Abstract
Tropoelastin, the soluble precursor of elastin, has been used for regenerative and wound healing purposes and noted for its ability to accelerate wound repair by enhancing vascularization at the site of implantation. However, it is not clear whether these effects are directly due to the interaction of tropoelastin with endothelial cells or communicated to endothelial cells following interactions between tropoelastin and neighboring cells, such as mesenchymal stem cells (MSCs). We adapted an endothelial tube formation assay to model in vivo vascularization with the goal of exploring the stimulatory mechanism of tropoelastin. In the presence of tropoelastin, endothelial cells formed less tubes, with reduced spreading into capillary-like networks. In contrast, conditioned media from MSCs that had been cultured on tropoelastin enhanced the formation of more dense, complex, and interconnected endothelial tube networks. This pro-angiogenic effect of tropoelastin is mediated indirectly through the action of tropoelastin on co-cultured cells. We conclude that tropoelastin inhibits endothelial tube formation, and that this effect is reversed by pro-angiogenic crosstalk from tropoelastin-treated MSCs. Furthermore, we find that the known in vivo pro-angiogenic effects of tropoelastin can be modeled in vitro, highlighting the value of tropoelastin as an indirect mediator of angiogenesis.
Highlights
Human umbilical vein endothelial cells (HUVECs) (Lonza; C2517A, Basel, Switzerland) were seeded into cell culture flasks at a density of 2500 cells/cm2 and cultured at 37 ◦ C, 5% CO2 in a humidified incubator in Endothelial Growth Medium-2 (EGM-2), which is endothelial cell basal medium (EBM-2) supplemented with 2% FBS, 0.4% hFGF-B, 0.1%VEGF, 0.1% R3-IGF-1, 0.04% hydrocortisone, 0.1% ascorbic acid, 0.1% heparin, 0.1%
Cell proliferation assays were performed on HUVECs and mesenchymal stem cells (MSCs) to explore the effects Cell proliferation assays were performed on HUVECs and MSCs to explore the efof tropoelastin on proliferation
HUVECs grown in the presence or absence of tropoelastin (Figure was found between HUVECs grown in the presence or absence of tropoelastin (Figure 1A)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Angiogenesis involves branching of novel vasculature from existing vasculature at a wound site, subsequently giving rise to a capillary network that perfuses the affected region and restores circulation. The presence of blood vessels within the forming granulation tissue promotes cell viability and repair at the wound site, allowing diverse cells such as stem cells and fibroblasts to infiltrate and proliferate deposit extracellular matrix. Viable blood flow is critical to biological repair for efficient tissue regeneration. This process is finely tuned, as demonstrated by an insufficiency of blood vessels during the latter stages of wound healing that can contribute to collagen accumulation and scar formation [1]
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