Abstract
BackgroundPeriventricular extracellular oedema, myelin damage, inflammation, and glial reactions are common neuropathological events that occur in the brain in congenital hydrocephalus. The periventricular white matter is the most affected region. The present study aimed to identify altered molecular and cellular biomarkers in the neocortex that can function as potential therapeutic targets to both treat and evaluate recovery from these neurodegenerative conditions. The hyh mouse model of hereditary hydrocephalus was used for this purpose.MethodsThe hyh mouse model of hereditary hydrocephalus (hydrocephalus with hop gait) and control littermates without hydrocephalus were used in the present work. In tissue sections, the ionic content was investigated using energy dispersive X-ray spectroscopy scanning electron microscopy (EDS-SEM). For the lipid analysis, matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) was performed in frozen sections. The expression of proteins in the cerebral white matter was analysed by mass spectrometry. The oligodendrocyte progenitor cells (OPCs) were studied with immunofluorescence in cerebral sections and whole-mount preparations of the ventricle walls.ResultsHigh sodium and chloride concentrations were found indicating oedema conditions in both the periventricular white matter and extending towards the grey matter. Lipid analysis revealed lower levels of two phosphatidylinositol molecular species in the grey matter, indicating that neural functions were altered in the hydrocephalic mice. In addition, the expression of proteins in the cerebral white matter revealed evident deregulation of the processes of oligodendrocyte differentiation and myelination. Because of the changes in oligodendrocyte differentiation in the white matter, OPCs were also studied. In hydrocephalic mice, OPCs were found to be reactive, overexpressing the NG2 antigen but not giving rise to an increase in mature oligodendrocytes. The higher levels of the NG2 antigen, diacylglycerophosphoserine and possibly transthyretin in the cerebrum of hydrocephalic hyh mice could indicate cell reactions that may have been triggered by inflammation, neurocytotoxic conditions, and ischaemia.ConclusionOur results identify possible biomarkers of hydrocephalus in the cerebral grey and white matter. In the white matter, OPCs could be reacting to acquire a neuroprotective role or as a delay in the oligodendrocyte maturation.
Highlights
In hereditary congenital obstructive hydrocephalus, the elevation of intracranial pressure and enlargement of the cerebral ventricles induce injury in the brain parenchyma [1]
The hyh mouse presented severe obstructive hydrocephalus at 20 days of age, and it was observed that the periventricular white matter in particular was seriously affected and exhibited an oedematous appearance (Fig. 1)
In the cerebral cortex of hyh mice with obstructive hereditary congenital hydrocephalus, these results support the presence of astrocyte reaction and alterations in the white matter, both common events previously described in experimental animal models of hydrocephalus and human cases [1, 41, 94, 95]
Summary
In hereditary congenital obstructive hydrocephalus, the elevation of intracranial pressure and enlargement of the cerebral ventricles induce injury in the brain parenchyma [1]. In congenital hydrocephalus, astrocyte and microglial cell activation is a common pathological event that can affect the cerebral white matter [9,10,11,12,13,14,15,16,17]. Other harmful conditions affecting the periventricular walls in congenital hydrocephalus need to be considered such as the presence of periventricular oedema, which is reflected by the levels of osmolytes [19], and high levels of the proinflammatory cytokine TNFα and neuroexcitotoxic glutamate [19, 20]. Periventricular extracellular oedema, myelin damage, inflammation, and glial reactions are common neuropathological events that occur in the brain in congenital hydrocephalus. The hyh mouse model of hereditary hydrocephalus was used for this purpose
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