Systemic inflammation occurring around the course of tumor progression and treatment are often correlated with adverse oncological outcomes. As such, it is suspected that neutrophils, the first line of defense against infection, may play important roles in linking inflammation and metastatic seeding. To decipher the dynamic roles of inflamed neutrophils during hematogenous dissemination, we employ a multiplexed microfluidic model of the human microvasculature enabling physiologically relevant transport of circulating cells combined with real-time, high spatial resolution observation of heterotypic cell-cell interactions. LPS-stimulated neutrophils (PMNs) and tumor cells (TCs) form heterotypic aggregates under flow, and arrest due to both mechanical trapping and neutrophil-endothelial adhesions. Surprisingly, PMNs are not static following aggregation, but exhibit a confined migration pattern near TC-PMN clusters. We discover that PMNs are chemotactically confined by self-secreted IL-8 and tumor-derived CXCL-1, which are immobilized by the endothelial glycocalyx. This results in significant neutrophil sequestration with arrested tumor cells, leading to the spatial localization of neutrophil-derived IL-8, which also contributes to increasing the extravasation potential of adjacent tumor cells through modulation of the endothelial barrier. Strikingly similar migration patterns and extravasation behaviors were also observed in an in vivo zebrafish model upon PMN-tumor cell coinjection into the embryo vasculature. These insights into the temporal dynamics of intravascular tumor-PMN interactions elucidate the mechanisms through which inflamed neutrophils can exert proextravasation effects at the distant metastatic site.

Tumor tissues are characterized by an elevated interstitial fluid flow from the tumor to the surrounding stroma. Macrophages in the tumor microenvironment are key contributors to tumor progression. While it is well established that chemical stimuli within the tumor tissues can alter macrophage behaviors, the effects of mechanical stimuli, especially the flow of interstitial fluid in the tumor microenvironment, on macrophage phenotypes have not been explored. Here, we used three-dimensional biomimetic models to reveal that macrophages can sense and respond to pathophysiological levels of interstitial fluid flow reported in tumors (∼3 µm/s). Specifically, interstitial flow (IF) polarizes macrophages toward an M2-like phenotype via integrin/Src-mediated mechanotransduction pathways involving STAT3/6. Consistent with this flow-induced M2 polarization, macrophages treated with IF migrate faster and have an enhanced ability to promote cancer cell migration. Moreover, IF directs macrophages to migrate against the flow. Since IF emanates from the tumor to the surrounding stromal tissues, our results suggest that IF could not only induce M2 polarization of macrophages but also recruit these M2 macrophages toward the tumor masses, contributing to cancer cell invasion and tumor progression. Collectively, our study reveals that IF could be a critical regulator of tumor immune environment.

96 microfluidic devices with independent electrical readouts are coupled with 192 micropumps to make a high-throughput organ-on-chip platform.

Influenza and other respiratory viruses represent a significant threat to public health, national security, and the world economy, and can lead to the emergence of global pandemics such as the current COVID-19 crisis. One of the greatest barriers to the development of effective therapeutic agents to treat influenza, coronaviruses, and many other infections of the respiratory tract is the absence of a robust preclinical model. Preclinical studies currently rely on high-throughput, low-fidelity in vitro screening with cell lines and/or low-throughput animal models that often provide a poor correlation to human clinical responses. Here, we introduce a human primary airway epithelial cell-based model integrated into a highthroughput platform where tissues are cultured at an air-liquid interface (PREDICT96-ALI). We present results on the application of this platform to influenza and coronavirus infections, providing multiple readouts capable of evaluating viral infection kinetics and potentially the efficacy of therapeutic agents in an in vitro system. Several strains of influenza A virus are shown to successfully infect the human primary cell-based airway tissue cultured at an air-liquid interface (ALI), and as a proof-of-concept, the effect of the antiviral oseltamivir on one strain of Influenza A is evaluated. Human coronaviruses NL63 (HCoV-NL63) and SARS-CoV-2 enter host cells via ACE2 and utilize the protease TMPRSS2 for protein priming, and we confirm expression of both in our ALI model. We also demonstrate coronavirus infection in this system with HCoV-NL63, observing sufficient viral propagation over 96 hours post-infection to indicate successful infection of the primary cell-based model. This new capability has the potential to address a gap in the rapid assessment of therapeutic efficacy of various small molecules and antiviral agents against influenza and other respiratory viruses including coronaviruses.