Abstracts

Rationale: Post-traumatic epilepsy (PTE) develops in 5-50% of patients after traumatic brain injury (TBI). There is much interest in the identification of antiepileptogenic agents. When such agents become available having biomarkers that predict PTE after TBI would allow treatment of TBI patients likely to develop PTE but not those unlikely to develop PTE. We studied microRNAs (miRNA) in rat blood after experimental TBI to identify potential biomarkers of susceptibility to develop PTE.Methods: Thirty-six adult male Sprague-Dawley rats were subjected to TBI via a controlled cortical impactor (CCI) and subsequently implanted with depth wire electrodes for continuous electrocorticography recording. Following surgery, rats were monitored using a 128 channel Xltek EEG recording machine system starting 10 days after completion of the TBI/depth electrode surgical procedure. Animals were recorded for 16 weeks after the initial injury to determine the time of onset, frequency, and duration of spontaneous seizures. Blood samples were collected prior to surgery as well as 4, 8, 12, and 16 weeks post-surgery and stored in Qiagen RNAprotect Animal Blood Tubes. Blood samples immediately preceding the first spontaneous seizure observed via EEG were used to isolate miRNA and then amplified by polymerase chain reaction (PCR) and analyzed using Qiagen miRNome miRNA PCR arrays and compared with time matched blood samples from rats that did not develop PTE. Statistical significance was set at p<0.05 using a Student’s t-test.Results: Eighty-one miRNAs were found to be significantly up-regulated in animals which later became epileptic. Of the miRNAs found to be appreciably altered, nine are potentially related to central nervous system function. Rno-miR-107 has been shown to inhibit glutamate transporter 1 expression resulting in an increase of glutamate concentration. Rno-miR-146a, rno-miR-181b-1, and rno-miR-181c are associated with inflammatory response. Rno-miR-7a-1 and -7a-2 are vital in maintaining homeostasis under environmental unrest. Rno-miR-210 is up-regulated under hypoxic conditions. Rno-miR-188 helps regulate plasticity and synaptic transmission in dendrites by inhibiting neuropilin 2. Rno-miR-494 may possibly down-regulate the expression of Parkinson protein 7 (Protein deglycase DJ-1), which is protective against oxidative stress.Conclusions: This study sought to determine if blood miRNA biomarkers exist that could be used to predict the development of CCI-induced PTE. Initial results identified 81 miRNAs that were up-regulated BEFORE the onset of seizures in animals which became epileptic. Of these, nine miRNAs are associated with the central nervous system: rno-miR-107, rno-miR-146a, rno-miR-181c, rno-miR-7a-1, rno-miR-210, rno-miR-181b-1, rno-miR-188, rno-miR-7a-2, and rno-miR-494. These data suggests that blood miRNA biomarkers may exist that are predictive of the development of PTE before the first seizure occurs. Study supported by the Barrow Neurological Foundation.