Zebrafish model of posttraumatic epilepsy

Abstract

Objective: Posttraumatic epilepsy (PTE) is defined as recurrent and unprovoked seizures occurring >1 week after traumatic brain injury (TBI). Animal studies of PTE are lengthy and expensive. In this study, we developed a cost-effective PTE animal model using zebrafish to bridge the gap between in vitro studies and low-throughput animal studies. Methods: We used two different sets of parameters (G1 and G2) to induce closedhead TBI in adult zebrafish using pulsed high-intensity focused ultrasound. Injured fish and naive controls were evaluated for behavioral deficits and spontaneous behavioral seizure activity up to 21 days postinjury (DPI). We also assessed behavioral seizure susceptibility to a subconvulsive dose of pentylenetetrazole (PTZ; 2.5 mmol•L-1) and recorded electrophysiological signals to confirm seizure activity up to 40 DPI. In addition, we investigated injury-related changes in the blood-brain barrier and expression levels of various proteins altered in rodent and human TBI. Results: The G2 parameters resulted in a more severe TBI, with a mortality rate of 25%, as well as motor dysfunction and heightened anxiety persisting at 21 DPI. One hundred percent of the G2 group showed spontaneous myocloniclike behavior, and 80% demonstrated tonic-clonic-like behavioral seizures by 21 DPI. Such activities were not detected in the naive group. After the application of 2.5 mmol•L-1 PTZ, 100% of injured zebrafish had cloniclike seizures at 21 DPI, versus 30% of the naive group. We also demonstrated electrographic seizure activity at 40 DPI, which was not detected in the naive controls. Lastly, we observed acute blood-brain barrier dysfunction and increased levels of HMGB1 and ratios of phosphorylated/total Akt and tau through 21 DPI. Significance: Together, the results indicate that severe TBI in the adult zebrafish leads to similar behavioral and physiological changes to those of more traditional models, including the development of PTE, and suggest this may be a useful model that can accelerate research in TBI/PTE.

Use of Zebrafish Models to Boost Research in Rare Genetic Diseases

“…Zebrafish larvae are mostly used as a model for epilepsy and seizures due to several advantages, such as high fecundity, leading to numerous fast-developing embryos ex utero allowing researchers to perform easy follow-ups of development and genetic manipulations; possibility for high-throughput analyses using larvae, where each can fit in one well of a 96-well plate; minimal ethical regulations; and relatively low costs for maintenance and housekeeping [121]. However, adult zebrafish are sometimes preferred due to a higher developed neural system, easier handling and certain parameters that sometimes cannot be observed in larvae, e.g., distinct seizure stages [128,129].…”

Two-Photon Imaging to Unravel the Pathomechanisms Associated with Epileptic Seizures: A Review

“…A recent study demonstrated that brain trauma can induce epileptogenesis and seizures associated with inflammation and blood-brain barrier dysfunction in zebrafish, which resembles pathophysiological processes in human posttraumatic epilepsy [92]. Additionally, the cerebral vasculature of zebrafish is morphologically and physiologically similar to humans and can readily be genetically manipulated [93].…”

Age Bias in Zebrafish Models of Epilepsy: What Can We Learn From Old Fish?

“…Recurrent administration of pilocarpine (Paudel et al, 2020) or pentylenetetrazole (PTZ) (Duy et al, 2017) does not induce recurrent spontaneous seizures. However, we recently modeled post-traumatic epilepsy (Cho et al, 2020b), which is the first adult zebrafish model that exhibits spontaneous seizures. This model also demonstrates disruption of the blood-brain barrier, increased markers of inflammation, and alterations in tau phosphorylation mTOR signaling, mechanisms relevant to epileptogenesis that cannot be as easily studied in larvae.…”

“…Each non-drug induced epilepsy model can show different types of seizure behaviors. An adult post-traumatic epilepsy model shows reduced motor behavior with spontaneous myoclonic and generalized tonic-clonic seizures (Cho et al, 2020b). SCN1A mutant larvae exhibit increased swim activity with whole-body convulsions and rapid undirected movements (Baraban et al, 2013).…”