In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.
The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.
Muscular dystrophies constitute a group of prevalent and heterogeneous human muscle diseases with specific histopathological features1,2. Symptoms typically associated with this devastating group of diseases include muscle weakness, muscle degeneration, loss of motility, and early mortality1,3. The primary pathomechanisms of muscular dystrophies are the loss of proteins that stabilize the sarcolemma, anchor transmembrane complexes, and mediate cell signaling across the membrane4-6. For example, complete loss of the protein dystrophin, a primary scaffold protein of the dystrophin-glycoprotein complex, results in destabilization of the muscle membrane in Duchenne muscular dystrophy7. Due to the fact that most muscular dystrophies result from mutations in proteins that participate in the link between the extracellular matrix and the sarcolemmal cytoskeleton, a common observation at the cellular level is the loss of sacrolemmal integrity8,9. This understanding of the primary pathomechanism(s) associated with muscular dystrophies is the product of numerous years of research employing animal model systems2,10-15. However, despite advances in the field, there are still limited therapeutic options for treatment or management of the range of dystrophy subtypes. This limitation of viable therapies is due to several key factors: 1) the difficulty of gene therapy strategies, 2) a high frequency of de-novo disease cases and the corresponding lack of translatable animal models, and 3) the lack of rigorous strategies to test the physiological consequences of putative therapeutic agents with clear and reproducible outcome measures.
To overcome some of these limitations, numerous labs including our own are employing zebrafish as a system to model and study human neuromuscular diseases2. To date, zebrafish have proven a valuable tool in disease research. The zebrafish model has been used to identify and validate novel human disease causing mutations16,17, elucidate uncharacterized disease causing mechanisms17,18, and identify novel therapeutic strategies12,19. These advances were made, in part, by the canonical strengths of the zebrafish system such as their optical clarity, ease of genetic manipulation, and ability to breed in large numbers20. Zebrafish have additionally proven amendable to large-scale drug screens21, a valuable method for the identification of novel therapeutics22-24. Regarding muscle disease research, these strengths are complemented by the ability to isolate single zebrafish skeletal muscle fibers via dissociation25 and by the ability to examine myofiber organization in vivo using the optical phenomenon called birefringence26, which collectively allows for rapid determination of macroscopic muscle integrity. Regardless of these available utilities, further tool development is continuously required to advance investigation.
We, and others, have adapted a protocol for EBD injection and analysis in the zebrafish model. EBD is a vital, cell permeable dye that is taken up by damaged, degenerating, or apoptotic cells and then visualized under fluorescence27. To date, EBD analysis has extensively been used to analyze muscle membrane integrity in mouse models of skeletal muscle and heart diseases8,9,27. However, in mammalian preparations, harvested muscle typically requires laborious sectioning or dissection prior to analysis. In zebrafish, direct analysis is possible in high numbers using live and intact animals. In this video article, we will demonstrate the methodology to perform EBD injection and analysis in live zebrafish larvae, with representative images of EBD uptake in the zebrafish dystrophy mutant line sapje15,28. Furthermore, we present a co-injection strategy that allows for increased quantification of EBD preparations.
Zebrafisk dukker op som et effektivt redskab til studiet af neuromuskulære sygdomme 2,29. Til dato har zebrafisk system, blevet brugt til at validere nye muskel sygdomsfremkaldende mutationer 16,17,30, belyse nye patomekanismer 18, og identificere potentielle nye terapeutiske lægemidler 12,24. Disse kollektive indsats har etableret nytten af zebrafisk til at modellere menneskelige neuromuskulære sygdomme. Men på trods af de fremskridt med zebrafisk og pattedyr modeller, der er begrænsede behandlingsmuligheder for patienter inden for det brede spektrum af neuromuskulære forhold. Der eksisterer derfor for terapiudvikling for denne gruppe af ødelæggende sygdomme en stor efterspørgsel. Parallelt denne efterspørgsel efter lægemidler er den tilsvarende behov for løbende eksperimenterende innovation, samt grundig analyse for at kontrollere nye dyremodeller og formodede terapeutiske strategier.
EBD-analyse er almindeligt anvendt i musemodeller tilundersøgelse væv og cellulære skader i hjerne, hjerte og skeletmuskulatur 27,31. Mest bemærkelsesværdigt er EBD udbredt i musemodeller af forskellige muskeldystrofi undertyper at vise sværhedsgraden af muskelmembranernes ustabilitet og beskadige 8. Anvendelsen af EBD at afsløre skader muskelmembranernes er en støttende parameter oprettelse ligheder i dyremodel for det menneskelige sygdomstilstand 9. Effekten af EBD i mus har fået flere laboratorier, herunder vores egen, at udvikle og anvende EBD til zebrafisk modeller af neuromuskulære sygdomme. På grund af anvendeligheden af EBD-analyse, er denne teknik aktivt at blive gennemført for at underbygge zebrafisk modeller til den menneskelige sygdomstilstand 11,15,22,24,32. Larver med beskadigede muskel membraner vil have EBD optagelse og derfor rød fluorescens inden muskelfibre. Fluorescens observeret i den inter-fiber plads, men ikke inden for de enkelte muskelfibre kan også være informativ af fibre aftagning fra basalmembranen i tHan fravær af skader membran, giver nyttige diagnostisk detaljer. EBD-analyse har potentiel anvendelse ud over validering dyremodel. Indsats fra vores laboratorium har for nylig vist, at EBD analyse er gavnlige i at validere potentielt nye terapeutiske lægemidler 24. Bestemmelse om potentielle terapeutiske behandlinger reducere eller afskaffe EBD optagelse i neuromuskulære sygdomsmodeller kan betyde relevant terapeutisk virkning 8. Denne type analyse kan hjælpe med at etablere mekanismen (e) af lægemidler og udvider anvendelsen af EBD-analyse.
Som med mange teknikker, er EBD-analyse har flere forbehold, der skal overholdes under eksperimentelle design og praksis. For eksempel kan det være en udfordring at identificere CCV grund af fortykkelse af vævet med alderen. Desuden er det let at beskadige larver som forberedelse før og under perikardial injektion reducere eksperimentelle tæller og øger behovet for at prep store antal larver.Endvidere kunne fysisk skade gjort for at larverne under håndtering og injektion resultere i falske positiver, som beskadigede muskel kan tage op EBD. For at overvinde nogle af disse hindringer, har vi beskrevet en co-injektion strategi i denne video artikel, der gør det nemt og pålidelig identifikation af larver med succes farvestof infusion umiddelbart efter injektion og før efterfølgende analyse. FITC-dextran Saminjektion kontrol for vellykket injektion ved at tillade bekræftelse af EBD i vaskulaturen før dens optagelse af muskelfibrene. Dette kan især være nyttigt som EBD fluorescens bliver meget diffus i larver efter flere timer, hvis ikke indsamlet i muskelfibrene; som sådan, kan det være vanskeligt at opdage. Desuden mangler CCV og injektion EBD i æggeblomme eller legemshulrum kan, efter inkubation, medføre diffus rød fluorescens ligner kontrollere embryoner, men med reduceret sandsynlighed for optagelse af beskadigede muskelfibre. Kollektivt, disse grotteATS tyder EBD injektion kræver tålmodighed og praksis for at opnå konsistente og pålidelige resultater.
I alt beskriver vi en praktisk og enkel metode til at udføre EBD analyse på zebrafisk larver. Til dato anvendelsen af zebrafisk som et modelsystem, især som en menneskelig sygdom model, er hastigt voksende. Denne ekspansion er delvist på grund af den fortsatte udvikling og ændring af eksperimentelle teknikker, der forbedrer på de nuværende fordele ved zebrafisk system. Den EBD injektionsteknik giver en ekstra og kraftfuldt værktøj til en forsker arsenal for validering og studiet af zebrafisk muskel sygdomsmodeller. Den igangværende gennemførelse og ændring af denne teknik har potentiale til at bidrage til at belyse nye terapeutiske strategier samt sygdom forårsager mekanismer.
The authors have nothing to disclose.
Vi vil gerne takke Trent Waugh for hans teknisk bistand. Vi anerkender også Department of Pediatrics på Hospital for Sick Children og Cure medfødt muskeldystrofi (CMD) for deres generøse støtte til dette projekt.
Fluorescein isothiocyanate-dextran MW 10,000 | Sigma | FD10S | |
Evan's Blue Dye | Sigma | E2129 | |
Ethyl 3-aminobenzoate methanesulfonate salt | Sigma | A5040 | |
100 mm Petri dish | Fischerbrand | FB0875712 | Injection mold base |
Thin wall glass capillaries | World Precision Instruments | TW100F-4 | For Injection needle |
Agarose | Bioshop | AGA001 | Injection mold |
Microinjection mold | Adaptive Science Tools | TU-1 | Injection mold |
Sodium chloride | Bioshop | SOD001 | Ringer's solution |
Potassium chloride | Bioshop | POC888 | Ringer's solution |
Magnessium chloride hexahydrate | Sigma | M2670 | Ringer's solution |
Sodium phosphate monobasic monohydrate | Sigma | S9638 | Ringer's solution |
HEPES | Sigma | H4034 | Ringer's solution |
Glucose | BioBasic | GB0219 | Ringer's solution |
Calcium chloride | Sigma | C1061 | Ringer's solution |