Human immune system adaptations to simulated microgravity revealed by single-cell mass cytometry

J M Spatz,J Hedou,M Angst,N Aghaeepour,E Ganio,D Gaudilliere,A Tsai,Brice Gaudilliere,M Hughes Fulford

doi:10.1038/s41598-021-90458-2

Abstract

Exposure to microgravity (µG) during space flights produces a state of immunosuppression, leading to increased viral shedding, which could interfere with long term missions. However, the cellular mechanisms that underlie the immunosuppressive effects of µG are ill-defined. A deep understanding of human immune adaptations to µG is a necessary first step to design data-driven interventions aimed at preserving astronauts’ immune defense during short- and long-term spaceflights. We employed a high-dimensional mass cytometry approach to characterize over 250 cell-specific functional responses in 18 innate and adaptive immune cell subsets exposed to 1G or simulated (s)µG using the Rotating Wall Vessel. A statistically stringent elastic net method produced a multivariate model that accurately stratified immune responses observed in 1G and sµG (p value 2E−4, cross-validation). Aspects of our analysis resonated with prior knowledge of human immune adaptations to µG, including the dampening of Natural Killer, CD4+ and CD8+ T cell responses. Remarkably, we found that sµG enhanced STAT5 signaling responses of immunosuppressive Tregs. Our results suggest µG exerts a dual effect on the human immune system, simultaneously dampening cytotoxic responses while enhancing Treg function. Our study provides a single-cell readout of sµG-induced immune dysfunctions and an analytical framework for future studies of human immune adaptations to human long-term spaceflights.

Highlights

Exposure to microgravity during space flights produces a state of immunosuppression, leading to increased viral shedding, which could interfere with long term missions
Two cell aliquots were obtained and subjected in parallel to (1) pooled and bead isolated Th cell gene arrays and transcriptomic analysis of select genes previously shown to be altered by sμG and spaceflight in immune cells; or (2) single-cell proteomic analysis with mass cytometry (Fig. 1)
In peripheral blood mononuclear cells (PBMCs) stimulated with ConA/Anti-CD28, exposure to sμG decreased the mRNA expression of the interleukin 2 receptor (IL2R)α, tumor necrosis factor (TNF)α, CD69, and CLL4 at the 1.5 h or 4 h stimulation time points

Summary

Introduction

Exposure to microgravity (μG) during space flights produces a state of immunosuppression, leading to increased viral shedding, which could interfere with long term missions. We employed a high-dimensional mass cytometry approach to characterize over 250 cell-specific functional responses in 18 innate and adaptive immune cell subsets exposed to 1G or simulated (s) μG using the Rotating Wall Vessel. Our study provides a single-cell readout of sμG-induced immune dysfunctions and an analytical framework for future studies of human immune adaptations to human long-term spaceflights. Emerging high-content, immune-profiling technologies, including mass cytometry, provide powerful means for the single-cell evaluation of complex physiological immune responses, such as that produced by μG9,11–15,21–24. We utilized a 41-parameter mass cytometry approach to comprehensively profile the effect of μG on human PBMC surface activation markers and intracellular signaling responses, cultured in the NASA developed Rotating Wall Vessel, one of the most commonly used models of simulated (s)μG25,26. This research will identify modifiable targets that can be exploited to decrease μG-induced immunological dysregulation

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Conclusion