Abstract Body: Introduction
Early brain injury (EBI), a complex collection of pathophysiological processes occurring within 72 hours aneurysmal subarachnoid hemorrhage (aSAH), is the key link connecting the initial event to the delayed and long-term complications. Cerebral edema is the major constituent of EBI, resulting from the direct toxicity of hemoglobin products and a critical increase in intracranial pressure. This study aims to identify serum protein biomarkers specifically targeting cerebral edema in EBI and cell-specific interventional targets.
Methods
This study is based on a prospective observational cohort at a single tertiary referral center. Plasma samples collected from three separate groups of aSAH patients were analyzed. Each consisted of 64, 71, and 16 samples collected within 48 hours of rupture. For the first cohort, a proximity extension assay by Olink was used to analyze 184 proteins. For the second corhot, commercially available enzyme linked immunosorbent assay (ELISA) kits were used to determine the plasma concentrations of the candidate proteins. For the last cohort, peripheral blood mononuclear cells were isolated and their single-cell transcriptomic (scRNA) data were extracted using the 10X genomics platform. For each patient, the subarachnoid hemorrhage early brain edema score (SEBES) based on initial scans was dichotomized with severe edema being defined as SEBES > 2.
Results
Overall, the median age was 52.5 years [IQR:45-63] and 76% were female. 35% had severe edema. Subpopulations divided by the outcome did not differ significantly, except for the Hunt-Hess grade (HH), with 71% and 32% of the patients with and without severe edema showing HH greater than three, respectively (p < 0.05). After adjusting for multiplicity, ten proteins showed overlapping, lowest p-values, and five were chosen as candidates based on their mechanistic relevance. Among the five candidate proteins, ALK1 and LAYN showed statistically different expressions, with patients with milder edema showing higher expression. scRNA analysis showed that ALK1 and LAYN were preferentially expressed in a cell cluster that co-expresses CST3, CLEC10A, and FCER1A but has lower levels of the markers for the known subtypes of type 2 conventional dendritic cells.
Conclusion
This study suggests ALK1 and LAYN as the serum protein biomarkers and the existence of a specific subtype of dendritic cells, potentially associated with less edema following aSAH.