Differential functional roles of fibroblasts and pericytes in the formation of tissue-engineered microvascular networks in vitro
AimsFormation of a perfusable microvascular network (VN) is critical for tissue engineering of solid organs. Stromal cells can support endothelial cell (EC) self-assembly into a VN, but distinct stromal cell populations may play different roles in this process. Here we investigated the effects that two widely used stromal cells populations, fibroblasts (FBs) and pericytes (PCs), have on VN formation. Methods and resultsWe examined the effects of adding defined stromal cell populations on the self-assembly of ECs derived from human endothelial colony forming cells (ECFCs) into perfusable VNs in fibrin gels cast within a microfluidics chamber. ECs alone fail to fully assemble a perfusable VN. Human lung FBs stimulate the formation of EC lined VNs within microfluidic devices. RNA-seq analysis suggested that FBs produce high levels of hepatocyte growth factor (HGF), and addition of recombinant HGF improved VN formation within devices. Human placental PCs could not substitute for FBs, but in the presence of FBs, PCs closely associated with ECs, formed a common basement membrane, extended microfilaments intercellularly, and reduced microvessel diameters. ConclusionsDifferent stromal cell types provide different functions in microvessel assembly by ECs. FBs support VN formation by providing paracrine growth factors whereas PCs directly interact with ECs to modify microvascular morphology. Statement of ContributionNatalia Kosyakova, Derek Kao, William G. Chang were primarily responsible for the conception, design, interpretation of experiments, and drafting of the manuscript. Francesc Lopez-Giraldez carried out analysis of RNA-seq data. Susann Spindler and Gregory Tietjen assisted with microvessel analysis software. Morven Graham and Xinran Liu assisted with the electron microscopy. Kevin J. James and Jee Won Shin assisted with data collection. Jordan Pober assisted with a critical review of manuscript and experimental design.