An In Vitro Model of Blast-Induced Traumatic Brain Injury

Objectives: Blast-induced traumatic brain injury (bTBI) has risen to a new level of importance and is recognized to be a major cause of injuries to the brain. A simplified, free field blast-injury model would facilitate studies to correlate biological outcomes with blast-injury mechanics to generate novel tolerance criteria for bTBI. Methods: Organotypic hippocampal slice cultures (OHSC) were cultured as previously described. OHSC were plated onto porous membranes in supplemented Neurobasal medium. Culture medium was changed to conditioned full-serum medium starting 3-5 days following plating. OHSC were cultured under standard conditions (37 C, 5% CO2) for 10-14 days. A 76 mm diameter shock-tube pressurized with helium was used to produce blast overpressures. A custom designed, water-filled receiver was maintained at 37 C. Cultures were placed into sealed bags with warmed culture medium and placed in the receiver. Pressure transducers at the shock-tube exit and adjacent to the sample characterized loading of the sample. Control OHSC were secured in the receiver but were not exposed to blast. To test the neuroprotective potential of hypothermia, a group of cultures were injured with the temperature of the water in the receiver at 25 C. All cultures were immediately returned to fresh culture medium and incubated. Propidium iodide (PI) fluorescence was used to measure tissue health prior to and at 1, 6, and 24 hours following injury. Cell death was determined for all OHSC regions as the percent area staining above an intensity threshold. Results: This in vitro blast-injury model was capable of producing 175 kPa overspressures, which elicited diffuse cell death in OHSC that increased over 24 hours following blast. Control cultures experienced minimal cell death. Hypothermia was significantly neuroprotective and prevented cell death in cultures exposed to 175 kPa or 325 kPa overpressures.