Fabrication of a 3D model of a lymphatic vessel using microfluidic devices

A. Ramirez, P. Lee, K. Maisel
University of Maryland, College Park,
United States

Keywords: biological barriers, devices, disease, model systems, in vitro


Lymphatic vessels are critical for maintenance of tissue homeostasis and forming the adaptive immune response, as they are the natural conduit between peripheral tissues and the lymph nodes (LNs), where the immune response is shaped, and eventually into systemic circulation via the thoracic duct. Because particulates are primarily shuttled via lymphatic vessels, lymphatics have received considerable attention in recent years as potential targets for drug delivery, particularly for immune modulation. However, we do not yet fully understand how physiological processes and conditions such as fluid flow, edema, or inflammation affect transport by lymphatics. It is difficult to study this phenomenon in vivo, as they are not easily visualized and often buried deep inside body cavities, but most in vitro models to study transport do not consider the 3-dimensional nature of lymphatic transport: lymphatics are collapsed under steady-state conditions and pushed open by interstitial fluid flow across lymphatic endothelial cells and into the vessel, which drives molecules and particulates into the vessel. Here, we created a 3D microfluidic in vitro model of a lymphatic vessel that can recapitulate in vivo lymphatic architecture, including interstitial and luminal flow (Figure 1). The device consists of an inlet port which connects to an external pump, delivering media at a constant flow rate. The media will be directed through the vessel chamber and out of the outlet port. We created a microfluidic device, made of polydimethylsiloxane (PDMS), that consists of three compartments: 1) a glass cover slip at the bottom for live imaging, 2) a PDMS device that houses the vessel and inlet/outlet ports, and 3) a collagen hydrogel compartment containing a thin vessel through which media and other materials can be transported. A fibronectin coated 0.5mm diameter channel within the collagen hydrogel provides support for the vessel and promotes cell adhesion. We have established cell viability in this device and found cells begin to form cell-cell connections within two hours on the channel wall. Cells adhere to the walls of the channel and have an elongated morphology like lymphatic endothelial cells, indicating a functional vessel (Figure 2). We have optimized this system to include gravity driven flow by placement on a rocker, simulating lymph flow within the lymphatic vessel. This model will allow us to probe lymphatic transport in various simulated conditions such as healthy and disease, various flows (i.e. interstitial and luminal flow), and during inflammatory processes.