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Three-Dimensional Explant Platform for Studies on Choroid Plexus Epithelium
Natalia Petersen1, Lola Torz2, Kristian H Reveles Jensen2
1Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Insights
Researchers developed a 3D in vitro model using choroid plexus (CP) explants to study immune cell trafficking across the blood-cerebrospinal fluid barrier (BCSFB). This novel platform allows for better understanding of brain entry mechanisms for immune cells and substances.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- The choroid plexus (CP) forms the blood-cerebrospinal fluid barrier (BCSFB), crucial for regulating brain entry.
- Dysregulated immune cell trafficking across the CP is implicated in brain infections and neurodegenerative diseases.
- Current in vitro models using CP epithelial cell monolayers do not fully replicate the CP's complex 3D structure.
Purpose of the Study:
- To develop and validate a novel 3D in vitro platform for studying immune cell migration across the CP.
- To investigate the cellular and molecular mechanisms of immune cell trafficking at the BCSFB.
- To provide a tool for identifying therapeutic targets to control substance and immune cell entry into the central nervous system.
Main Methods:
- Generation of 3D choroid plexus explants from mouse CPs embedded in Matrigel.
- Culture and maintenance of explants for up to 8 weeks.
- Assessment of CP marker expression (transthyretin, aquaporin 1, ZO1, ICAM-1, transferrin, occludin) via microscopy and gene expression analysis.
- Monitoring of immune cell (dendritic cells, neutrophils) migration and interaction with CP epithelium using microscopy.
Main Results:
- CP explants successfully formed luminal spaces, maintained CP marker expression, and exhibited CP-like cell polarization and an intact epithelial barrier.
- The explants preserved the expression of key genes associated with CP function, similar to native CP.
- The 3D model allowed for the visualization and study of immune cell migration and interaction with the CP epithelium.
Conclusions:
- The 3D choroid plexus explant model effectively mimics the native BCSFB structure and function in vitro.
- This platform is suitable for studying immune cell trafficking and interactions at the CP epithelium.
- The model offers a promising tool for developing therapeutic strategies to modulate substance and immune cell entry into the brain.
Abstract:
The choroid plexus (CP) plays a major role in controlling the entry of substances and immune cells into the brain as it forms the blood-cerebrospinal fluid barrier (BCSFB) in the brain ventricles. Dysregulated immune cell trafficking through the epithelial cell (EC) layer of CP is central for the pathogenesis of infectious diseases in the brain and many neurodegenerative disorders. In vitro studies elucidating the function of the CP have so far been limited to the monolayer culture of CP ECs. To mimic immune cell migration across the CP barrier, a three-dimensional model would be advantageous. Here, we present an in vitro platform for studies of the immune cell trafficking based on CP explants/organoids. The explants were generated from fragments of mouse CPs in Matrigel, where the cells formed luminal spaces and could be maintained in culture for at least 8 weeks. We demonstrate expression of the major CP markers in the explants, including transthyretin and aquaporin 1 as well as ZO1 and ICAM-1, indicating a capacity for secretion of cerebrospinal fluid (CSF) and presence of tight junctions. CP explants displayed CP-like cell polarization and formed an intact EC barrier. We also show that the expression of transthyretin, transferrin, occludin and other genes associated with various functions of CP was maintained in the explants at similar levels as in native CP. By using dendritic cells and neutrophils, we show that the migration activity of immune cells and their interactions with CP epithelium can be monitored by microscopy. Thereby, the three-dimensional CP explant model can be used to study the cellular and molecular mechanisms mediating immune cell migration through CP epithelium and other functions of choroid EC. We propose this platform can potentially be used in the search for therapeutic targets and intervention strategies to improve control of (drug) substances and (immune) cell entry into the central nervous system.
