Impact of hyaluronan size on localization and solubility of the extracellular matrix in the mouse brain

Abstract

Hyaluronan (HA) is a central component of the extracellular matrix (ECM) in the brain and plays a pivotal role in neural development and plasticity. Brain HA exists in two distinct forms of the ECM: the diffuse ECM, which is soluble in saline and detergents, and the condensed ECM, which forms aggregates, such as perineuronal nets. Although the physiological functions of HA significantly differ depending on its size, size differences in HA have not yet been examined in the two ECM types, which is partly due to the lack of methods to rapidly and accurately measure the molecular weight (MW) of HA. In this study, we established a simple method to simultaneously assess the MW of HA in multiple crude biological samples. HA was purified through single-step precipitation from tissue extracts using biotinylated HA-binding protein and streptavidin-coupled magnetic beads, followed by separation on gel electrophoresis. By applying this method to HA in the mouse brain, we revealed that the condensed ECM contained higher MW HA than the diffuse ECM. Higher MW HA and lower MW HA exhibited different spatial distributions: the former was confined to perineuronal nets, while the latter was widely present throughout the brain. Furthermore, the limited degradation of HA showed that only higher MW HA was required to form an insoluble HA-aggrecan complex. The present study demonstrated that the MW of HA in the brain strongly correlates with the localization and solubility of the ECM it forms.

Assembly of neuron- and radial glial-cell-derived extracellular matrix molecules promotes radial migration of developing cortical neurons

“…After washing with PBS, HA bound to agarose resin was released by denaturation at 95 °C for 10 min. HA concentrations were measured by enzyme-linked immunosorbent assays (ELISA), as previously reported ( Egorova et al, 2023 ). Briefly, each well of a 96-well plate (Iwaki) was coated with 0.1% HABP (Cosmo-bio) at 4 °C overnight.…”

Hyaluronan hydrates and compartmentalises the CNS/PNS extracellular matrix and provides niche environments conducive to the optimisation of neuronal activity

“…HA is a central component of the brain ECM with pivotal roles in neural development and plasticity. Brain HA exists both as a diffuse component soluble in saline and detergents and a condensed ECM in PG aggregate formations in PNNs which predominantly contain large-molecular-weight HA networked with lectican CS-PGs (Egorova et al, 2023). The brain ECM surrounds the space around and between neurons, glia and astrocytes and constitutes ~20% of the total brain volume.…”