Age-Dependent Neuroinflammatory Effects of Red Blood Cells and Their Exosomes in a Human Brain-on-Chip Model Open Access

• RBCs and their exosomes from old donors promote neuroinflammation by activating microglial cells.

• RBCs and their exosomes from old donors disrupt metabolic signaling, promote heme accumulation, and modulate neurobiological processes.

The systemic blood milieu profoundly influences the cellular function across tissues, acting as a key driver of age-related cognitive decline. Therapeutic plasma exchange and heterochronic parabiosis have widely explored the role of plasma and blood age on various tissues. However, the role of red blood cells (RBCs) remains largely unexplored. In this study, we investigated the impact of RBCs and their exosomal cargo from young (20-40yo) and old (50-70yo) donors on human brain cells using a human brain microphysiological system (hB-MPS). The RBCs and their exosomes from the donors were circulated in the vascular channel of the hB-MPS device. Compared to that obtained from young donors, RBCs and their exosomes from old donors exhibited elevated levels of the inflammatory marker CD-68 and increased the accumulation of heme in the brain cells. Molecular profiling of the RBC-derived exosomes using proteomics and microRNA seq analysis revealed age-associated differences in cargo, including downregulation of proteins linked to neuroprotective pathways and upregulation of those involved in inflammation and synaptic dysregulation. Proteomic analysis of the brain cells in response to the RBC-derived exosomes from older donors altered brain cell homeostasis by modulating key signalling pathways directly correlated to neurobiological processes such as cytokine signalling, neurotrophins signalling, metabolic activity, and DNA repair. This highlights a novel role for RBCs in brain aging and neuroinflammation, and points toward RBCs and their exosomal profiling as a biomarker for age-associated pathologies.