Summary Aims Previous studies indicated that intraventricular injection of thrombin would induce hydrocephalus. But how thrombin works in this process remains unclear. Since cadherin plays a critical role in hydrocephalus, we aimed to explore the mechanisms of how thrombin acted on choroid plexus vascular endothelium and how thrombin interacted with vascular endothelial‐cadherin (VE‐cadherin) during hydrocephalus. Methods There were two parts in this study. Firstly, rats received an injection of saline or thrombin into the right lateral ventricle. Magnetic resonance imaging was applied to measure the lateral ventricle volumes. Albumin leakage and Evans blue content were assessed to test the blood‐brain barrier function. Immunofluorescence and Western blot were applied to detect the location and the expression of VE‐cadherin. Secondly, we observed the roles of protease‐activated receptors‐1 (PAR1) inhibitor (SCH79797), Src inhibitor (PP2), p21‐activated kinase‐1 (PAK1) inhibitor (IPA3) in the thrombin‐induced hydrocephalus, and their effects on the regulation of VE‐cadherin. Results Our study demonstrated that intraventricular injection of thrombin caused significant downregulation of VE‐cadherin in choroid plexus and dilation of ventricles. In addition, the inhibition of PAR1/p‐Src/p‐PAK1 pathway reversed the decrease of VE‐cadherin and attenuated thrombin‐induced hydrocephalus. Conclusions Our results suggested that the thrombin‐induced hydrocephalus was associated with the inhibition of VE‐cadherin via the PAR1/p‐Src/p‐PAK1 pathway.

Hydrocephalus has been reported to occur in spontaneous hypertensive rats (SHRs). The purposes of this study were (1) to use T2 magnetic resonance imaging to examine time of onset, (2) to elucidate potential underlying mechanisms and (3) to determine whether minocycline could prevent hydrocephalus development. Ventriculomegaly was evaluated by T2 imaging in SHRs and Wistar-Kyoto rats from weeks 4 to 7 after birth. Brain histology and transmission electron microscopy were used to assess the periventricular and choroid plexus damage. SHRs were also treated with either vehicle or minocycline. We found that hydrocephalus was observed in SHRs but not in Wistar-Kyoto rats. It occurred at seven weeks of age but was not present at four and five weeks. The hydrocephalus was associated with epiplexus cell (macrophage) activation, choroid plexus cell death and damage to the ventricle wall. Treatment with minocycline from week 5 attenuated hydrocephalus development and pathological changes in choroid plexus and ventricular wall at week 7. The current study found that spontaneous hydrocephalus arises at ∼7 weeks in male SHRs. The early development of hydrocephalus (persistent ventricular dilatation) may result from epiplexus cell activation, choroid plexus cell death and periventricular damage, which can be ameliorated by treatment with minocycline.

Objective Choke vessels, vascular anastomosis between adjacent angiosome, play an important role in flap expansion and survival. Here we established a flap model with single and multiple perforators to detect and compare the changes in choke vessels, discuss the effect of hemodynamics on the vascular morphology, and explore the underlying mechanism. Methods One hundred mice (7–8 weeks) were subjected to a “choke zone” surrounded by 4 perforators on their backs. Delayed surgery was performed by the ligation of 1, 2, or 3 perforators to establish flap models. The blood flow of the choke zone was measured by laser Doppler flowmetry preoperatively and 6 hours and 1, 3, 5, and 7 days. The morphological changes of choke vessels in the choke zone were observed by gross and histological analyses. Levels of angiogenesis-related markers such as endothelial nitric oxide synthase (eNOS), metalloproteinase 2, hypoxia-inducible factor 1α (HIF-1α), and intercellular adhesion molecule 2 (ICAM-2) were detected by Western blotting and enzyme-linked immunosorbent assay. Results Blood flow and microvascular count were obviously increased postoperatively and peaked and were maintained for 1 week (P < 0.01). Meanwhile, the diameters of the choke vessels expanded. The eNOS level was increased at 7 days (P < 0.05); however, the enzyme-linked immunosorbent assay results showed that the HIF-1α and ICAM-2 levels were decreased at 7 days. Conclusions (1) The delayed surgery that kept a single perforator had the greatest impact on the choke zone. (2) Changes in choke vessels were closely related to the shear stress caused by enhanced blood perfusion after surgery. (3) Choke vessel growth was regulated by eNOS, metalloproteinase 2, HIF-1α, and ICAM-2.

Hydrocephalus is a complicated disorder that affects both adult and pediatric populations. The mechanism of hydrocephalus development, especially when there is no mass lesion present causing an obstructive, is poorly understood. Prior studies have demonstrated that spontaneously hypertensive rats (SHRs) develop hydrocephalus by week 7, which was attenuated with minocycline. The aim of this study was to determine sex differences in hydrocephalus development and to examine the effect of minocycline administration after hydrocephalus onset. Male and female Wistar–Kyoto rats (WKYs) and SHRs underwent magnetic resonance imaging at weeks 7 and 9 to determine ventricular volume. Choroid plexus epiplexus cell activation, cognitive deficits, white matter atrophy, and hippocampal neuronal loss were examined at week 9. In the second phase of the experiment, male SHRs (7 weeks old) were treated with either saline or minocycline (20 mg/kg) for 14 days, and similar radiologic, histologic, and behavior tests were performed. Hydrocephalus was present at week 7 and increased at week 9 in both male and female SHRs, which was associated with greater epiplexus cell activation than WKYs. Male SHRs had greater ventricular volume and epiplexus cell activation compared to female SHRs. Minocycline administration improved cognitive function, white matter atrophy, and hippocampal neuronal cell loss. In conclusion, while both male and female SHRs developed hydrocephalus and epiplexus cell activation by week 9, it was more severe in males. Delayed minocycline treatment alleviated hydrocephalus, epiplexus macrophage activation, brain pathology, and cognitive impairment in male SHRs.