Introduction: In intraventricular hemorrhage (IVH), the choroid plexus epithelium drives cerebrospinal fluid (CSF) secretion. Mechanisms of increased CSF production do not support changes in protein and cellular concentrations. The blood-CSF barrier is formed by intercellular tight and adherens junctions in the epithelium. We hypothesize that breakdown of these junctions follows IVH.
Methods: A rodent model of IVH was used and euthanized at 6-, 24-, 48-hours, 7 days post-injury. Intraventricular injection of normal saline was used as control. The expression of claudin-1, N-cadherin and zonula adherens-1 (ZO-1) was tested with immunohistochemistry, western blotting, electron microscopy.
Results: A time-dependent reduction in claudin-1 and N-cadherin expression was noticed after 6-, 24- and 48-hours. Alteration of the linear structure of intercellular junctions was noted after IVH, with significantly increased intra-cytoplasmic claudin-1 and N-cadherin signal. Partial reconstitution of the junctions was detected 48 hours post-IVH and progressed through day 7. Automated choroid plexus analysis using adjusted mean fluorescence of claudin-1 and N-cadherin signal showed a significant difference between IVH and control. ZO-1 ridges, a cytoplasmic marker of junctional integrity, were significantly reduced in number and length after 24 hours. Electron microscopy showed widening of the intercellular spaces (blebbing, separation, reduced junctional length) 48 hours post-IVH. Assessment of 50 scans/group showed a significant decrease in junctional integrity in IVH.
Conclusion : The BCSFB is a complex structure formed by tight and adherens junctions in the choroid plexus. Here, we demonstrated breakdown of these structures after IVH with immunohistochemistry, western blotting and electron microscopy. Changes in barrier function might explain the changes in protein and cellular CSF content observed in animal models and IVH patients. Further characterization of their functional consequences on CSF composition is warranted.
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