Temporal patterns of inflammatory biomarkers measured in the cerebrospinal fluid of patients with aneurysmal subarachnoid hemorrhage using multiplex Proximity Extension Assay technology.

Background Neuroinflammation has been extensively studied in the context of subarachnoid hemorrhage (SAH) in recent years. A common approach is correlation of levels of single or few inflammatory biomarkers with clinical parameters such as cerebral vasospasm and outcome. However, the complexity of the inflammatory response post SAH may require a more comprehensive overall approach by analyzing multiple biomarkers simultaneously. Methods Twenty-nine patients with SAH requiring insertion of external ventricular drainage were enrolled and ventricular cerebrospinal fluid was collected at days 1, 4 and 10 after hemorrhage. The levels of 92 inflammatory biomarkers were simultaneously measured in the samples using Proseek Multiplex Inflammation 1® assay (Olink Proteomics, Uppsala, Sweden) based on Proximity Extension Assay (PEA) technology. Thirty-eight proteins were excluded from further analysis due to lack of >10% of measurable values. Temporal patterns for each of the remaining 54 proteins were illustrated on graphs with medians and quartiles. Wilcoxon matched pairs test was used for comparison of the medians between time points. Results Four different patterns were visually observed with an early peak and gradually decreasing trend (9 proteins), middle peak (14 proteins), late peak after a gradually increasing trend (27 proteins) and no specific pattern (4 proteins). Several biomarkers showed statistically significant increasing trends (defined as day 1 < day 4 < day 10 values) and late peaks (day 4 < day 10), such as chemokines CXCL6 and CCL23, or significant early peaks (that is, day 1 > day 4) such as leukemia inhibitor factor (LIF) and macrophage inflammatory factor-1β (MIP-1β). No statistically significant decreasing trends (defined as day 1 > day 4 > day 10) were observed. Two proteins showed statistically significant middle peaks (chemokine CCL28 and Delta and Notch epidermal growth factor-related receptor-DNER). Conclusion The comprehensive data set provided in this study may act as an illustration of an inflammatory profile of the acute phase of SAH showing groups of biomarkers with similar temporal patterns of activation. Further studies can be designed based on these data in order to explore potential implications on early and late clinical events in the disease course.