The CD44 ligand hyaluronic acid is elevated in the cerebrospinal fluid of suicide attempters and is associated with increased blood–brain barrier permeability

Abstract Background The glycosaminoglycan hyaluronic acid (HA) is an important component of the extracellular matrix (ECM) in the brain. CD44 is a cell adhesion molecule that binds to HA in the ECM and is present on astrocytes, microglia and certain neurons. Cell adhesion molecules have been reported to be involved in anxiety and mood disorders. CD44 levels are decreased in the cerebrospinal fluid (CSF) of depressed individuals, and the CD44 gene has been identified in brain GWAS studies as a possible risk gene for suicidal behavior. Method We measured the CSF levels of HA and the soluble CD44 (sCD44) in suicide attempters ( n =94) and in healthy controls ( n =45) using ELISA and electrochemiluminescence assays. We also investigated other proteins known to interact with CD44, such as osteopontin and the matrix metalloproteinases MMP1, MMP3 and MMP9. Results The suicide attempters had higher CSF levels of HA ( p =.003) and MMP9 ( p =.004). The CSF levels of HA correlated with BBB-permeability (rho=0.410, p