Mesial temporal lobe epilepsy (MTLE) is the most common form of adult-onset focal epilepsy. Current standard of care includes anti-seizure medications, however, these are often poorly tolerated (Meador et al., 2007) and over 30% of patients with epilepsy are medically refractory (Kwan and Brodie, 2000). Rates of medical refractoriness may be even higher in MTLE secondary to hippocampal sclerosis (Pohlen et al., 2017). Risk factors for epilepsy are readily identifiable (Junna et al., 2013), however, there are currently no long-term preventative therapies for high-risk patients (Temkin, 2001). In order to develop potential antiepileptogenic and disease-modifying treatments, it is critical to understand the underlying pathways responsible for epileptogenesis, and determine how these can be modulated to prevent the formation of seizure networks.

Rodent epilepsy models re-capitulate critical aspects of human clinical epilepsy (Blumcke et al., 2009; Crespel et al., 2005; de Lanerolle et al., 1989; Houser, 1990; Mathern et al., 2002), and therefore provide a unique opportunity to examine the earliest stages of epileptogenesis. In the intrahippocampal kainate mouse model of temporal lobe epilepsy, induction of status epilepticus is followed by a 7–14 day latent period, after which rodents develop spontaneous recurrent seizures (Bouilleret et al., 1999; Riban et al., 2002; Twele et al., 2016b). It is well-recognized that unilateral intrahippocampal kainate injection in rodents results in bilateral hippocampal seizures (Häussler et al., 2012) and the development of seizure networks in rodent epilepsy models (Sheybani et al., 2018; Sparks et al., 2020), analogous to seizure networks observed clinically (Bartolomei et al., 2017; Wendling et al., 2010). Associated with this, pathological remodeling and transcriptional changes have also been observed in both the epileptogenic zone and the seizure network, including in the ventral and contralateral hippocampus (Berger et al., 2020; Gupta and Schnell, 2019; Häussler et al., 2012; Kralic et al., 2005; Mardones and Gupta, 2022). Notably, failure to control distant seizure foci within the seizure network is associated with seizure recurrence in clinical epilepsy (Barba et al., 2016). Despite these observations, the signaling pathways responsible for forming the epileptogenic zone and peri-ictal seizure network still need to be more adequately defined. Investigating seizure generation within the seizure network in rodent epilepsy models thus emerges as a critical step for the discovery and clinical translation of novel anti-epileptic and antiepileptogenic therapies.

There is emerging evidence that Wnt signaling provides early signaling cues in epileptogenesis. The Wnt pathway comprises a family of 19 secreted Wnt ligands, which bind a family of 10 transmembrane frizzled receptors and co-receptors; these signal to downstream canonical beta-catenin dependent and independent pathways (Gordon and Nusse, 2006). Through several observational studies, Wnt signaling has been observed to be upregulated early during epileptogenesis (Dingledine et al., 2017; Mardones and Gupta, 2022; Theilhaber et al., 2013) and the anti-epileptic effects of therapies such as intermittent hypoxia and carbamazepine have been associated with upregulated canonical Wnt signaling in chronic epilepsy models (Jean et al., 2022; Sun et al., 2020). Importantly, Wnt signaling changes have been observed in human epilepsy tissue studies (Dixit et al., 2016; Marinowic et al., 2023), strongly suggesting that this pathway may be translationally relevant. However, to date there is a scarcity of experimental studies on Wnt pathway manipulation as a therapeutic strategy in anti-epileptogenesis. In our previous work, we applied a canonical Wnt inhibitor during the latent epileptogenic period after induction of status epilepticus. Remarkably, we found that Wnt inhibition exacerbated pro-epileptogenic neuronal remodeling in both the epileptogenic and peri-ictal zones (Gupta and Schnell, 2019). Building on these insights, we hypothesized that the activation of canonical Wnt signaling during the latent period could serve as a preventive measure against epileptogenesis.

To test our hypothesis, mice were treated with canonical Wnt activator Chir99021 shortly after seizure induction by administration of intrahippocampal kainate (IHK), modeling a potential clinical scenario whereby an anti-epileptogenic compound may be administered during the acute care episode after a first seizure. The IHK model was selected to model MTLE with hippocampal sclerosis, the most common cause of focal epilepsy in adults clinically. We examined epileptogenesis after IHK with bilateral hippocampal electrocorticography and investigated pathological remodeling of immature dentate granule cell neurons. Electrocorticographic recordings were continued during a drug-free washout period to determine the durability of the effect of Wnt activation on epileptogenesis. Finally, the effect of early treatment with Wnt activator Chir99021 on hippocampus-dependent learning was assessed during the chronic epilepsy phase to determine whether Wnt activation during epileptogenesis can ameliorate hippocampal learning deficits that manifest in the chronic epilepsy phase.