We thank Hyesuk Park for the technical help. This research was supported by funding from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH (R01 2DK083283, to NJT), the National Institute on Aging (NIA), NIH (1R01AG060726, to NJT).&#160;We gratefully acknowledge Jon Mulholland and Kitty Lee of the Cell Sciences Imaging Facility in the Beckman Center for technical assistance with the two-photon microscopy imaging.&#160;

Animal experiments are performed according to the experimental procedures approved by the institutional animal care and use committees (IACUCs) of Stanford University and the Veterans Affairs Hospital in Palo Alto. 6-8 week-old male C57BL/6J mice were fed either chow or a fast-food diet supplemented with 4.2% high-fructose corn syrup (see Table of Materials) in drinking water for 14 weeks5. The mice were kept in standard cages at a 12 h dark/light cycle.
1. Surgical preparation and procedures of liver perfusion
<ol>
	<li>Weigh the mouse before the procedure.</li>
	<li>Anesthetize the mouse by administering Ketamine (90 mg/kg) and Xylazine (10 mg/kg) (see Table of Materials) via an intraperitoneal injection. Ensure that the mouse is fully anesthetized by toe pinching before proceeding to the next step. 
	NOTE: Isoflurane is not needed here since this is a non-survival surgery.</li>
	<li>Shave the ventral area using a hair clipper and disinfect the skin with 70% ethanol. Place the mouse on its back, and immobilize the legs on the surgical board with tape.</li>
	<li>After reconfirming the depth of anesthesia by a toe-pinch, use Mayo scissors and Adson forceps (see Table of Materials) to make a 3 cm incision laterally in the lower abdomen and then a 5 cm incision vertically from the low abdomen to the xiphoid process. Be careful not to open the chest cavity.</li>
	<li>After opening the peritoneum, gently place the intestines to the animal&#39;s left, and elevate the right lobe of the liver with a Rayon tipped applicator (see Table of Materials) to expose the portal vein.</li>
	<li>Catheterize the portal vein using a 24 G IV catheter. Introduce the catheter into the distal end of the portal vein. Place the catheter tip before the portal vein branches out into the hepatic lobes.</li>
	<li>Withdraw the needle immediately when the catheter enters the vein. Check that the catheter is correctly positioned inside the vein by perfusing the liver with PBS using a 1mL syringe via the catheter. 
	&#8203;NOTE: Upon PBS perfusion, all lobes should immediately blanch. If the catheter is correctly placed, venous blood will quickly flow through the catheter.</li>
	<li>Use Dumont micro forceps, a Castroviejo microneedle holder, and 4-0 suture (see Table of Materials) to place a stitch below the branching of the portal vein and a second stitch 1 cm below to secure the catheter.</li>
</ol>
2. Tissue decellularization
<ol>
	<li>Connect the catheter to a silicone tubing (~1 m length, 3 mm inner diameter, and 4.1 mm outer diameter) with a Luer connector. Connect the silicone tubing to a peristaltic pump and a reservoir containing deionized water (see Table of Materials).</li>
	<li>Carefully remove the air bubbles inside the tube and avoid generating new bubbles during the perfusion. Set the peristaltic pump at a &#64258;ow output of 0.2 mL/min (i.e., 288 mL/24 h).</li>
	<li>Perfuse first with deionized water (~50 mL/mouse) for 2 h. The color of the liver will change from red to yellow during perfusion. 
	NOTE: The animal will expire after 10 minutes of perfusion.</li>
	<li>Switch the perfusion solution to 0.5% (wt/vol) sodium deoxycholate (DOC, see Table of Materials) and continue overnight (18 h, ~250mL/mouse).The liver will become white at the end of perfusion (Figure 1).</li>
	<li>Switch the perfusion solution to deionized water (~50 mL/mouse) and perfuse for 2 h.</li>
	<li>Use Dumont micro forceps and micro-spring scissors (see Table of Materials) to collect the decellularized liver and wash it carefully in a Petri-dish with PBS.</li>
	<li>Cut the decellularized tissue into small pieces for immediate imaging or freeze at -80 &#176;C for further biochemical analysis such as tandem mass spectrometry, ELISA, or western blot.</li>
</ol>
3. Slide preparation for imaging (with a multiphoton/confocal fluorescence microscope)
<ol>
	<li>Transfer a small piece of decellularized liver (&#60;3 x 3 x 3 mm) to a microscope slide and place the tissue in the middle.</li>
	<li>Add 10 &#181;L of antifade mounting medium (see Table of Materials) to the tissue with a pipette to avoid tissue drying.</li>
	<li>Cover the tissue with a cover glass and apply a small force to flatten the sample. Seal the edges of the cover glass with colorless and transparent nail polish (Figure 2). 
	&#8203;NOTE: Due to the setting of the upright two-photon through the microscope, a cover glass was used on the sample. However, samples could be placed differently if an inverted microscope is used.</li>
</ol>
4. Image acquisition
<ol>
	<li>Place a drop of immersion oil on the top of the cover glass and place the slide on the microscope slide holder. Lower the 20x oil objective lens until it contacts the immersion oil.</li>
	<li>Switch to the violet (405 nm) channel, turn on the shutter, and focus on the sample. Navigate and position the area of interest for imaging. Turn off the shutter before moving to image acquisition using laser light.</li>
	<li>Switch to the computer control and start the two-photon laser. Turn on the two-photon laser first (Figure 3A), then turn on the two-photon laser controller (see Table of Materials) and shutter (Figure 3B,C). Ensure that the output power is higher than 2.5 W. 
	Reduce the laser power to prevent fluorescence quenching. Select and adjust detectors (both photomultipliers and the hybrid) to accommodate the chosen fluorophores. 
	NOTE: Two-photon imaging was performed at an excitation wavelength of 860 nm. Two channels were selected for collagen SHG and two-photon excited fluorescence (TPEF)&#160;images, respectively. One channel corresponding to the wavelength range of 415-445 nm detected the detailed structure of collagen from SHG signals. Another channel covered the range of 465-669 nm to collect TPEF signals.</li>
	<li>Choose simultaneous or sequential image acquisitions. Adjust the pinhole to the highest value. Adjust laser wavelengths, gain, power, and offset. Adjust pixel dwell time, the pixel size, averaging, and the zoom (Figure 4A).</li>
	<li>Scroll the computer z-controller and set the z-dimensions, define the start and endpoints, and choose the numbers of images given within a volume (z-stack). Acquire images. 
	NOTE: Here, a 20 &#181;m Z volume and 1 &#181;m Z-step size was chosen (Figure 4B).</li>
</ol>

<ol>
	<li>Friedman, S. L., Pinzani, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatic+fibrosis:+2022+unmet+needs+and+a+blueprint+for+the+future.">Hepatic fibrosis: 2022 unmet needs and a blueprint for the future.</a> Hepatology. 75 (2), 473-488 (2021).</li><li>Ye, Q., 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=Global+prevalence,+incidence,+and+outcomes+of+non-obese+or+lean+non-alcoholic+fatty+liver+disease:+A+systematic+review+and+meta-analysis.">Global prevalence, incidence, and outcomes of non-obese or lean non-alcoholic fatty liver disease: A systematic review and meta-analysis.</a> The Lancet Gastroenterology and Hepatology. 5 (8), 739-752 (2020).</li><li>Schwabe, R. F., Tabas, I., Pajvani, U. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+fibrosis+development+in+non-alcoholic+steatohepatitis.">Mechanisms of fibrosis development in non-alcoholic steatohepatitis.</a> Gastroenterology. 158 (7), 1913-1928 (2020).</li><li>Arteel, G. E., Naba, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+liver+matrisome+-+looking+beyond+collagens.">The liver matrisome - looking beyond collagens.</a> JHEP Reports. 2 (4), 100115 (2020).</li><li>Jiang, J. X., 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=Nonphagocytic+activation+of+NOX2+is+implicated+in+progressive+non-alcoholic+steatohepatitis+during+aging.">Nonphagocytic activation of NOX2 is implicated in progressive non-alcoholic steatohepatitis during aging.</a> Hepatology. 72 (4), 1204-1218 (2020).</li><li>Dehnad, 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=AGER1+downregulation+associates+with+fibrosis+in+non-alcoholic+steatohepatitis+and+type+2+diabetes.">AGER1 downregulation associates with fibrosis in non-alcoholic steatohepatitis and type 2 diabetes.</a> Journal of Clinical Investigation. 130 (8), 4320-4330 (2020).</li><li>Mayorca-Guiliani, A. E., 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=Decellularization+and+antibody+staining+of+mouse+tissues+to+map+native+extracellular+matrix+structures+in+3D.">Decellularization and antibody staining of mouse tissues to map native extracellular matrix structures in 3D.</a> Nature Protocols. 14 (12), 3395-3425 (2019).</li><li>Mazza, G., 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=Cirrhotic+human+liver+extracellular+matrix+3D+scaffolds+promote+smad-dependent+tgf-beta1+epithelial+mesenchymal+transition.">Cirrhotic human liver extracellular matrix 3D scaffolds promote smad-dependent tgf-beta1 epithelial mesenchymal transition.</a> Cells. 9 (1), 83 (2019).</li><li>Klaas, 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=The+alterations+in+the+extracellular+matrix+composition+guide+the+repair+of+damaged+liver+tissue.">The alterations in the extracellular matrix composition guide the repair of damaged liver tissue.</a> Scientific Reports. 6, 27398 (2016).</li><li>Mattei, G., 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=Mechanostructure+and+composition+of+highly+reproducible+decellularized+liver+matrices.">Mechanostructure and composition of highly reproducible decellularized liver matrices.</a> Acta Biomaterialia. 10 (2), 875-882 (2014).</li><li>Ren, 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=Evaluation+of+two+decellularization+methods+in+the+development+of+a+whole-organ+decellularized+rat+liver+scaffold.">Evaluation of two decellularization methods in the development of a whole-organ decellularized rat liver scaffold.</a> Liver International. 33 (3), 448-458 (2013).</li><li>Piersma, B., Hayward, M. K., Weaver, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fibrosis+and+cancer:+A+strained+relationship.">Fibrosis and cancer: A strained relationship.</a> Biochimica et Biophysica Acta - Reviews on Cancer. 1873 (2), 188356 (2020).</li><li>Cox, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+matrix+in+cancer.">The matrix in cancer.</a> Nature Reviews Cancer. 21 (4), 217-238 (2021).</li><li>Mirdamadi, E. S., Kalhori, D., Zakeri, N., Azarpira, N., Solati-Hashjin, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liver+tissue+engineering+as+an+emerging+alternative+for+liver+disease+treatment.">Liver tissue engineering as an emerging alternative for liver disease treatment.</a> Tissue Engineering Part B: Reviews. 26 (2), 145-163 (2020).</li><li>Mazza, G., 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=Decellularized+human+liver+as+a+natural+3D-scaffold+for+liver+bioengineering+and+transplantation.">Decellularized human liver as a natural 3D-scaffold for liver bioengineering and transplantation.</a> Scientific Reports. 5, 13079 (2015).</li><li>Jia, Z., 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=3D+culture+system+for+liver+tissue+mimicking+hepatic+plates+for+improvement+of+human+hepatocyte+(C3A)+function+and+polarity.">3D culture system for liver tissue mimicking hepatic plates for improvement of human hepatocyte (C3A) function and polarity.</a> BioMed Research International. 2020, 6354183 (2020).</li><li>Shimoda, 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=Decellularized+liver+scaffolds+promote+liver+regeneration+after+partial+hepatectomy.">Decellularized liver scaffolds promote liver regeneration after partial hepatectomy.</a> Scientific Reports. 9 (1), 12543 (2019).</li></ol>

The authors declare that there are no conflicts of interest regarding this article.

The present protocol shows that decellularization through a low flow rate DOC in situ perfusion preserves the frangible triple-helical and native fibrillar collagen structures, providing a reliable and cost-effective platform to capture dynamic ECM remodeling in NASH liver fibrosis. Although decellularization was performed in normal and fibrotic livers before identifying ECM components or generating biological scaffolds for cell culture, the dynamics of ECM remodeling in liver fibrosis have not been well studied8,9,10. This method allows investigators to draw comparisons across various fibrosis models.
Currently, there are varieties of perfusion protocols using DNase, sodium dodecyl sulfate (SDS), or Triton X-10011. The cost of DNase is high because large volumes of solutions are required. SDS is a harsh denaturing solution, an anionic detergent that disrupts the cellular membranes and denatures proteins. Therefore, preserving the entire collagen network after SDS perfusion is challenging. In contrast, Triton X-100, as a mild non-denaturing, non-ionic detergent, disrupts lipid-lipid and lipid-protein interactions and preserves protein-protein interactions. However, it has been reported that Triton X-100 perturbs the ECM scaffolds, making the decellularized liver ECM unsuitable for further mass spectrometry analysis11.
The perfusion protocol with DOC was modified from the previous work7, demonstrating better preservation of the triple-helical and native fibrillar collagen structures in most tissues. The collagen network was studied with second harmonic generation (SHG) microscopy without antibodies, reflecting the triple-helical and native fibrillar collagen structures. The decellularized liver ECM from FFD mice was also tested, and structural changes in NASH were confirmed.
The most critical steps in the protocol are catheter placement and setting up the perfusion system. The portal vein catheterization is vital, but the inferior vena cava could also be used if the portal vein is damaged. Bubbles in the buffer and tubes must be avoided because they affect perfusion. Because an upright two-photon microscope was used, the sample size was limited. This can be modified if an inverted microscope is to be used.
There is an increasing interest in the remodeled ECM in chronic liver diseases and hepatocarcinogenesis12,13,14. Decellularized ECM scaffolds have been employed in surgical repair and regenerative medicine as an appropriate biological scaffold material15,16,17. However, this mild decellularization process also has limitations, as some cellular components such as DNA or lipid remnants may not be entirely removed. Longer DOC perfusion time and an increase in flow rate may help get ultra-purified decellularized scaffolds. Adding DNase into the washing solution after the DOC perfusion may also help remove DNA. The protocol can be adjusted for human liver biopsies, thus enhancing the understanding of ECM alterations during NASH progression.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease, affecting 20%-25% of the adult population. 25% of NAFLD patients progress to non-alcoholic steatohepatitis (NASH), where the risk of cirrhosis, liver failure, and hepatocellular carcinoma increases1. In the next 20 years, it is estimated that NASH will account for 2 million liver-related deaths in U.S2. As there are no approved treatments, there is an urgent need to decipher the mechanisms that cause liver fibrosis in NASH patients and develop targeted treatment3.
The extracellular matrix (ECM) is a dynamic, complex microenvironment that exerts bi-directional communication with cells to regulate tissue homeostasis4. The liver ECM is composed of structural elements such as proteoglycans, collagens, fibronectin, elastin, and other non-structural proteins (e.g., olfactomedin and thrombospondin) to provide physical and structural support4.
Liver fibrosis is a chronic wound-healing response to liver damage of various etiologies, including NASH3. It results from an imbalance in the dynamic ECM matrix remodeling process and is characterized by excessive structural proteins in the injured liver4. Fibrogenesis depends on the dynamic cell-cell communication among different hepatic cell types. Hepatic stellate cells (HSCs),&#160;when activated, differentiate into Smooth Muscle Alpha 2 Actin-expressing, migrating, and proliferating myofibroblast-like cells and synthesize ECM proteins as a wound-closing action. Activated HSCs are the central collagen-producing cells in the liver1.
The molecular mechanism of ECM remodeling, patterns of fibrosis, and their relationship with cellular events are not clear. A better understanding of the three-dimensional (3D)&#160;ECM structure is still needed, even though mass spectrometry techniques have helped analyze ECM protein composition4. Traditionally, Masson&#39;s trichrome stain, Picro Sirius Red stains, and second harmonic generation (SHG) imaging have been performed on two-dimensional (2D) thin liver sections. The typical fibrosis pattern of NASH is called &#34;chicken wire,&#34; which extends to zone 3 and is perisinusoidal/pericellular fibrosis5,6. However, there has been a lack of studies focusing on the 3D structure of the native liver, particularly those that do not involve tissue sectioning. Robust imaging approaches to identify patterns and characteristics of fibrosis throughout dynamic ECM remodeling in liver fibrosis would significantly strengthen the understanding of NASH mechanisms and identify new therapeutic targets.
To address these challenges, a fast and efficient protocol was optimized to image the native liver ECM via decellularization7. Whole-liver decellularization is an approach to remove the hepatic cellular content while maintaining the native 3D ECM network through detergent perfusion. Mice were fed either chow or fast-food diet (FFD) for 14 weeks. Decellularization was performed after in situ portal vein perfusion with mild detergent and low flow rates to preserve triple-helical and native fibrillar collagen structures. Two-photon microscopy was applied to analyze changes in collagen structures in ECM. The 3D images of the native ECM structure in normal and NASH livers were reconstituted and analyzed. Performing in situ perfusion decellularization and analyzing the scaffold by two-photon microscopy provides a practical and affordable platform to visualize the dynamic ECM remodeling in the liver.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-0 MONOCRYL UNDYED 1 x 18&#34; P-3</td>
			<td>MONOCRYL</td>
			<td>Y494G</td>
			<td></td>
		</tr>
		<tr>
			<td>4-0 suture</td>
			<td>fisher scientific</td>
			<td>10-000-649</td>
			<td>https://www.fishersci.com/shop/products/monomid-nylon-non-absorbable-sutures-7/10000649?keyword=true</td>
		</tr>
		<tr>
			<td>AnaSed Injection (xylazine)</td>
			<td>AnaSed</td>
			<td>NDC 59399-110-20</td>
			<td>this drug to use by or on the order of a licensed veterinarian.</td>
		</tr>
		<tr>
			<td>BD INSYTE AUTOGUARD I.V. CATHETER WITH BC TECHNOLOGY</td>
			<td>BD</td>
			<td>382612</td>
			<td></td>
		</tr>
		<tr>
			<td>Chow diet</td>
			<td>Envigo</td>
			<td># 2918</td>
			<td>Control diet. A fixed formula, non-autoclavable diet manufactured with high quality ingredients and designed to support gestation, lactation, and growth of rodents.</td>
		</tr>
		<tr>
			<td>Fast-food diet (AIN76A Western Diet)</td>
			<td>Test Diet</td>
			<td>1810060</td>
			<td>https://www.testdiet.com/cs/groups/lolweb/@testdiet/documents/web_content/mdrf/mdux/~edisp/ducm04_051601.pdf</td>
		</tr>
		<tr>
			<td>Hematoxylin and Eosin Stain Kit</td>
			<td>vectorlabs</td>
			<td>H-3502</td>
			<td>https://vectorlabs.com/hematoxylin-and-eosin-stain-kit.html</td>
		</tr>
		<tr>
			<td>Kent Scientific Rat Surgical Kit</td>
			<td>fisher scientific</td>
			<td>13-005-205</td>
			<td>https://www.fishersci.com/shop/products/rat-surgical-kit/13005205#?keyword=mouse%20surgery%20kit</td>
		</tr>
		<tr>
			<td>KETAMINE HYDROCHLORIDE INJECTION</td>
			<td>Vedco</td>
			<td>NDC 50989-996-06 - 10 mL - vial.</td>
			<td>KetaVed has been clinically studied in subhuman primates in addition to those species listed under Administration and Dosage.</td>
		</tr>
		<tr>
			<td>Leica SP5 upright Confocal, multi-photon</td>
			<td>Leica</td>
			<td>SP5</td>
			<td></td>
		</tr>
		<tr>
			<td>Luer connector (Three-way stopcock with SPIN-LOCK&#174;)</td>
			<td>bbraun</td>
			<td>D300</td>
			<td>https://www.bbraunusa.com/en/products/b0/three-way-stopcockwithspin-lock.html</td>
		</tr>
		<tr>
			<td>Picrosirius Red Stain Kit</td>
			<td>Polysciences, Inc.</td>
			<td>24901</td>
			<td>https://www.polysciences.com/default/picrosirius-red-stain-kit-40771</td>
		</tr>
		<tr>
			<td>Rayon tipped applicator</td>
			<td>puritan</td>
			<td>25-806 1PR</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium deoxycholate</td>
			<td>sigmaaldrich</td>
			<td>D6750-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Syrup</td>
			<td>www.target.com</td>
			<td>24 fl oz</td>
			<td>https://www.target.com/p/pancake-syrup-24-fl-oz-market-pantry-8482/-/A-13007801</td>
		</tr>
		<tr>
			<td>Variable Speed Peristaltic Pump</td>
			<td>INTLLAB</td>
			<td>BT100</td>
			<td>https://www.amazon.com/gp/product/B082K97W5W/ref=ox_sc_saved_title_2?smid=A12NUUP87ZRRAR&#38;psc=1</td>
		</tr>
		<tr>
			<td>VECTASHIELD Antifade Mounting Medium</td>
			<td>vectorlabs</td>
			<td>H-1000-10</td>
			<td>https://vectorlabs.com/vectashield-mounting-medium.html</td>
		</tr>
	</tbody>
</table>

3d imaging of the liver extracellular matrix in a mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is the most common chronic liver disease in the United States, affecting more than 70 million Americans. NASH can progress to fibrosis and eventually to cirrhosis, a significant risk factor for hepatocellular carcinoma. The extracellular matrix (ECM) provides structural support and maintains liver homeostasis via matricellular signals. Liver fibrosis results from an imbalance in the dynamic ECM remodeling process and is characterized by excessive accumulation of structural elements and associated changes in glycosaminoglycans. The typical fibrosis pattern of NASH is called &#34;chicken wire,&#34; which usually consists of zone 3 perisinusoidal/pericellular fibrosis, based on features observed by Masson&#39;s trichrome stain and Picrosirius Red stains. However, these traditional thin two-dimensional (2D) tissue slide-based imaging techniques cannot demonstrate the detailed three-dimensional (3D) ECM structural changes, limiting the understanding of the dynamic ECM remodeling in liver fibrosis.
The current work optimized a fast and efficient protocol to image the native ECM structure in the liver via decellularization to address the above challenges. Mice were fed either with chow or fast-food diet for 14 weeks. Decellularization was performed after in situ portal vein perfusion, and the two-photon microscopy techniques were applied to image and analyze changes in the native ECM. The 3D images of the normal and NASH livers were reconstituted and analyzed. Performing in situ perfusion decellularization and analyzing the scaffold by two-photon microscopy provided a practical and reliable platform to visualize the dynamic ECM remodeling in the liver.

The collagen fibers were detected with second harmonic generation and two-photon microscopy. The signal is from the frangible triple-helical and native fibrillar collagen structures. Specific antibodies were not used to analyze collagen subtypes; however, this could be added to the imaging&#160;technique.
When the liver tissue is studied without decellularization, it is challenging to get high-resolution images of the collagen network (Figure 5A). In decellularized ECM, collagen fibers (green) appear parallel or interweaving (Figure 5B). There were apparent differences in the morphology and spatial distribution of the ECM components between Chow and FFD livers. Collagen fibers in mice on a chow diet exhibited an interweaving and well-organized network. In mice on FFD, however, collagen bundles were observed with less connectivity (Figure 5B).
To further study the 3D structure of liver ECM, images of the slices were captured with a 20 &#181;m of Z-volume (thickness) and 1 &#181;m of Z-step size. Collagen fibers in mice on chow diet showed a well-organized network but not in the mice on FFD (Figure 6). To confirm the quality of the fibrillar collagen in the decellularized ECM, the slides were fixed and embedded in paraffin and stained with Hematoxylin and eosin (H&#38;E) and Picrosirius red (PSR) (see Table of Materials). H&#38;E shows that all the cells have been removed. The PSR is a commonly used histological technique to highlight collagen in paraffin-embedded tissue sections (Figure 7).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63106/63106fig01.jpg" /> 
Figure 1: Mouse liver during perfusion. The liver&#160;becomes white and semi-transparent at the end of the perfusion. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63106/63106fig02.jpg" /> 
Figure 2: Slide preparation for imaging. The tissue is covered with a cover glass, and a small force is applied to flatten the sample. The edges of the cover glass are sealed with colorless and transparent nail polish. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63106/63106fig03.jpg" /> 
Figure 3: Screenshot of the two-photon laser software, starting the two-photon laser. (A) First, the two-photon laser is turned on. (B)(C) The two-photon laser controller and the shutter are turned on. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/63106/63106fig04.jpg" /> 
Figure 4: Screenshot of the two-photon laser software during image acquisition. (A) Ensure to set the pinhole to the highest value (red arrows). Adjust laser wavelengths, gain, power, and offset. Adjust pixel dwell time, the pixel size, averaging, and the zoom. (B) Set the Z volume to 20 &#181;m and Z-step size to 1 &#181;m. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/63106/63106fig05.jpg" /> 
Figure 5: Decellularized ECM imaged with two-photon microscopy. (A) SHG images of collagen fibers from a 6 &#181;m liver slice (fresh frozen) without decellularization. (B) SHG images depict a well-organized collagen network in livers of mice on normal control, chow diet. Remodeled collagen network in mice on fast-food diet (FFD). Arrow, fibrosis area. Star, remodeled collagen network. Scale bar = 100 &#181;m. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/63106/63106fig06.jpg" /> 
Figure 6: 3D structure of liver collagen network. The collagen fibers in mice on the chow diet showed a well-organized network but not in fast-food diet (FFD)&#160;mice. The images were captured with a 20 &#181;m Z-volume (thickness) and 1 &#181;m Z-step size. Scale bar = 100 &#181;m. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/63106/63106fig07.jpg" /> 
Figure 7: Hematoxylin and eosin staining (H&#38;E) and Picrosirius red (PSR) staining of the decellularized ECM. H&#38;E shows that all the cells have been removed. In the PSR staining images, the ECM from the chow-fed mice revealed a well-organized network, and in contrast, mice on fast-food diet (FFD) showed denser collagen fibers. Z-volume (thickness) = 6 &#181;m. Scale bar = 100 &#181;m. <a href="https://www.jove.com/files/ftp_upload/63106/63106fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about 3D Imaging of the Liver Extracellular Matrix in a Mouse Model of Non-Alcoholic Steatohepatitis at JoVE.com

3D Imaging of the Liver Extracellular Matrix in a Mouse Model of Non-Alcoholic Steatohepatitis

The present protocol optimizes the liver in situ perfusion/decellularization and two-photon microscopy methods to establish a reliable platform to visualize the dynamics of extracellular matrix (ECM) remodeling during non-alcoholic steatohepatitis (NASH).

Non-alcoholic steatohepatitis (NASH) is the most common chronic liver disease in the United States, affecting more than 70 million Americans. NASH can ...

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1.8K 조회수.  Stanford University. The present protocol optimizes the liver in situ perfusion/decellularization and two-photon microscopy methods to establish a reliable platform to visualize the dynamics of extracellular matrix (ECM) remodeling during non-alcoholic steatohepatitis (NASH).

비디오: 3D Imaging of the Liver Extracellular Matrix in a Mouse Model of Non-Alcoholic Steatohepatitis

Multi-photon Imaging of Tumor Cell Invasion in an Orthotopic Mouse Model of Oral Squamous Cell Carcinoma

Loco-regional invasion of head and neck cancer is linked to metastatic risk and presents a difficult challenge in designing and implementing patient management strategies. Orthotopic mouse models of oral cancer have been developed to facilitate the study of factors that impact invasion and serve as model system for evaluating anti-tumor therapeutics. In these systems, visualization of disseminated tumor cells within oral cavity tissues has typically been conducted by either conventional histology or with in vivo bioluminescent methods. A primary drawback of these techniques is the inherent inability to accurately visualize and quantify early tumor cell invasion arising from the primary site in three dimensions. Here we describe a protocol that combines an established model for squamous cell carcinoma of the tongue (SCOT) with two-photon imaging to allow multi-vectorial visualization of lingual tumor spread. The OSC-19 head and neck tumor cell line was stably engineered to express the F-actin binding peptide LifeAct fused to the mCherry fluorescent protein (LifeAct-mCherry). Fox1nu/nu mice injected with these cells reliably form tumors that allow the tongue to be visualized by ex-vivo application of two-photon microscopy. This technique allows for the orthotopic visualization of the tumor mass and locally invading cells in excised tongues without disruption of the regional tumor microenvironment. In addition, this system allows for the quantification of tumor cell invasion by calculating distances that invaded cells move from the primary tumor site. Overall this procedure provides an enhanced model system for analyzing factors that contribute to SCOT invasion and therapeutic treatments tailored to prevent local invasion and distant metastatic spread. This method also has the potential to be ultimately combined with other imaging modalities in an in vivo setting.

A comprehensive overview of the techniques involved in generating a mouse model of oral cancer and quantitative monitoring of tumor invasion within the tongue through multi-photon microscopy of labeled cells is presented. This system can serve as a useful platform for the molecular assessment and drug efficacy of anti-invasive compounds.

구강 편평 세포 암종의 Orthotopic 마우스 모델에서 종양 세포 침략의 다중 광자 이미징

Loco-regional invasion of head and neck cancer is linked to metastatic risk and presents a difficult challenge in designing and implementing patient ...

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Imaging- and Flow Cytometry-based Analysis of Cell Position and the Cell Cycle in 3D Melanoma Spheroids

Three-dimensional (3D) tumor spheroids are utilized in cancer research as a more accurate model of the in vivo tumor microenvironment, compared to traditional two-dimensional (2D) cell culture. The spheroid model is able to mimic the effects of cell-cell interaction, hypoxia and nutrient deprivation, and drug penetration. One characteristic of this model is the development of a necrotic core, surrounded by a ring of G1 arrested cells, with proliferating cells on the outer layers of the spheroid. Of interest in the cancer field is how different regions of the spheroid respond to drug therapies as well as genetic or environmental manipulation. We describe here the use of the fluorescence ubiquitination cell cycle indicator (FUCCI) system along with cytometry and image analysis using commercial software to characterize the cell cycle status of cells with respect to their position inside melanoma spheroids. These methods may be used to track changes in cell cycle status, gene/protein expression or cell viability in different sub-regions of tumor spheroids over time and under different conditions.

We describe two complementary methods using the fluorescence ubiquitination cell cycle indicator (FUCCI) and image analysis or flow cytometry to identify and isolate cells in the inner G1 arrested and outer proliferating regions of 3D spheroids.

Imaging- 및 유동 세포 계측법 기반의 셀 위치의 분석 및 3D 흑색 종 회전 타원체의 세포주기

Three-dimensional (3D) tumor spheroids are utilized in cancer research as a more accurate model of the in vivo tumor microenvironment, compared to ...

Evaluation of Planar-Cell-Polarity Phenotypes in Ciliopathy Mouse Mutant Cochlea

In recent years, primary cilia have emerged as key regulators in development and disease by influencing numerous signaling pathways. One of the earliest signaling pathways shown to be associated with ciliary function was the non-canonical Wnt signaling pathway, also referred to as planar cell polarity (PCP) signaling. One of the best places in which to study the effects of planar cell polarity (PCP) signaling during vertebrate development is the mammalian cochlea. PCP signaling disruption in the mouse cochlea disrupts cochlear outgrowth, cellular patterning and hair cell orientation, all of which are affected by cilia dysfunction. The goal of this protocol is to describe the analysis of PCP signaling in the developing mammalian cochlea via phenotypic analysis, immunohistochemistry and scanning electron microscopy. Defects in convergence and extension are manifested as a shortening of the cochlear duct and/or changes in cellular patterning, which can be quantified following dissection from developing mouse mutants. Changes in stereociliary bundle orientation and kinocilia length or positioning can be observed and quantitated using either immunofluorescence or scanning electron microscopy (SEM). A deeper insight into the role of ciliary proteins in cellular signaling pathways and other biological phenomena is crucial for our understanding of cellular and developmental biology, as well as for the development of targeted treatment strategies.

Primary cilia influence various signaling pathways. The mammalian cochlea is ideal for examining planar cell polarity (PCP) signaling. Cilia dysfunction affects cochlear outgrowth, cellular patterning and hair cell orientation, readouts of PCP. Our goal is to analyze PCP signaling in mouse cochlea via phenotypic analysis, immunohistochemistry and scanning electron microscopy.

Ciliopathy 마우스 돌연변이 달팽이관의 평면 셀 극성 표현형의 평가

In recent years, primary cilia have emerged as key regulators in development and disease by influencing numerous signaling pathways. One of the earliest ...

Strategic Endothelial Cell Tube Formation Assay: Comparing Extracellular Matrix and Growth Factor Reduced Extracellular Matrix

Malignant tumors require a blood supply in order to survive and spread. These tumors obtain their needed blood from the patient's blood stream by hijacking the process of angiogenesis, in which new blood vessels are formed from existing blood vessels. The CXCR2 (chemokine (C-X-C motif) receptor 2) receptor is a transmembrane G-protein-linked molecule found in many cells that is closely associated with angiogenesis1. Specific blockade of the CXCR2 receptor inhibits angiogenesis, as measured by several assays such as the endothelial tube formation assay. The tube formation assay is useful for studying angiogenesis because it is an excellent method of studying the effects that any given compound or environmental condition may have on angiogenesis. It is a simple and quick in vitro assay that generates quantifiable data and requires relatively few components. Unlike in vivo assays, it does not require animals and can be carried out in less than two days. This protocol describes a variation of the extracellular matrix supporting endothelial tube formation assay, which tests the CXCR2 receptor.

This manuscript describes a tube formation assay to quantify the effects of a given compound or condition on angiogenesis by using endothelial cell tube formation in a controlled environment.

전략적 내피 세포 관 형성의 분석 : 감소 세포 외 매트릭스 세포 외 기질과 성장 인자를 비교

Malignant tumors require a blood supply in order to survive and spread. These tumors obtain their needed blood from the patient's blood stream by ...

The Dimethylnitrosamine Induced Liver Fibrosis Model in the Rat

Four to six week old, male Wistar rats were used to produce animal models of liver fibrosis. The process requires four weeks of administration of 10 mg/kg dimethylnitrosamine (DMN), given intraperitoneally for three consecutive days per week. Intraperitoneal injections were performed in the fume hood as DMN is a known hepatoxin and carcinogen. The model has several advantages. Firstly, liver changes can be studied sequentially or at particular stages of interest. Secondly, the stage of liver disease can be monitored by measurement of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzymes. Thirdly, the severity of liver damage at different stages can be confirmed by sacrifice of animals at designated time points, followed by histological examination of Masson&#39;s Trichome stained liver tissues. After four weeks of DMN dosing, the typical fibrosis score is 5 to 6 on the Ishak scale. The model can be reproduced consistently and has been widely used to assess the efficacy of potential anti-fibrotic agents.

We describe a method to produce an animal model of liver fibrosis in the rat, and assess the degree of fibrosis by histological examination of the liver. The model can be used to study the development of liver disease as well as to test the efficacy of potential anti-fibrotic agents.

쥐에이 dimethylnitrosamine 유도 된 간 섬유화 모델

Four to six week old, male Wistar rats were used to produce animal models of liver fibrosis. The process requires four weeks of administration of 10 mg/kg ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

Myography 와이어를 사용 하 여 마우스 Mesenteric 동맥의 isometric 수축 측정

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Incorporation of a Survivable Liver Biopsy Procedure in Mice to Assess Non-alcoholic Steatohepatitis (NASH) Resolution

Clinical trials assessing therapies for the treatment of non-alcoholic steatohepatitis (NASH) involve a baseline and end of study liver biopsy, and assessment of improvement in disease endpoints, often reflected as a percent of each treatment arm that improved, worsened or remained unchanged. Traditional preclinical rodent studies for putative NASH therapies are often limited by not knowing the level of liver disease/NASH present at the start of therapeutic intervention, instead of randomizing treatment groups on easily measurable endpoints such as body weight, metabolic status or similar. Here, we describe a liver biopsy technique in a diet-induced NASH mouse model, for the assessment of baseline liver disease in order to exclude mice that do not exhibit fibrosis and to equally distribute animals with similar fibrosis between treatment groups. These levels can then be compared to the terminal, post-intervention levels for a truer understanding of in vivo pharmacological effects and thus more accurately reflect clinical trial design strategies. The mouse is properly anesthetized and prepared for the surgery using sterile conditions. A small incision is made in the upper abdomen and the left lateral lobe of the liver is exposed. A wedge of the liver is surgically removed, and a similar-sized piece of absorbable gelatin is put in its place to stop any bleeding. The mouse is surgically sutured and stapled closed and will recover back to normal within 1 day. The entire process takes 5-10 min per mouse. Here we exemplify the utility of this procedure by leveraging the pre-study biopsy to assess the impact of the glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide on NASH endpoints in mice.

Incorporation of a Survivable Liver Biopsy Procedure in Mice to Assess Non-alcoholic Steatohepatitis NASH Resolution

In clinical settings, a liver biopsy is used to assess stages of non-alcoholic steatohepatitis (steatosis, inflammation, hepatocyte ballooning, and fibrosis). Here, we illustrate a survivable liver biopsy in mice which can be used for histological analyses to enable assessment of therapeutic agents in a manner more aligned with clinical trials.

무알코올 Steatohepatitis (NASH) 해상도 평가 하기 위해 쥐에 지속 가능 간 생 검 절차의

Clinical trials assessing therapies for the treatment of non-alcoholic steatohepatitis (NASH) involve a baseline and end of study liver biopsy, and ...

Murine Precision-Cut Liver Slices as an Ex Vivo Model of Liver Biology

Understanding the mechanisms of liver injury, hepatic fibrosis, and cirrhosis that underlie chronic liver diseases (i.e., viral hepatitis, non-alcoholic fatty liver disease, metabolic liver disease, and liver cancer) requires experimental manipulation of animal models and in vitro cell cultures. Both techniques have limitations, such as the requirement of large numbers of animals for in vivo manipulation. However, in vitro cell cultures do not reproduce the structure and function of the multicellular hepatic environment. The use of precision-cut liver slices is a technique in which uniform slices of viable mouse liver are maintained in laboratory tissue culture for experimental manipulation. This technique occupies an experimental niche that exists between animal studies and in vitro cell culture methods. The presented protocol describes a straightforward and reliable method to isolate and culture precision-cut liver slices from mice. As an application of this technique, ex vivo liver slices are treated with bile acids to simulate cholestatic liver injury and ultimately assess the mechanisms of hepatic fibrogenesis.

This protocol provides a simple and reliable method for the production of viable precision-cut liver slices from mice. The ex vivo tissue samples can be maintained under laboratory tissue culture conditions for multiple days, providing a flexible model to examine liver pathobiology.

뮤린 정밀 절단 간 슬라이스 간 생물학의 Ex Vivo 모델로

Understanding the mechanisms of liver injury, hepatic fibrosis, and cirrhosis that underlie chronic liver diseases (i.e., viral hepatitis, non-alcoholic ...

Drug Treatment by Central Venous Catheter in a Mouse Model of Angiotensin II Induced Abdominal Aortic Aneurysm and Monitoring by 3D Ultrasound

Since pharmaceutical treatment options are lacking in the clinical management of abdominal aortic aneurysm (AAA), animal models, in particular mouse models, are applied to advance the understanding of the disease pathogenesis and to identify potential therapeutic targets. Testing novel drug candidates to block AAA growth in these models generally requires repeated drug administration during the time course of the experiment. Here, we describe a compiled protocol for AAA induction, insertion of an intravenous catheter to facilitate prolonged therapy, and serial AAA monitoring by 3D ultrasound. Aneurysms are induced in apolipoprotein E (ApoE) deficient mice by angiotensin II release over 28 days from osmotic mini-pumps implanted subcutaneously into the mouse back. Subsequently, the surgical procedure for external jugular vein catheterization is conducted to allow for daily intravenous drug treatment or repeated blood sampling via a subcutaneous vascular access button. Despite the two dorsal implants, the monitoring of AAA development is readily facilitated by sequential semi-automated 3D ultrasound analysis, which yields comprehensive information on the expansion of aortic diameter and volume and on aneurysm morphology, as illustrated by experimental examples.

This protocol describes the consecutive implantation of an osmotic pump to induce abdominal aortic aneurysm by angiotensin II release in apolipoprotein E (ApoE) deficient mice and of a vascular access port with a jugular vein catheter for repeated drug treatment. Monitoring of aneurysm development by 3D ultrasound is effectively conducted despite dorsal implants.

안지오텐신 II의 마우스 모델에서 중앙 정맥 카테터에 의한 약물 치료 유도 복부 대동맥류 및 3D 초음파에 의한 모니터링

Since pharmaceutical treatment options are lacking in the clinical management of abdominal aortic aneurysm (AAA), animal models, in particular mouse ...

Investigating the Protective Effects of Platycodin D on Non-Alcoholic Fatty Liver Disease in a Palmitic Acid-Induced In Vitro Model

The occurrence of non-alcoholic fatty liver disease (NAFLD) has been increasing at an alarming rate worldwide. Platycodon grandiflorum is widely used as a traditional ethnomedicine for the treatment of various diseases and is a typical functional food that can be incorporated into the everyday diet. Studies have suggested that platycodin D (PD), one of the main active ingredients in Platycodon grandiflorum, has high bioavailability and significantly mitigates the progress of NAFLD, but the underlying mechanism of this is still unclear. This study aims to investigate the therapeutic effect of PD against NAFLD in vitro. AML-12 cells were pretreated with 300 &#181;M palmitic acid (PA) for 24 h to model NAFLD in vitro. Then, the cells were either treated with PD or received no PD treatment for 24 h. The levels of reactive oxygen species (ROS) were analyzed using 2&#8242;,7&#8242;-dichloro-dihydro-fluorescein diacetate (DCFH-DA) staining, and the mitochondrial membrane potential was determined by the JC-1 staining method. Moreover, the protein expression levels of LC3-II/LC3-I and p62/SQSTM1 in the cell lysates were analyzed by western blotting. PD was found to significantly decrease the ROS and mitochondrial membrane potential levels in the PA-treated group compared to the control group. Meanwhile, PD increased the LC3-II/LC3-I levels and decreased the p62/SQSTM1 levels in the PA-treated group compared to the control group. The results indicated that PD ameliorated NAFLD in vitro by reducing oxidative stress and stimulating autophagy. This in vitro model is a useful tool for studying the role of PD in NAFLD.