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Method Article
The protocol described here highlights the major steps in the differentiating induced pluripotent stem-cell derived brain-like endothelial cells, the preparation of Neisseria meningitidis for infection, and sample collection for other molecular analyses.
Meningococcal meningitis is a life-threatening infection that occurs when Neisseria meningitidis (meningococcus, Nm) can gain access to the central nervous system (CNS) by penetrating highly specialized brain endothelial cells (BECs). As Nm is a human-specific pathogen, the lack of robust in vivo model systems makes study of the host-pathogen interactions between Nm and BECs challenging and establishes a need for a human based model that mimics native BECs. BECs possess tighter barrier properties when compared to peripheral endothelial cells characterized by complex tight junctions and elevated trans-endothelial electrical resistance (TEER). However, many in vitro models, such as primary BECs and immortalized BECs, either lack or rapidly lose their barrier properties after removal from the native neural microenvironment. Recent advances in human stem-cell technologies have developed methods for deriving brain-like endothelial cells from induced pluripotent stem-cells (iPSCs) that better phenocopy BECs when compared to other in vitro human models. The use of iPSC-derived BECs (iPSC-BECs) to model Nm-BEC interaction has the benefit of using human cells that possess BEC barrier properties, and can be used to examine barrier destruction, innate immune activation, and bacterial interaction. Here we demonstrate how to derive iPSC-BECs from iPSCs in addition to bacterial preparation, infection, and sample collection for analysis.
The blood-brain barrier (BBB), and the meningeal blood-CSF barrier (mBCSFB) are extremely tight cellular barriers that separate the circulation from the central nervous system (CNS) and are primarily comprised of highly specialized brain endothelial cells (BECs)1,2. Together, BECs maintain proper brain homeostasis by regulating nutrients and waste products in and out of the brain, while excluding many toxins, drugs, and pathogens1,2. Bacterial meningitis occurs when blood-borne bacteria are able to interact with, and penetrate the barrier formed by BECs and cause inflammation. Neisseria meningitidis (Nm, meningococcus) is a Gram-negative bacterium that colonizes the nasopharaynx of 10‒40 % of healthy individuals, but in some cases can cause serious systemic disease3. In affected individuals, Nm can gain access to the blood stream where it can cause purpura fulminans as well as penetrate BECs gaining access to the CNS causing meningitis3. Nm is a leading cause of bacterial meningitis world-wide, and despite vaccination efforts, is still a primary cause of meningitis4. Modern medical intervention, such as antibiotic treatment, have made these conditions survivable, however those affected with meningitis often are left with permanent neurological damage5,6.
Previous studies have identified bacterial factors and host signaling that contribute to Nm-BEC interactions7,8,9,10,11. The identified adhesins and invasins such as the opacity protein Opc, and type-IV pili, as well as receptors such as CD147, have been conducted on various BEC models in vitro, however these models lack many defining BBB properties7,9,11,12. Complete understanding of Nm-BEC interactions remain elusive due partially to the inability to utilize in vivo models, incomplete vaccination protection, and lack of robust human BEC models in vitro.
Modeling hBECs in vitro has been challenging due to the unique properties of BECs. Compared with peripheral endothelial cells, BECs have a number of phenotypes that enhance their barrier properties such as high trans-endothelial electrical resistance (TEER) due to complex tight junctions12. Once removed from the brain microenvironment, BECs rapidly lose their barrier properties limiting the usefulness of primary or immortalized in vitro models that only form a weak barrier12,13. The combination of the human specificity of Nm infections, lack of robust in vivo models, and challenges modeling human BECs in vitro creates a need for better models to understand the complex host-pathogen interaction between Nm and BECs. Recently using model human induced pluripotent stem cell (iPSC) technologies BEC-like cells have been derived from iPSCs that better mimic BECs in vivo12,13,14,15. iPSC-BECs are of human origin, easily scalable, and possess expected BEC phenotypes compared to their primary or immortalized counterparts12,13,14,15. Additionally we and others have demonstrated that iPSC-BECs are useful for modeling various diseases of the CNS such as host-pathogen interaction, Huntington’s disease, and MCT8 deficiency that causes Allan-Hurndon-Dudley syndrome16,17,18,19,20,21. Here, we demonstrate how to derive iPSC-BECs from renewable iPSC sources and the infection of iPSC-BECs with Nm leading to activation of the innate immune response. We believe that this model is useful to interrogate host-pathogen interaction that is unable to be recapitulated in other in vitro models and is especially useful when examining interactions with human specific pathogens such as Nm.
NOTE: All media / reagent preparation, stem-cell maintenance, and differentiation steps are adapted from Stebbins et al.22.
1. Preparation of materials required for iPSC culture and BEC differentiation.
2. Maintenance IMR90-4 cell culture
NOTE: Here we use the IMR90-4 cell line as an example, however other induced pluripotent stem-cell lines such as CC3, CD10, CD12, DF19-9-11T, 83iCTR, 00iCTR, and CS03iCTRn2 have been successfully employed for differentiation into BECs13,14,15,16,17,23,27,28.
3. Differentiation of brain endothelial cells from human iPSCs
4. Transendothelial electrical resistance (TEER) as a measure of barrier tightness
NOTE: TEER is usually read on membrane inserts on days 9 and 10 of differentiation to confirm successful generation of barrier forming iPSC-BECs (Figure 1A).
5. Immunofluorescence (IF) staining to validate BEC phenotype
NOTE: To validate the quality of the fully differentiated and purified cells, iPSC-BEC monolayers are stained for the characteristic markers of brain endothelial cells on day 10 of the differentiation process as previously described (Figure 1B‒G) 13,14,15,16,17,19,22.
6. Preparation of bacteria and infection of iPSC-BECs
7. Innate immune activation by quantitative PCR
NOTE: Using a preferred RNA isolation, cDNA synthesis, and qPCR protocol, collect samples and run qPCR on selected cytokines.
The protocol described here is adapted from Stebbins et al. and highlights the process to differentiate iPSCs into brain-like endothelial cells that possess BBB properties, and how to utilize this model for infection studies using iPSC-BECs with Nm19,22. The iPSC-BECs, when differentiated properly, exhibit tight barrier properties measured by TEER that are often greater than 2000 Ω·cm2, and express endothelial markers such as VE-cadherin and ...
Modeling BECs and the BBB has had challenges, as primary and immortalized human BECs, in vitro, tend to lack robust barrier phenotypes. The advent of human stem cell technologies has allowed for the generation of iPSC derived BEC-like cells that retain expected hallmark BBB phenotypes such as endothelial markers, tight junction expression, barrier properties, response to other CNS cell types, and functional efflux transporters12,
The authors have nothing to disclose.
L.M.E. is supported by the DFG research training program GRK2157 entitled “3D Tissue Models for Studying Microbial Infections by Human Pathogens” awarded to A. S-U. B.J.K. is supported by a postdoctoral fellowship by the Alexander von Humboldt Foundation. Additionally, we acknowledge Lena Wolter for her technical assistance in the generation of the iPSC-BECs in culture.
Name | Company | Catalog Number | Comments |
Accutase (1x) | Sigma | A6964 | Enzymatic cell dissociation reagent |
Acetic acid | Sigma | A6283 | |
All-trans retinoic acid (RA) | Sigma | R2625 | |
Anti-CD31 (PECAM-1) | Thermo Scientific (Labvision) | RB-10333 | |
Anti-Claudin-5 | Invitrogen | 4C3C2 | |
Anti-Glut-1 | Thermo Scientific (Labvision) | SPM498 (MA5-11315) | |
Anti-Occludin | Invitrogen | 33-1500 | |
Anti-VE-cadherin | Santa Cruz | sc-52751 | |
Anti-ZO-1 | Invitrogen | 33-9100 | |
Bacto Proteose Peptone | BD | 211684 | |
b-Mercaptoethanol | Merck (Sigma-Aldrich) | 805740 | |
Cell culture plates and flasks | Sarstedt | ||
Centrifuge (Heraeus Megafuge 1.0R) | Thermo Scientific | ||
Class II biosafety cabinet | Nuaire | NU-437-400E | |
CO2 Incubator (DHD Autoflow CO2 Air-Jacketed Incubator) | Nuaire | ||
Collagen IV | Sigma | C5533 | |
Columbia ager + 5 % sheep blood | Biomerieux | 43049 | |
Costar Transwell polyester filters (12- or 24-well) | Corning | 3460, 3470 | |
D(+)-Glucose | Merck (Sigma-Aldrich) | G8270 | |
DAPI | Invitrogen | D1306 | |
DMEM/F12 | Gibco | 31330-038 | |
DMSO | ROTH | A994.1 | |
Dulbecco's phosphate-buffered saline (DPBS) | Gibco | 21600-069 | |
Epithelial Volt-Ohm Meter (Millicell ERS-2) with STX electrode | Merck (Millipore) | MERS00002 | |
Fe(NO3)3 | ROTH | 5632.1 | |
Fibronectin | Sigma | F1141 | |
Fluoresence microscope (Eclipse Ti) | Nikon | ||
Hemacytometer (Neubauer) | A. Hartenstein | ZK06 | |
Human basic fibroblast growth factor (bFGF) | PeproTech | 100-18B | |
Human Endothelial Serum Free Medium (hESFM) | Gibco | 11111-044 | |
Inverted microscope (Wilovert) | Hund (Will Wetzlar) | ||
iPS(IMR90)-4 cells | WiCell | ||
Kellogg's supplement | To prepare 110 ml of Kellogg's supplement, prepare 100 ml of 4 g/ml glucose, 0.1 g/ml glutamine, and 0.2 mg/ml thiamine pyrophosphate and 10 ml of 5 mg/ml Fe(NO3)3 and combine the solutions. Filter sterilize and store aliquoted at -20 °C. | ||
Knockout serum replacement (KOSR) | Gibco | 10828-028 | |
L-glutamine (GlutaMAX) | Invitrogen | 35050-038 | |
LunaScript RT SuperMix Kit | NEB | E3010L | cDNA synthesis kit |
Matrigel Matrix | Corning | 354230 | |
Methanol | ROTH | 4627.5 | |
MgCl2 | ROTH | KK36.1 | |
Micropipettes (Research Plus) | Eppendorf | ||
NaHCO3 | ROTH | 6329 | |
Nonessential amino acids (NEAA) | Gibco | 11140-035 | |
NucleoSpin RNA isolation kit | Machery-Nagel | 740955 | RNA isolation kit |
Pipette boy (Accu-Jet Pro) | Brand | ||
Platelet poor plasma-derived serum, bovine (PDS) | Fisher | 50-443-029 | |
PowerUp SYBR Green Master Mix | Applied Biosystems | A25742 | qPCR master mix |
qPCR film (MicroAmp Optical Adhesive Film) | Applied Biosystems | 4211971 | |
qPCR plates (MicroAmp Fast 96-well) | Applied Biosystems | 4346907 | |
ROCK inhibitor, Y27632 dihydrochloride | Tocris | 1254 | |
RT-PCR thermo cycler (StepOnePlus) | Applied Biosystems | 4376600 | |
Serological pipettes | Sarstedt | ||
StemFlex basal medium + 50x StemFlex supplement | Gibco | A3349401 | Stem-cell maintenance medium |
Swinging Bucket Rotor (Heraeus #2704) | Thermo Scientific | ||
Thiamine pyrophosphate | Sigma | C8754-5G | |
Trypan Blue Solution, 0.4% | Gibco | 15250061 | |
Versene | Gibco | 15040-033 | Non-enzymatic cell dissociation reagent (EDTA) |
An erratum was issued for: Neisseria meningitidis Infection of Induced Pluripotent Stem-Cell Derived Brain Endothelial Cells Larvae. The Authors section was updated from:
Leo M. Endres1
Alexandra Schubert-Unkmeir1
Brandon J. Kim1,2
1Institute for Hygiene and Microbiology, University of Würzburg
2Department of Biological Sciences, University of Alabama
to:
Leo M. Endres1
Sarah F. Hathcock2
Alexandra Schubert-Unkmeir1
Brandon J. Kim1,2
1Institute for Hygiene and Microbiology, University of Würzburg
2Department of Biological Sciences, University of Alabama
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