The Heterogeneity of Perineuronal Nets in Specific Subregions of the Hippocampus

Abstract

Perineuronal nets (PNNs) are structured forms of the extracellular matrix that surround neurons across brain regions. Enriched with chondroitin sulfate proteoglycans (CSPGs) that contain chondroitin sulfate (CS) chains, researchers have found that PNNs develop during early life in conjugation with the closure of critical periods. Therefore, they are known to limit plasticity as well as act as a barrier to protect the neuron from oxidative stress. Researchers have found that in limiting plasticity, PNNs may be linked to stress, aging, and memory. Because PNNs can be found across many brain regions and are implicated in plasticity, this preliminary study investigated whether the components of PNNs are heterogeneous in subregions of the hippocampus, including the ventral CA1 and the dentate gyrus (DG). Previous research found that nearly all of the PNNs in the hippocampus express the CSPG aggrecan, therefore, this study utilized aggrecan and plant lectin-agglutinin isolated from Wisteria floribunda (WFA) in order to assess this question. This study also explored if PNN components were altered in these regions across young adult and older adult mice. My findings show that a significant percentage of PNNs in the ventral CA1 were single- labeled with WFA, but not aggrecan. I observed that this significant finding was true in only the young adult mice. Additionally, this study found that neither aggrecan nor WFA fully represented the PNNs found in the DG. These findings suggest that PNNs in the hippocampus vary in their composition both within and across subregions, which may have implications for the different functions of these areas. Furthermore, these findings raise questions about the best technical approaches for assessing the entirety of the PNN population in a given region.