Beatty, H. E. | bioRxiv Science

bioRxiv2024

Single-Cell Temporal Atlas of Myeloid Cells in the Live Haemorrhagic Brain

Innate immune cells contribute to both secondary brain injury and repair following intracerebral hemorrhage (ICH). However, the specific signaling pathways that govern initial inflammatory and subsequent reparative myeloid programs in living patients remain poorly understood. To better characterize mononuclear phagocyte cell changes over time, we generated a single-cell transcriptomic dataset of paired hematoma clot evacuates and peripheral blood samples from 10 patients following ICH (5 - 290 hours). We identified distinct populations of activated and TNF-low microglia, as well as a unique, highly activated population of CD14+ monocytes in the hematoma. Perturbation analysis identified TNF signaling as the primary driver of hematoma monocyte activation. Custom temporal trajectory analysis using single-cell foundation model embeddings found that this TNF response in monocytes was transient, peaking early after hemorrhage and decreasing over the following 48 hours as monocytes shifted to reparative transcriptional programs. Transiently activated microglia emerged as the likely acute source of TNF, signaling through monocyte TNFR2. Surprisingly, acute TNF signaling in CD14+ monocytes was also associated with better severity-adjusted neurological outcomes both in our cohort and an independent validation cohort. These findings suggest acute TNF signaling between activated microglia and hematoma-associated monocytes, particularly through TNFR2, may contribute to recovery following ICH. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/630187v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@ff4fa0org.highwire.dtl.DTLVardef@1c4cc5borg.highwire.dtl.DTLVardef@1449761org.highwire.dtl.DTLVardef@2e7ea6_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2020

Leukocyte dynamics after intracerebral hemorrhage in a living patient reveal rapid adaptations to tissue milieu

Intracerebral hemorrhage (ICH) is a devastating form of stroke with a high mortality rate and few treatment options. Discovery of therapeutic interventions has been slow given the challenges associated with studying acute injury, particularly over time, in the human brain. Inflammation induced by exposure of brain tissue to blood appears to be a major part of brain tissue injury. Here we longitudinally profiled blood and cerebral hematoma effluent from a patient enrolled in the Minimally Invasive Surgery with Thrombolysis in Intracerebral Haemorrhage Evacuation (MISTIEIII) trial, offering a rare window into the local and systemic immune responses to acute brain injury. Using single-cell RNA-sequencing, we characterized the local cellular response during ICH in the brain of a living patient at single-cell resolution for the first time. Our analysis revealed rapid shifts in the activation states of myeloid and T cells in the brain over time, suggesting that leukocyte responses are dynamically reshaped by the hematoma microenvironment. Interestingly, the patient had an asymptomatic re-bleed (second local exposure to blood) that our transcriptional data indicated occurred more than 30 hours prior to detection by CT scan. This case highlights the rapid immune dynamics in the brain after ICH and suggests that sensitive methods like scRNA-seq can inform our understanding of complex intracerebral events.

immunology↗