Epileptogenesis after traumatic brain injury in Plaur-deficient mice

- CCI increases seizure susceptibility in wild-type and Plaur-deficient mice.
- Plaur deficiency does not worsen neurodegeneration after CCI.
- Plaur deficiency does not worsen epileptogenesis after CCI.
- Plaur deficiency worsens motor impairment and emotional learning after CCI.

Binding of the extracellular matrix proteinase urokinase-type plasminogen activator (uPA) to its receptor, uPAR, regulates tissue remodeling during development and after injury in different organs, including the brain. Accordingly, mutations in the Plaur gene, which encodes uPAR, have been linked to language deficits, autism, and epilepsy, both in mouse and human. Whether uPAR deficiency modulates epileptogenesis and comorbidogenesis after brain injury, however, is unknown. To address this question, we induced traumatic brain injury (TBI) by controlled cortical impact (CCI) in 10 wild-type (Wt-CCI) and 16 Plaur-deficient (uPAR-CCI) mice. Sham-operated mice served as controls (10 Wt-sham, 10 uPAR-sham). During the 4-month follow-up, the mice were neurophenotyped by assessing the somatomotor performance with the composite neuroscore test, emotional learning and memory with fear conditioning to tone and context, and epileptogenesis with videoelectroencephalography monitoring and the pentylenetetrazol (PTZ) seizure susceptibility test. At the end of the testing, the mice were perfused for histology to analyze cortical and hippocampal neurodegeneration and mossy fiber sprouting. Fourteen percent (1/7) of the mice in the Wt-CCI and 0% in the uPAR-CCI groups developed spontaneous seizures (p > 0.05; chi-square). Both the Wt-CCI and uPAR-CCI groups showed increased seizure susceptibility in the PTZ test (p < 0.05), impaired recovery of motor function (p < 0.001), and neurodegeneration in the hippocampus and cortex (p < 0.05) compared with the corresponding sham-operated controls. Motor recovery and emotional learning showed a genotype effect, being more impaired in uPAR-CCI than in Wt-CCI mice (p < 0.05). The findings of the present study indicate that uPAR deficiency does not increase susceptibility to epileptogenesis after CCI injury but has an unfavorable comorbidity-modifying effect after TBI.