Spatially resolved microfluidic stimulation of lymphoid tissue ex vivo

Abstract

The lymph node is a structurally complex organ of the immune system, whose dynamic cellular arrangements are thought to control much of human health. Currently, no methods exist to precisely stimulate substructures within the lymph node or analyze local stimulus-response behaviors, making it difficult to rationally design therapies for inflammatory disease. Here we describe a novel integration of live lymph node slices with a microfluidic system for local stimulation. Slices maintained the cellular organization of the lymph node while making its core experimentally accessible. The 3-layer polydimethylsiloxane device consisted of a perfusion chamber stacked atop stimulation ports fed by underlying microfluidic channels. Fluorescent dextrans similar in size to common proteins, 40 and 70 kDa, were delivered to live lymph node slices with 284 ± 9 μm and 202 ± 15 μm spatial resolution, respectively, after 5 s, which is sufficient to target functional zones of the lymph node. The spread and quantity of stimulation were controlled by varying the flow rates of delivery; these were predictable using a computational model of isotropic diffusion and convection through the tissue. Delivery to two separate regions simultaneously was demonstrated, to mimic complex intercellular signaling. Delivery of a model therapeutic, glucose-conjugated albumin, to specific regions of the lymph node indicated that retention of the drug was greater in the B-cell zone than in the T-cell zone. Together, this work provides a novel platform, the lymph node slice-on-a-chip, to target and study local events in the lymph node and to inform the development of new immunotherapeutics.

Biomaterials as Tools to Decode Immunity

“…For example, since microfluidic systems provide control over the flow rate, concentration of stimulus (e.g., antigens, adjuvants, and cytokines), and location (i.e., defined inlet channel) that stimulus is applied to, these technologies are well‐suited to study how signals are processed at the tissue level. To investigate specific functions in LN subdomains, one recent example used a microfluidic device to deliver signals precisely to the T or B cell zones within a live LN slice . This system employed a polydimethylsiloxane (PDMS, silicone) device with a chamber that accommodates a thin slice of live LN tissue.…”

“…The green port indicates the controlled delivery of stimulus through a specific port to the tissue slice located above. Reproduced with permission . Copyright 2017, Royal Society of Chemistry.…”

“…In the bottom images, fluorescent glucose was delivered to the B cell zone. Reproduced with permission . Copyright 2017, Royal Society of Chemistry.…”

“…c) Quantification of images in (b). Reproduced with permission . Copyright 2017, Royal Society of Chemistry.…”

Fitting tissue chips and microphysiological systems into the grand scheme of medicine, biology, pharmacology, and toxicology

“…107 This approach might be implemented in microfluidic bioreactors, but there does not yet appear to be a pressing need to do so. The spatial complexity of the lymph node has been examined with a microfluidic device that can separately stimulate B-cell and T-cell zones within an isolated slice of a mouse lymph node, 108 but such zones have yet to be reconstructed with a tissue-engineered human lymph node equivalent. (The authors note that the use of microfluidics to perfuse a lymph node slice has similarities to the use of microfluidic devices to perfuse brain slices.…”