We thank Mohamed Lehar for his assistance with this project. This work was partially supported by the National Institutes of Health (T32DC000027, NSA).

This protocol was developed with IRB (IRB00250002) approval and in accordance with institutional policies for the use of human tissue and infectious material. Each temporal bone donor provided written consent before death, or consent was obtained posthumously from the donor&#39;s family. See the Table of Materials for details about all materials, equipment, and software used in this protocol.
1. Temporal bone harvest
<ol>
	<li>Obtain local institutional review board (IRB) board approval, review institutional policies for the use of human and infectious material, and obtain consent for tissue donation before utilizing this protocol.</li>
	<li>Put on proper personal protective equipment (PPE) before working with tissue from COVID-19-positive temporal bone donors. Ensure that the PPE consists of an N-95 respirator and face shield (or alternatively a positive pressure air purification system), gown, and two pairs of gloves. Review techniques for properly donning and doffing PPE before beginning this protocol10.</li>
	<li>Harvest temporal bone tissue within 12-24 h of donor death. If the body is not refrigerated, ensure that the harvest occurs within 8 h of death.
	<ol>
		<li>Harvest temporal bones during autopsy using the four-incision, block method by osteotome7.
		<ol>
			<li>Following craniotomy, remove the brain and divide the cranial nerves to the internal auditory canal sharply.</li>
			<li>Make the first bony incision with the osteotome parallel to and just medial to the squamous portion of the temporal bone.</li>
			<li>Perform the second bony incision parallel to the first at the medial border of the temporal bone.</li>
			<li>Then, make the third incision 3-4 cm anterior and parallel to the petrous ridge.</li>
			<li>Make the fourth incision roughly parallel to the third, 2 cm posterior to the petrous ridge. 
			NOTE: Ensure that all incisions extend through the skull base.</li>
			<li>Then, remove the temporal bone using sharp dissection to free the soft tissue attachment along the inferior edge of the specimen. If embalming is to be performed following temporal bone harvest, tie off the stump of the carotid artery.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
2. Tissue fixation, decalcification, and sectioning
<ol>
	<li>Immediately place the tissue in 200-300 mL of 10% buffered formalin (formaldehyde) so that the tissue is fully submerged. Leave the tissue in formaldehyde for a minimum of 72 h at room temperature, changing the solutions daily. Store the tissue in an air-tight container and perform solution changes under a fume hood while wearing appropriate PPE to prevent virus spread. 
	NOTE: Following the 72 h fixation period, the specimens no longer need to be considered infectious.</li>
	<li>Use a precision microsaw with twin diamond blades to cut each specimen into three &#34;thick&#34; sections to allow for more rapid tissue decalcification. Set the twin diamond blades to a distance of 5 mm, so that the central section of temporal bone is 5 mm thick. Ensure that the sections of tissue on either end are 3-5 mm thick.</li>
	<li>Place the thick sections in 200-300 mL of 23% w/w formic acid decalcifying solution for 7-10 days at room temperature, until the tissue is soft enough for paraffin embedding. Change the solutions daily. Check for adequate tissue decalcification by palpating the specimen, which should feel soft. 
	NOTE: Decalcification may also be verified by x-ray.</li>
	<li>Rinse the specimens in running tap water for 24 h by placing them in a large beaker underneath a running faucet.</li>
	<li>Dehydrate the tissue in a series of alcohols of increasing concentration7. Submerge the tissue in 100-200 mL of 70% ethanol for 1.5 h, followed by three washes in 95% and 100% ethanol for 1.5 h each, respectively. Next, wash the tissue 3 x 1.5 h in Xylene.</li>
	<li>Embed the thick sections in paraffin, with four treatments of 45 min each.</li>
	<li>Use a cryotome to cut thin (10 &#181;m) sections. Position the tissue so that the tissue is cut in the axial plane. Cut thicker (20 &#181;m) sections if desired.</li>
</ol>
3. Immunohistochemistry and imaging
<ol>
	<li>If traditional hematoxylin and eosin staining is desired (not described here), perform staining before mounting the sections on glass slides7.</li>
	<li>Mount the sections on positively charged glass slides.</li>
	<li>Bake the slides on a hot plate at 60 &#176;C for 20 min.</li>
	<li>Place the slides in a holder and submerge them in a commercial pretreatment solution containing an organic solvent (diethanolamine in this case) and ethanol to deparaffinize, rehydrate, and unmask the tissue. 
	NOTE: This step is necessary to achieve satisfactory results with immunohistochemistry for formalin-fixed and paraffin-embedded tissue.</li>
	<li>Heat the slides in a pressure cooker on high pressure for 20 min.</li>
	<li>Place the slides in a humidified chamber and block the tissue with a commercial blocking solution.</li>
	<li>Probe the tissue sections with the primary antibody against angiotensin-converting enzyme 2 (ACE2; 1:50), transmembrane protease serine 2 (TMPRSS2, 1:1,000), and the Furin protease (1:250). 
	NOTE: The ACE2, TMPRSS2, and Furin antibodies are used because these proteins are believed to play a role in SARS-CoV-2 infectivity11,12, and this protocol sought to investigate the possible mechanisms by which SARS-CoV-2 may infect the middle ear13.</li>
	<li>Treat with HRP-conjugated anti-rabbit secondary antibody (ACE2, Furin; 1:100 dilution) or anti-goat (TMPRSS2, 1:100 dilution) secondary antibody.</li>
	<li>Counterstain the slides with 70% hematoxylin in water.</li>
	<li>Acquire images on a light microscope with a mounted digital camera. Obtain images of the middle ear mucosa and Eustachian tube at 20x and 10x magnification, respectively.</li>
</ol>

<ol>
	<li>Nogueira, J. 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=A+brief+history+of+otorhinolaryngology:+Otology,+laryngology+and+rhinology.">A brief history of otorhinolaryngology: Otology, laryngology and rhinology.</a> Brazilian Journal of Otorhinolaryngology. 73 (5), 693-703 (2007).</li><li>Pappas, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Otology+through+the+ages.">Otology through the ages.</a> Otolaryngology-Head and Neck Surgery. 114 (2), 173-196 (1996).</li><li>Schuknecht, H. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Otopathology:+The+past,+present,+and+future.">Otopathology: The past, present, and future.</a> Auris Nasus Larynx. 23, 43-45 (1996).</li><li>Monsanto, R. D. C., Pauna, H. F., Paparella, M. M., Cureoglu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Otopathology+in+the+United+States:+History,+current+situation,+and+future+perspectives.">Otopathology in the United States: History, current situation, and future perspectives.</a> Otology &amp; Neurotology. 39 (9), 1210-1214 (2018).</li><li>Crowe, S. J., Guild, S. R., Polvogt, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observations+on+the+pathology+of+high-tone+deafness.">Observations on the pathology of high-tone deafness.</a> Journal of Nervous and Mental Disease. 80, 480 (1934).</li><li>Andresen, N. S., 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=Insights+into+presbycusis+from+the+first+temporal+bone+laboratory+within+the+United+States.">Insights into presbycusis from the first temporal bone laboratory within the United States.</a> Otology &amp; Neurotology. 43 (3), 400-408 (2022).</li><li>Schuknecht, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Pathology of the Ear. , (1993).</li><li>Chole, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Labs+in+crisis:+Protecting+the+science--and+art--of+otopathology.">Labs in crisis: Protecting the science--and art--of otopathology.</a> Otology &amp; Neurotology. 31 (4), 554-556 (2010).</li><li>Nager, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Pathology of the Ear and Temporal Bone. , (1993).</li><li>. COVID-19 Personal Protective Equipment (PPE) Available from: <a target="_blank" href="https://www.cdc.gov/niosh/emres/2019_ncov_ppe.html">https://www.cdc.gov/niosh/emres/2019_ncov_ppe.html</a> (2022)</li><li>Essalmani, R., 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=Distinctive+roles+of+Furin+and+TMPRSS2+in+SARS-CoV-2+infectivity.">Distinctive roles of Furin and TMPRSS2 in SARS-CoV-2 infectivity.</a> Journal of Virology. 96 (8), 0012822 (2022).</li><li>Ueha, R., Kondo, K., Kagoya, R., Shichino, S., Yamasoba, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ACE2,+TMPRSS2,+and+Furin+expression+in+the+nose+and+olfactory+bulb+in+mice+and+humans.">ACE2, TMPRSS2, and Furin expression in the nose and olfactory bulb in mice and humans.</a> Rhinology. 59 (1), 105-109 (2021).</li><li>Frazier, K. M., Hooper, J. E., Mostafa, H. H., Stewart, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SARS-CoV-2+virus+isolated+from+the+mastoid+and+middle+ear:+Implications+for+COVID-19+precautions+during+ear+surgery.">SARS-CoV-2 virus isolated from the mastoid and middle ear: Implications for COVID-19 precautions during ear surgery.</a> JAMA Otolaryngology - Head &amp; Neck Surgery. 146 (10), 964-966 (2020).</li><li>Cunningham, C. D., Schulte, B. A., Bianchi, L. M., Weber, P. C., Schmiedt, B. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwave+decalcification+of+human+temporal+bones.">Microwave decalcification of human temporal bones.</a> Laryngoscope. 111 (2), 278-282 (2001).</li><li>Stephenson, R., 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=Immunohistochemical+location+of+Na+,+K+-ATPase+&#945;1+subunit+in+the+human+inner+ear.">Immunohistochemical location of Na+, K+-ATPase &#945;1 subunit in the human inner ear.</a> Hearing Research. 400, 108113 (2021).</li><li>McCall, A. A., 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=Extralabyrinthine+manifestations+of+DFNA9.">Extralabyrinthine manifestations of DFNA9.</a> Journal of the Association for Research in Otolaryngology. 12 (2), 141-149 (2011).</li><li>Wu, P. Z., O'Malley, J. T., de Gruttola, V., Liberman, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+hearing+loss+is+dominated+by+damage+to+inner+ear+sensory+cells,+not+the+cellular+battery+that+powers+them.">Age-related hearing loss is dominated by damage to inner ear sensory cells, not the cellular battery that powers them.</a> The Journal of Neuroscience. 40 (33), 6357-6366 (2020).</li><li>Miller, M. E., Lopez, I. A., Linthicum, F. H., Ishiyama, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Connexin+26+immunohistochemistry+in+temporal+bones+with+cochlear+otosclerosis.">Connexin 26 immunohistochemistry in temporal bones with cochlear otosclerosis.</a> Annals of Otology, Rhinology &amp; Laryngology. 127 (8), 536-542 (2018).</li><li>Lopez, I. A., 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=Immunohistochemical+techniques+for+the+human+inner+ear.">Immunohistochemical techniques for the human inner ear.</a> Histochemistry and Cell Biology. 146 (4), 367-387 (2016).</li></ol>

The authors have no conflicts of interest to declare.

Human temporal bone research is critical for studying inner and middle ear pathology but remains a time- and resource-intensive endeavor. This paper describes a technique that uses a diamond microsaw to generate thick temporal bone sections that can be rapidly decalcified before further sectioning so that the time from tissue harvest to study can be reduced from 9-10 months to 10-14 days. This technique may reduce the resources required for temporal bone processing and facilitate time-sensitive studies, such as those related to COVID-19 middle and inner ear pathology13, which was the motivation for developing this protocol. This protocol allowed for the visualization of ACE2, TMPRS22, and Furin expression within the middle ear and Eustachian tube, providing a likely mechanism by which SARS-CoV-2 may infect the middle ear by spreading from the nasopharynx through the Eustachian tube.
The primary innovation of this protocol is the use of a diamond saw that cuts the tissue before decalcification, which generates &#34;thick&#34; sections of temporal bone that may be rapidly decalcified by increasing the surface area of the tissue exposed to the decalcifying agent. This step allows for tissue decalcification to occur within 7-10 days instead of the 1-2 months that traditional protocols may require for decalcification. The &#34;thick&#34; sections of tissue created with the diamond saw may also be dehydrated more quickly than a standard block of temporal bone tissue, thereby reducing the time between decalcification and embedding. Further, this protocol utilizes paraffin as an embedding agent rather than celloidin, which takes approximately 3 months to harden7. While celloidin provides superior preservation of cochlear structures, paraffin hardens much quicker and facilitates immunostaining. With these modifications, temporal bone tissue can be processed in 10-14 days as opposed to the 9-10 months required in more traditional processing strategies7,9.
This protocol has several limitations. Cutting the tissue with the diamond saw before embedding risks damaging the organ of Corti (OOC). The OOC was severely damaged in most specimens during the development of this technique, which may limit the value of this technique for studying pathologies such as age-related hearing loss, where it is vital that the delicate structures of the inner ear are preserved. It may be possible to position the specimen so that the diamond saw does not directly cut through the otic capsule bone and preserves inner ear structures, but this remains an area of active investigation. Animal models may provide a valuable tool to further refine this protocol and increase the chance of preserving inner ear structures in these valuable human specimens. Tissue quality in this protocol is additionally limited by the use of the paraffin-embedding agent, which was selected due to time constraints. Celloidin embedding better maintains cellular integrity in otopathologic specimens but takes months to harden7. Last, this protocol still requires significant time and resource investment. The use of a diamond microsaw is an additional cost to the materials required for traditional temporal bone preparation, and the 7-10 days required for decalcification is still lengthy. In the future, it may be possible to combine these methods with microwave-assisted decalcification14 to further shorten the time required for processing.
Despite its limitations, the protocol for high-speed temporal bone processing described here offers another tool for studying middle ear, and potentially inner ear, pathology. This technique has been useful during the COVID-19 pandemic and may also reduce the costs associated with maintaining an active temporal bone laboratory by reducing the time and labor necessary for tissue processing. Temporal bone research has decreased in popularity within the United States, decreasing from 28 active laboratories in the 1980s to only 4 active laboratories at present4. This decline in the number of operating temporal bone laboratories may be related to the significant costs associated with harvesting and processing temporal bones4,8. Consequently, it is important that we aim to develop techniques that reduce the resources necessary for temporal bone processing and also those that allow for the study of temporal bone pathology in new contexts, such as the COVID-19 pandemic. Further, high-speed tissue processing, such as that outlined in this protocol, may aid the use of new biologic techniques (e.g., immunohistochemistry, transcriptomics) that allow for the assessment of middle and inner ear pathology at the molecular level15,16,17,18,19. We have barely scratched the surface in terms of utilizing molecular techniques to study human tissue in otologic disease, and they may provide important insights that cannot be provided by animal models.

Human temporal bone research provides an invaluable resource to study the pathology and pathophysiology of the inner and middle ear. Before the 19th century, little was known regarding otologic disease1,2,3. To better understand otologic disease and &#34;rescue aural surgery from the hands of quacks,&#34; Joseph Toynbee (1815-1866) developed methods to study histologic sections of the human temporal bone3. This work was furthered by Adam Politzer (1835-1920) in Vienna and others across Europe during the remainder of the 19th century, who used temporal bone sections to describe the histopathology of many common conditions affecting the ear2,3,4.
The first human temporal bone laboratory in the United States was opened in 1927 at Johns Hopkins Hospital, where Stacy Guild (1890-1966) developed methods for temporal bone sectioning5,6. The methods developed by Guild consisted of a 9-10 month process that included postmortem harvest, fixation, decalcification in nitric acid, dehydration in ethanol, celloidin embedding, sectioning, staining, and mounting. Modifications to this technique were later made by Harold Schuknecht (1917-1996)7; however, the basic components of this process remain essentially unchanged.
The significant resources required to maintain a temporal bone laboratory have presented a challenge for temporal bone research and likely contributed to its declining popularity over the past 30 years4,8. A significant portion of temporal bone laboratory resources must be devoted to the 9-10 month process of temporal bone preparation. One of the most time-consuming steps in preparation is the decalcification of the temporal bone, which is the densest bone in the human body. Decalcification is typically performed in nitric acid or ethylenediaminetetraacetic acid (EDTA) and takes weeks to months while requiring the frequent changing of solutions7,9. Further, time-sensitive studies of the human ear, such as those related to the COVID-19 pandemic, may be hindered by this slow preparation process. This paper describes a technique for high-speed temporal bone sectioning that uses a diamond microsaw to generate thick sections that allow for rapid decalcification and tissue analysis within 10-14 days of temporal bone harvest.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Anti-ACE-2 Antibody (1:50 applied dilution)</td>
			<td>Novus Biologicals</td>
			<td>SN0754</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Furin Antibody (1:250 dilution)</td>
			<td>Abcam</td>
			<td>EPR 14674</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-TMPRSS2 Antibody (1:1,000 dilution)</td>
			<td>Novus Biologicals</td>
			<td>NBP1-20984</td>
			<td></td>
		</tr>
		<tr>
			<td>BX43 Manual System Microscope</td>
			<td>Olympus Life Science Solutions</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CBN/Diamond Hybrid Wafering Blade</td>
			<td>Pace Technologies</td>
			<td>WB-007GP</td>
			<td></td>
		</tr>
		<tr>
			<td>Collin Mallet - 8&#39;&#39;</td>
			<td>Surgical Mart</td>
			<td>SM1517</td>
			<td></td>
		</tr>
		<tr>
			<td>DS-Fi3 Microscope Camera</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dual Endogenous Enzyme Block (commercial blocking solution)</td>
			<td>Dako</td>
			<td>S2003</td>
			<td></td>
		</tr>
		<tr>
			<td>Eaosin Stain</td>
			<td>Sigma-Aldrich</td>
			<td>548-24-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Formalin solution, neutral buffered 10%</td>
			<td>Sigma-Aldrich</td>
			<td>HT501128</td>
			<td></td>
		</tr>
		<tr>
			<td>Formical-4 Decalcifier (formic acid decalcifying solution)</td>
			<td>StatLab</td>
			<td>1214-1 GAL</td>
			<td></td>
		</tr>
		<tr>
			<td>Hematoxylin Stain</td>
			<td>Sigma-Aldrich</td>
			<td>H9627</td>
			<td></td>
		</tr>
		<tr>
			<td>HRP-Conjugated Anti-Rabbit Secondary Antibody (1:100 dilution)</td>
			<td>Leica Biosystems</td>
			<td>PV6119</td>
			<td></td>
		</tr>
		<tr>
			<td>ImmPRESS HRP Horse Anti-Goat igG Detection Kit, Peroxidase (1:100 dilution)</td>
			<td>Vector Laboratories</td>
			<td>MP-7405</td>
			<td></td>
		</tr>
		<tr>
			<td>Lambotte Osteotome</td>
			<td>Surgical Mart</td>
			<td>SM1553</td>
			<td></td>
		</tr>
		<tr>
			<td>Metallographic PICO 155P Precision Saw</td>
			<td>Pace Technologies</td>
			<td>PICO 155P</td>
			<td>microsaw</td>
		</tr>
		<tr>
			<td>NIS Elements Software Version 4.6</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Paraplast Plus</td>
			<td>Sigma-Aldrich</td>
			<td>P3683</td>
			<td>paraffin</td>
		</tr>
		<tr>
			<td>Positive Charged Microscope Slides with White Frosted End</td>
			<td>Walter Products</td>
			<td>1140B15</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermo Shandon Crytome FSE Cryostat Microtome</td>
			<td>New Life Scientific Inc.</td>
			<td>A78900104</td>
			<td>cryotome</td>
		</tr>
		<tr>
			<td>Triology Pretreatment Solution (commercial pretreatment solution)</td>
			<td>Sigma-Aldrich</td>
			<td>920P-05</td>
			<td></td>
		</tr>		
 <tr>
			<td>Xylene</td>
			<td>Sigma-Aldrich</td>
			<td>920P-05</td>
			<td></td>
		</tr>
	</tbody>
</table>

high-speed human temporal bone sectioning for the assessment of covid-19-associated middle ear pathology

Histopathologic analysis of human temporal bone sections is a fundamental technique for studying inner and middle ear pathology. Temporal bone sections are prepared by postmortem temporal bone harvest, fixation, decalcification, embedding, and staining. Due to the density of the temporal bone, decalcification is a time-consuming and resource-intensive process; complete tissue preparation may take 9-10 months on average. This slows otopathology research and hinders time-sensitive studies, such as those relevant to the COVID-19 pandemic. This paper describes a technique for the rapid preparation and decalcification of temporal bone sections to speed tissue processing.
Temporal bones were harvested postmortem using standard techniques and fixed in 10% formalin. A precision microsaw with twin diamond blades was used to cut each section into three thick sections. Thick temporal bone sections were then decalcified in decalcifying solution for 7-10 days before being embedded in paraffin, sectioned into thin (10 &#181;m) sections using a cryotome, and mounted on uncharged slides. Tissue samples were then deparaffinized and rehydrated for antibody staining (ACE2, TMPRSS2, Furin) and imaged. This technique reduced the time from harvest to tissue analysis from 9-10 months to 10-14 days. High-speed temporal bone sectioning may increase the speed of otopathology research and reduce the resources necessary for tissue preparation, while also facilitating time-sensitive studies such as those related to COVID-19.

Hematoxylin and eosin staining of the middle ear mucosa and Eustachian tube showed preservation of the middle ear mucosa and submucosal middle ear tissue following processing (Figure 1). Immunohistochemical images showed expression of the ACE2, TMPRSS2, and Furin proteins within the middle ear mucosa and Eustachian tube (Figure 1). The presence of these proteins within the middle ear provides a possible route by which SARS-CoV-2 may infect the respiratory epithelium within the middle ear11,12,13. Further, the expression of these proteins within the Eustachian tube may explain a route by which the virus enters the middle ear, traveling to the middle ear from the nasopharynx via the Eustachian tube.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64012/64012fig01.jpg" /> 
Figure 1: Example of stained middle ear tissue. The figure shows hematoxylin and eosin, ACE2, TMPRSS2, and Furin staining of the middle ear mucosa (top row, 20x magnification) and Eustachian tube (bottom row, 10x magnification). Scale bars = 50 &#181;m (top row); 100 &#181;m (bottom row). Abbreviations: H&#38;E = hematoxylin and eosin; angiotensin-converting enzyme 2; TMPRSS2 = transmembrane protease, serine 2. <a href="https://www.jove.com/files/ftp_upload/64012/64012fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about High-Speed Human Temporal Bone Sectioning for the Assessment of COVID-19-Associated Middle Ear Pathology at JoVE.com

High-Speed Human Temporal Bone Sectioning for the Assessment of COVID-19-Associated Middle Ear Pathology

This article describes a technique for rapid human temporal bone sectioning that utilizes a microsaw with twin diamond blades to generate thin slices for rapid decalcification and analysis of temporal bone immunohistochemistry.

Histopathologic analysis of human temporal bone sections is a fundamental technique for studying inner and middle ear pathology. Temporal bone sections ...

high-speed-human-temporal-bone-sectioning-for-assessment-covid-19

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

2.2K Views.  Johns Hopkins University School of Medicine. This article describes a technique for rapid human temporal bone sectioning that utilizes a microsaw with twin diamond blades to generate thin slices for rapid decalcification and analysis of temporal bone immunohistochemistry. 

Video: High-Speed Human Temporal Bone Sectioning for the Assessment of COVID-19-Associated Middle Ear Pathology

Preparation of Mouse Pituitary Immunogen for the Induction of Experimental Autoimmune Hypophysitis

Autoimmune hypophysitis is a chronic inflammation of the pituitary gland caused or accompanied by autoimmunity1. It has traditionally been considered a rare disease but reporting has increased markedly in recent years. Hypophysitis, in fact, develops not uncommonly as a "side effect" in cancer patients treated with antibodies that block inhibitory receptors expressed on T lymphocytes, such as CTLA-42 and PD-1 receptors. Autoimmune hypophysitis can be induced experimentally by injecting mice with pituitary proteins mixed with an adjuvant3. In this video article we demonstrate how to extract proteins from mouse pituitary glands and how to prepare them in a form suitable for inducing autoimmune hypophysitis in SJL mice.

Autoimmune hypophysitis can be reproduced in mice by injecting an extract of mouse pituitary proteins.

Autoimmune hypophysitis is a chronic inflammation of the pituitary gland caused or accompanied by autoimmunity1.  It has traditionally been considered a ...

Bioenergetics and the Oxidative Burst: Protocols for the Isolation and Evaluation of Human Leukocytes and Platelets

Mitochondrial dysfunction is known to play a significant role in a number of pathological conditions such as atherosclerosis, diabetes, septic shock, and neurodegenerative diseases but assessing changes in bioenergetic function in patients is challenging.&#160;Although diseases such as diabetes or atherosclerosis present clinically with specific organ impairment, the systemic components of the pathology, such as hyperglycemia or inflammation, can alter bioenergetic function in circulating leukocytes or platelets. This concept has been recognized for some time but its widespread application has been constrained by the large number of primary cells needed for bioenergetic analysis.&#160;This technical limitation has been overcome by combining the specificity of the magnetic bead isolation techniques, cell adhesion techniques, which allow cells to be attached without activation to microplates, and the sensitivity of new technologies designed for high throughput microplate respirometry.&#160;An example of this equipment is the extracellular flux analyzer. Such instrumentation typically uses oxygen and pH sensitive probes to measure rates of change in these parameters in adherent cells, which can then be related to metabolism. Here we detail the methods for the isolation and plating of monocytes, lymphocytes, neutrophils and platelets, without activation, from human blood and the analysis of mitochondrial bioenergetic function in these cells. In addition, we demonstrate how the oxidative burst in monocytes and neutrophils can also be measured in the same samples. Since these methods use only 8-20 ml human blood they have potential for monitoring reactive oxygen species generation and bioenergetics in a clinical setting.

Blood leukocytes and platelets can be used as a marker of overall bioenergetic health of an individual and so have the potential to monitor pathological processes and the impact of treatments. Here&#160;we describe a method to isolate and measure mitochondrial function and the oxidative burst in these cells.

Mitochondrial dysfunction is known to play a significant role in a number of pathological conditions such as atherosclerosis, diabetes, septic shock, and ...

A Novel In vitro Model for Studying the Interactions Between Human Whole Blood and Endothelium

The majority of all known diseases are accompanied by disorders of the cardiovascular system. Studies into the complexity of the interacting pathways activated during cardiovascular pathologies are, however, limited by the lack of robust and physiologically relevant methods. In order to model pathological vascular events we have developed an in vitro assay for studying the interaction between endothelium and whole blood. The assay consists of primary human endothelial cells, which are placed in contact with human whole blood. The method utilizes native blood with no or very little anticoagulant, enabling study of delicate interactions between molecular and cellular components present in a blood vessel.
We investigated functionality of the assay by comparing activation of coagulation by different blood volumes incubated with or without human umbilical vein endothelial cells (HUVEC). Whereas a larger blood volume contributed to an increase in the formation of thrombin antithrombin (TAT) complexes, presence of HUVEC resulted in reduced activation of coagulation. Furthermore, we applied image analysis of leukocyte attachment to HUVEC stimulated with tumor necrosis factor (TNF&#945;) and found the presence of CD16+ cells to be significantly higher on TNF&#945; stimulated cells as compared to unstimulated cells after blood contact. In conclusion, the assay may be applied to study vascular pathologies, where interactions between the endothelium and the blood compartment are perturbed.

A Novel In vitro Model for Studying the Interactions Between Human Whole Blood and Endothelium

The accessibility of reliable models to investigate vascular blood interactions in humans is lacking. We present an in vitro model of cultured primary human endothelial cells combined with human whole blood to investigate cellular interactions both in the blood (ELISA) and the vascular compartment (microscopy).

The majority of all known diseases are accompanied by disorders of the cardiovascular system. Studies into the complexity of the interacting pathways ...

Super-resolution Imaging of the Natural Killer Cell Immunological Synapse on a Glass-supported Planar Lipid Bilayer

The glass-supported planar lipid bilayer system has been utilized in a variety of disciplines. One of the most useful applications of this technique has been in the study of immunological synapse formation, due to the ability of the glass-supported planar lipid bilayers to mimic the surface of a target cell while forming a horizontal interface. The recent advances in super-resolution imaging have further allowed scientists to better view the fine details of synapse structure. In this study, one of these advanced techniques, stimulated emission depletion (STED), is utilized to study the structure of natural killer (NK) cell synapses on the supported lipid bilayer. Provided herein is an easy-to-follow protocol detailing: how to prepare raw synthetic phospholipids for use in synthesizing glass-supported bilayers; how to determine how densely protein of a given concentration occupies the bilayer's attachment sites; how to construct a supported lipid bilayer containing antibodies against NK cell activating receptor CD16; and finally, how to image human NK cells on this bilayer using STED super-resolution microscopy, with a focus on distribution of perforin positive lytic granules and filamentous actin at NK synapses. Thus, combining the glass-supported planar lipid bilayer system with STED technique, we demonstrate the feasibility and application of this combined technique, as well as intracellular structures at NK immunological synapse with super-resolution.

We describe here a combination of the glass-supported lipid bilayer technique of forming immunological synapses with the super-resolution imaging technique of stimulated emission depletion (STED) microscopy. The goal of this protocol is to provide users with the instructions necessary to successfully carry out these two techniques.

The glass-supported planar lipid bilayer system has been utilized in a variety of disciplines. One of the most useful applications of this technique has ...

Assessment of the Immunomodulatory Properties of Human Mesenchymal Stem Cells (MSCs)

The immunomodulatory properties of multilineage human mesenchymal stem cells (MSCs) appear to be highly relevant for clinical use towards a wide-range of immune-related diseases. Mechanisms involved are increasingly being elucidated and in this article, we describe the basic experiment to assess MSC immunomodulation by assaying for suppression of effector leukocyte proliferation. Representing activation, leukocyte proliferation can be assessed by a number of techniques, and we describe in this protocol the use of the fluorescent cellular dye carboxyfluorescein succinimidyl ester (CFSE) to label leukocytes with subsequent flow cytometric analyses. This technique can not only assess proliferation without radioactivity, but also the number of cell divisions that have occurred as well as allowing for identification of the specific population of proliferating cells and intracellular cytokine/factor expression. Moreover, the assay can be tailored to evaluate specific populations of effector leukocytes by magnetic bead surface marker selection of single peripheral blood mononuclear cell populations prior to co-culture with MSCs. The flexibility of this co-culture assay is useful for investigating cellular interactions between MSCs and leukocytes.

Assessment of the Immunomodulatory Properties of Human Mesenchymal Stem Cells MSCs

The immunomodulatory properties of human mesenchymal stem cells (MSC) appear increasingly relevant for clinical application. Using a co-culture system of MSCs and peripheral blood leukocytes pre-stained with the fluorescent dye carboxyfluorescein succinimidyl ester (CFSE), we describe the in vitro assessment of MSC immunomodulation on effector leukocyte proliferation and specific subpopulations.

The immunomodulatory properties of multilineage human mesenchymal stem cells (MSCs) appear to be highly relevant for clinical use towards a wide-range of ...

Magnetic Stirrer Method for the Detection of Trichinella Larvae in Muscle Samples

Trichinellosis is a debilitating disease in humans and is caused by the consumption of raw or undercooked meat of animals infected with the nematode larvae of the genus Trichinella. The most important sources of human infections worldwide are game meat and pork or pork products. In many countries, the prevention of human trichinellosis is based on the identification of infected animals by means of the artificial digestion of muscle samples from susceptible animal carcasses.
There are several methods based on the digestion of meat but the magnetic stirrer method is considered the gold standard. This method allows the detection of Trichinella larvae by microscopy after the enzymatic digestion of muscle samples and subsequent filtration and sedimentation steps. Although this method does not require special and expensive equipment, internal controls cannot be used. Therefore, stringent quality management should be applied throughout the test. The aim of the present work is to provide detailed handling instructions and critical control points of the method to analysts, based on the experience of the European Union Reference Laboratory for Parasites and the National Reference Laboratory of Germany for Trichinella.

Magnetic Stirrer Method for the Detection of Trichinella Larvae in Muscle Samples

The prevention of human trichinellosis in many countries worldwide is based on the laboratory examination of muscle samples from susceptible animals by methods of digestion, of which the magnetic stirrer method is considered the gold standard.

Trichinellosis is a debilitating disease in humans and is caused by the consumption of raw or undercooked meat of animals infected with the nematode ...

A Flow Cytometry-Based Cytotoxicity Assay for the Assessment of Human NK Cell Activity

Within the innate immune system, effector lymphocytes known as natural killer (NK) cells play an essential role in host defense against aberrant cells, specifically eliminating tumoral and virally infected cells. Approximately 30 known monogenic defects, together with a host of other pathological conditions, cause either functional or classic NK cell deficiency, manifesting in reduced or absent cytotoxic activity. Historically, cytotoxicity has been investigated with radioactive methods, which are cumbersome, expensive and potentially hazardous. This article describes a streamlined, clinically applicable flow cytometry-based method to quantify NK cell cytotoxic activity. In this assay, peripheral blood mononuclear cells (PBMCs) or purified NK cell preparations are co-incubated at different ratios with a target tumor cell line known to be sensitive to NK cell-mediated cytotoxicity (NKCC). The target cells are pre-labeled with a fluorescent dye to allow their discrimination from the effector cells (NK cells). After the incubation period, killed target cells are identified by a nucleic acid stain, which specifically permeates dead cells. This method is amenable to both diagnostic and research applications and, thanks to the multi-parameter capabilities of flow cytometry, has the added advantage of potentially enabling a deeper analysis of NK cell phenotype and function.

A flow cytometry-based method to quantitatively determine the cytotoxic activity of human natural killer cells is shown here.

Within the innate immune system, effector lymphocytes known as natural killer (NK) cells play an essential role in host defense against aberrant cells, ...

Assessment of the Cytotoxic and Immunomodulatory Effects of Substances in Human Precision-cut Lung Slices

Respiratory diseases in their broad diversity need appropriate model systems to understand the underlying mechanisms and enable development of new therapeutics. Additionally, registration of new substances requires appropriate risk assessment with adequate testing systems to avoid the risk of individuals being harmed, for example, in the working environment. Such risk assessments are usually conducted in animal studies. In view of the 3Rs principle and public skepticism against animal experiments, human alternative methods, such as precision-cut lung slices (PCLS), have been evolving. The present paper describes the ex vivo technique of human PCLS to study the immunomodulatory potential of low-molecular-weight substances, such as ammonium hexachloroplatinate (HClPt). Measured endpoints include viability and local respiratory inflammation, marked by altered secretion of cytokines and chemokines. Pro-inflammatory cytokines, tumor necrosis factor alpha (TNF-&#945;), and interleukin 1 alpha (IL-1&#945;) were significantly increased in human PCLS after exposure to a sub-toxic concentration of HClPt. Even though the technique of PCLS has been substantially optimized over the past decades, its applicability for the testing of immunomodulation is still in development. Therefore, the results presented here are preliminary, even though they show the potential of human PCLS as a valuable tool in respiratory research.

In view of the 3Rs principle, respiratory models as alternatives to animal studies are evolving. Especially for risk assessment of respiratory substances, there is a lack of appropriate assays. Here, we describe the use of human precision-cut lung slices for the assessment of airborne substances.

Respiratory diseases in their broad diversity need appropriate model systems to understand the underlying mechanisms and enable development of new ...

Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can have pathological significance. An ideal method for examining alterations to monocytes is whole blood flow cytometry as the minimal handling of samples by this method limits artifactual cell activation. However, many different approaches are taken to gate the monocyte subsets leading to inconsistent identification of the subsets between studies. Here we demonstrate a method using whole blood flow cytometry to identify and characterize human monocyte subsets (classical, intermediate, and non-classical). We outline how to prepare the blood samples for flow cytometry, gate the subsets (ensure contaminating cells have been removed), and determine monocyte subset expression of surface markers &#8212; in this example M1 and M2 markers. This protocol can be extended to other studies that require a standard gating method for assessing monocyte subset proportions and monocyte subset expression of other functional markers.

Here we present a protocol for characterizing monocyte subsets by whole blood flow cytometry. This includes outlining how to gate the subsets and assess their expression of surface markers and giving an example of the assessment of the expression of M1 (inflammatory) and M2 markers (anti-inflammatory).

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can ...

Assessment of the Synaptic Interface of Primary Human T Cells from Peripheral Blood and Lymphoid Tissue

The current understanding of the dynamics and structural features of T-cell synaptic interfaces has been largely determined through the use of glass-supported planar bilayers and in vitro-derived T-cell clones or lines1,2,3,4. How these findings apply to the primary human T cells isolated from blood or lymphoid tissues is not known, partly due to significant difficulties in obtaining a sufficient number of cells for analysis5. Here we address this through the development of a technique exploiting multichannel flow slides to build planar lipid bilayers containing activating and adhesion molecules. The low height of the flow slides promotes rapid cell sedimentation in order to synchronize cell:bilayer attachment, thereby allowing researchers to study the dynamic of the synaptic interface formation and the kinetics of the granules release. We apply this approach to analyze the synaptic interface of as few as 104 to 105 primary cryopreserved T cells isolated from lymph nodes (LN) and peripheral blood (PB). The results reveal that the novel planar lipid bilayer technique enables the study of the biophysical properties of primary human T cells derived from blood and tissues in the context of health and disease.

The protocol describes a technique to study the ability of primary polyclonal human T cells to form synaptic interfaces using planar lipid bilayers. We use this technique to show the differential synapse formation capability of human primary T cells derived from lymph nodes and peripheral blood.