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Method Article
The epithelial cells of the choroid plexus (CP) form the blood-cerebrospinal fluid barrier (BCSFB). An in vitro model of the BCSFB employs human choroid plexus papilloma (HIBCPP) cells. This article describes culturing and basolateral infection of HIBCPP cells using a cell culture filter insert system.
The epithelial cells of the choroid plexus (CP), located in the ventricular system of the brain, form the blood-cerebrospinal fluid barrier (BCSFB). The BCSFB functions in separating the cerebrospinal fluid (CSF) from the blood and restricting the molecular exchange to a minimum extent. An in vitro model of the BCSFB is based on cells derived from a human choroid plexus papilloma (HIBCPP). HIBCPP cells display typical barrier functions including formation of tight junctions (TJs), development of a transepithelial electrical resistance (TEER), as well as minor permeabilities for macromolecules. There are several pathogens that can enter the central nervous system (CNS) via the BCSFB and subsequently cause severe disease like meningitis. One of these pathogens is Neisseria meningitidis (N. meningitidis), a human-specific bacterium. Employing the HIBCPP cells in an inverted cell culture filter insert system enables to study interactions of pathogens with cells of the BCSFB from the basolateral cell side, which is relevant in vivo. In this article, we describe seeding and culturing of HIBCPP cells on cell culture inserts. Further, infection of the cells with N. meningitidis along with analysis of invaded and adhered bacteria via double immunofluorescence is demonstrated. As the cells of the CP are also involved in other diseases, including neurodegenerative disorders like Alzheimer`s disease and Multiple Sclerosis, as well as during the brain metastasis of tumor cells, the model system can also be applied in other fields of research. It provides the potential to decipher molecular mechanisms and to identify novel therapeutic targets.
The blood-cerebrospinal fluid barrier (BCSFB) is one of the three barrier sites between the blood and the brain1. Its morphological correlate are the epithelial cells of the choroid plexus (CP)2,3, an endothelial-epithelial convolute, which is strongly vascularized and located in the ventricles of the brain. The CP serves to produce the cerebrospinal fluid (CSF) as well as to separate the latter from the blood. In order to achieve barrier function, the CP epithelial cells show a low pinocytotic activity, express specific transporters, and are densely connected by a continuous network of tight junctions (TJs)2,3.
Human choroid plexus papilloma (HIBCPP) cells, derived from a malignant choroid plexus papilloma of a Japanese woman4, were used to construct a functional in vitro model of the BCSFB. HIBCPP cells show a couple of characteristics of a functional BCSFB as the formation of TJ strands, the development of a high transepithelial membrane potential that can be determined as transepithelial electrical resistance (TEER), and minor permeabilities for macromolecules. Moreover, HIBCPP cells express characteristic transporters, which may serve to regulate the ionic microenvironment, and show apical/basolateral polarity5,6,7.
The BCSFB has been shown to function as an entry site for pathogens (bacteria, viruses, and fungi) into the central nervous system (CNS)8. The invasion of pathogens, including Neisseria meningitidis (N. meningitidis), a Gram-negative bacterium, can cause severe diseases like meningitis. Evidence that it overcomes the protective epithelial barrier of the CP is supported by histopathological observations in patients with meningococcal disease exhibiting increased amounts of meningococci in the vessels and CP epithelial cells9,10. To gain entry into host cells bacteria often hijack endocytotic mechanisms, which are mediated or triggered by specific surface receptors located on the host cells. Since interactions of pathogens with these receptors can be species specific11, animal models can only be consulted to a restricted extent. The HIBCPP cell line provides the opportunity to study the invasion process as well as the underlying molecular mechanisms in a human model system. Employing cell culture inserts enables us to analyze interactions of pathogens with host cells from two distinct cell sides. Many bacteria, including N. meningitidis, are strongly subject to the impact of gravity during infection assays. For optimal interaction of pathogens with the HIBCPP cells during the assays, the bacteria are initially added into the upper compartment of the cell culture filter insert system. To enable infection from the apical or the basolateral cell side, respectively, two variations of the in vitro system have been established: In the standard system HIBCPP cells are seeded into the upper compartment of the filter insert, mimicking the situation when microorganisms are located on the CSF-side and get into contact with the apical side of the cells (Figure 1A, C). In contrast, using the HIBCPP cells in an inverted cell culture filter insert system reflects the conditions when bacteria have entered the blood stream. Microorganisms disseminate in the blood and encounter CP epithelial cells from the basolateral side (Figure 1B, D). Noteworthy, in this model system it has been shown that bacteria invade HIBCPP cells in a polar fashion specifically from the basolateral cell side5,7.
Subsequently to infection of the CP, the invaded pathogens can be recognized by the innate immune system through ligation to pattern-recognition receptors (PRRs). Well-described members of the PRRs belong to the Toll-like receptor (TLR) family. TLRs can bind to characteristic structures of infectious microorganisms, which are termed pathogen-associated molecular patterns (PAMPs). Ligation of the receptors leads to activation of host cell signaling cascades that trigger expression of cytokines and chemokines12, which in turn stimulate transmigration of immune cells across the BCSFB13,14. It has been shown that HIBCPP cells express several TLRs at mRNA level and that infection with N. meningitidis results in secretion of several cytokines and chemokines, including CXCL1-3, IL6, IL8 and TNFα15,16.
Here, we describe cultivation and infection of the human cell line HIBCPP in an inverted cell culture insert system that mimics the BCSFB. This model system enables to study interactions of pathogens with the in vivo relevant basolateral cell side as well as the subsequent cellular response.
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1. Prepare Cell Culture Filter Inserts for Seeding HIBCPP Cells in an Inverted Model System
2. Cultivation and Passaging of HIBCPP Cells
3. Seeding Inverted Cell Culture Filter Inserts with HIBCPP Cells
4. Measurement of Transepithelial Electrical Resistance (TEER)
5. Determination of Paracellular Permeability
6. Preparation of Bacteria for Infection of HIBCPP Cells on Cell Culture Filter Inserts
7. Infection of HIBCPP Cells on Cell Culture Filter Inserts and Determination of Bacterial Invasion by Double Immunofluorescence
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Here we describe culturing and infection of HIBCPP cells in an inverted cell culture insert system. This model allows us to study invasion mechanisms and the underlying molecular signaling pathways from the basolateral cell side, reproducing a physiological situation of bacteria disseminating and entering epithelial cells via the blood stream (Figure 1).
The HIBCPP cells display certain barrier functions, which ...
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The epithelial cells of the CP form the BCSFB that separates the CSF from the blood2,3. We recently established the HIBCPP cell line as a functional human model of the BCSFB. The cells display important barrier functions of the BCSFB in vitro, including the development of a high membrane potential, a low permeability for macromolecules, as well as the presence of continuous strands of TJs5. The TJ proteins contribute to an apical/basolateral polarity of the cells. The polarity is of high im...
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The authors have nothing to disclose.
The authors would like to thank Prof. Hartwig Wolburg for performing the electron microscopy.
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Name | Company | Catalog Number | Comments |
0.25% Trypsin-EDTA | Gibco | 25200-056 | |
4´,6 diamidino-2-phenylindole (DAPI) | Life Technologies | D1306 | |
12-well plates | Starlab | CC7682-7512 | |
24-well plates | Starlab | CC7682-7524 | |
Anti Neisseria meningitidis α-OMP | This antibody was a gift from Drs. H. Claus and U. Vogel (University of Würzburg, Germany) | ||
Alexa Fluor 488 (chicken anti rabbit) | Invitrogen | A21441 | |
Alexa Fluor 594 (chicken anti rabbit) | Invitrogen | A21442 | |
Alexa Fluor 660 Phalloidin | Invitrogen | A22285 | |
Bovine serum albumine (BSA) | Calbiochem | 12659 | |
Chocolate agar plates | Biomerieux | 43109 | |
Cytochalasin D | Sigma | C8273 | |
DMEM/F12 + L-Glut + 15 mM HEPES | Gibco | 31330-095 | |
DMEM/F12 + L-Glut + 15 mM HEPES w/o Phenolred | Gibco | 11039-047 | |
Dimethyl sulfoxide | Sigma | D2650 | |
Fetal calf serum (FCS) | Life Technologies | 10270106 | |
FITC-Inulin | Sigma | F3272 | |
Insulin | Sigma | 19278 | |
MgCl2 | Sigma | 2393 | |
NaHCO3 | Sigma | 55761 | |
PBS + Mg + Ca | Gibco | 14040-174 | |
Penicillin/Streptomycin | MP Biomedicals | 1670049 | |
Polyvitex | Biomerieux | 55651 | |
Proteose peptone | BD | 211684 | |
Serum-free medium | Gibco | 10902-096 | |
Thincert cell culture inserts for 24-well plates, pore size 3 µm | Greiner | 662630 | |
Tissue culture flask 75 cm² red cap sterile | Greiner | 658175 | |
Triton X-100 | Sigma | T8787 | |
Volt-Ohm Meter Millicell-ERS2 with MERSSTX01 electrode | Millipore | MERSSTX00 |
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