Abstracts

Rationale: Antiepileptogenic therapies remain limited, even in preclinical models. Thus, identifying targets to prevent the development of epilepsy (i.e., epileptogenesis) is a large unmet need. In animal models, a common epileptogenic insult is prolonged seizure activity (status epilepticus [SE]) which leads to significant pathological changes. These changes include neuronal apoptosis, DNA damage, oxidative stress, and inflammation, and are thought to contribute to the emergence of spontaneous recurrent seizures [SRS] in the days-weeks following SE. Interestingly, these cellular responses are also common hallmarks of cellular senescence, a conserved cellular program which halts proliferation of damaged or dysfunctional cells. While cellular senescence is a growing topic of interest in a variety of neurological and neurodegenerative disorders, it remains under-examined in epilepsy.

Methods: To test the hypothesis that senescent cells (SCs) play a role in epileptogenesis, we induced SE in mice, and examined markers of cellular senescence through immunofluorescence. We also compared this profile to that in a reporter mouse line, which expresses GFP under the control of the senescence-associated p16Ink4a promoter. We examined the profile of p16 positive senescent cells (or cells in the reporter line) 1, 7, 14, 28, 46, and 84 days following status epilepticus. We performed co-localization experiments with p16 (late senescence marker) and p21 (early senescence marker) with NeuN (neuronal marker), doublecortin (immature neuron marker), prox1 (granule cell marker), iba1 and cd11b (microglia markers), and GFAP (reactive astrocyte marker).

Results: Our data suggest that p16+ SCs, but not p21+ SCs accumulate in hippocampi as early as two weeks following SE and continue to accumulate as time progresses following epileptogenesis. Interestingly, of the p16+ SCs, approximately 85% colocalize with microglia at all time points. However, p16+ SCs significantly colocalize with astrocytes by 60% immediately after epilepsy development but not later time points. Further, doublecortin positive immature neurons colocalize with p16+ senescent cells at later time points following SE, and ectopic hilar prox1+ granule cells colocalize with p16+ after the development of recurrent seizures.

Conclusions: These findings suggest that cellular senescence is induced, predominantly in microglia, following status epilepticus. Whether these senescent cells contribute to epileptogenesis remains to be determined.

Funding: Please list any funding that was received in support of this abstract.: This research was supported by 5R01HD09199402, 5R01NS09776204, and 5T32NS041218.