A bioengineered lymphatic vessel model for studying lymphatic endothelial cell‐cell junction and barrier function

Abstract

Objective Lymphatic vessels (LVs) maintain fluid homeostasis by draining interstitial fluid. A failure in lymphatic drainage triggers lymphatic diseases such as lymphedema. Since lymphatic drainage is regulated by lymphatic barrier function, developing experimental models that assess lymphatic barrier function is critical for better understanding of lymphatic physiology and disease. Methods We built a lymphatic vessel‐on‐chip (LV‐on‐chip) by fabricating a microfluidic device that includes a hollow microchannel embedded in three‐dimensional (3D) hydrogel. Employing luminal flow in the microchannel, human lymphatic endothelial cells (LECs) seeded in the microchannel formed an engineered LV exhibiting 3D conduit structure. Results Lymphatic endothelial cells formed relatively permeable junctions in 3D collagen 1. However, adding fibronectin to the collagen 1 apparently tightened LEC junctions. We tested lymphatic barrier function by introducing dextran into LV lumens. While LECs in collagen 1 showed permeable barriers, LECs in fibronectin/collagen 1 showed reduced permeability, which was reversed by integrin α5 inhibition. Mechanistically, LECs expressed inactivated integrin α5 in collagen 1. However, integrin α5 is activated in fibronectin and enhances barrier function. Integrin α5 activation itself also tightened LEC junctions in the absence of fibronectin. Conclusions Lymphatic vessel‐on‐chip reveals integrin α5 as a regulator of lymphatic barrier function and provides a platform for studying lymphatic barrier function in various conditions.

Podoplanin is Responsible for the Distinct Blood and Lymphatic Capillaries

“…To mimic blood and lymphatic sprouting into 3D matrices, we performed angiogenesis assay using IdenTX chip (AIM Biotech, Singapore) following manufacture protocol and previous studies. 24 , 29 Briefly, the middle channel was filled with fibrin gel by mixing 6 μ L of 7 wt% fibrinogen solution with 4 μ L of thrombin solution provided by Fibrin In vitro Angiogenesis Assay kit (Sigma Aldrich). To induce angiogenesis, 2 μ M of S1P (Sphingosine-1 phosphate) and 100 ng/mL of VEGF-C were encapsulated into the fibrin gel.…”

A Challenge for Engineering Biomimetic Microvascular Models: How do we Incorporate the Physiology?

“…Most common in vitro models can be characterized as bottom-up approaches that add one, two, or three cell types into a matrix environment ( Kaunus et al, 2011 ). More technologically influenced approaches involve patterning cell and/or matrix through, for example, bioprinting or microfluidic based platforms ( Song and Munn, 2011 ; Wang et al, 2016 ; Haase and Kamm, 2017 ; Campisi et al, 2018 ; Osaki et al, 2018 ; Henderson et al, 2021 ; Shirure et al, 2021 ; Ren et al, 2022 ). In recent years, these models have enabled reductionist experiments focused on isolating the effects of the individual components.…”

“…Physiological relevance is increased within this platform by tuning the material used for patterning the channels and the verification of vessel permeability ( Qiu et al, 2018 ). Finally, an application for investigating lymphangiogenesis is made possible by seeding the channels with lymphatic endothelial cells ( Osaki et al, 2018 ; Henderson et al, 2021 ). The second common microfluidic platform for mimicking the microcirculation is best described by a matrix region with an inlet and outlet channel ( Wang et al, 2016 ; Shirure et al, 2021 ).…”

The Microvascular-Lymphatic Interface and Tissue Homeostasis: Critical Questions That Challenge Current Understanding

“…Do variations in local extracellular matrix cues help determine lymphatic endothelial junctional patterns? There is recent evidence that when fibronectin activates integrin α 5 , this can signal enhanced lymphatic endothelial barrier function [80]. Also, what exactly is the role of secondary valves for lymph flow in initial lymphatic networks?…”