Enabling the recirculation of leukocytes in a high-throughput microphysiological system (MPS) to study immune cell-vascular tissue interactions.

Microphysiological systems (MPS) are promising technologies that can enhance the drug development pipeline and fill gaps in identifying medical countermeasures for a variety of public health contexts. The integration of immune cells with MPS is increasingly recognized as a critical element for accurately modeling inflammatory responses in disease, injury, and infection. Specifically, the recruitment of circulating leukocytes to the vascular endothelium is an important first step in the inflammatory cascade. However, developing an MPS that supports physiologically relevant immune cell circulation poses significant biological and engineering challenges due to the delicate, short-lived nature of immune cells and the physical stresses imparted by many pumping systems. Here we present advancements to a previously established high-throughput MPS platform, PREDICT96, to enable recirculation of neutrophil-rich flow within microfluidics-based vascular tissue models. To maintain cells in suspension during recirculation, density adjustments to the culture media were made. Hardware and software controls were integrated to develop a pumping strategy that reduced the peak velocity and acceleration on the recirculating cells, maintaining high viability (90%) and minimal activation of neutrophils for up to 24 hours of continuous recirculation through vascular tissue models. Additionally, an analytical model was developed that mapped pump configuration changes to altered flow characteristics through the system. These technical advancements will enable more accurate modeling of immune cell interactions with tissues in a high-throughput testing platform, which will enhance the understanding of and ability to respond to a range of human health threats.