Ivery and permeability control for ECs. Although phenotypically similar, MSCs from different tissues promote tubulogenesis through distinct mechanisms. In this report, we describe differences and similarities regarding molecular interactions in order to investigate which of these two cell types displays more Lenvatinib favorable characteristics to be used in clinical applications. Our comparative study shows that ASCs as well as BMSCs are both promising cell types to induce vascularization with ECs in vitro and consequently are promising candidates to support in vivo vascularization. Keywords: Vascularization, Endothelial cells, Mesenchymal stem cells, Co-culture, Molecular mechanismsIntroduction One of the major challenges in tissue engineering today is the realization of an integrated vascular network to provide adequate blood supply for living cells in tissue constructs. Limited by oxygen diffusion only, tissueengineered products for skin- and cartilage-regeneration are already used in clinics [1]. However, organs with a more complex structure need a vascular system which integrates with the host vascular system to provide sufficient oxygen and nutrient PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/22993420 supply to the cells [2]. To overcome the problem of missing ingrowth of host vessels into the construct, different approaches have been investigated [3]. Integration of signaling molecules in scaffolds to stimulate the growth of blood vessels* Correspondence: wolfgang.holnthoner@trauma.lbg.ac.at 1 Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Donaueschingenstrasse 13 1200, Vienna, Austria 2 Austrian Cluster for Tissue Regeneration, Vienna, Austria Full list of author information is available at the end of the articlefrom the host after in vivo implantation is a currently pursued strategy. Another method represents the in vitro generation of pre-vascularized tissues that will be connected to the host upon implantation. In the latter case, critical parameters for vascularization are the choice of cells, in addition to the culture medium, appropriate matrix, and cell seeding parameters [4?]. Physiological microvasculature compromises endothelial cells (ECs) and in addition supportive cells, termed mural cells, to ensure controlled permeability, contraction, and stability and to supply growth factors. Mesenchymal stem cells (MSCs), a population of adult stem cells, develop into mural cells in vitro when co-cultured with ECs [9]. MSCs present a heterogeneous population of cells found in various tissues. Adipose tissue-derived stem/stromal cells (ASCs) [10] PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/8627573 and bone marrow derived stem cells (BMSCs) provide autologous sources for adult stem cells. While both cell types are phenotypically very similar, they promote vascular tube formation via?2015 Pill et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Pill et al. Cell Regeneration (2015) 4:Page 2 ofdistinct molecular interactions [11]. These tube formations have been shown being capable of anast.