Serum Biomarkers for Experimental Acute Spinal Cord Injury: Rapid Elevation of Neuron-specific Enolase and S-100β

OBJECTIVE: We evaluated whether serum levels of neuron-specific enolase (NSE) and S-100β protein are biomarkers for traumatic injury in an animal model of spinal cord injury (SCI). METHODS: Enzyme-linked immunosorbent assay serum measurements of NSE and S-100β and assays of serum protein were compared at 6 and 24 hours after a graded contusive SCI (150 or 200 kdyn IH impactor injury (Infinite Horizons, L.L.C., Lexington, KY) or sham laminectomy at T9 in 30 female Sprague-Dawley rats. Serum from control animals was also analyzed. RESULTS: Increases in serum levels of NSE were observed for 200-kdyn (3.1-fold, P < 0.001) and 150-kdyn (2.3-fold, P < 0.001) injury groups at 6 hours after injury, which decreased by 73.7% (P < 0.001) and 65.2% (P < 0.001) at 24 hours after SCI, respectively; the levels were still greater than in sham animals (P < 0.001, P = 0.001). The 200- and 150-kdyn injury groups were not different at either time point. S-100β serum levels increased at 6 hours in the 200-kdyn injury group (P < 0.05), and no differences from sham levels were seen at 24 hours. No differences in total protein concentrations were observed between the injury and control groups. CONCLUSION: Present data suggest that NSE and S-100β serum levels may be useful experimental tools for the acute measurement of tissue loss after SCI. Despite significant shortcomings, NSE and S-100β serum measurements in acute SCI patients with clinically defined functional deficits should allow comparisons with well-characterized SCI animal models. Future efforts to develop biomarkers that predict functional outcomes in the acute phase should focus on axon-specific proteins as markers of secondary axonal loss and regeneration.