity of angiogenic factors (VEGF and Ang-1) without increasing the proinlammatory factor (IL-8). In addition, the increased MMP activity contributed to matrix degradation, which facilitated capillary formation. 1. Introduction Endothelial cells (ECs) lining the vascular tree form a strict monolayer of lattened noncycling (quiescent) cells [1]. Angiogenesis is a complex biological process involving the activation of ECs and the outgrowth of new blood vessels from existing vessels. he activated cell (tip cell) migrates towards stimuli in the extracellular matrix by degrading the matrix. Adjacent cells (stack cells) begin to proliferate and fol- low the leader cell. Aterwards, a capillary sprout and lumen formation take place, and these then mature into a newly formed capillary [2, 3]. Angiogenesis takes place during normal physiological processes such as ovulation, embryonic development, and wound healing [4]. However, angiogenesis is also seen in pathological conditions such as cancer, psoriasis, diabetes, and arthritis [5]. Its presence in both healthy and pathological situations makes angiogenesis an intriguing area of research [6]. he formation of capillary-like tubes (CLTs) by ECs has been undertaken in in vitro assays [7, 8] as well as in tissue-engineering applications [9]. In the context of tissue engineering, the main objective is the survival of grats ater transplantation [9]. In in vitro assays, the investigation focuses on the mechanistic aspects of capillary morphogen- esis in a controlled environment [10]. here are numerous types of assays, but most involve EC suspensions with or without supportive cells [6] in either a three-dimensional extracellular matrix gel such as ibrin [11–13] or collagen [11, 14, 15], or in polymer-based scafolds [16–19] and three- dimensional engineered tissues [9, 20, 21]. he methods mentioned above have shown that forma- tion of CLTs in vitro generally relies on the self-organization of ECs, either by themselves or with supportive cells. Media supplements have been seen to contribute to the proliferation and maintenance of cell morphology and phenotype. Rochon et al. (2010) [21] studied the efect of epithelial cells on the size of CLTs. hey observed that keratinocytes were able to regulate CLT size and morphology. Rochon’s bilayered skin model showed smaller and regular CLTs when compared with dermal models without keratinocytes. In addition, when they Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 630461, 9 pages http://dx.doi.org/10.1155/2015/630461