Human GFAP degradome in cerebrospinal fluid after moderate/severe traumatic brain injury for proteolysis dynamic, product fates and outcome prognosis

STUDY PURPOSE: The objective of this study was to investigate the temporal profiles of biomarker glial fibrillary acidic protein (GFAP) and its trauma-induced proteolytic breakdown products (GFAP-BDPs) in cerebrospinal fluid (CSF) to assess longitudinal proteolysis, fragment fates and long-term outcome prognosis in moderate/severe traumatic brain injury (TBI) patients. The biofluid frequency of different fragments of this biomarker informs on the pathophysiological processes including disturbed proteostasis, proteolysis, astrocyte death and proteinopathy following TBI. DATA COLLECTED: TBI-associated GFAP-BDPs were sequenced and quantified using label-free Mass spectrometry that is reported in CCMS MassIVE repository (https://identifiers.org/massive:MSV000099415).The data was then independently corroborated using unbiased, band-specific scaled immunoblot densitometry in an observational cohort of 23 moderate to severe TBI patients (see Supplemental and Methodology Files for SOPs and Infographic). Calibration was done using known protein dilutions of recombinant full-length as well as His-tagged coil1 fragment GFAP protein with calibration curves given in Supplemental infographic file. GFAP-BDPs were measured in 108 serial CSF samples over two postinjury weeks followed by assessment for long-term outcome prognosis. Densitometry was performed on eight exposures from each blot (2s-20min) after background correction. Subsaturated band measurements were standardized to 1min, see Supplemental infographic file, dynamic range, detection limits and inter-experimental coefficient of variation. Adult TBI patients were admitted to neurocritical care at level one trauma centers at UCLA and at the University of Florida, Gainesville, and a commercial control serum sample was obtained from Precision Med. Patient median age was 40±19 years, 22 subjects were male and 4 were female, and median score on the Glasgow Coma Scale (GCS) was 6 ±3.4. Enrollment occurred between 2018-2023 at UCLA and between 2007-2010 at University of Florida. Deidentified baseline demographic and clinical parameters were included. All except one patient had recovery scores on the Glasgow Outcome Scale (GOS) reported at hospital discharge and all except two patients had recovery scores determined by phone interview at six-month postinjury on extended GOS (GOSE). Outcome was binarized as good (GOSE 5-8), and poor (GOSE 1-4) outcomes. Alternative partitioning of favorable outcome (GOSE7+8) versus unfavorable outcome (GOSE =6) corroborated findings for enhanced rigor, as defining good recovery is inherently personal (Wilson et al, 2021; Ann Surg 273: 500-506; Doi 10.1097/SLA.0000000000003389). DATA USAGE NOTES: