マウスにおける多発性硬化症のEAEモデルにおける視神経炎と脳炎症の生物発光と近赤外イメージング
Summary
我々は、in vivoでのライブ生物発光およびSJL / Jマウスにおける多発性硬化症の実験的自己免疫性脳脊髄炎（EAE）モデルにおける視神経炎や脳炎の近赤外イメージングのための技術を示します。
Abstract
SJL / Jマウスにおける実験的自己免疫性脳脊髄炎（EAE）は、再発寛解型多発性硬化症（RRMS）のモデルです。運動機能障害を記述する臨床EAEスコアは、脊髄の免疫媒介炎症の基本的な読み出しです。しかし、スコアおよび体重は脳の炎症と視神経炎のin vivoで評価することができません。後者は、約2/3のMS患者の早期かつ頻繁な症状です。ここでは、 インビボイメージングシステムを用いて、生きているマウスにおける生物発光およびEAEの視神経炎を誘発評価するための近赤外ライブイメージング、脳の炎症、及び血液脳関門（BBB）破壊するための方法を示します。酸化酵素によって活性化された生物発光基質は、主に視神経炎を示しました。信号は特異的であり、臨床スコアを並列薬の効果や病気の時間のコース、の可視化を可能にしました。 vasculatur内に留まったペグ化蛍光ナノ粒子長時間eがBBBの完全性を評価するために使用しました。近赤外イメージングは、疾患のピーク時BBB漏れを明らかにしました。信号は、目の周りの最も強かったです。マトリックスメタロプロテアーゼのための近赤外基質は、EAE誘発炎症を評価しました。自家蛍光は、定量化のためのスペクトルアンミキシングを必要とし、信号を妨害しました。全体として、生物発光イメージングは、EAEに関連する視神経炎および薬物の効果を評価するための信頼性の高い方法であり、シグナルの特異性、堅牢性、定量化の容易さ、及びコストの観点から近赤外の技術よりも優れていました。
Introduction
Multiple sclerosis is caused by the autoimmune-mediated attack and destruction of the myelin sheath in the brain and the spinal cord1. With an overall incidence of about 3.6 cases per 100,000 people a year in women and about 2.0 in men, MS is the second most common cause of neurological disability in young adults, after traumatic injuries2,3. The disease pathology is contributed to by genetic and environmental factors4 but is still not completely understood. Autoreactive T lymphocytes enter the central nervous system and trigger an inflammatory cascade that causes focal infiltrates in the white matter of the brain, spinal cord, and optic nerve. In most cases, these infiltrates are initially reversible, but persistence increases with the number of relapses. A number of rodent models have been developed to study the pathology of the disease. The relapsing-remitting EAE in SJL/J mice and the primary-progressive EAE in C57BL6 mice are the most popular models.
The clinical EAE scores, which describe the extent of the motor function deficits, and body weight are the gold standards to assess EAE severity. These clinical signs agree with the extent of immune cell infiltration and myelin destruction in the spinal cord and moderately predict drug treatment efficacy in humans5. However, these signs mainly reflect the destruction of the ventral fiber tracts in the spinal cord. Presently, there is no easy, non-invasive, reliable, and reproducible method to assess in vivo brain infiltration and optic neuritis in living mice.
The in vivo imaging agrees with the 3 “R” principles of Russel and Burch (1959), which claim a Replacement, Reduction, and Refinement of animal experiments6, because imaging increases the readouts of one animal at several time points and allows for a reduction of the overall numbers. Presently, inflammation or myelin status is mainly assessed ex vivo via immunohistochemistry, FACS-analysis, or different molecular biological methods7, all requiring euthanized mice at specific time points.
A number of in vivo imaging system probes have been developed to assess inflammation in the skin, joints, and vascular system. The techniques rely on the activation of bioluminescent or near-infrared fluorescent substrates by tissue peroxidases, including myeloperoxidase (MPO), matrix metalloproteinases (MMPs)8, and cathepsins9 or cyclooxygenase2. These probes have been mainly validated in models of arthritis or atherosclerosis9,10. A cathepsin-sensitive probe has also been used for fluorescence molecular tomographic imaging of EAE11. MMPs, particularly MMP2 and MMP9, contribute to the protease-mediated BBB disruption in EAE and are upregulated at sites of immune cell infiltration12, suggesting that these probes may be useful for EAE imaging. The same holds true for peroxidase or cathepsin-based probes. Technically, imaging of inflammation in the brain or spinal cord is substantially more challenging because the skull or spine absorb bioluminescent and near-infrared signals.
In addition to inflammation indicators, fluorescent chemicals have been described, which specifically bind to myelin and may allow for quantification of myelination13. A near-infrared fluorescent probe, 3,3′-diethylthiatricarbocyanine iodide (DBT), was found to specifically bind to myelinated fibers and was validated as a quantitative tool in mouse models of primary myelination defects and in cuprizone-evoked demyelination14. In EAE, the DBT signal was rather increased, reflecting the inflammation of the myelin fibers5.
An additional hallmark of EAE and MS is the BBB breakdown, resulting in increased vascular permeability and the extravasation of blood cells, extracellular fluid, and macromolecules into the CNS parenchyma. This can lead to edema, inflammation, oligodendrocyte damage, and, eventually, demyelination15,16. Hence, visualization of the BBB leak using fluorescent probes, such as fluorochrome-labeled bovine serum albumin5, which normally distribute very slowly from blood to tissue, may be useful to assess EAE.
In the present study, we have assessed the usefulness of different probes in EAE and show the procedure for the most reliable and robust bioluminescent technique. In addition, we discuss the pros and cons of near-infrared probes for MMP activity and BBB integrity.
Protocol
Representative Results
Discussion
現在のビデオは、SJL / JマウスにおけるEAEのin vivoイメージングにおける生物発光と近赤外蛍光のための技術を示しています。我々は、炎症感受性プローブを用いた生物発光イメージングは、主に視神経炎を示し、そして定量化はEAEの重症度の臨床評価および薬物の効果と一致することを示します。信号は脊柱によって吸収されるためしかし、生物発光イメージング法は、お?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
この研究はドイツ学術協会（CRC1039 A3）と研究助成プログラムヘッセン州の「LandesoffensiveツアEntwicklung wissenschaftlich-ökonomischerExzellenz」（LOEWE）、トランスレーショナル医学・薬理学TMPとそうでないクローネ-フレゼニウス財団研究センターによってサポートされていました（EKFS）、研究研修グループトランスレーショナルリサーチイノベーション – ファーマ（TRIP）。
Materials
| AngioSpark-680 | Perkin Elmer, Inc., Waltham, USA | NEV10149 | Imaging probe, pegylated nanoparticles, useful for imaging of blood brain barrier integrity |
| MMP-sense 680 | Perkin Elmer, Inc., Waltham, USA | NEV10126 | Imaging probe, activatable by matrix metalloproteinases, useful for imaging of inflammation |
| XenoLight RediJect Inflammation Probe | Perkin Elmer, Inc., Waltham, USA | 760535 | Imaging probe, activatable by oxidases, useful for imaging of inflammation |
| PLP139-151/CFA emulsion | Hooke Labs, St Lawrence, MA | EK-0123 | EAE induction kit |
| Pertussis Toxin | Hooke Labs, St Lawrence, MA | EK-0123 | EAE induction kit |
| IVIS Lumina Spectrum | Perkin Elmer, Inc., Waltham, USA | Bioluminescence and Infrared Imaging System | |
| LivingImage 4.5 software | Perkin Elmer, Inc., Waltham, USA | CLS136334 | IVIS analysis software |
| Isoflurane | Abbott Labs, Illinois, USA | 26675-46-7 | Anaesthetic |
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