Component-specific reduction in perineuronal nets in senescence-accelerated mouse strains

With increased life expectancy, age-related diseases are a significant health concern in Western societies. Animal models (e.g., rodents) have been used to understand age-related changes in brain function—particularly through the senescence-accelerated mouse (SAM) strain. Previous reports have shown that the senescence-accelerated mouse propensity (SAMP)8 and SAMP10 strains have learning disabilities. In this study, we analyzed the prefrontal cortex, which is involved in cognitive function. We aimed to clarify the changes in parvalbumin-positive interneurons (PV-positive neurons), which are related to cognitive function, and perineuronal nets (PNNs), which are special extracellular matrix molecules formed around them. We performed histological analysis of PV-positive neurons and PNNs in the prefrontal cortex to elucidate the mechanism of behavioral abnormalities in SAMP8 and SAMP10 strains. Expression of Cat-315-positive PNN was not confirmed in the prefrontal cortex of SAMP10 mice. However, the density of AB1031-positive PNN, tenascin-R-positive PNN, and brevican-positive PNN decreased in the prefrontal cortex of SAMP8 and SAMP10 mice compared to that of the senescence-accelerated mouse resistance (SAMR1) mice. In addition, the density of PV-positive neurons was lower in SAMP8 mice than in SAMR1 mice. These mice, which exhibited behavioral and neuropathological phenotypes with age, showed different PV-positive neurons and PNNs in the prefrontal cortex compared with the SAMR1 mice. We believe that the results of this study will be useful for elucidating the mechanisms of age-related decline in cognitive and learning functions using SAM.