Micro- and Nanotechnologies
SELA-Chip: A microfluidic airway organ-on-a-chip system for studying respiratory health
Wednesday, February 7
3:00 PM - 3:30 PM
The lung airway tissue environment is comprised of different cell types, including airway epithelial cells (ECs) and smooth muscle cells (SMCs) that have been shown to play major roles in the pathogenesis of chronic lung diseases (CLDs). Communication between ECs and SMCs is a crucial aspect in CLDs triggered by exacerbations such as air pollutants and pathogens. SMC-EC interactions are thus central to elucidating mechanisms in CLDs, and important for revealing new opportunities for CLD therapy. However, our understanding of SMC-EC interactions in lung airways remains limited due to a lack of experimental models that can accurately mimic the human physiology of the lung. Recent advances in organ-on-a-chip lung models have demonstrated excellent physiologic mimicry of the alveoli and small airway function. However, these systems have yet to recapitulate airway SMC-EC interactions in microfluidic cell culture, and have relied on biologically inert polyester membranes to separate culture compartments. Furthermore, existing microfluidic devices face challenges in throughput due to use of PDMS and designs that are not amenable to parallelization.
Our objective was to address these limitations by developing a multi-layer microfluidic organ-on-a-chip device, called SELA-Chip, which uses a biocompatible hydrogel for compartmentalization, as well as an arrayable design to increase experimental throughput, with specific application to studying EC-SMC interactions of the lung airway. The SELA-Chip was fabricated in acrylic using a combination of micromilling and solvent bonding techniques. The chip consisted of 3 vertically stacked microfluidic compartments representing a top epithelial chamber, a middle ECM gel layer, and a bottom reservoir chamber for SMC culture. The key design element that realized this concept was the protruding ledge on each side of the middle microfluidic compartment, which created a unique cross-section that enabled gel suspension. A hydrogel mixture consisting of Type I collagen and Matrigel was used to form the suspended hydrogel layer. Once the gel was suspended, we cultured Calu-3 epithelial cells on the top surface for 21 days, and co-cultured human bronchial SMCs on the bottom surface for an additional 14 days. In separate experiments, we removed the liquid medium above the Calu-3 cells after 14 days, and introduced air-liquid interface (ALI) culture for 31 days. Immunostaining was performed to visualize cell markers including ZO-1 tight junctions, MUC5AC, F-actin, and α-SMA. SMC alignment was analyzed using ImageJ to measure cell orientation angles with respect to the gel cross-section. After 31 days of ALI culture, we observed positive staining of MUC5AC, an indication of differentiated mucin-producing goblet cells. Cocultures of ECs and SMCs showed excellent ZO-1 tight junction formation, and increased SMC alignment from days 4 to 7. Future work will involve introducing airflow, pollutants and airborne pathogens to examine EC-SMC interactions under physiologic conditions.