Adipose Tissue Progenitor Cells Directly Interact with Endothelial Cells to Induce Vascular Network Formation

Abstract

Adipose stromal cells (ASCs) express markers and functional properties of pericytes in vitro and, in combination with endothelial cells (ECs), are able to establish multilayer functional vessels in vivo. However, the factors that coordinate EC-ASC communications to promote migration of these cells toward one another, and their heterotypic assembly into vascular structures are not well defined. To understand the mechanisms of EC-ASC interaction, we developed an in vitro model of coculturing ECs with ASCs in a system containing serum but no additional exogenous cytokines or extracellular matrix (ECM) proteins. We demonstrated that ASCs have a profound potential to stimulate morphogenesis of ECs into branching networks of cord structures. The vascular networks developed in 6 days and were stable for at least 3 weeks. This process was associated with an increase in ECM protein production by ASCs and ECs, alpha-smooth muscle actin expression by ASCs, and increased CD31/platelet endothelial cell adhesion molecule-1 (PECAM-1) surface presentation by ECs. The vascular network formation (VNF) was dependent on matrix metalloproteinase activity and cell communications through vascular endothelial growth factor, hepatocyte growth factor, and platelet-derived growth factor-BB pathways. ASCs exhibited significantly higher potential to stimulate VNF than smooth muscle cells and fibroblasts. Media conditioned by ASCs promoted VNF by ECs cultured on smooth muscle cells and fibroblasts, but could not replace the presence of ASCs in coculture. The presence of ASCs in EC-fibroblast cocultures in a low fraction efficiently stimulated VNF. These findings demonstrate that the vasculogenesis-promoting potential of ASCs depends on interaction with ECs involving contact and likely bi-directional interaction, resulting in modulated secretion of cytokines and ECM proteins.

Hydrogel-based microfluidics for vascular tissue engineering

“…This phenomenon was associated with an increased expression of ECM proteins such as laminin, collagen IV, as well as cellular αSMA [2,4]. In our study, we applied a 1:4 co-culture ratio of hASCs to HUVECs for encapsulation into PEGylated fibrin hydrogel constructs and confirmed that the considerable expression of collagen IV, laminin and αSMA is dependent on co-culture of hASCs and HUVECs within the PEGylated fibrin gel (Figure 2).…”

“…There are two explicit mechanisms of blood vessel growth: vasculogenesis, the de novo formation of blood vessels by endothelial progenitor cells, and angiogenesis, the sprouting of new vessels from preexisting ones. For engineering of microvasculature within a 3-D cell laden biomaterial construct, many biological extracellular matrix (ECM) materials and cell co-cultures have been studied with respect to their vasculogenic potential [1][2][3][4]. Mimicking the embryonic environment for vasculogenesis is a popular strategy; for example, experiments on encapsulation of vascular progenitor cells within 3-D biological ECM have been undertaken, in which angioblasts and mesenchymal stem cells self-organize into a microvascular network and form a capillary bed [5].…”

“…Human umbilical vein endothelial cells (HUVECs) were used as vascular precursor cells and human adipose derived stem cells (hASCs) were used as stromal cells to support HUVEC morphogenesis via secretion of pro-angiogenic growth factors [2,4]. It is hypothesized (a) that a cell friendly environment will support in vitro vasculogenesis that is induced by the interaction of HUVECs and hASCs, and (b) that PEGylated fibrin gel can be a strong candidate material for cell encapsulation and hydrogel based microfluidic device fabrication.…”

Human vascular model with defined stimulation medium – a characterization study

“…We and others have shown that adipose stromal cells and umbilical vein endothelial cells are capable of self-assembling into a dense, three-dimensional vascular-like network (Sarkanen et al, 2012;Merfeld-Clauss et al, 2010;Verseijden et al, 2010). While adipose stromal cells secrete factors that induce endothelial cell (EC) sprouting and lumen formation (Rubina et al, 2009;Traktuev et al, 2008;Rehman et al, 2004;Kilroy et al, 2007;Bishop et al, 1999), the supporting stromal cells also enhance vascular basement membrane and lumen formation (Merfeld-Clauss et al, 2010;Newman et al, 2013;Stratman et al, 2009).…”

Tasisulam Sodium, an Antitumor Agent That Inhibits Mitotic Progression and Induces Vascular Normalization

“…Because endothelial proliferation is a process critical for angiogenesis, tasisulam was next assessed for inhibition of in vitro endothelial cord formation, a surrogate assay that models key morphogenic features of blood vessel formation (21). Tasisulam inhibited VEGF-, fibroblast growth factor (FGF)-and epidermal growth factor (EGF)-induced cords in a concentration-dependent manner, with EC 50 values of 47, 103, and 34 nmol/L, respectively ( Fig.…”