Senior Research Scientist Expesicor Missoula, Montana
Rationale: Despite the advent of various new anti-seizure drugs over the past 30 years, newer substances do not demonstrate efficacy or tolerability superior to that of first-generation drugs. Thus, novel treatments are urgently needed to bring seizure freedom to the one-third of epilepsy patients suffering from refractory epilepsy. The development, validation, and implementation of new epilepsy disease models that accurately mimic the human condition are crucial first steps toward fulfilling this unmet need. We developed and patented the rKaL method1, which can reliably reproduce fundamental characteristics of refractory human epilepsy in rats. With this work complete, there is a need to translate the model to mice for further innovation. Mice have significant practical advantages, such as their much smaller size (requiring less drug/substance) and relative ease of producing knock-out or knock-in strains. Our goal was to convert our rat model into mice with the same results: hippocampal sclerosis, spontaneous seizures, but with a complete lack of status epilepticus and mortality. Methods: We injected C57Bl6/N mice with kainic acid and lorazepam and monitored for four days. The mice were then perfused, and brains were extracted into 4% PFA. Next, the brains were dehydrated with ethanol and infused with paraffin wax for sectioning. Brain sections were mounted on slides and paraffin wax was removed for treatment with FluoroJade B to quantify hippocampal neurodegeneration. Results: Based on our seminal work developing the KaL method in rats, we evaluated similar combinations of kainic acid and lorazepam in C57Bl6/N mice. While mice exhibited signs of behavioral seizures (Racine scale less than 4), no hippocampal neurodegeneration was detected. We suspected that either the rat doses, which we scaled to mice, was incorrect for mice or the C57Bl6/N mouse strain was inappropriate. Therefore, we next performed a variety of dose combinations in C57Bl6/N mice. In these experiments for some drug combinations we again observed signs of nonconvulsive seizures but again no hippocampal neurodegeneration. These experiments expand and further support previous studies showing that C57Bl6/N mice are resistant to hippocampal neurodegeneration. For future experiments we plan to repeat the above studies in different strains of mice to re-capitulate our previous work in rats. Conclusions: The problem of drug-resistant epilepsy is highly significant to human health and the challenge of developing effective therapies is formidable. Our preliminary work showed a lack of hippocampal neurodegeneration in C57Bl6/N mice and suggests there may be greater nuance in mice than in rat our KaL epilepsy model. Further refinement and studies in other mouse strains are on-going, with initially positive results. Our unique approach using concurrent doses of kainic acid and lorazepam in rats is fundamentally unlike all existing models of epilepsy. Therefore, developing our technology for use in mice offers not only novel methodology, but also the potential to substantially change epilepsy R&D.
References: 1. Kienzler‐Norwood, et al., (2017). A novel animal model of acquired human temporal lobe epilepsy based on the simultaneous administration of kainic acid and lorazepam. Epilepsia, 58: 222-230. Funding: Please list any funding that was received in support of this abstract.: Private investment and NIH Grant R44NS112039.