Questo lavoro è stato generosamente sostenuto dal National Institutes of Health / Istituto Nazionale di Malattie Neurologiche e Stroke (/ NINDS NIH) concessione 1R01NS086981 e l&#39;Hilton Fondazione Conrad N.. Ringraziamo il Dr. Laurent Bentolila e il Dr. Matthew Schibler per la preziosa assistenza con microscopia confocale. Ringraziamo coloro che hanno contribuito al forum chiarezza (http://forum.claritytechniques.org). Ringraziamo in modo particolare il Dr. Karl Deisseroth per aprire il suo laboratorio per insegnare questa affascinante tecnica. Gli autori sono grati per il generoso sostegno da parte della Organizzazione Brain Mapping Medical Research, Cervello Fondazione supporta il mapping, Pierson-Lovelace Foundation, la Fondazione Ahmanson, Capital Group Aziende Charitable Foundation, William M. e Linda R. Dietel Fondo filantropico, e il Fondo Northstar . La ricerca riportato nella presente pubblicazione è anche parzialmente sostenuto dal Centro nazionale per le risorse di ricerca e dall&#39;Ufficio del direttore della NazioneAl Institutes of Health ai numeri premio C06RR012169, C06RR015431, e S10OD011939. Il contenuto è di esclusiva responsabilità degli autori e non rappresentano necessariamente il punto di vista ufficiale del National Institutes of Health.

Tutti gli esperimenti sono stati eseguiti in conformità con Istituzionale cura degli animali e le linee guida Comitato Usa (IACUC). Thy1-YFP, PLP-EGFP e PV-TdTomato topi sono stati utilizzati per questi esperimenti, ma qualsiasi topi che esprimono proteine ​​fluorescenti possono essere cancellati e ripreso con successo. 1. Preparazione del tessuto Attenzione: paraformaldeide (PFA) e acrilammide sono tossici e irritanti. Effettuare esperimenti che utilizzano questi reagenti in una cappa aspirante e con attrezzature adeguate di protezione individuale (camice, guanti e protezioni per gli occhi). <ol><li> Sacrificare l&#39;animale in camera di eutanasia con ~ 1 ml di isoflurano fino respirazione cessa (~ 2 - 3 min). </li><li> Utilizzare una pompa peristaltica impostato ~ 5 ml / min per defluire in intracardiaca il mouse con la soluzione di perfusione (Tabella 1) a 4 ° C fino a quando il sangue viene cancellato dai tessuti (5 - 10 min). </li><li> Modificare il perfusato di soluzione fissativa (Tabella 1)a 4 ° C fino al collo e coda sono notevolmente irrigidito (5 - 10 min). </li><li> Terminare la perfusione e decapitare il animali. Sezionare delicatamente il cervello dal cranio rimuovendo prima il tessuto connettivo circostante cranio e quindi la rimozione di osso dalla superficie ventrale del cranio e sollevando il cervello (figura 1a), come descritto in 20. Nota: Prestare particolare attenzione alla rimozione di osso che circonda i lobi flocculonodular del cervelletto e dei bulbi olfattivi. <ol><li> Sezionare il midollo spinale dalla colonna vertebrale, inserendo delicatamente la punta di una multa, tagliente forbice tra il midollo spinale e la colonna vertebrale e il taglio dei singoli segmenti della colonna vertebrale di distanza, come descritto in 21. </li></ol></li><li> Hemisect cervello ponendolo in una matrice plastica cervello di topo e tagliando lungo la linea mediana con una lama di matrice. </li><li> Aggiungere ogni emisfero e del midollo spinale per separare 50 ml vasca centrifugaes con ~ 40 ml di soluzione di idrogel (Tabella 1). Da questa copertura in avanti punto le provette con un foglio di alluminio per proteggere i fluorofori durante tutte le fasi successive. </li><li> Incubare la provetta contenente il campione in idrogel a 4 ° C con agitando delicatamente (~ 30 rpm) per 7 giorni. </li></ol> 2. polimerizzazione <ol><li> Scartare ~ 25 ml di idrogel, mantenendo il campione e ~ 25 ml di idrogel nella provetta da centrifuga. </li><li> Deoxygenate campione rimuovendo il tappo e posizionare il tubo da centrifuga in barattolo essiccatore e collega il vaso ad un vuoto. Applicare il vuoto per almeno 10 minuti per consentire gas disciolti venire dalla soluzione e formare bolle. Agitare delicatamente per rimuovere le bolle. </li><li> Sostituire il vuoto nel vaso essiccatore 100% azoto oltre 2 - 3 min. Una volta che la pressione equalizza (una volta all&#39;inizio della giara essiccatore può essere aperto), tappare rapidamente il tubo per impedire la reintroduzione di ossigeno. </li><li> Polimeroizzare l&#39;idrogel ponendo la provetta con il campione in un bagno d&#39;acqua a 37 ° C per 3 ore fino polimerizzazione è completa. Idrogel polimerizzato assumerà una consistenza gelatinosa (Figura 1b). Nota: Una piccola quantità di idrogel non polimerizzato in alto è accettabile. </li><li> Utilizzare una spatola per rimuovere il campione polimerizzato dalla provetta, poi tagliare via l&#39;eccesso idrogel dal campione. </li><li> Rimuovere l&#39;idrogel restante ponendo il campione su un panno senza pulire e delicatamente sfregamento e rotolare il tessuto su di esso, lasciando solo un sottile strato di idrogel polimerizzato sul campione. </li></ol> 3. La rimozione dei lipidi Nota: il tessuto lipidico-eliminato è fragile, maneggiare con cura. Utilizzare un filtro cella quando lo svuotamento del tubo per evitare di perdere del campione. Inoltre, il campione si gonfiano in tutto il processo di compensazione, tuttavia, gonfiore può essere invertito durante il processo di indice di rifrazione corrispondente. Attenzione: Sodium solfato dodecil (SDS) e l&#39;acido borico sono irritanti. Effettuare esperimenti li utilizzano in una cappa aspirante e con attrezzature adeguate di protezione individuale (camice, guanti e protezioni per gli occhi). <ol><li> Trasferire campione polimerizzato di clean 50 ml tubo di centrifuga, aggiungere 45 ml di compensazione tampone (Tabella 1). Incubare a 45 ° C con un leggero scuotimento (~ 30 rpm). Modificare il buffer al giorno per un periodo iniziale di 7 giorni versando fuori il buffer di compensazione utilizzato in rifiuti chimici e l&#39;aggiunta di ~ 45 ml di tampone di compensazione fresco. Tenere le provette da centrifuga contenenti i campioni coperti in un foglio di alluminio per proteggere i fluorofori. </li><li> Dopo i primi 7 giorni, incubare il campione a 40 ° C e lo scambio di compensazione tampone ogni 2 - 3 giorni. Continuare compensazione fino a quando tutti i lipidi sono solubilizzati e tessuti raggiunge la trasparenza (Figura 1c). Questo sarà il 4 - 6 settimane per un emisfero del cervello del mouse e 2 - 4 settimane per un midollo spinale. </li><li> Una volta che il tessuto viene cancellato, il trasferimentocampione in un tubo da 50 ml centrifuga e lavare 4 volte in PBST (Tabella 1) a 40 ° C agitando delicatamente (~ 30 rpm) su 24 ore per rimuovere residui di SDS. </li></ol> 4. La colorazione molecolare Attenzione: 4 &#39;, 6-Diamidino-2-phenylindole Dihydrochloride (DAPI) è un irritante e gli esperimenti che utilizzano dovrebbe essere eseguita in una cappa aspirante e con attrezzature adeguate di protezione individuale (camice, guanti e protezioni per gli occhi). <ol><li> Trasferire il campione in una provetta da centrifuga da 15 ml pulito e riempire con 1 mg / ml DAPI in 1x PBST, pH 7.5. Incubare a temperatura ambiente (RT) per 24 ore. Tenere le provette da centrifuga contenenti i campioni coperti in un foglio di alluminio per proteggere i fluorofori. </li><li> Lavare 3 volte in PBST a temperatura ambiente per almeno 6 ore / lavaggio. </li></ol> 5. indice di rifrazione di corrispondenza Attenzione: 2,2&#39;-tiodietanolo (TDE) è un irritante e gli eventuali esperimenti utilizzandolo should essere eseguita in una cappa aspirante e con attrezzature adeguate di protezione individuale (camice, guanti e protezioni per gli occhi). <ol><li> Trasferire il campione in una provetta da centrifuga da 15 ml pulito e riempire con il 30% (v / v) TDE in 1x PBS, pH 7,5. Incubare a 40 ° C agitando delicatamente (~ 30 rpm) per 24 ore. </li><li> Scambio 30% TDE con 63% (v / v) TDE in 1x PBS, pH 7,5. Incubare a 40 ° C con delicata agitazione per 24 ore. Nota: Il campione si restringerà torna a dimensioni approssimative di originale. </li><li> Su una superficie piana e pulita rotolare un pezzo di adesivo riutilizzabile in un cilindro con diametro uniforme solo leggermente maggiore dello spessore del campione. </li><li> Disporre il cilindro adesivo riutilizzabile in un cerchio aperto (~ diametro 25 mm interno con una piccola apertura nella parte superiore) su un piatto fondo di vetro 40mm. Se correzioni devono essere fatte, togliere il cilindro dal vetro e tagliato con una lama di rasoio. </li><li> Utilizzare una punta P1000 pipetta per creare una tenuta tra l&#39;adesivo riutilizzabile e vetro darotolare intorno al bordo esterno del cilindro. </li><li> Luogo ~ 100 ml 63% TDE sul piatto di vetro e diffuso in tutto per coprire la superficie di vetro all&#39;interno del cerchio di adesivo riutilizzabile. </li><li> Utilizzando una spatola, posizionare accuratamente il campione al centro del cerchio, facendo attenzione a non formare bolle. </li><li> Pipetta altri 100 ml di 63% TDE direttamente sul campione, quindi collocare immediatamente a 40 millimetri di vetro di copertura circolare su l&#39;adesivo riutilizzabile. </li><li> Utilizzando l&#39;indice, medio e anulare di entrambe le mani, premere con attenzione intorno al perimetro del cerchio finché il vetro di copertura ha preso contatto con il campione. </li><li> Portare lentamente il piatto fondo di vetro in posizione verticale di riposo contro una superficie, quindi aggiungere 63% TDE con una pipetta finché la soluzione raggiunge la piccola apertura nella parte superiore. Usare un panno senza pulire per asciugare la punta della pipetta in modo che la soluzione non cola sul vetro. Per evitare bolle nella camera, non svuotare la pipetta fino in fondo. </li><li> Ala piccola apertura, aggiungere elastomero silicio per racchiudere il cerchio e creare una camera chiusa. Attendere 5 minuti che si asciughi prima di imaging. </li></ol> 6. Microscopia Attenzione: I laser utilizzati in confocale, illuminazione piano singolo e la microscopia foglio di luce sono molto potente e può causare la cecità. Tutti gli esperimenti che utilizzano il laser deve essere eseguita dopo una formazione completa e con grande cautela e protezione per gli occhi adeguata. <ol><li> Posizionare la camera di imaging con il campione all&#39;interno sul palco di un microscopio confocale a scansione laser. </li><li> Aprire il software di imaging (vedi Tabella dei Materiali). Per accendere il laser ad argon di eccitazione, fare clic sulla scheda di configurazione nella parte superiore del programma quindi l&#39;icona del laser. Seleziona la casella accanto a argon per alimentare il laser e spostare la scala slitta al 30%. Osservare il puntatore lentamente riscaldare nella posizione selezionata. <ol><li> Ritorna alla scheda acquisiscono in alto. Nella grande scatola &quot;Impostazioni percorso del fascio &amp;# 34; andare al carico / salva casella di impostazione e selezionare il menu a tendina per selezionare un canale di lunghezza d&#39;onda appropriata per immagine YFP (527 nm). </li></ol></li><li> Selezionare obiettivi appropriati per l&#39;imaging individuando il collegamento ipertestuale rosso con l&#39;etichetta &quot;Obiettivo: oggetto corrente&quot; sotto la casella impostazioni del canale. Facendo clic sulla scheda si apre tutti gli obiettivi disponibili e una selezione ruoterà automaticamente la torretta. <ol><li> Utilizzare obiettivi (ad es., 10X) con una distanza grande lavoro (maggiore dello spessore del tessuto per creare l&#39;immagine, ad esempio, 11 mm) e una apertura numerica (ad es., 0,3) per massimizzare risoluzione in piano dell&#39;immagine e minimizzare lo spessore della sezione ottica. </li></ol></li><li> Sulla colonna di sinistra del menu a discesa, aprire il &quot;XY: risoluzione&quot; finestra per impostare matrice di acquisizione, chiamato &quot;format&quot;, a 1.024 x 1.024 o un valore appropriato per il limite laterale risoluzione dell&#39;obiettivo. Impostare il fattore di zoom più basso possibile (ad es., 1.7). </li><li> Nella stessa finestra, impostare parametri medi 8 media di linea e 1 fotogramma facendo cadere giù i menu etichettate singolarmente di conseguenza. Utilizzare valori grandi per un alto rapporto segnale-rumore e piccoli valori per l&#39;acquisizione rapida. Nota: 8 medie di linea e 1 media struttura acquisiranno immagini di alta qualità di un emisfero del cervello del mouse in circa 4 ore. </li><li> Individuare il campione utilizzando i controlli di scena. Una volta che un campo rappresentativo è visibile, impostare il guadagno e offset. Nota: Il guadagno e offset varia considerevolmente in base al tipo di tessuto, fluorofori, e / o caratteristica anatomica di essere ripreso. Per YFP, impostare i valori 760-780 per il guadagno e da -1,0 a -1,5 per l&#39;offset. </li><li> Selezionare &quot;scan tile&quot; e selezionare i confini della regione di interesse. Impostare i limiti superiore e inferiore della z-stack da acquisire. Impostare lo spessore della sezione ottica basato su limite di risoluzione ottica sezione del oggettivo. Nota: Un obiettivo dilimite di risoluzione ottica sezione è definita principalmente dalla sua apertura numerica. La maggior parte del software di controllo microscopio calcolerà automaticamente un valore appropriato per l&#39;obiettivo in uso. Per un obiettivo 10X con una apertura numerica di 0,3 sarebbe di circa 11 micron. </li><li> Avviare l&#39;acquisizione. Nota: Questo può richiedere più ore. </li><li> Raccogliere immagini ad alta risoluzione usando obiettivi ingrandimento superiore di specifiche regioni di interesse. </li></ol>

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The authors have nothing to disclose.

compensazione passiva di idrogel incorporato tessuti (chiarezza passivo) è un metodo semplice e poco costoso per la compensazione grandi pezzi di tessuto. Questo approccio non richiede attrezzature dedicate e può essere facilmente eseguita con un agitatore a temperatura controllata. Nell&#39;arco di poche settimane, anche di grandi dimensioni, i tessuti altamente mieliniche, come ad esempio un intero cervello o del midollo spinale, diventeranno trasparenti e adatto per la microscopia. Anche se questo rapporto è conce...

The ability to image complete neuroanatomical structures is immensely valuable for understanding the brain in health and disease. Traditionally, 3D imaging has required tissue sectioning to provide the axial resolution and to visualize deep anatomical structures. This approach can produce high-resolution data sets, but requires sophisticated image reconstruction techniques and is very labor intensive. As a result, it has been limited to the imaging of small volumes of tissue1-3. Optical sectioning, on the other hand, is well suited for the creation of high-resolution 3D images of fluorescently labeled tissues. Since optical sectioning is inherently three dimensional, it does not require extensive computation to produce a 3D image volume. However, light scattering and tissue opacity limit the depth at which tissues can be optically sectioned. The depth of imaging is limited to about 150 &#181;m in laser scanning confocal microscopy and to less than 800 &#181;m using two-photon excitation microscopy4-8.
In order to overcome these limitations, several optical clearing techniques have been recently developed and then further refined to permit the deep microscopic imaging of intact tissues. The use of benzyl alcohol and benzyl benzoate (BABB) to render fixed tissues transparent was among one of the earliest approaches9. However, this approach was limited by the quenching of fluorescence in the samples and incomplete clearing of highly myelinated structures10. Refinements of this technique, such as 3D Imaging of Solvent Cleared Organs (3DISCO), have led to very rapid and complete tissue clearing, but still suffer from rapid loss of fluorescent signals, especially yellow fluorescent protein (YFP)10. Water-based clearing solutions, such as Sca/e11 and SeeDB12, preserve fluorescent signals, but do not completely clear highly myelinated tissues. Clear, Unobstructed Brain Imaging Cocktails and Computational analysis (CUBIC) is a promising new optical clearing technology that appears to overcome the limitations of previously developed water-based clearing solutions13. In contrast with other optical clearing techniques, Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY)14 embeds the brain in a porous matrix that provides structural integrity to proteins, nucleic acids and small molecules, while leaving lipids unbound. The lipids are then removed electrophoretically, culminating in an optically cleared brain that can be easily visualized and equally easily probed using commonly available techniques.
Electrophoretic tissue clearing (ETC) is used to remove lipids from hydrogel embedded tissues in CLARITY, however, ETC can be difficult to implement consistently and tissues subject to electrophoresis can exhibit tissue distortion, browning, loss of fluorescence and antibody reactivity. Passive lipid clearing avoids these limitations, but requires increased clearing times15-17. Passive clearing also permits the clearing of large numbers of samples in parallel, since it is not limited by the number of ETC apparatuses available. Decreasing the concentration of paraformaldehyde and excluding bis-acrylamide from the hydrogel have led to great increases in the speed of clearing at the expense of greater tissue expansion16. Less expensive alternatives to the refractive index matching solution used in the original CLARITY technique have been developed17-19. 2,2'-thiodiethanol (TDE) is an inexpensive and rapid brain clearing agent that reverses some of the tissue expansion that occurs during lipid removal18. This report incorporates passive clearing of hydrogel embedded tissue and the use of TDE as a refractive index matching solution to the original CLARITY technique to produce a highly reproducible and inexpensive protocol for the optical clearing of the mouse central nervous system.

<table border="0" cellpadding="0" cellspacing="0" width="750">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">10X phosphate buffered saline (PBS)</td>
			<td style="width:212px;">Fisher</td>
			<td style="width:119px;">BP399-1</td>
			<td style="width:203px;">buffers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">32% paraformaldehyde (PFA)</td>
			<td style="width:212px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">15714-5</td>
			<td>perfusion and hydrogel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">2,2&#39;-thiodiethanol (TDE)</td>
			<td style="width:212px;">Sigma-Aldrich</td>
			<td style="width:119px;">166782-500G</td>
			<td>refractive index matching solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">40% acrylamide</td>
			<td style="width:212px;">Bio-Rad</td>
			<td style="width:119px;">161-0140</td>
			<td>hydrogel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">2% bis-acrylamide</td>
			<td style="width:212px;">Bio-Rad</td>
			<td style="width:119px;">161-0142</td>
			<td>hydrogel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">VA-044 initiator</td>
			<td>Wako Pure Chemical Industries, Ltd.</td>
			<td>VA044</td>
			<td>hydrogel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">boric acid</td>
			<td style="width:212px;">Sigma-Aldrich</td>
			<td style="width:119px;">B7901</td>
			<td>clearing buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">sodium dodecyl sulfate (SDS)</td>
			<td style="width:212px;">Fisher</td>
			<td style="width:119px;">BP166-5</td>
			<td>clearing buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">sodium hydroxide</td>
			<td style="width:212px;">Fisher</td>
			<td style="width:119px;">55255-1</td>
			<td>buffers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">sodium azide</td>
			<td style="width:212px;">Sigma-Aldrich</td>
			<td style="width:119px;">52002-100G</td>
			<td>preservative</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">triton x-100</td>
			<td style="width:212px;">Sigma-Aldrich</td>
			<td style="width:119px;">X100-500G</td>
			<td>buffers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">heparin</td>
			<td style="width:212px;">Sigma-Aldrich</td>
			<td style="width:119px;">H3393-50KU</td>
			<td>perfusion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">sodium nitrate</td>
			<td style="width:212px;">Fisher</td>
			<td style="width:119px;">BP360-500</td>
			<td>perfusion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DAPI</td>
			<td style="width:212px;">Molecular Probes</td>
			<td style="width:119px;">D1306</td>
			<td>nuclear stain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">99.9% isoflurane</td>
			<td style="width:212px;">Phoenix</td>
			<td style="width:119px;">57319-559-06</td>
			<td>anesthetic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">hydrocholoric acid</td>
			<td style="width:212px;">Fisher</td>
			<td style="width:119px;">A1445-500</td>
			<td>buffers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">glass bottom dish</td>
			<td style="width:212px;">Willco</td>
			<td style="width:119px;">HBSB-5040</td>
			<td>Willco dishes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">reusable adhesive</td>
			<td style="width:212px;">Bostick</td>
			<td style="width:119px;">371351</td>
			<td>Blu-Tack</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">silicon elastomer</td>
			<td style="width:212px;">World Precision Instruments</td>
			<td style="width:119px;">KWIK-CAST</td>
			<td>Kwik-Cast</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">lint-free wipe</td>
			<td style="width:212px;">Kimberly-Clark</td>
			<td style="width:119px;">34120</td>
			<td>KimWipe</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">mouse brain matrix</td>
			<td style="width:212px;">Roboz</td>
			<td style="width:119px;">SA-2175</td>
			<td>sectioning tissue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">matrix blades</td>
			<td style="width:212px;">Roboz</td>
			<td style="width:119px;">RS-9887</td>
			<td>sectioning tissue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">peristaltic pump</td>
			<td style="width:212px;">Cole-Parmer</td>
			<td style="width:119px;">77122-24</td>
			<td>pefusion</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">laser scanning confocal microscope</td>
			<td>Leica</td>
			<td>SP5</td>
			<td>microscopy</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">imaging software</td>
			<td style="width:212px;">Leica</td>
			<td style="width:119px;">LAS AF</td>
			<td>microscopy</td>
		</tr>
	</tbody>
</table>

optical clearing of the mouse central nervous system using passive clarity

Traditionally, tissue visualization has required that the tissue of interest be serially sectioned and imaged, subjecting each tissue section to unique non-linear deformations, dramatically hampering one's ability to evaluate cellular morphology, distribution and connectivity in the central nervous system (CNS). However, optical clearing techniques are changing the way tissues are visualized. These approaches permit one to probe deeply into intact organ preparations, providing tremendous insight into the structural organization of tissues in health and disease. Techniques such as Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY) achieve this goal by providing a matrix that binds important biomolecules while permitting light-scattering lipids to freely diffuse out. Lipid removal, followed by refractive index matching, renders the tissue transparent and readily imaged in 3 dimensions (3D). Nevertheless, the electrophoretic tissue clearing (ETC) used in the original CLARITY protocol can be challenging to implement successfully and the use of a proprietary refraction index matching solution makes it expensive to use the technique routinely. This report demonstrates the implementation of a simple and inexpensive optical clearing protocol that combines passive CLARITY for improved tissue integrity and 2,2&#8242;-thiodiethanol (TDE), a previously described refractive index matching solution.

Visualizzare l&#39;organizzazione strutturale del cervello è fondamentale per capire come la morfologia e la connettività influenzano la funzione del cervello in salute e malattia. tecniche di compensazione ottici permettono di popolazioni di cellule immagine in 3D nei tessuti intatti, che ci permette di studiare la morfologia e la connettività coeso. I topi che esprimono proteine ​​fluorescenti guidata da promotori spe...

Watch this Scientific Journal Video about Optical Clearing of the Mouse Central Nervous System Using Passive CLARITY at JoVE.com

Optical Clearing of the Mouse Central Nervous System Using Passive CLARITY

Optical clearing techniques are revolutionizing the way tissues are visualized. In this report we describe modifications of the original Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY) protocol that yields more consistent and less expensive results.

Clearing ottica del sistema nervoso centrale del mouse Utilizzando CHIAREZZA passivo

Traditionally, tissue visualization has required that the tissue of interest be serially sectioned and imaged, subjecting each tissue section to unique ...

optical-clearing-mouse-central-nervous-system-using-passive

Research

JoVE Journal

Neuroscience

13.4K Views.  University of California, Los Angeles. Optical clearing techniques are revolutionizing the way tissues are visualized. In this report we describe modifications of the original Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY) protocol that yields more consistent and less expensive results.

Video: Optical Clearing of the Mouse Central Nervous System Using Passive CLARITY

Optic Nerve Transection: A Model of Adult Neuron Apoptosis in the Central Nervous System

Retinal ganglion cells (RGCs) are CNS neurons that output visual information from the retina to the brain, via the optic nerve. 
The optic nerve can be accessed within the orbit of the eye and completely transected (axotomized), cutting the axons of the entire RGC population. Optic nerve 
transection is a reproducible model of apoptotic neuronal cell death in the adult CNS 1-4. This model is particularly attractive because the vitreous
 chamber of the eye acts as a capsule for drug delivery to the retina, permitting experimental manipulations via intraocular injections. The diffusion of chemicals 
through the vitreous fluid ensures that they act upon the entire RGC population. Moreover, RGCs can be selectively transfected by applying short interfering RNAs 
(siRNAs), plasmids, or viral vectors to the cut end of the optic nerve 5-7 or injecting vectors into their target, the superior colliculus 8. 
This allows researchers to study apoptotic mechanisms in the desired neuronal population without confounding effects on other bystander neurons or surrounding glia. 
An additional benefit is the ease and accuracy with which cell survival can be quantified after injury. The retina is a flat, layered tissue and RGCs are localized in 
the innermost layer, the ganglion cell layer. The survival of RGCs can be tracked over time by applying a fluorescent tracer (3% Fluorogold) to the cut end of the 
optic nerve at the time of axotomy, or by injecting the tracer into the superior colliculus (RGC target) one week prior to axotomy. The tracer is retrogradely transported, labeling 
the entire RGC population. Because the ganglion cell layer is a monolayer (one cell thick), RGC densities can be quantified in flat-mounted tissue, without the need 
for stereology. Optic nerve transection leads to the apoptotic death of 90% of injured RGCs within 14 days postaxotomy 9-11. RGC apoptosis has a 
characteristic time-course whereby cell death is delayed 3-4 days postaxotomy, after which the cells rapidly degenerate. This provides a time window for 
experimental manipulations directed against pathways involved in apoptosis.

Optic Nerve transection is a widely used model of adult CNS injury. Ninety percent of retinal ganglion cells (RGCs) whose axons are completely transected (axotomy) die within 14 days after axotomy. This model is easily amenable to experimental manipulations and highly reproducible.

Resezione del nervo ottico: un modello di apoptosi Neuron adulti nel Sistema Nervoso Centrale

Retinal ganglion cells (RGCs) are CNS neurons that output visual information from the retina to the brain, via the optic nerve. 
The optic nerve can be ...

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Neuroscienze

Multimodal Imaging of Stem Cell Implantation in the Central Nervous System of Mice

During the past decade, stem cell transplantation has gained increasing interest as primary or secondary therapeutic modality for a variety of diseases, both in preclinical and clinical studies. However, to date results regarding functional outcome and/or tissue regeneration following stem cell transplantation are quite diverse. Generally, a clinical benefit is observed without profound understanding of the underlying mechanism(s)1. Therefore, multiple efforts have led to the development of different molecular imaging modalities to monitor stem cell grafting with the ultimate aim to accurately evaluate survival, fate and physiology of grafted stem cells and/or their micro-environment. Changes observed in one or more parameters determined by molecular imaging might be related to the observed clinical effect. In this context, our studies focus on the combined use of bioluminescence imaging (BLI), magnetic resonance imaging (MRI) and histological analysis to evaluate stem cell grafting.
BLI is commonly used to non-invasively perform cell tracking and monitor cell survival in time following transplantation2-7, based on a biochemical reaction where cells expressing the Luciferase-reporter gene are able to emit light following interaction with its substrate (e.g. D-luciferin)8, 9. MRI on the other hand is a non-invasive technique which is clinically applicable10 and can be used to precisely locate cellular grafts with very high resolution11-15, although its sensitivity highly depends on the contrast generated after cell labeling with an MRI contrast agent. Finally, post-mortem histological analysis is the method of choice to validate research results obtained with non-invasive techniques with highest resolution and sensitivity. Moreover end-point histological analysis allows us to perform detailed phenotypic analysis of grafted cells and/or the surrounding tissue, based on the use of fluorescent reporter proteins and/or direct cell labeling with specific antibodies.
In summary, we here visually demonstrate the complementarities of BLI, MRI and histology to unravel different stem cell- and/or environment-associated characteristics following stem cell grafting in the CNS of mice. As an example, bone marrow-derived stromal cells, genetically engineered to express the enhanced Green Fluorescent Protein (eGFP) and firefly Luciferase (fLuc), and labeled with blue fluorescent micron-sized iron oxide particles (MPIOs), will be grafted in the CNS of immune-competent mice and outcome will be monitored by BLI, MRI and histology (Figure 1).

This article describes an optimized sequence of events for multimodal imaging of cellular grafts in rodent brain using: (i) in vivo bioluminescence and magnetic resonance imaging, and (ii) post mortem histological analysis. Combining these imaging modalities on a single animal allows cellular graft evaluation with high resolution, sensitivity and specificity.

Imaging multimodale impianto di cellule staminali nel sistema nervoso centrale di topi

During the past decade, stem cell transplantation has gained increasing interest as primary or secondary therapeutic modality for a variety of diseases, ...

Production of Lentiviral Vectors for Transducing Cells from the Central Nervous System

Efficient gene delivery in the central nervous system (CNS) is important in studying gene functions, modeling neurological diseases and developing therapeutic approaches. Lentiviral vectors are attractive tools in transduction of neurons and other cell types in CNS as they transduce both dividing and non-dividing cells, support sustained expression of transgenes, and have relatively large packaging capacity and low toxicity 1-3. Lentiviral vectors have been successfully used in transducing many neural cell types in vitro 4-6 and in animals 7-10.
Great efforts have been made to develop lentiviral vectors with improved biosafety and efficiency for gene delivery. The current third generation replication-defective and self-inactivating (SIN) lentiviral vectors are depicted in Figure 1. The required elements for vector packaging are split into four plasmids. In the lentiviral transfer plasmid, the U3 region in the 5' long terminal repeat (LTR) is replaced with a strong promoter from another virus. This modification allows the transcription of the vector sequence independent of HIV-1 Tat protein that is normally required for HIV gene expression 11. The packaging signal (&Psi;) is essential for encapsidation and the Rev-responsive element (RRE) is required for producing high titer vectors. The central polypurine tract (cPPT) is important for nuclear import of the vector DNA, a feature required for transducing non-dividing cells 12. In the 3' LTR, the cis-regulatory sequences are completely removed from the U3 region. This deletion is copied to 5' LTR after reverse transcription, resulting in transcriptional inactivation of both LTRs. Plasmid pMDLg/pRRE contains HIV-1 gag/pol genes, which provide structural proteins and reverse transcriptase. pRSV-Rev encodes Rev which binds to the RRE for efficient RNA export from the nucleus. pCMV-G encodes the vesicular stomatitis virus glycoprotein (VSV-G) that replaces HIV-1 Env. VSV-G expands the tropism of the vectors and allows concentration via ultracentrifugation 13. All the genes encoding the accessory proteins, including Vif, Vpr, Vpu, and Nef are excluded in the packaging system. The production and manipulation of lentiviral vectors should be carried out according to NIH guidelines for research involving recombinant DNA (<a href="http://oba.od.nih.gov/oba/rac/Guidelines/NIH_Guidelines.pdf" target="_blank">http://oba.od.nih.gov/oba/rac/Guidelines/NIH_Guidelines.pdf</a>). An approval from individual Institutional Biological and Chemical Safety Committee may be required before using lentiviral vectors. Lentiviral vectors are commonly produced by cotransfection of 293T cells with lentiviral transfer plasmid and the helper plasmids encoding the proteins required for vector packaging. Many lentiviral transfer plasmids and helper plasmids can be obtained from Addgene, a non-profit plasmid repository (<a href="http://www.addgene.org/" target="_blank">http://www.addgene.org/</a>). Some stable packaging cell lines have been developed, but these systems provide less flexibility and their packaging efficiency generally declines over time 14, 15. Commercially available transfection kits may support high efficiency of transfection 16, but they can be very expensive for large scale vector preparations. Calcium phosphate precipitation methods provide highly efficient transfection of 293T cells and thus provide a reliable and cost effective approach for lentiviral vector production.
In this protocol, we produce lentiviral vectors by cotransfection of 293T cells with four plasmids based on the calcium phosphate precipitation principle, followed by purification and concentration with ultracentrifugation through a 20% sucrose cushion. The vector titers are determined by fluorescence- activated cell sorting (FACS) analysis or by real time qPCR. The production and titration of lentiviral vectors in this protocol can be finished with 9 days. We provide an example of transducing these vectors into murine neocortical cultures containing both neurons and astrocytes. We demonstrate that lentiviral vectors support high efficiency of transduction and cell type-specific gene expression in primary cultured cells from CNS.

In this protocol we describe production, purification and titration of lentiviral vectors. We provide an example of lentiviral vector-mediated gene delivery in primary cultured neurons and astrocytes. Our methods may also apply to other cell types in vitro and in vivo.

Produzione di vettori lentivirali per Celle di trasduzione del Sistema Nervoso Centrale

Efficient gene delivery in the central nervous system (CNS) is important in studying gene functions, modeling neurological diseases and developing ...

Labeling of Single Cells in the Central Nervous System of Drosophila melanogaster

In this article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the lipophilic fluorescent membrane marker DiI. This method allows the visualization of neuronal cell morphology in great detail. It is possible to label any cell in the CNS: cell bodies of target neurons are visualized under DIC optics or by expression of a fluorescent genetic marker such as GFP. After labeling, the DiI can be transformed into a permanent brown stain by photoconversion to allow visualization of cell morphology with transmitted light and DIC optics. Alternatively, the DiI-labeled cells can be observed directly with confocal microscopy, enabling genetically introduced fluorescent reporter proteins to be colocalised. The technique can be used in any animal, irrespective of genotype, making it possible to analyze mutant phenotypes at single cell resolution.

Labeling of Single Cells in the Central Nervous System of Drosophila melanogaster

We present a technique for labeling single neurons in the central nervous system (CNS) of Drosophila embryos, which allows the analysis of neuronal morphology by either transmitted light or confocal microscopy.

Etichettatura di singole cellule nel sistema nervoso centrale di<em&gt; Drosophila melanogaster</em

In this  article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the ...

Direct Intraventricular Delivery of Drugs to the Rodent Central Nervous System

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses specifically on antisense oligonucleotides (ASOs), though the techniques shown in the video here can also be used to deliver a plethora of other drugs to the CNS. Antisense oligonucleotides (ASOs) have the capability to knockdown sequence-specific targets 1 as well as shift isoform ratios of specific genes 2. To achieve widespread gene knockdown or splicing in the CNS of mice, the ASOs can be delivered into the brain using two separate routes of administration, both of which we demonstrate in the video.
The first uses Alzet osmotic pumps, connected to a catheter that is surgically implanted into the lateral ventricle. This allows the ASOs to be continuously infused into the CNS for a designated period of time. The second involves a single bolus injection of a high concentration of ASO into the right lateral ventricle. Both methods use the mouse cerebral ventricular system to deliver the ASO to the entire brain and spinal cord, though depending on the needs of the study, one method may be preferred over the other.

We describe a method to target drugs to the central nervous system by either implanting a catheter or performing a bolus injection into the right lateral ventricle in mice. We focus specifically on the delivery of antisense oligonucleotides. This technique is readily adaptable to other drugs and to rats.

Consegna diretta intraventricolare di farmaci per il sistema nervoso centrale, Roditore

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses ...

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution has been a long sought tool for neuroscientists in the systems-level search for the neural circuitry governing complex behavioral states. Optogenetics is a cutting-edge tool that is revolutionizing the field of neuroscience and represents one of the first systematic approaches to enable causal testing regarding the relation between neural signaling events and behavior. By combining optical and genetic approaches, neural signaling can be bi-directionally controlled through expression of light-sensitive ion channels (opsins) in mammalian cells. The current protocol describes delivery of specific wavelengths of light to opsin-expressing cells in deep brain structures of awake, freely-moving rodents for neural circuit modulation. Theoretical principles of light transmission as an experimental consideration are discussed in the context of performing in vivo optogenetic stimulation. The protocol details the design and construction of both simple and complex laser configurations and describes tethering strategies to permit simultaneous stimulation of multiple animals for high-throughput behavioral testing.

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

Optogenetics has become a powerful tool for use in behavioral neuroscience experiments. This protocol offers a step-by-step guide to the design and set-up of laser systems, and provides a full protocol for carrying out multiple and simultaneous in vivo optogenetic stimulations compatible with most rodent behavioral testing paradigms.

In vivo optogenetic stimolazione del sistema nervoso centrale Roditore

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution ...

Novel Passive Clearing Methods for the Rapid Production of Optical Transparency in Whole CNS Tissue

Since the development of CLARITY, a bioelectrochemical clearing technique that allows for three-dimensional phenotype mapping within transparent tissues, a multitude of novel clearing methodologies including CUBIC (clear, unobstructed brain imaging cocktails and computational analysis), SWITCH (system-wide control of interaction time and kinetics of chemicals), MAP (magnified analysis of the proteome), and PACT (passive clarity technique), have been established to further expand the existing toolkit for the microscopic analysis of biological tissues. The present study aims to improve upon and optimize the original PACT procedure for an array of intact rodent tissues, including the whole central nervous system (CNS), kidneys, spleen, and whole mouse embryos. Termed psPACT (process-separate PACT) and mPACT (modified PACT), these novel techniques provide highly efficacious means of mapping cell circuitry and visualizing subcellular structures in intact normal and pathological tissues. In the following protocol, we provide a detailed, step-by-step outline on how to achieve maximal tissue clearance with minimal invasion of their structural integrity via psPACT and mPACT.

Here, we present two novel methodologies, psPACT and mPACT, for achieving maximal optical transparency and subsequent microscopic analysis of tissue vasculature in the intact rodent whole CNS.

Romanzo passivo metodi di compensazione per la produzione rapida di trasparenza ottica nell'intero tessuto dello SNC

Since the development of CLARITY, a bioelectrochemical clearing technique that allows for three-dimensional phenotype mapping within transparent tissues, ...

Electrophysiological Recording of The Central Nervous System Activity of Third-Instar Drosophila Melanogaster

The majority of the currently available insecticides target the nervous system and genetic mutations of invertebrate neural proteins oftentimes yield deleterious consequences, yet the current methods for recording nervous system activity of an individual animal is costly and laborious. This suction electrode preparation of the third-instar larval central nervous system of Drosophila melanogaster, is a tractable system for testing the physiological effects of neuroactive agents, determining the physiological role of various neural pathways to CNS activity, as well as the influence of genetic mutations to neural function. This ex vivo preparation requires only moderate dissecting skill and electrophysiological expertise to generate reproducible recordings of insect neuronal activity. A wide variety of chemical modulators, including peptides, can then be applied directly to the nervous system in solution with the physiological saline to measure the influence on the CNS activity. Further, genetic technologies, such as the GAL4/UAS system, can be applied independently or in tandem with pharmacological agents to determine the role of specific ion channels, transporters, or receptors to arthropod CNS function. In this context, the assays described herein are of significant interest to insecticide toxicologists, insect physiologists, and developmental biologists for which D. melanogaster is an established model organism. The goal of this protocol is to describe an electrophysiological method to enable the measurement of electrogenesis of the central nervous system in the model insect, Drosophila melanogaster, which is useful for testing a diversity of scientific hypotheses.

Electrophysiological Recording of The Central Nervous System Activity of Third-Instar  Drosophila Melanogaster

This protocol describes a method to record the descending electrical activity of the Drosophila melanogaster central nervous system to enable the cost-efficient and convenient testing of pharmacological agents, genetic mutations of neural proteins, and/or the role of unexplored physiological pathways.

Registrazione elettrofisiologica dell'attività del sistema nervoso centrale di terza-Instar Drosophila Melanogaster

The majority of the currently available insecticides target the nervous system and genetic mutations of invertebrate neural proteins oftentimes yield ...

Transplantation of Chemogenetically Engineered Cortical Interneuron Progenitors into Early Postnatal Mouse Brains

Neuronal development is regulated by a complex combination of environmental and genetic factors. Assessing the relative contribution of each component is a complicated task, which is particularly difficult in regards to the development of &#947;-aminobutyric acid (GABA)ergic cortical interneurons (CIs). CIs are the main inhibitory neurons in the cerebral cortex, and they play key roles in neuronal networks, by regulating both the activity of individual pyramidal neurons, as well as the oscillatory behavior of neuronal ensembles. They are generated in transient embryonic structures (medial and caudal ganglionic eminences -&#160;MGE and CGE) that are very difficult to efficiently target using in utero electroporation approaches. Interneuron progenitors migrate long distances during normal embryonic development, before they integrate in the cortical circuit. This remarkable ability to disperse and integrate into a developing network can be hijacked by transplanting embryonic interneuron precursors into early post-natal host cortices. Here, we present a protocol that allows genetic modification of embryonic interneuron progenitors using focal ex vivo electroporation. These engineered interneuron precursors are then transplanted into early post-natal host cortices, where they will mature into easily identifiable CIs. This protocol allows the use of multiple genetically encoded tools, or the ability to regulate the expression of specific genes in interneuron progenitors, in order to investigate the impact of either genetic or environmental variables on the maturation and integration of CIs.

Here we present a protocol, designed to use chemogenetic tools to manipulate the activity of cortical interneuron progenitors transplanted into the cortex of early postnatal mice.

Trapianto di progenitori interneuroni corticali chemiogeneticamente ingegnerizzati nei primi cervelli dei topi postnatali

Neuronal development is regulated by a complex combination of environmental and genetic factors. Assessing the relative contribution of each component is ...

Intrathecal Delivery of Antisense Oligonucleotides in the Rat Central Nervous System

The blood brain barrier (BBB) is an important defense against the entrance of potentially toxic or pathogenic agents from the blood into the central nervous system (CNS). However, its existence also dramatically lowers the accessibility of systemically administered therapeutic agents to the CNS. One method to overcome this, is to inject those agents directly into the cerebrospinal fluid (CSF), thus bypassing the BBB. This can be done via implantation of a catheter for either continuous infusion using an osmotic pump, or for single bolus delivery. In this article, we describe a surgical protocol for delivery of CNS-targeting antisense oligonucleotides (ASOs) via a catheter implanted directly into the cauda equina space of the adult rat spine. As representative results, we show the efficacy of a single bolus ASO intrathecal (IT) injection via this catheterization system in knocking down the target RNA in different regions of the rat CNS. The procedure is safe, effective and does not require expensive equipment or surgical tools. The technique described here can be adapted to deliver drugs in other modalities as well.

Here, we describe a method for delivering drugs to the rat central nervous system by implanting a catheter into the lumbar intrathecal space of the spine. We focus on the delivery of antisense oligonucleotides, though this method is suitable for delivery of other therapeutic modalities as well.

Consegna intratecala di Oligonucleotidi Antisense nel Rat Central Nervous System

The blood brain barrier (BBB) is an important defense against the entrance of potentially toxic or pathogenic agents from the blood into the central ...