Microfluidic model of monocyte extravasation reveals the role of hemodynamics and subendothelial matrix mechanics in regulating endothelial integrity

Abstract

Extravasation of circulating cells is an essential process that governs tissue inflammation and the body's response to pathogenic infection. To initiate anti-inflammatory and phagocytic functions within tissues, immune cells must cross the vascular endothelial barrier from the vessel lumen to the subluminal extracellular matrix. In this work, we present a microfluidic approach that enables the recreation of a three-dimensional, perfused endothelial vessel formed by human endothelial cells embedded within a collagen-rich matrix. Monocytes are introduced into the vessel perfusate, and we investigate the role of luminal flow and collagen concentration on extravasation. In vessels conditioned with the flow, increased monocyte adhesion to the vascular wall was observed, though fewer monocytes extravasated to the collagen hydrogel. Our results suggest that the lower rates of extravasation are due to the increased vessel integrity and reduced permeability of the endothelial monolayer. We further demonstrate that vascular permeability is a function of collagen hydrogel mass concentration, with increased collagen concentrations leading to elevated vascular permeability and increased extravasation. Collectively, our results demonstrate that extravasation of monocytes is highly regulated by the structural integrity of the endothelial monolayer. The microfluidic approach developed here allows for the dissection of the relative contributions of these cues to further understand the key governing processes that regulate circulating cell extravasation and inflammation.

Integrated role of human thymic stromal cells in hematopoietic stem cell extravasation

“…Several in vitro models have been developed to investigate cellular extravasation in other contexts, that is, cancer [34][35][36][37][38][39][40] and immune cells extravasation. 41,42 The methods have so far focused on the innate extravasation potential of the cells themselves with less attention on the influence of the microenvironment in which this extravasation occurs. We have therefore sought to develop an assay that mimics the vasculature while also incorporating the thymic stroma to better understand the influence of thymus microenvironment on progenitor seeding and T-cell development.…”

“…High‐throughput analysis with minimal cell number requirements, spatiotemporally high‐resolution live microscopy, and retrieval of biological material are key advantages of microfluid‐based 3D culture systems compared to bioreactors or organotypic culturing. Several in vitro models have been developed to investigate cellular extravasation in other contexts, that is, cancer 34–40 and immune cells extravasation 41,42 . The methods have so far focused on the innate extravasation potential of the cells themselves with less attention on the influence of the microenvironment in which this extravasation occurs.…”

A bone‐on‐a‐chip collagen hydrogel‐based model using pre‐differentiated adipose‐derived stem cells for personalized bone tissue engineering

“…However, collagen density is a tunable value: it can be diluted or concentrated depending on the final mechanical and rheological properties required. 36 For instance, for in vitro creation of endothelial vessels, Pérez et al 51 compared two different collagen hydrogel concentrations (2.5 and 6 mg/ml) and showed that this directly affects the integrity of endothelial vessels, which decreases when high‐concentration hydrogels were used. This fact makes collagen hydrogels a versatile tool for different fields of tissue engineering.…”

A microfluidic-based analysis of 3D macrophage migration after stimulation by Mycobacterium, Salmonella and Escherichia

“…In addition, we analyzed macrophage migration in gels of different collagen concentration, at 2.5, 4 and 6 mg/mL. These concentration changes imply structural changes in the hydrogel, such as smaller pore size or porosity, higher storage shear modulus and a decreasing hydraulic permeability with increasing collagen concentration [34].…”