Distinct Serum GFAP and Nf-L Time-Courses after Rapid Head Rotations.

Abstract

Traumatic brain injury (TBI) causes significant neurophysiological deficits and is typically associated with rapid head accelerations common in sports-related incidents and automobile accidents. There are over 1.5 million TBIs in the US each year, with children aged 0-4 being particularly vulnerable. TBI diagnosis is currently achieved through interpretation of clinical signs and symptoms and neuroimaging; however, there is increasing interest in minimally invasive fluid biomarkers to detect TBI objectively across all ages. Preclinical porcine models offer controlled conditions to evaluate TBI with known biomechanical conditions and without co-morbidities. The objective of the current study was to establish pediatric porcine healthy reference ranges (RR) of common human serum TBI biomarkers and to report their acute time-course after non-impact rotational head injury. A retrospective analysis was completed to quantify biomarker concentrations in porcine serum samples collected from four-week-old female (n = 215) and uncastrated male (n = 6) Yorkshire piglets. Subjects were assigned to one of three experimental groups (sham, sagittal-single, sagittal-multiple) or to a baseline only group. A rapid non-impact rotational (RNR) head injury model was used to produce mild to moderate TBI in piglets following a single rotation and moderate to severe TBI following multiple rotations. The Quanterix Simoa Human Neurology 4-Plex A (N4PA) assay was used to quantify glial fibrillary acidic protein (GFAP), neurofilament light (Nf-L), tau, and ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1). The 95% healthy RR for females were calculated and validated for GFAP (6.3-69.4 pg/mL), Nf-L (9.5-67.2 pg/mL), and UCH-L1 (3.8-533.7 pg/mL). Rising early, GFAP increased significantly above the healthy RR for sagittal-single (to 164 and 243 pg/mL) and increased significantly higher in sagittal-multiple (to 494 and 413 pg/mL) groups at 30 min and 1 h post-injury, respectively, returning to healthy RR ranges by 1-week post-injury. Rising later, Nf-L increased significantly above the healthy RR by 1 day in sagittal-single (to 69 pg/mL) and sagittal-multiple groups (to 140 pg/mL) and rising further at 1 week (single = 231 pg/mL, multiple = 481 pg/mL). Sagittal-single and sagittal-multiple UCH-L1 serum samples did not differ from shams or the healthy RR. Sex differences were observed but inconsistent. Serum GFAP and Nf-L levels had distinct time-courses following head rotations in piglets, and both corresponded to load exposure. We conclude that serum GFAP and Nf-L offer promise for early TBI diagnosis and intervention decisions for TBI and other neurological trauma.