Name: nanoscopic imaging of human tissue sections via physical and isotropic expansion
Uploaded: 2019-09-25T14:45:00
Description: Watch this Scientific Journal Video about Nanoscopic Imaging of Human Tissue Sections via Physical and Isotropic Expansion at JoVE.com

This work was supported by the Faculty Start-up fund from the Carnegie Mellon University (YZ) and NIH Director&#8217;s New Innovator Award (DP2 OD025926-01 to YZ).

1. Preparation of Stock Reagents and Solutions
<ol>
	<li>Prepare gelling solution components. 
	NOTE: Solution concentrations are given in g/mL (w/v percent).
	<ol>
		<li>Make the following stock solutions: 38% (w/v) sodium acrylate (SA), 50% (w/v) acrylamide (AA), 2% (w/v) N,N&#8242;-methylenebisacrylamide (Bis), and 29.2% (w/v) sodium chloride (NaCl). Dissolve the compounds in doubly deionized water (ddH2O). Use the amounts in Table 1 as a reference; prepared solution...

<ol>
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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion+microscopy.">Expansion microscopy.</a> Science. 347 (6221), 543-548 (2015).</li><li>Tillberg, P. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein-retention+expansion+microscopy+of+cells+and+tissues+labeled+using+standard+fluorescent+proteins+and+antibodies.">Protein-retention expansion microscopy of cells and tissues labeled using standard fluorescent proteins and antibodies.</a> Nature Biotechnology. 34, 987-992 (2016).</li><li>Chozinski, T. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion+microscopy+with+conventional+antibodies+and+fluorescent+proteins.">Expansion microscopy with conventional antibodies and fluorescent proteins.</a> Nature Methods. 13 (6), 485-488 (2016).</li><li>Ku, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiplexed+and+scalable+super-resolution+imaging+of+three-dimensional+protein+localization+in+size-adjustable+tissues.">Multiplexed and scalable super-resolution imaging of three-dimensional protein localization in size-adjustable tissues.</a> Nature Biotechnology. 34 (9), 973-981 (2016).</li><li>Truckenbrodt, S., Maidorn, M., Crzan, D., Wildhagen, H., Kabatas, S., Rizzoli, S. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=X10+expansion+microscopy+enables+25-nm+resolution+on+conventional+microscopes.">X10 expansion microscopy enables 25-nm resolution on conventional microscopes.</a> EMBO Reports. 19 (9), e45836 (2018).</li><li>Asano, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expansion+Microscopy:+Protocols+for+Imaging+Proteins+and+RNA+in+Cells+and+Tissues.">Expansion Microscopy: Protocols for Imaging Proteins and RNA in Cells and Tissues.</a> Current Protocols in Cell Biology. 80 (1), 1-41 (2018).</li><li>Chen, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+imaging+of+RNA+with+expansion+microscopy.">Nanoscale imaging of RNA with expansion microscopy.</a> Nature Methods. 13 (8), 679-684 (2016).</li><li>Tsanov, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SmiFISH+and+FISH-quant+-+A+flexible+single+RNA+detection+approach+with+super-resolution+capability.">SmiFISH and FISH-quant - A flexible single RNA detection approach with super-resolution capability.</a> Nucleic Acids Research. 44 (22), e165 (2016).</li><li>Wang, G., Moffitt, J. R., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiplexed+imaging+of+high-density+libraries+of+RNAs+with+MERFISH+and+expansion+microscopy.">Multiplexed imaging of high-density libraries of RNAs with MERFISH and expansion microscopy.</a> Scientific Reports. 8 (1), 1-13 (2018).</li><li>Chang, J. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Iterative+expansion+microscopy.">Iterative expansion microscopy.</a> Nature Methods. 14 (6), 593-599 (2017).</li><li>Cipriano, B. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superabsorbent+hydrogels+that+are+robust+and+highly+stretchable.">Superabsorbent hydrogels that are robust and highly stretchable.</a> Macromolecules. 47 (13), 4445-4452 (2014).</li><li>Truckenbrodt, S., Sommer, C., Rizzoli, S. O., Danzl, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+optimization+in+X10+expansion+microscopy.">A practical guide to optimization in X10 expansion microscopy.</a> Nature Protocols. 14 (3), 832-863 (2019).</li><li>Zhao, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+imaging+of+clinical+specimens+using+pathology-optimized+expansion+microscopy.">Nanoscale imaging of clinical specimens using pathology-optimized expansion microscopy.</a> Nature Biotechnology. 35 (8), 757-764 (2017).</li></ol>

Here, we present the ExPath protocol16, a variant of proExM5 that can be applied to the most common types of clinical biopsy samples used in pathology, including FFPE, H&#38;E stained, and fresh-frozen specimens on glass slides. Format conversion, antigen retrieval, and immunostaining of the specimens follow commonly used protocols that are not specific to ExPath. Unlike the original proExM protocol9, ExPath relies on a higher concentration of EDTA i...

Investigating the molecular organization of tissues in a three-dimensional (3D) context can provide new understanding of biological functions and disease development. However, these nanoscale environments are beyond the resolution capabilities of conventional diffraction limited microscopes (200&#8722;300 nm), where the minimal resolvable distance, d is defined by d &#945; &#955;/NA. Here &#955; is the wavelength of light and NA is the numerical aperture (NA) of the imaging system. Recently, direct visualization of fluorescently labeled molecules has been made possible by newly developed super-resolution imaging techniques1,2,3, including stimulated emission depletion (STED), photo-activated localization microscopy (PALM), stochastic optical reconstruction microscopy (STORM), and structured illumination microscopy (SIM). Although these imaging techniques have revolutionized understanding of biological function at the nanoscale, in practice, they often rely on expensive and/or specialized equipment and image processing steps, can have slower acquisition time comparing to conventional optical imaging, require fluorophores with specific characteristics (such as photo-switching capability and/or high photostability). In addition, it remains a challenge to perform 3D super-resolution imaging on tissue specimens.
Expansion microscopy (ExM), first introduced in 20154, provides an alternative means of imaging nanoscale features (&#60;70 nm) by physically expanding preserved samples embedded in a swellable polyelectrolyte hydrogel. Here, key biomolecules and/or labels are anchored in situ to a polymer network that can be isotopically expanded after chemical processing. Because the physical expansion increases the total effective resolution, molecules of interest can then be resolved using conventional diffraction-limited imaging systems. Since the publication of the original protocol, where custom synthesized fluorescent labels were anchored to the polymer network4, new strategies have been used to directly anchor proteins (protein retention ExM, or proExM)5,6,7,8,9 and RNA9,10,11,12 to the hydrogel, and increase physical magnification through iterative expansion13 or adapting gel chemistry8,14,15.
Here we present an adapted version of proExM, called expansion pathology (ExPath)16, which has been optimized for clinical pathology formats. The protocol converts clinical samples, including formalin-fixed paraffin-embedded (FFPE), hematoxylin and eosin (H&#38;E) stained, and fresh-frozen human tissue specimens mounted on glass slides, into a state compatible with ExM. Proteins are then anchored to the hydrogel and mechanical homogenization is performed (Figure 1)16. With a 4-fold linear expansion of the samples, multicolor super-resolution (~70 nm) images can be obtained using a conventional confocal microscope having only a ~300 nm resolution and can also be combined with other super-resolution imaging techniques.

<table>
	<tbody>
		<tr>
			<td>4-hydroxy-TEMPO (4HT)</td>
			<td>Sigma Aldrich</td>
			<td>176141</td>
			<td>Inhibitor</td>
		</tr>
		<tr>
			<td>6-well glass-bottom plate (#1.5 coverglass)</td>
			<td>Cellvis</td>
			<td>P06-1.5H-N</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Fischer Scientifc</td>
			<td>A18-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Acrylamide</td>
			<td>Sigma Aldrich</td>
			<td>A8887</td>
			<td></td>
		</tr>
		<tr>
			<td>Acryloyl-X, SE (AcX)</td>
			<td>Invitrogen</td>
			<td>A20770</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Fischer Scientifc</td>
			<td>BP160-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulfate (APS)</td>
			<td>Sigma Aldrich</td>
			<td>A3678</td>
			<td>Initiatior</td>
		</tr>
		<tr>
			<td>Anti-ACTN4 antibody produced in rabbit</td>
			<td>Sigma Aldrich</td>
			<td>HPA001873</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Collagen IV antibody produced in mouse</td>
			<td>Santa Cruz Biotech</td>
			<td>sc-59814</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Vimentin antibody produced in chicken</td>
			<td>Abcam</td>
			<td>ab24525</td>
			<td></td>
		</tr>
		<tr>
			<td>Aqua Hold II hydrophobic pen</td>
			<td>Scientific Device</td>
			<td>980402</td>
			<td></td>
		</tr>
		<tr>
			<td>Breast Common Disease Tissue Array</td>
			<td>Abcam</td>
			<td>ab178113</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI (1 mg/mL)</td>
			<td>Thermo Scientific</td>
			<td>62248</td>
			<td>Nuclear stain</td>
		</tr>
		<tr>
			<td>Diamond knife No. 88 CM</td>
			<td>General Tools</td>
			<td>31116</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Pharmco</td>
			<td>111000200</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic 
			acid (EDTA) 0.5 M</td>
			<td>VWR</td>
			<td>BDH7830-1</td>
			<td></td>
		</tr>
		<tr>
			<td>FFPE Kidney Sample</td>
			<td>USBiomax</td>
			<td>HuFPT072</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Goat Anti-Chicken IgY (H+L), Highly Cross-Adsorbed CF488A</td>
			<td>Biotium</td>
			<td>20020</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat Anti-Chicken IgY (H+L), Highly Cross-Adsorbed CF633</td>
			<td>Biotium</td>
			<td>20121</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG (H+L) Highly Cross-Adsorbed Alexa Fluor 546</td>
			<td>Invitrogen</td>
			<td>A11010</td>
			<td></td>
		</tr>
		<tr>
			<td>MAXbind Staining Medium</td>
			<td>Active Motif</td>
			<td>15253</td>
			<td>Can be substituted with non-commercial staning buffer of choice.</td>
		</tr>
		<tr>
			<td>MAXblock Blocking Medium</td>
			<td>Active Motif</td>
			<td>15252</td>
			<td>Can be substituted with non-commercial blocking buffer of choice.</td>
		</tr>
		<tr>
			<td>MAXwash Washing Medium</td>
			<td>Active Motif</td>
			<td>15254</td>
			<td>Can be substituted with non-commercial washing buffer of choice.</td>
		</tr>
		<tr>
			<td>Micro cover Glass #1 (24x60mm)</td>
			<td>VWR</td>
			<td>48393 106</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro cover Glass #1.5 (24x60mm)</td>
			<td>VWR</td>
			<td>48393 251</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N,N&#8242;,N&#8242;- 
			Tetramethylethylenediamine (TEMED)</td>
			<td>Sigma Aldrich</td>
			<td>T9281</td>
			<td>Accelerator</td>
		</tr>
		<tr>
			<td>N,N&#8242;-Methylenebisacrylamide</td>
			<td>Sigma Aldrich</td>
			<td>M7279</td>
			<td></td>
		</tr>
		<tr>
			<td>Normal goat serum</td>
			<td>Jackson Immunoresearch</td>
			<td>005-000-121</td>
			<td>For preparing blocking buffer. Dependent on animal host of secondary antibodies.</td>
		</tr>
		<tr>
			<td>Nunclon 4-Well x 5 mL MultiDish Cell Culture Dish</td>
			<td>Thermo Fisher</td>
			<td>167063</td>
			<td>Multi-well plastic culture dish</td>
		</tr>
		<tr>
			<td>Nunclon 6-Well Cell Culture Dish</td>
			<td>Thermo Fisher</td>
			<td>140675</td>
			<td></td>
		</tr>
		<tr>
			<td>Nunc 15mL&#160;Conical</td>
			<td>Thermo Fisher</td>
			<td>339651</td>
			<td></td>
		</tr>
		<tr>
			<td>Nunc 50mL&#160;Conical</td>
			<td>Thermo Fisher</td>
			<td>339653</td>
			<td></td>
		</tr>
		<tr>
			<td>Orbital Shaker</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Paint brush</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pH Meter</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS), 10x Solution</td>
			<td>Fischer Scientifc</td>
			<td>BP399-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic Petri Dish (100 mm)</td>
			<td>Fischer Scientifc</td>
			<td>FB0875713</td>
			<td></td>
		</tr>
		<tr>
			<td>Proteinase K (Molecular Biology Grade)</td>
			<td>Thermo Scientific</td>
			<td>EO0491</td>
			<td></td>
		</tr>
		<tr>
			<td>Razor blade</td>
			<td>Fischer Scientifc</td>
			<td>12640</td>
			<td></td>
		</tr>
		<tr>
			<td>Safelock Microcentrifuge Tubes 1.5 mL</td>
			<td>Thermo Fisher</td>
			<td>3457</td>
			<td></td>
		</tr>
		<tr>
			<td>Safelock Microcentrifuge Tubes 2.0 mL</td>
			<td>Thermo Fisher</td>
			<td>3459</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium acrylate</td>
			<td>Sigma Aldrich</td>
			<td>408220</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma Aldrich</td>
			<td>S6191</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium citrate tribasic dihydrate</td>
			<td>Sigma Aldrich</td>
			<td>C8532-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris Base</td>
			<td>Fischer Scientifc</td>
			<td>BP152-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr>
			<td>Wheat germ agglutinin labeled with CF640R</td>
			<td>Biotium</td>
			<td>29026</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylenes</td>
			<td>Sigma Aldrich</td>
			<td>214736</td>
			<td></td>
		</tr>
	</tbody>
</table>

nanoscopic imaging of human tissue sections via physical and isotropic expansion

In modern pathology, optical microscopy plays an important role in disease diagnosis by revealing microscopic structures of clinical specimens. However, the fundamental physical diffraction limit prevents interrogation of nanoscale anatomy and subtle pathological changes when using conventional optical imaging approaches. Here, we describe a simple and inexpensive protocol, called expansion pathology (ExPath), for nanoscale optical imaging of common types of clinical primary tissue specimens, including both fixed-frozen or formalin-fixed paraffin embedded (FFPE) tissue sections. This method circumvents the optical diffraction limit by chemically transforming the tissue samples into tissue-hydrogel hybrid and physically expanding them isotropically across multiple scales in pure water. Due to expansion, previously unresolvable molecules are separated and thus can be observed using a conventional optical microscope.

If the protocol has been successfully carried out (Figure 1), samples will appear as a flat and transparent gel after mechanical homogenization (Figure 3A) and can expand by a factor of 3&#8722;4.5x in water (Figure 3B), providing an effective resolution of ~70 nm depending on the final expansion factor and imaging system used5,16. <strong c...

Watch this Scientific Journal Video about Nanoscopic Imaging of Human Tissue Sections via Physical and Isotropic Expansion at JoVE.com

Nanoscopic Imaging of Human Tissue Sections via Physical and Isotropic Expansion

Nanoscale imaging of clinical tissue samples can improve understanding of disease pathogenesis. Expansion pathology (ExPath) is a version of expansion microscopy (ExM), modified for compatibility with standard clinical tissue samples, to explore the nanoscale configuration of biomolecules using conventional diffraction limited microscopes.

In modern pathology, optical microscopy plays an important role in disease diagnosis by revealing microscopic structures of clinical specimens. However, ...

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