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Updated: Mar 17, 2026
Microdissection and Whole Mount Scanning Electron Microscopy Visualization of Mouse Choroid Plexus
Published on: December 16, 2022
Fibrosis of the Choroid Plexus Filtration Membrane
John W Prineas1, John D E Parratt2, Paul D Kirwan2
1From the The Institute of Clinical Neurosciences and the Nerve Research Foundation, Department of Medicine, University of Sydney, NSW, Australia (JWP, JDEP)Department of Neurology, Royal North Shore Hospital, St. Leonards, Sydney, NSW, Australia (JDEP)Electron Microscope Unit, Department of Anatomical Pathology, Concord Repatriation Hospital, Concord, Sydney, NSW, Australia (PDK) john.prineas@sydney.edu.au.
Abstract:
We report a previously undescribed inflammatory lesion consisting of deposition of activated complement (C3d and C9neo) in association with major histocompatibility complex type II (MHC2)-positive activated microglia in choroid plexus villi exhibiting classical fibrous thickening of the pericapillary filtration membrane. The proportion of villi affected ranged from 5% to 90% in 56 adult subjects with diseases of the CNS and 11 subjects with no preexisting disease of the CNS. In 3 of the 4 children studied, 2% or less of examined villi showed stromal thickening, complement deposition, and the presence of MHC2-positive microglia; in adults, the proportion of villi affected increased with age. Other features of the lesion included loss of capillaries and failure by macrophages to clear extracellular particulate electron-dense material by clathrin-mediated phagocytosis. This choroid plexus lesion may relate pathogenetically to age-related macular degeneration and to Alzheimer disease, 2 other conditions with no known risk factors other than increasing age. All 3 conditions are characterized by the presence of damaged capillaries, inflammatory extracellular aggregates of mixed molecular composition and defective clearance of the deposits by macrophages.
Insights
A novel inflammatory lesion in the choroid plexus, involving complement deposition and microglia activation, is described. This finding, more prevalent in adults, may link to age-related diseases like Alzheimer's.
Area of Science:
- Neuroscience
- Immunology
- Pathology
Background:
- The choroid plexus plays a crucial role in maintaining brain homeostasis.
- Age-related changes in the central nervous system (CNS) are not fully understood.
- Inflammatory processes are implicated in various neurodegenerative diseases.
Purpose of the Study:
- To describe a previously unrecognized inflammatory lesion in choroid plexus villi.
- To investigate the prevalence and characteristics of this lesion in relation to age and CNS diseases.
- To explore potential pathogenetic links between this lesion and age-related CNS conditions.
Main Methods:
- Histopathological examination of choroid plexus villi from adult and pediatric subjects.
- Immunohistochemical staining for complement components (C3d, C9neo) and major histocompatibility complex type II (MHC2)-positive microglia.
- Assessment of pericapillary filtration membrane thickening, capillary loss, and macrophage phagocytic activity.
Main Results:
- A novel inflammatory lesion characterized by complement deposition (C3d, C9neo) and MHC2-positive microglia was identified in choroid plexus villi.
- The lesion prevalence increased with age, affecting 5-90% of villi in adults, with minimal presence in children.
- Associated features included capillary loss and impaired macrophage clearance of extracellular material.
Conclusions:
- The described choroid plexus lesion is a previously unrecognized pathological finding.
- Its age-dependent increase and association with impaired clearance suggest a role in neuroinflammation.
- This lesion may share pathogenetic mechanisms with age-related diseases such as Alzheimer's disease and age-related macular degeneration.
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