Alternatively, degradation of PNNs in the PC may result from the secretion of matrix metalloproteinase-9 (MMP-9) and a disintegrin-like and metalloproteinase with thrombospondin motifs (ADAMTS) from reactive astrocytes and neurones as shown in an epilepsy model (Pollock et al., 2014; Dzyubenko et al., 2016). Here, MMP9 is linked to epilepsy.