Vascular endothelial growth factor (VEGF) and platelet (PF-4) factor 4 inputs modulate human microvascular endothelial signaling in a three-dimensional matrix migration context

Comparative Evaluation of the Angiogenic Potential of Hypoxia Preconditioned Blood-Derived Secretomes and Platelet-Rich Plasma: An In Vitro Analysis

Blood-derived factor preparations are being clinically employed as tools for promoting tissue repair and regeneration. Here we set out to characterize the in vitro angiogenic potential of two types of frequently used autologous blood-derived secretomes: platelet-rich plasma (PRP) and hypoxia preconditioned plasma (HPP)/serum (HPS). The concentration of key pro-angiogenic (VEGF) and anti-angiogenic (TSP-1, PF-4) protein factors in these secretomes was analyzed via ELISA, while their ability to induce microvessel formation and sprouting was examined in endothelial cell and aortic ring cultures, respectively. We found higher concentrations of VEGF in PRP and HPP/HPS compared to normal plasma and serum. This correlated with improved induction of microvessel formation by PRP and HPP/HPS. HPP had a significantly lower TSP-1 and PF-4 concentration than PRP and HPS. PRP and HPP/HPS appeared to induce similar levels of microvessel sprouting; however, the length of these sprouts was greater in HPP/HPS than in PRP cultures. A bell-shaped angiogenic response profile was observed with increasing HPP/HPS dilutions, with peak values significantly exceeding the PRP response. Our findings demonstrate that optimization of peripheral blood cell-derived angiogenic factor signalling through hypoxic preconditioning offers an improved alternative to simple platelet concentration and release of growth factors pre-stored in platelets.

Human Th17 Migration in Three-Dimensional Collagen Involves p38 MAPK

T cell migration across extracellular matrix (ECM) is an important step of the adaptive immune response but is also involved in the development of inflammatory autoimmune diseases. Currently, the molecular mechanisms regulating the motility of effector T cells in ECM are not fully understood. Activation of p38 MAPK has been implicated in T cell activation and is critical to the development of immune and inflammatory responses. In this study, we examined the implication of p38 MAPK in regulating the migration of human Th17 cells through collagen. Using specific inhibitor and siRNA, we found that p38 is necessary for human Th17 migration in three-dimensional (3D) collagen and that 3D collagen increases p38 phosphorylation. We also provide evidence that the collagen receptor, discoidin domain receptor 1 (DDR1), which promotes Th17 migration in 3D collagen, is involved in p38 activation. Together, our findings suggest that targeting DDR1/p38 MAPK pathway could be beneficial for the treatment of Th17-mediated inflammatory diseases. J. Cell. Biochem. 118: 2819-2827, 2017. © 2017 Wiley Periodicals, Inc.

The Fibrin Matrix Regulates Angiogenic Responses within the Hemostatic Microenvironment through Biochemical Control

Conceptually, premature initiation of post-wound angiogenesis could interfere with hemostasis, as it relies on fibrinolysis. The mechanisms facilitating orchestration of these events remain poorly understood, however, likely due to limitations in discerning the individual contribution of cells and extracellular matrix. Here, we designed an in vitro Hemostatic-Components-Model (HCM) to investigate the role of the fibrin matrix as protein factor-carrier, independent of its cell-scaffold function. After characterizing the proteomic profile of HCM-harvested matrix releasates, we demonstrate that the key pro-/anti-angiogenic factors, VEGF and PF4, are differentially bound by the matrix. Changing matrix fibrin mass consequently alters the balance of releasate factor concentrations, with differential effects on basic endothelial cell (EC) behaviors. While increasing mass, and releasate VEGF levels, promoted EC chemotactic migration, it progressively inhibited tube formation, a response that was dependent on PF4. These results indicate that the clot’s matrix component initially serves as biochemical anti-angiogenic barrier, suggesting that post-hemostatic angiogenesis follows fibrinolysis-mediated angiogenic disinhibition. Beyond their significance towards understanding the spatiotemporal regulation of wound healing, our findings could inform the study of other pathophysiological processes in which coagulation and angiogenesis are prominent features, such as cardiovascular and malignant disease.

Harnessing developmental processes for vascular engineering and regeneration

The formation of vasculature is essential for tissue maintenance and regeneration. During development, the vasculature forms via the dual processes of vasculogenesis and angiogenesis, and is regulated at multiple levels: from transcriptional hierarchies and protein interactions to inputs from the extracellular environment. Understanding how vascular formation is coordinated in vivo can offer valuable insights into engineering approaches for therapeutic vascularization and angiogenesis, whether by creating new vasculature in vitro or by stimulating neovascularization in vivo. In this Review, we will discuss how the process of vascular development can be used to guide approaches to engineering vasculature. Specifically, we will focus on some of the recently reported approaches to stimulate therapeutic angiogenesis by recreating the embryonic vascular microenvironment using biomaterials for vascular engineering and regeneration.