7th Edition of Neurology World Conference 2027

Abstract

Abstract: Background: Perineuronal nets (PNNs) are specialized extracellular matrix structures that regulate neuronal excitability and protect fast-spiking parvalbumin-positive (PV) interneurons. By stabilizing synaptic inputs and limiting excessive plasticity, PNNs play a critical role in maintaining network balance. Age-related differences in PNN maturity may influence seizure susceptibility, while the inhibition of PNN-degrading enzymes, such as matrix metalloproteinases (MMPs), offers therapeutic potential for PNN restoration in epilepsy. Methods: We investigated age-dependent seizure susceptibility and PNN integrity using intrahippocampal kainic acid (IHKA) injection in juvenile (P30) and adult (P60) mice. Seizure burden was assessed via continuous EEG monitoring. PNN and PV neuron integrity were evaluated by Wisteria floribunda agglutinin (WFA) and PV immunostaining in the hippocampus, and neuronal injury and loss were assessed by Nissl staining. To test whether MMP inhibition restores PNNs and reduces seizure burden, doxycycline (100 mg/kg, i.p., 8 days) was administered to P60 mice 4 weeks after IHKA. Results: Juvenile mice (P30) exhibited significantly greater seizure susceptibility than adults (P60), characterized by earlier onset, higher frequency, and longer seizure duration following IHKA. This vulnerability was associated with lower baseline PNN density and maturity. IHKA induced more pronounced PNN degradation in P30 mice, reflected by reduced WFA⁺ cell counts, fewer WFA⁺/PV⁺ co-localized cells (i.e., WFA-protected PV interneurons), and decreased WFA intensity per cell. Although neuronal loss did not differ significantly between groups, P30 mice exhibited greater damage and disorganization of CA3 pyramidal cells. Spontaneous recurrent seizures emerged as early as day 3 post-IHKA in P30 mice, whereas P60 mice developed seizures more gradually, plateauing around 4 weeks. Doxycycline treatment during the chronic phase reduced seizure burden and frequency, while restoring WFA⁺ PNNs (WFA⁺ cell counts) and enhancing PNN protection of PV interneurons (WFA⁺/PV⁺ co-localized cells). Conclusions: Immature PNNs in juvenile mice confer heightened vulnerability to epileptogenesis, whereas MMP inhibition via doxycycline provides neuroprotection through PNN restoration. These findings reveal a developmental window of seizure susceptibility linked to PNN maturity and support MMP-targeted therapy as a promising strategy for epilepsy, particularly in pediatric populations with immature PNNs.