Single-nucleus transcriptomics reveals sepsis-related neurovascular dysfunction in the human hippocampus

Liu Liu¹Pengfei Li¹Brent Wilkerson²Yan Wu³Meng Liu³Wei Jiang⁴Eric Daniel Hamlett¹Steven L Carroll¹Hongkuan Fan^1*

• ¹Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, United States
• ²Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, United States
• ³Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, United States
• ⁴Department of Pharmacology and Immunology, Medical University of South Carolina, Charleston, United States

Sepsis is increasingly recognized as a major precipitant of long-term cognitive impairment, yet the cellular mechanisms underlying hippocampal vulnerability remain elusive. Using single-nucleus RNA sequencing of human hippocampal tissues from sepsis and control patients, we identified profound neurovascular alterations involving 21 distinct cell populations. Notably, astrocytes and microglia exhibited marked polarization: Astrocyte 2 showed simultaneous upregulation of neurotoxic A1 and neuroprotective A2 gene signatures in sepsis, whereas Astrocyte 1 displayed reduced A1 activity and a relatively quiescent profile. In parallel, Microglia 2 demonstrated a prominent M1-like inflammatory signature, including elevated expression of HLA-DRA, IL1B, and TNF, while Microglia 1 downregulated both M1 and M2 markers, suggesting a hypo-responsive state. Intercellular communication analysis revealed intensified astrocyte-microglia interactions in the septic hippocampus, potentially amplifying inflammatory signaling loops. Concurrently, endothelial and mural cells exhibited transcriptional signatures of blood-brain barrier (BBB) disruption, oxidative stress, and compromised vascular homeostasis. Key molecular pathways associated with antigen presentation, cytokine signaling, and vascular permeability were selectively activated across neurovascular compartments. Together, our findings uncover a coordinated glial and vascular response to systemic inflammation, driven in part by dysfunctional astrocyte-microglia crosstalk and proinflammatory polarization. These changes may underlie BBB breakdown and contribute to sustained neuroinflammation and cognitive decline in sepsis survivors. Targeting glial-vascular signaling axes and modulating astrocyte or microglial polarization states may offer promising avenues for therapeutic intervention in post-sepsis neurological sequelae.