Dose dependent ventricular enlargement, neurodegeneration and mortality rates in kaolin-induced hydrocephalus in adult mice

Abstract

Intra-cisternal injection of kaolin is the most common method of experimentally inducing hydrocephalus. A reduction in kaolin dosage has been reported to reduce the mortality rate. Thus, the mortality rate and degree of ventricular enlargement in adult male mice with the use of different concentrations of kaolin suspension to induce hydrocephalus and observed the morphological changes in pyramidal neurons of layer V of the sensorimotor cortex and hippocampus were compared.

Hydrocephalus was induced intracisternally in adult male mice subdivided into 5 groups (n=27) using 0.02mL of 50, 100, 150, 200 and 250 mg/mL of kaolin respectively while controls (n=15) received sham injection. Mice were weighed biweekly for 4 weeks. Harvested brains were processed for Cresyl violet and NeuN Immunostaining to assess neuronal damage. Data were analyzed using GraphPad Prism 8 and ImageJ software. The hydrocephalic rates of 50, 100, 150, 200 and 250 mg/mL groups were 40.0%, 58.8%, 78.6%, 88.9% and 94.4% respectively while their mortality rates were 21.1%, 22.7%, 26.3%, 28.0% and 30.8% respectively. The mortality rate and frequency of hydrocephalus in 250 mg/mL group were significantly higher than 50 and 100 mg/L groups (p<0.0001), while there was no significant difference between the ventricular diameter in 250 mg/mL group and others (p=0.0002). Pyknotic pyramidal neurons of the sensorimotor cortex of mice induced with 250 mg/mL group of kaolin concentration were significantly more numerous than the control (p<0.05).  The pyknotic index (PI) of the dentate gyrus in the 250 mg/mL group was significantly higher than the control. NeuN immunohistochemistry of Layer V of hydrocephalic brains demonstrated decreased staining intensity and fewer NeuN-positive cells compared to controls. The findings from this study suggest that for the induction of hydrocephalus in adult mice, the use of 150 mg/mL and 250 mg/mL concentrations are suitable for long and short-term studies respectively.