Temple University School of Medicine, Pennsylvania, United States
Abstract: Sepsis, a major healthcare problem, is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection with over 1.7 million cases/year and >250,000 deaths in the US. To date, treatment of sepsis is largely based on supportive care and there are no drugs available that target immune cell dysregulation. Drug development has been hindered as a result of the highly heterogeneous nature of the disease that impacts immune function and response to infection. We examined a critical aspect of neutrophil function in sepsis patients, specifically neutrophil-endothelial cell interaction and migration, key components of neutrophil-induced injury. We employed an organ-on-chip assay to phenotype sepsis patients. Our organ-on-chip reproduces vascular networks on a chip in a 3D physiologically relevant in vitro system which can evaluate the entire neutrophil adhesion cascade including circulation, rolling, adhesion, and migration of neutrophils under physiologically realistic (e.g. topology and shear conditions) microvascular environments. Utilizing this organ-on-chip assay, we identified three functional phenotypes in sepsis patients in the Temple University Hospital ICU based on ex vivo neutrophil adhesion and migration patterns. The phenotypes were classified as: Hyperimmune characterized by enhanced neutrophil adherence and migration, Hypoimmune that was unresponsive to stimulation, and Hybrid with increased adherence but blunted migration. These functional phenotypes were associated with distinct proteomic signatures and differentiated sepsis patients by important clinical parameters related to disease severity. The Hyperimmune group had increased systemic neutrophils, poorer pulmonary function, increased mechanical ventilation requirements, and increased ICU length of stay. These ex vivo functional studies of neutrophils, utilizing organ-on-chip technology, provides important insight into neutrophil dysregulation during sepsis and can also provide a novel methodology for immunophenotyping. Identification of these distinct neutrophil phenotypes in sepsis patients may provide important insight into the failure of some sepsis drugs in clinical trials. Further, recognition of diverse functional neutrophil responses and protein expression may help distinguish sepsis patients who would benefit from specific treatments, such as immunosuppressive therapies and those who may be negatively impacted. Supported by DTRA (HDTRA11910012) and NIH (GM134701 and 1F31AI164870).