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 studied...

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><tbody><tr><td>4-0 MONOCRYL UNDYED 1 x 18&quot; 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&amp;reg;)</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&amp;amp;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)....

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 Views.  Stanford University. NASH is een van de belangrijkste chronische leverziekten ter wereld. Het kan zich ontwikkelen tot fibrose, cirrose en uiteindelijk de leverkanker. Het bestuderen van de dynamische verandering van de ECM in de NASH kan helpen om de fibrose beter te begrijpen.Traditionele beeldvorming kan geen 3D ECM-structuurveranderingen aantonen, waardoor het begrip van het dynamische ECM-remodelleringsproces in de leverfibrose wordt beperkt. Weeg om te beginnen de muis vóór de procedure. Na het ver...

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

A Biomimetic Model for Liver Cancer to Study Tumor-Stroma Interactions in a 3D Environment with Tunable Bio-Physical Properties

Hepatocellular carcinoma (HCC) is a primary liver tumor developing in the wake of chronic liver disease. Chronic liver disease and inflammation leads to a fibrotic environment actively supporting and driving hepatocarcinogenesis. Insight into hepatocarcinogenesis in terms of the interplay between the tumor stroma micro-environment and tumor cells is thus of considerable importance. Three-dimensional (3D) cell culture models are proposed as the missing link between current in vitro 2D cell culture models and in vivo animal models. Our aim was to design a novel 3D biomimetic HCC model with accompanying fibrotic stromal compartment and vasculature. Physiologically relevant hydrogels such as collagen and fibrinogen were incorporated to mimic the bio-physical properties of the tumor ECM. In this model LX2 and HepG2 cells embedded in a hydrogel matrix were seeded onto the inverted transmembrane insert. HUVEC cells were then seeded onto the opposite side of the membrane. Three formulations consisting of ECM-hydrogels embedded with cells were prepared and the bio-physical properties were determined by rheology. Cell viability was determined by a cell viability assay over 21 days. The effect of the chemotherapeutic drug doxorubicin was evaluated in both 2D co-culture and our 3D model for a period of 72h. Rheology results show that bio-physical properties of a fibrotic, cirrhotic and HCC liver can be successfully mimicked. Overall, results indicate that this 3D model is more representative of the&#160;in vivo&#160;situation compared to traditional 2D cultures.&#160;Our 3D tumor model showed a decreased response to chemotherapeutics, mimicking drug resistance typically seen in HCC patients.&#160;

This protocol presents a 3D biomimetic model with accompanying fibrotic stromal compartment. Prepared with physiologically relevant hydrogels in ratios mimicking the bio-physical properties of the stromal extracellular matrix, an active mediator of cellular interactions, tumor growth and metastasis.

Hepatocellular carcinoma (HCC) is a primary liver tumor developing in the wake of chronic liver disease. Chronic liver disease and inflammation leads to a ...

Cancer Research

Long Term Intravital Multiphoton Microscopy Imaging of Immune Cells in Healthy and Diseased Liver Using CXCR6.Gfp Reporter Mice

Liver inflammation as a response to injury is a highly dynamic process involving the infiltration of distinct subtypes of leukocytes including monocytes, neutrophils, T cell subsets, B cells, natural killer (NK) and NKT cells. Intravital microscopy of the liver for monitoring immune cell migration is particularly challenging due to the high requirements regarding sample preparation and fixation, optical resolution and long-term animal survival. Yet, the dynamics of inflammatory processes as well as cellular interaction studies could provide critical information to better understand the initiation, progression and regression of inflammatory liver disease. Therefore, a highly sensitive and reliable method was established to study migration and cell-cell-interactions of different immune cells in mouse liver over long periods (about 6 hr) by intravital two-photon laser scanning microscopy (TPLSM) in combination with intensive care monitoring.
The method provided includes a gentle preparation and stable fixation of the liver with minimal perturbation of the organ; long term intravital imaging using multicolor multiphoton microscopy with virtually no photobleaching or phototoxic effects over a time period of up to 6 hr, allowing tracking of specific leukocyte subsets; and stable imaging conditions due to extensive monitoring of mouse vital parameters and stabilization of circulation, temperature and gas exchange.
To investigate lymphocyte migration upon liver inflammation CXCR6.gfp knock-in mice were subjected to intravital liver imaging under baseline conditions and after acute and chronic liver damage induced by intraperitoneal injection(s) of carbon tetrachloride (CCl4).
CXCR6 is a chemokine receptor expressed on lymphocytes, mainly on Natural Killer T (NKT)-, Natural Killer (NK)- and subsets of T lymphocytes such as CD4 T cells but also mucosal associated invariant (MAIT) T cells1. Following the migratory pattern and positioning of CXCR6.gfp+ immune cells allowed a detailed insight into their altered behavior upon liver injury and therefore their potential involvement in disease progression.

Stable intravital high-resolution imaging of immune cells in the liver is challenging. Here we provide a highly sensitive and reliable method to study migration and cell-cell-interactions of immune cells in mouse liver over long periods (about 6 hours) by intravital multiphoton laser scanning microscopy in combination with intensive care monitoring.

Liver inflammation as a response to injury is a highly dynamic process involving the infiltration of distinct subtypes of leukocytes including monocytes, ...

Immunology and Infection

Assessing Hepatic Steatosis with 3D Fluorescence Lipid Droplet Reconstruction

Analysis of Fluorescent-Stained Lipid Droplets with 3D Reconstruction for Hepatic Steatosis Assessment

Lipid droplets (LDs) are specialized organelles that mediate lipid storage and play a very important role in suppressing lipotoxicity and preventing dysfunction caused by free fatty acids (FAs). The liver, given its critical role in the body's fat metabolism, is persistently threatened by the intracellular accumulation of LDs in the form of both microvesicular and macrovesicular hepatic steatosis. The histologic characterization of LDs is typically based on lipid-soluble diazo dyes, such as Oil Red O (ORO) staining, but a number of disadvantages consistently hamper the use of this analysis with liver specimens. More recently, lipophilic fluorophores 493/503 have become popular for visualizing and locating LDs due to their rapid uptake and accumulation into the neutral lipid droplet core. Even though most applications are well-described in cell cultures, there is less evidence demonstrating the reliable use of lipophilic fluorophore probes as an LD imaging tool in tissue samples. Herein, we propose an optimized boron dipyrromethene (BODIPY) 493/503-based protocol for the evaluation of LDs in liver specimens from an animal model of high-fat diet (HFD)-induced hepatic steatosis. This protocol covers liver sample preparation, tissue sectioning, BODIPY 493/503 staining, image acquisition, and data analysis. We demonstrate an increased number, intensity, area ratio, and diameter of hepatic LDs upon HFD feeding. Using orthogonal projections and 3D reconstructions, it was possible to observe the full content of neutral lipids in the LD core, which appeared as nearly spherical droplets. Moreover, with the fluorophore BODIPY 493/503, we were able to distinguish microvesicles (1 &#181;m &lt; d &#8804; 3 &#181;m), intermediate vesicles (3 &#181;m &lt; d &#8804; 9 &#181;m), and macrovesicles (d &gt; 9 &#181;m), allowing the successful discrimination of microvesicular and macrovesicular steatosis. Overall, this BODIPY 493/503 fluorescence-based protocol is a reliable and simple tool for hepatic LD characterization and may represent a complementary approach to the classical histological protocols.

Author Spotlight: Analysis of Fluorescent-Stained Lipid Droplets with 3D Reconstruction for Hepatic Steatosis Assessment  

Herein, we demonstrate an optimized BODIPY 493/503 fluorescence-based protocol for lipid droplet characterization in liver tissue. Through the use of orthogonal projections and 3D reconstructions, the fluorophore allows for successful discrimination between microvesicular and macrovesicular steatosis and may represent a complementary approach to the classical histological protocols for hepatic steatosis assessment.

Lipid droplets (LDs) are specialized organelles that mediate lipid storage and play a very important role in suppressing lipotoxicity and preventing ...

Biochemistry

An Advanced Murine Model for Nonalcoholic Steatohepatitis in Association with Type 2 Diabetes

Obesity is associated with chronic low-grade inflammation and insulin resistance, contributing to an increasing prevalence of chronic metabolic diseases, such as type 2 diabetes and nonalcoholic steatohepatitis (NASH). Recent research has established that pro-inflammatory immune cells infiltrate obese hypertrophic adipose tissue and liver. Given the emerging importance of immune cells in the context of metabolic homeostasis, there is a critical need to quantify and characterize their modification during the development of type 2 diabetes and NASH. However, animal models that induce pathophysiological features typical of human NASH are sparse.
In this article, we provide a detailed protocol to identify immune cell subsets isolated from liver and adipose tissue in a reliable mouse model of NASH, established by housing high-fat diet (HFD) mice under non-specific pathogen-free (SPF) conditions without a barrier for at least seven weeks. We demonstrate the handling of mice in non-SPF conditions, digestion of the tissues and identification of macrophages, natural killer (NK) cells, dendritic cells, B and T cell subsets by flow cytometry. Representative flow cytometry plots from SPF HFD mice and non-SPF mice are provided. To obtain reliable and interpretable data, the use of antibodies, accurate and precise methods for tissue digestion and proper gating in flow cytometry experiments are critical elements.
The intervention to restore physiological antigen exposure in mice by housing them in non-SPF conditions and unspecific exposure to microbial antigens could provide a relevant tool for investigating the link between immunological alterations, diet-induced obesity and related long term complications.

A simple and reliable diet-induced rodent animal model for nonalcoholic steatohepatitis (NASH) is described, achieved through non-SPF housing of the animals and administration of a specific high-fat diet. We describe identification of hepatic and adipose immune cell subsets to recapitulate human immunological conditions by exposing mice to environmental germs.

Obesity is associated with chronic low-grade inflammation and insulin resistance, contributing to an increasing prevalence of chronic metabolic diseases, ...

Three-Dimensional Collagen Matrix Scaffold Implantation as a Liver Regeneration Strategy

Liver diseases are the leading cause of death worldwide. Excessive alcohol consumption, a high-fat diet, and hepatitis C virus infection promote fibrosis, cirrhosis, and/or hepatocellular carcinoma. Liver transplantation is the clinically recommended procedure to improve and extend the life span of patients in advanced disease stages. However, only 10% of transplants are successful, with organ availability, presurgical and postsurgical procedures, and elevated costs directly correlated with that result. Extracellular matrix (ECM) scaffolds have emerged as an alternative for tissue restoration. Biocompatibility and graft acceptance are the main beneficial characteristics of those biomaterials. Although the capacity to restore the size and correct function of the liver has been evaluated in liver hepatectomy models, the use of scaffolds or some kind of support to replace the volume of the extirpated liver mass has not been assessed.
Partial hepatectomy was performed in a rat liver with the xenoimplantation of a collagen matrix scaffold (CMS) from a bovine condyle. Left liver lobe tissue was removed (approximately 40%), and an equal proportion of CMS was surgically implanted. Liver function tests were evaluated before and after the surgical procedure. After days 3, 14, and 21, the animals were euthanized, and macroscopic and histologic evaluations were performed. On days 3 and 14, adipose tissue was observed surrounding the CMS, with no clinical evidence of rejection or infection, as was vessel neoformation and CMS reabsorption at day 21. There was histologic evidence of an insignificant inflammation process and migration of adjacent cells to the CMS, observed with the hematoxylin and eosin (H&#38;E) and Masson&#39;s trichrome staining. The CMS was shown to perform well in liver tissue and could be a useful alternative for studying tissue regeneration and repair in chronic liver diseases.

Liver diseases are induced by many causes that promote fibrosis or cirrhosis. Transplantation is the only option for recovering health. However, given the scarcity of transplantable organs, alternatives must be explored. Our research proposes the implantation of collagen scaffolds in liver tissue from an animal model.

Liver diseases are the leading cause of death worldwide. Excessive alcohol consumption, a high-fat diet, and hepatitis C virus infection promote fibrosis, ...

Quantitative Analysis of Liver Stiffness Distribution

A Three-Dimensional Digital Model for Early Diagnosis of Hepatic Fibrosis Based on Magnetic Resonance Elastography

Hepatic fibrosis is an early stage of liver cirrhosis, and there are no better non-invasive and convenient methods for the detection and evaluation of the disease. Despite the good progress made with the liver stiffness map (LSM) based on magnetic resonance elastography (MRE), there are still some limitations that need to be overcome, including manual focus determination, manual selection of regions of interest (ROIs), and discontinuous LSM data without structural information, which makes it impossible to evaluate the liver as a whole. In this study, we propose a novel three-dimensional (3D) digital model for the early diagnosis of hepatic fibrosis based on MRE.
MRE is a non-invasive imaging technique that employs magnetic resonance imaging (MRI) to measure the liver stiffness at the scanning site through human-computer interaction. Studies have indicated a significant positive correlation between the LSM obtained through MRE and the degree of hepatic fibrosis. However, for clinical purposes, a comprehensive and precise quantification of the degree of hepatic fibrosis is necessary. To address this, the concept of Liver Stiffness Distribution (LSD) was proposed in this study, which refers to the 3D stiffness volume of each liver voxel obtained by the alignment of 3D liver tissue images and MRE indicators. This provides a more effective clinical tool for the diagnosis and treatment of hepatic fibrosis.

Author Spotlight: Advancing Hepatic Fibrosis Diagnosis Using Magnetic Resonance Elastography and AI 

The objective of this study was to develop a novel three-dimensional digital model for the early diagnosis of hepatic fibrosis, which includes the stiffness of each voxel in the patient's liver and can thus, be used to calculate the distribution ratio of the patient's liver at different fibrosis stages.

Hepatic fibrosis is an early stage of liver cirrhosis, and there are no better non-invasive and convenient methods for the detection and evaluation of the ...

Isolation and 3D Collagen Sandwich Culture of Primary Mouse Hepatocytes to Study the Role of Cytoskeleton in Bile Canalicular Formation In Vitro

Hepatocytes are the central cells of the liver responsible for its metabolic function. As such, they form a uniquely polarized epithelium, in which two or more hepatocytes contribute apical membranes to form a bile canalicular network through which bile is secreted. Hepatocyte polarization is essential for correct canalicular formation and depends on interactions between the hepatocyte cytoskeleton, cell-cell contacts, and the extracellular matrix. In vitro studies of hepatocyte cytoskeleton involvement in canaliculi formation and its response to pathological situations are handicapped by the lack of cell culture, which would closely resemble the canaliculi network structure in vivo. Described here is a protocol for the isolation of mouse hepatocytes from the adult mouse liver using a modified collagenase perfusion technique. Also described is the production of culture in a 3D collagen sandwich setting, which is used for immunolabeling of cytoskeletal components to study bile canalicular formation and its response to treatments in vitro. It is shown that hepatocyte 3D collagen sandwich cultures respond to treatments with toxins (ethanol) or actin cytoskeleton altering drugs (e.g., blebbistatin) and serve as a valuable tool for in vitro studies of bile canaliculi formation and function.

Presented here is a protocol for the isolation of mouse hepatocytes from adult mouse livers using a modified collagenase perfusion technique. Also described is the long-term culture of hepatocytes in a 3D collagen sandwich setting as well as immunolabeling of the cytoskeletal components to study bile canalicular formation and its response to treatment.

Hepatocytes are the central cells of the liver responsible for its metabolic function. As such, they form a uniquely polarized epithelium, in which two or ...

Biology

Application of Ultrasound and Shear Wave Elastography Imaging in a Rat Model of NAFLD/NASH

Nonalcoholic Steatohepatitis (NASH) is a condition within the spectrum of Non-Alcoholic Fatty Liver Disease (NAFLD), which is characterized by liver fat accumulation (steatosis) and inflammation leading to fibrosis. Preclinical models closely recapitulating human NASH/NAFLD are essential in drug development. While liver biopsy is currently the gold standard for measuring NAFLD/NASH progression and diagnosis in the clinic, in the preclinical space, either collection of whole liver samples at multiple timepoints during a study or biopsy of liver is needed for histological analysis to assess the disease stage.
Conducting a liver biopsy mid-study is an invasive and labor-intensive procedure, and collecting liver samples to assess disease level increases the number of research animals needed for a study. Thus, there is a need for a reliable, translatable, non-invasive imaging biomarker to detect NASH/NAFLD in these preclinical models. Non-invasive ultrasound-based B-mode images and Shear Wave Elastography (SWE) can be used to measure steatosis as well as liver fibrosis. To assess the utility of SWE in preclinical rodent models of NASH, animals were placed on a pro-NASH diet&#160;and underwent non-invasive ultrasound B-mode and shear wave elastography imaging to measure hepatorenal (HR) index and liver elasticity, measuring progression of both liver fat accumulation and tissue stiffness, respectively, at multiple time points over the course of a given NAFLD/NASH study.
The HR index and elasticity numbers were compared to histological markers of steatosis and fibrosis. The results showed strong correlation between the HR index and percentage of Oil Red O (ORO) staining, as well as between elasticity and Picro-Sirius Red (PSR) staining of livers. The strong correlation between classic ex vivo methods and in vivo imaging results provides evidence that shear wave elastography/ultrasound-based imaging can be used to assess disease phenotype and progression in a preclinical model of NAFLD/NASH.

This protocol describes the use of an enhanced ultrasound technique to non-invasively observe and quantify liver tissue changes in rodent models of nonalcoholic fatty liver disease.

Nonalcoholic Steatohepatitis (NASH) is a condition within the spectrum of Non-Alcoholic Fatty Liver Disease (NAFLD), which is characterized by liver fat ...

Isolation and Characterization of Mouse Primary Liver Sinusoidal Endothelial Cells

Liver sinusoidal endothelial cells (LSECs) are specialized endothelial cells located at the interface between the circulation and the liver parenchyma. LSECs have a distinct morphology characterized by the presence of fenestrae and the absence of basement membrane. LSECs play essential roles in many pathological disorders in the liver, including metabolic dysregulation, inflammation, fibrosis, angiogenesis, and carcinogenesis. However, little has been published about the isolation and characterization of the LSECs. Here, this protocol discusses the isolation of LSEC from both healthy and nonalcoholic fatty liver disease (NAFLD) mice. The protocol is based on collagenase perfusion of the mouse liver and magnetic beads positive selection of nonparenchymal cells to purify LSECs. This study characterizes LSECs using specific markers by flow cytometry and identifies the characteristic phenotypic features by scanning electron microscopy. LSECs isolated following this protocol can be used for functional studies, including adhesion and permeability assays, as well as downstream studies for a particular pathway of interest. In addition, these LSECs can be pooled or used individually, allowing multi-omics data generation including RNA-seq bulk or single cell, proteomic or phospho-proteomics, and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq), among others. This protocol will be useful for investigators studying LSECs&#39; communication with other liver cells in health and disease and allow an in-depth understanding of the role of LSECs in the pathogenic mechanisms of acute and chronic liver injury.

Here we outline and demonstrate a protocol for primary mouse liver sinusoidal endothelial cell (LSEC) isolation. The protocol is based on liver collagenase perfusion, nonparenchymal cell purification by low-speed centrifugation, and CD146 magnetic bead selection. We also phenotype and characterize these isolated LSECs using flow cytometry and scanning electron microscopy.

Liver sinusoidal endothelial cells (LSECs) are specialized endothelial cells located at the interface between the circulation and the liver parenchyma. ...

Novel In Vivo Micro-Computed Tomography Imaging Techniques for Assessing the Progression of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a growing global health issue, and the impact of NAFLD is compounded by the current lack of effective treatments. Considerable limiting factors hindering the timely and accurate diagnosis (including grading) and monitoring of NAFLD, as well as the development of potential therapies, are the current inadequacies in the characterization of the hepatic microenvironment structure and the scoring of the disease stage in a spatiotemporal and non-invasive manner. Using a diet-induced NAFLD mouse model, we investigated the use of in vivo micro-computed tomography (CT) imaging techniques as a non-invasive method to assess the progression stages of NAFLD, focusing predominantly on the hepatic vascular network due to its significant involvement in NAFLD-related hepatic dysregulation. This imaging methodology allows for longitudinal analysis of liver steatosis and functional tissue uptake, as well as the evaluation of the relative blood volume, portal vein diameter, and density of the vascular network. Understanding the adaptations of the hepatic vascular network during NAFLD progression and correlating this with other ways of characterizing the disease progression (steatosis, inflammation, fibrosis) using the proposed method can pave the way toward the establishment of new, more efficient, and reproducible approaches for NAFLD research in mice. This protocol is also expected to upgrade the value of preclinical animal models for investigating&#160;the development of novel therapies against disease progression.

Novel In Vivo Micro-Computed Tomography Imaging Techniques for Assessing the Progression of Non-Alcoholic Fatty Liver Disease

Using a diet-induced non-alcoholic fatty liver disease (NAFLD) mouse model, we describe the use of novel in vivo micro-computed tomography imaging techniques as a non-invasive method to assess the progression stages of NAFLD, focusing predominantly on the hepatic vascular network due to its significant involvement in NAFLD-related hepatic dysregulation.

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

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