Name: an ex vivo tissue culture model for fibrovascular complications in proliferative diabetic retinopathy
Uploaded: 2019-01-25T15:00:00
Description: Watch this Scientific Journal Video about An Ex Vivo Tissue Culture Model for Fibrovascular Complications in Proliferative Diabetic Retinopathy at JoVE.com

The authors are most grateful to the medical and surgical retina colleagues, nurses and whole staff of the Diabetic Unit and Vitreoretinal Surgery Unit at the Department of Ophthalmology, Helsinki University Hospital for actively participating in the recruitment of patients. We thank Biomedicum Molecular Imaging Unit for imaging facilities. We thank Anastasiya Chernenko for excellent technical assistance. This study was supported by grants from the Academy of Finland (KL), University of Helsinki (KL), Sigrid Juselius Foundation (KL), K. Albin Johansson Foundation (KL), Finnish Cancer Institute (KL), Karolinska Institutet (KL), Finnish Eye Foundation (SL), Eye and Tissue Bank Foundation (SL), Mary and Georg C. Ehrnrooth Foundation (SL), and HUCH Clinical Research Grants (TYH2018127 after TYH2016230, SL), Diabetes Research Foundation (SL, KL, AK, EG) as well as the Doctoral Programme in Biomedicine (EG).

This research was approved by the Institutional Review Board and Ethical committee of Helsinki University Hospital. Signed informed consent was obtained from each patient.
1. Preparation of Solutions, Media and Equipment
<ol>
	<li>Prepare the following equipment prior to collection of the fibrovascular tissue (FT) to ensure rapid processing.
	<ol>
		<li>Sterile-autoclave two microdissection tweezers.</li>
		<li>Prepare 1x phosphate-buffered saline (PBS) by dissolving 1 pre-weighed PBS tablet...

<ol>
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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mini+Review:+Changes+in+the+Incidence+of+and+Progression+to+Proliferative+and+Sight-Threatening+Diabetic+Retinopathy+Over+the+Last+30+Years.">Mini Review: Changes in the Incidence of and Progression to Proliferative and Sight-Threatening Diabetic Retinopathy Over the Last 30 Years.</a> Ophthalmic Epidemiology. 24 (2), 73-80 (2017).</li><li>Loukovaara, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Indications+of+lymphatic+endothelial+differentiation+and+endothelial+progenitor+cell+activation+in+the+pathology+of+proliferative+diabetic+retinopathy.">Indications of lymphatic endothelial differentiation and endothelial progenitor cell activation in the pathology of proliferative diabetic retinopathy.</a> Acta Ophthalmologica. 93 (6), 512-523 (2015).</li><li>Stitt, A. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+progress+in+understanding+and+treatment+of+diabetic+retinopathy.">The progress in understanding and treatment of diabetic retinopathy.</a> Progress in Retinal and Eye Research. 51, 156-186 (2016).</li><li>Duh, E. J., Sun, J. K., Stitt, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diabetic+retinopathy:+current+understanding,+mechanisms,+and+treatment+strategies.">Diabetic retinopathy: current understanding, mechanisms, and treatment strategies.</a> JCI Insight. 2 (14), (2017).</li><li>Gross, J. 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S., Montesano, R., Mandriota, S. J., Orci, L., Vassalli, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Angiogenesis:+a+paradigm+for+balanced+extracellular+proteolysis+during+cell+migration+and+morphogenesis.">Angiogenesis: a paradigm for balanced extracellular proteolysis during cell migration and morphogenesis.</a> Enzyme, Protein. 49 (1-3), 138-162 (1996).</li><li>Lafleur, M. A., Handsley, M. M., Knauper, V., Murphy, G., Edwards, D. 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M., Struyf, S., Opdenakker, G., Van Damme, J., Geboes, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+stem+cell+factor/c-kit+signaling+pathway+components+in+diabetic+fibrovascular+epiretinal+membranes.">Expression of stem cell factor/c-kit signaling pathway components in diabetic fibrovascular epiretinal membranes.</a> Molecular Vision. 16, 1098-1107 (2010).</li><li>Loukovaara, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ang-2+upregulation+correlates+with+increased+levels+of+MMP-9,+VEGF,+EPO+and+TGFbeta1+in+diabetic+eyes+undergoing+vitrectomy.">Ang-2 upregulation correlates with increased levels of MMP-9, VEGF, EPO and TGFbeta1 in diabetic eyes undergoing vitrectomy.</a> Acta Ophthalmologica. 91 (6), 531-539 (2013).</li><li>Sugiyama, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EphA2+cleavage+by+MT1-MMP+triggers+single+cancer+cell+invasion+via+homotypic+cell+repulsion.">EphA2 cleavage by MT1-MMP triggers single cancer cell invasion via homotypic cell repulsion.</a> Journal of Cell Biology. 201 (3), 467-484 (2013).</li><li>Tatti, O., 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=MMP16+Mediates+a+Proteolytic+Switch+to+Promote+Cell-Cell+Adhesion,+Collagen+Alignment,+and+Lymphatic+Invasion+in+Melanoma.">MMP16 Mediates a Proteolytic Switch to Promote Cell-Cell Adhesion, Collagen Alignment, and Lymphatic Invasion in Melanoma.</a> Cancer Research. 75 (10), 2083-2094 (2015).</li><li>Zudaire, E., Gambardella, L., Kurcz, C., Vermeren, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+computational+tool+for+quantitative+analysis+of+vascular+networks.">A computational tool for quantitative analysis of vascular networks.</a> PLoS One. 6 (11), e27385 (2011).</li><li>Senger, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+framework+for+angiogenesis:+a+complex+web+of+interactions+between+extravasated+plasma+proteins+and+endothelial+cell+proteins+induced+by+angiogenic+cytokines.">Molecular framework for angiogenesis: a complex web of interactions between extravasated plasma proteins and endothelial cell proteins induced by angiogenic cytokines.</a> American Journal of Pathology. 149 (1), 1-7 (1996).</li><li>Senger, D. R., Davis, G. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Angiogenesis.">Angiogenesis.</a> Cold Spring Harbor Perspectives in Biology. 3 (8), a005090 (2011).</li><li>Bishop, P. 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Considering the importance of relevant tissue microenvironment for reliable functional cell and molecular mechanistic results, it is imperative to find appropriate experimental models that provide this tissue environment. The herein described ex vivo PDR culture model for the fibrin-embedded FTs allows the investigation of the mechanisms of PDR pathophysiology in the native, complex and multicellular context of the PDR clinical samples.
Critical steps within the protocol are the prope...

DR is a serious ocular complication of diabetes, a disease that has reached enormous proportions in the last three decades1. Twenty years after diagnosis, virtually every patient with type 1 diabetes and 60% of patients with type 2 diabetes present signs of retinopathy, making diabetes per se one of the leading causes of blindness in working age adults2. According to the level of microvascular degeneration and ischemic damage, DR is classified into non-proliferative DR (non-PDR) and proliferative DR (PDR). The end-stage disease, PDR, is characterized by ischemia- and inflammation-induced neovascularization and fibrotic responses at the vitreoretinal interface. In untreated conditions, these processes will lead to blindness due to vitreous hemorrhage, retinal fibrosis, tractional retinal detachment, and neovascular glaucoma3,4. Despite recent advances, current treatment options target only DR stages, including diabetic macular edema and PDR, when retinal damage has already ensued. Moreover, a great proportion of DR patients does not benefit from current treatment armamentarium, indicating an urgent need for improved therapies4,5,6.
Multiple other in vivo disease/developmental models and diabetic animal models have been developed to date, but none of them recapitulates the full range of pathologic features observed in human PDR7,8. Moreover, increasing evidence indicates that treatment responses are tightly connected to the ECM composition as well as the spatial arrangement and interaction between the cellular and acellular microenvironment9. We, therefore, set out to develop a clinically relevant model of human PDR by utilizing the FT pathological material that is commonly excised from eyes undergoing vitrectomy as part of the surgical management of PDR10.
This manuscript describes the protocol for the 3D ex vivo culture and characterization of the surgically-excised, PDR patient-derived pathological FT. The method described here has been used in a recent publication that demonstrated successful deconstruction of the native 3D PDR tissue landscape, and recapitulation of features of PDR pathophysiology including angiogenic and fibrotic responses of the abnormal vascular structures11. This model also revealed novel features that cannot be easily appreciated from thin histological sections, such as spatially confined apoptosis and proliferation as well as vascular islet formation11. Vitreous fluid has been successfully used by others on 3D endothelial spheroid cultures to evaluate its angiogenic potential and the efficacy of angiostatic molecules12. When combined with an in vitro 3D lymphatic endothelial cell (LEC) spheroid sprouting assay using PDR vitreous as stimulant, our model revealed the contribution of both soluble vitreal factors as well as local cues within the neovascular tissue to the as yet poorly understood LEC involvement in PDR pathophysiology3,11. In the management of PDR, vitreoretinal surgery is a routinely performed yet challenging procedure. As surgical instrumentations and techniques are seeing continuous advancement and sophistication, timely and conservative removal of fibrovascular proliferative specimen not only improves vision outcome but also provides invaluable tissue material for the investigation of PDR pathophysiology and treatment responses in the complex translational aspects of the live human tissue microenvironment.

<table>
	<tbody>
		<tr>
			<td>Material</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microforceps</td>
			<td>Medicon</td>
			<td>07.60.03</td>
			<td>Used for handling the FTs</td>
		</tr>
		<tr>
			<td>Disposable Scalpels - Sterile</td>
			<td>Swann-Morton</td>
			<td>0513</td>
			<td>Used for FT dissection</td>
		</tr>
		<tr>
			<td>Culture dish, vented, 28 ml (60mm)</td>
			<td>Greiner Bio-One</td>
			<td>391-3210</td>
			<td>Used for dissection and for testing fibrin gel formation</td>
		</tr>
		<tr>
			<td>Cell culture plates, 12-well</td>
			<td>Greiner Bio-One</td>
			<td>392-0049</td>
			<td>Used for FT dissection and whole-mount immunofluorescence</td>
		</tr>
		<tr>
			<td>Reagent/centrifuge tube with screw cap, 15 mL</td>
			<td>Greiner Bio-One</td>
			<td>391-3477</td>
			<td></td>
		</tr>
		<tr>
			<td>Reagent/centrifuge tube with screw cap, 50 mL</td>
			<td>Greiner Bio-One</td>
			<td>525-0384</td>
			<td></td>
		</tr>
		<tr>
			<td>Millex-GV Syringe Filter Unit, 0.22&#160;&#181;m, PVDF</td>
			<td>Millipore</td>
			<td>SLGV033RS</td>
			<td>Used to sterile-filter the fibrinogen solution</td>
		</tr>
		<tr>
			<td>Syringe, 10 mL</td>
			<td>Braun</td>
			<td>4606108V</td>
			<td>Used to sterile-filter the fibrinogen solution</td>
		</tr>
		<tr>
			<td>Polypropylene Microcentrifuge Tubes, 1.5 mL</td>
			<td>Fisher</td>
			<td>FB74031</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell-Culture Treated Multidishes, 24-well</td>
			<td>Nunc</td>
			<td>142475</td>
			<td>Used for casting the FT/fibrin gels for native FT characterization and ex vivo culture</td>
		</tr>
		<tr>
			<td>Cell culture plates, 96-well, U-bottom</td>
			<td>Greiner Bio-One</td>
			<td>392-0019</td>
			<td>Used for whole-mount immunofluorescence</td>
		</tr>
		<tr>
			<td>Round/Flat Spatulas, Stainless Steel</td>
			<td>VWR</td>
			<td>82027-528</td>
			<td>Used for whole-mount immunofluorescence</td>
		</tr>
		<tr>
			<td>Coverslips 22x22mm #1</td>
			<td>Menzel/Fisher</td>
			<td>15727582</td>
			<td>Used for mounting</td>
		</tr>
		<tr>
			<td>Microscope slides</td>
			<td>Fisher</td>
			<td>Kindler K102</td>
			<td>Used for mounting</td>
		</tr>
		<tr>
			<td>Absorbent paper</td>
			<td>VWR</td>
			<td>115-0202</td>
			<td>Used for mounting</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS tablets</td>
			<td>Medicago</td>
			<td>09-9400-100</td>
			<td>Used for preparing 1x PBS</td>
		</tr>
		<tr>
			<td>Fibrinogen, Plasminogen-Depleted, Human Plasma</td>
			<td>Calbiochem</td>
			<td>341578</td>
			<td></td>
		</tr>
		<tr>
			<td>Hanks Balanced Salt Solution</td>
			<td>Sigma-Aldrich</td>
			<td>H9394-500ML</td>
			<td>Used for preparing the fibrinogen and TA solution</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Gibco</td>
			<td>10270106</td>
			<td>Used for preparing the blocking solution</td>
		</tr>
		<tr>
			<td>Human Serum</td>
			<td>Sigma-Aldrich</td>
			<td>H4522</td>
			<td>Aliquoted in -20 &#176;C, thaw before preparing the ex vivo culture media</td>
		</tr>
		<tr>
			<td>Gentamicin Sulfate 10mg/ml</td>
			<td>Biowest</td>
			<td>L0011-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Endothelial cell media MV Kit</td>
			<td>Promocell</td>
			<td>C-22120</td>
			<td>Contains 500 ml of Endothelial Cell Growth Medium MV, 25 mL of fetal calf serum, 2 mL of endothelial cell growth supplement,&#160; 500 &#956;L of recombinant human epidermal growth factor (10 &#956;g/ mL) and 500 &#956;L of hydrocortisone (1 g/ mL)</td>
		</tr>
		<tr>
			<td>Sodium azide</td>
			<td>Sigma-Aldrich</td>
			<td>S2002</td>
			<td>Used for storage of the native and ex vivo cultured FTs. TOXIC: wear protective gloves and/or clothing, and eye and/or face protection. Use in fume hood.</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Sigma-Aldrich</td>
			<td>32201-2.5L-M</td>
			<td>Used to prepare the post-fixation solution. HARMFUL: wear protective gloves and/or clothing. Use in fume hood.</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma-Aldrich</td>
			<td>32213</td>
			<td>Used to prepare the post-fixation solution. TOXIC: wear protective gloves and/or clothing. Use in fume hood.</td>
		</tr>
		<tr>
			<td>Triton X-100 (octyl phenol ethoxylate)</td>
			<td>Sigma-Aldrich</td>
			<td>T9284</td>
			<td>Used for whole-mount immunofluorescence. HARMFUL: wear protective gloves and/or clothing.</td>
		</tr>
		<tr>
			<td>Hoechst 33342, 20mM</td>
			<td>Life Technologies</td>
			<td>62249</td>
			<td>For nuclei counterstaining. HARMFUL: wear protective gloves and/or clothing, and eye and/or face protection.</td>
		</tr>
		<tr>
			<td>VECTASHIELD Antifade Mounting Medium</td>
			<td>Vector Laboratories</td>
			<td>H-1000</td>
			<td>Wear protective gloves and/or clothing, and eye protection. Use in fume hood.</td>
		</tr>
		<tr>
			<td>VECTASHIELD Antifade Mounting Medium with DAPI</td>
			<td>Vector Laboratories</td>
			<td>H-1200</td>
			<td>Mounting medium with nuclei counterstaining. Wear protective gloves and/or clothing, and eye protection. Use in fume hood.</td>
		</tr>
		<tr>
			<td>Eukitt Quick-hardening mounting medium</td>
			<td>Sigma-Aldrich</td>
			<td>03989-100ml</td>
			<td>TOXIC: Wear protective gloves and/or clothing, and eye protection. Use in fume hood.</td>
		</tr>
		<tr>
			<td>Thrombin from bovine plasma, lyophilized powder</td>
			<td>Sigma-Aldrich</td>
			<td>T9549-500UN&#160;</td>
			<td>Dissolve at 100 units/ mL, aliquote and store at -20 &#176;C, avoid repeated freeze/ thaw</td>
		</tr>
		<tr>
			<td>Aprotinin from bovine lung, lyophilized powder</td>
			<td>Sigma</td>
			<td>A3428</td>
			<td>Dissolve at 50 mg/ mL, aliquote and store at -20 &#176;C, avoid repeated freeze/ thaw</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Growth factors</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant human VEGFA</td>
			<td>R&#38;D Systems</td>
			<td>293-VE-010</td>
			<td>50 ng/ mL final concentration</td>
		</tr>
		<tr>
			<td>Recombinant human VEGFC</td>
			<td>R&#38;D Systems</td>
			<td>752-VC-025</td>
			<td>200 ng/ mL final concentration</td>
		</tr>
		<tr>
			<td>Recombinant human TGF&#946;</td>
			<td>Millipore</td>
			<td>GF346</td>
			<td>1 ng/ mL final concentration</td>
		</tr>
		<tr>
			<td>Recombinant human bFGF</td>
			<td>Millipore</td>
			<td>01-106</td>
			<td>50 ng/ mL final concentration</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Primary antibodies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CD31 (JC70A)</td>
			<td>Dako</td>
			<td>M0823</td>
			<td>Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab</td>
		</tr>
		<tr>
			<td>CD34 (QBEND10)</td>
			<td>Dako</td>
			<td>M716501-2</td>
			<td>Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab</td>
		</tr>
		<tr>
			<td>CD45 (2B11+PD7/26)</td>
			<td>Dako</td>
			<td>M070129-2</td>
			<td>Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab</td>
		</tr>
		<tr>
			<td>CD68</td>
			<td>ImmunoWay</td>
			<td>RLM3161</td>
			<td>Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab</td>
		</tr>
		<tr>
			<td>Cleaved caspase-3 (5A1E)</td>
			<td>Cell Signalling</td>
			<td>9664</td>
			<td>Used at 1:200 dilution, Goat anti Rabbit Alexa 594 Secondary Ab</td>
		</tr>
		<tr>
			<td>ERG (EP111)</td>
			<td>Dako</td>
			<td>M731429-2</td>
			<td>Used at 1:100 dilution, Goat anti Rabbit Alexa 594 Secondary Ab</td>
		</tr>
		<tr>
			<td>GFAP</td>
			<td>Dako</td>
			<td>Z0334</td>
			<td>Used at 1:100 dilution, Goat anti Rabbit Alexa 594 Secondary Ab</td>
		</tr>
		<tr>
			<td>Ki67</td>
			<td>Leica Microsystems</td>
			<td>NCL-Ki67p</td>
			<td>Used at 1:1500 dilution, Goat anti Rabbit Alexa 594 Secondary Ab</td>
		</tr>
		<tr>
			<td>Lyve1</td>
			<td>R&#38;D Systems</td>
			<td>AF2089</td>
			<td>Used at 1:100 dilution, Donkey anti Goat Alexa 568 Secondary Ab</td>
		</tr>
		<tr>
			<td>NG2</td>
			<td>Millipore</td>
			<td>AB5320</td>
			<td>Used at 1:100 dilution, Goat anti Rabbit Alexa 594 Secondary Ab</td>
		</tr>
		<tr>
			<td>Prox1</td>
			<td>ReliaTech</td>
			<td>102-PA32</td>
			<td>Used at 1:200 dilution, Goat anti Rabbit Alexa 568 Secondary Ab</td>
		</tr>
		<tr>
			<td>Prox1</td>
			<td>R&#38;D Systems</td>
			<td>AF2727</td>
			<td>Used at 1:40 dilution, Chicken anti Goat Alexa 594 Secondary Ab</td>
		</tr>
		<tr>
			<td>VEGFR3 (9D9F9)</td>
			<td>Millipore</td>
			<td>MAB3757</td>
			<td>Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab</td>
		</tr>
		<tr>
			<td>&#945;-SMA (1A4)</td>
			<td>Sigma</td>
			<td>C6198</td>
			<td>Used at 1:400 dilution, Cy3 conjugated</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Secondary antibodies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor488 Donkey Anti-Mouse IgG</td>
			<td>Life Technologies</td>
			<td>A-21202</td>
			<td>Used at 1:500 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor594 Goat Anti-Rabbit IgG</td>
			<td>Invitrogen</td>
			<td>A-11012</td>
			<td>Used at 1:500 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor568 Donkey anti-Goat IgG</td>
			<td>Thermo Scientific</td>
			<td>A-11057</td>
			<td>Used at 1:500 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor568 Goat anti-Rabbit IgG</td>
			<td>Thermo Scientific</td>
			<td>A-11036</td>
			<td>Used at 1:500 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor594 Chicken Anti-Goat IgG</td>
			<td>Molecular Probes</td>
			<td>A-21468</td>
			<td>Used at 1:500 dilution</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Microscopes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Axiovert 200 inverted epifluorescence microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>For imaging of the fresh and fibrin-embedded FT</td>
		</tr>
		<tr>
			<td>SZX9 upright dissection stereomicroscope</td>
			<td>Olympus</td>
			<td></td>
			<td>For FT dissection</td>
		</tr>
		<tr>
			<td>LSM 780 confocal microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>For imaging of whole-mount immunostained FT</td>
		</tr>
		<tr>
			<td>AxioImager.Z1 upright epifluorescence microscope with Apotome</td>
			<td>Zeiss</td>
			<td></td>
			<td>For imaging of whole-mount immunostained FT</td>
		</tr>
	</tbody>
</table>

an ex vivo tissue culture model for fibrovascular complications in proliferative diabetic retinopathy

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of blindness in working-age adults. No current animal models of diabetes and oxygen-induced retinopathy develop the full-range progressive changes manifested in human proliferative diabetic retinopathy (PDR). Therefore, understanding of the disease pathogenesis and pathophysiology has relied largely on the use of histological sections and vitreous samples in approaches that only provide steady-state information on the involved pathogenic factors. Increasing evidence indicates that dynamic cell-cell and cell-extracellular matrix (ECM) interactions in the context of three-dimensional (3D) microenvironments are essential for the mechanistic and functional studies towards the development of new treatment strategies. Therefore, we hypothesized that the pathological fibrovascular tissue surgically excised from eyes with PDR could be utilized to reliably unravel the cellular and molecular mechanisms of this devastating disease and to test the potential for novel clinical interventions. Towards this end, we developed a novel method for 3D ex vivo culture of surgically-excised patient-derived fibrovascular tissue (FT), which will serve as a relevant model of human PDR pathophysiology. The FTs are dissected into explants and embedded in fibrin matrix for ex vivo culture and 3D characterization. Whole-mount immunofluorescence of the native FTs and end-point cultures allows thorough investigation of tissue composition and multicellular processes, highlighting the importance of 3D tissue-level characterization for uncovering relevant features of PDR pathophysiology. This model will allow the simultaneous assessment of molecular mechanisms, cellular/tissue processes and treatment responses in the complex context of dynamic biochemical and physical interactions within the PDR tissue architecture and microenvironment. Since this model recapitulates PDR pathophysiology, it will also be amenable for testing or developing new treatments.

Deeper understanding of the PDR fibrovascular tissue properties and protein expression has relied mainly on vitreous samples and thin histological FT sections3,15,16,17. To develop a method for thorough investigation of the 3D tissue organization and multicellular physiopathological processes of PDR, we set out to utilize the surgically excised, patient-derived ...

Watch this Scientific Journal Video about An Ex Vivo Tissue Culture Model for Fibrovascular Complications in Proliferative Diabetic Retinopathy at JoVE.com

An Ex Vivo Tissue Culture Model for Fibrovascular Complications in Proliferative Diabetic Retinopathy

Here, we present a protocol to study the pathophysiology of proliferative diabetic retinopathy by using patient-derived, surgically-excised, fibrovascular tissues for three-dimensional native tissue characterization and ex vivo culture. This ex vivo culture model is also amenable for testing or developing new treatments.

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of blindness in working-age adults. No ...

Diabetic retinopathy is the most common microvascular complication of diabetes.This method can help answer key questions on the pathophysiology of the end stage disease proliferative diabetic retinopathy.This technique allows the deconstruction of the native three dimensional tissue landscape and the investigation of tissue pathophysiology in live patient material with direct clinical relevance.Refer to the text protocol for details on the surgery and the instrumentation utilized in the dissection.To begin, place fibrovascular tissue that has been excised from human subjects undergoing transconjunctival microincision vitreoretinal surgery in a cell culture dish containing sterile PBS.Using an upright dissection stereo microscope, cut the fibrovascular tissue into approximately one square millimeter pieces.Submerge the tissue in PBS and hold the tissue in place with micro dissection tweezers.Make clear cuts in the tissue with a sterile scalpel taking care to avoid tearing the fibrovascular tissue.Place each individual piece of tissue into a well of a 12 well cell culture plate containing one milliliter of sterile PBS.First, prepare 25 microliter aliquots of fibrinogen solution at room temperature.Place one piece of fibrovascular tissue at the center of the well of a 24 well plate and remove any excess PBS.Next, add 25 microliters of TA solution to one of the prepared fibrinogen aliquots.And using another pipette set to 50 microliters mix by pipetting.Dispense the mixture onto the piece of fibrovascular tissue and pipette up and down to insure the tissue piece is contained within the droplet.The time of fibrinogen formation critical for the three dimensionality of the ex vivo culture, is tested in an empty droplet prior tissue embedding as described in the protocol.Incubate the plate in a cell culture incubator.After 30 to 60 minutes tilt the plate to check that the fibrin gel is completely formed.Next, overlay the fibrovascular tissue fibrin gels with ex vivo culture medium supplemented with aprotinin.After this, return the culture plates to the cell culture incubator for the desired time period.First, replace the ex vivo culture medium with one milliliter of paraformaldehyde solution per well to fix the cultures.After one hour, rinse the gels with three five-minute PBS washes.Next, replace the PBS wash with two milliliters of sodium azide solution per well.Store the fixed gels at four degrees Celsius.Use a stainless steel squared edge spatula to lift the droplets from the plate carefully, starting at the edges before lifting the center of the droplet.Using a round edged spatula transfer the droplets to individual wells of a 12 well plate containing one milliliter of PBS.After this, tilt the plate on a support and postfix the droplets with one milliliter of ice-cold acetone methanol solution for one minute.Then, rinse with three to five two milliliter washes of PBS.Centrifuge the blocking solution for 15 minutes to remove any debris.Then, tilt the plate on a support and incubate the droplets in 500 microliters of blocking solution for two hours at room temperature.Prepare the primary antibody mixture according to the text protocol.Then use a round edged spatula to transfer the droplets to a round bottom 96 well plate.Incubate the droplets in 30 microliters of primary antibody mixture per droplet overnight at four degrees celsius.The next day, transfer the droplets to a 12 well plate containing two milliliters of washing solution per well.Rinse the droplets with three five-minute washes.Then, wash the droplets with nine 30-minute washes.The following day, rinse the droplets three times with PBS.Prepare the appropriate fluorophore-conjugated secondary antibody mixture according to the text protocol.Transfer the droplets to a round bottom 96 well plate, as previously demonstrated, and incubate the plate with 30 microliters of secondary antibody mixture for four hours at room temperature, protected from light.After four hours, transfer the droplets to a 12 well plate containing two milliliters of washing solution per well.First, rinse the droplets with three five-minute washes.Then, wash the droplets with four 30-minute washes.The next day, rinse the droplets five times with washing solution for 30 minutes, and three times with PBS for 30 minutes.The next day, transfer the droplets to a round bottom 96 well plate, as previously demonstrated.Counterstain the droplets with Hoechst nuclear stain for 30 minutes at room temperature.Transfer the droplets to a 12 well plate containing two milliliters of PBS per well and rinse three times with PBS.Next, apply a narrow layer of quick hardening mounting medium along the edges of a square cover glass and allow it to dry for one minute.Then, rinse the droplet by dipping it into a well of a 12 well plate containing deionized water.And transfer the droplet to a microscope slide.Next, dispense 15 microliters of non-hardening anti-fade mounting medium onto the droplet.Gently position the cover glass over the droplet with the mounting medium facing the slide and let it settle.Let the slides dry for two hours at room temperature and store them at four degrees Celsius overnight.Finally, image the slides with an upright epifluorescence microscope equipped with an optical sectioning function at 20x or 40x objective.In this protocol fibrovascular tissue was prepared and imaged.The representative data showed that PDR ex vivo cultures induce the sprouting of CD-31 positive endothelium and vasculature preservation in response to VEGFA.Conversely, TGF

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Ex Vivo Culture of Patient Tissue &amp; Examination of Gene Delivery

This video describes the use of patient tissue as an ex vivo model for the study of gene delivery. Fresh patient tissue obtained at the time of surgery is sliced and maintained in culture. The ex vivo model system allows for the physical delivery of genes into intact patient tissue and gene expression is analysed by bioluminescence imaging using the IVIS detection system. The bioluminescent detection system demonstrates rapid and accurate quantification of gene expression within individual slices without the need for tissue sacrifice. This slice tissue culture system may be used in a variety of tissue types including normal and malignant tissue and allows us to study the effects of the heterogeneous nature of intact tissue and the high degree of variability between individual patients. This model system could be used in certain situations as an alternative to animal models and as a complementary preclinical mode prior to entering clinical trial.

Ex Vivo Culture of Patient Tissue &amp; Examination of Gene Delivery

This article describes the culture of patient tissue slices for gene delivery studies and subsequent analysis of gene expression using IVIS bioluminescence imaging.

This video describes the use of patient tissue as an ex vivo model for the study of gene delivery.  Fresh patient tissue obtained at the time of surgery ...

Ex Vivo Infection of Live Tissue with Oncolytic Viruses

Oncolytic Viruses (OVs) are novel therapeutics that selectively replicate in and kill tumor cells1. Several clinical trials evaluating the effectiveness of a variety of oncolytic platforms including HSV, Reovirus, and Vaccinia OVs as treatment for cancer are currently underway2-5. One key characteristic of oncolytic viruses is that they can be genetically modified to express reporter transgenes which makes it possible to visualize the infection of tissues by microscopy or bio-luminescence imaging6,7. This offers a unique advantage since it is possible to infect tissues from patients ex vivo prior to therapy in order to ascertain the likelihood of successful oncolytic virotherapy8. To this end, it is critical to appropriately sample tissue to compensate for tissue heterogeneity and assess tissue viability, particularly prior to infection9. It is also important to follow viral replication using reporter transgenes if expressed by the oncolytic platform as well as by direct titration of tissues following homogenization in order to discriminate between abortive and productive infection. The object of this protocol is to address these issues and herein describes 1. The sampling and preparation of tumor tissue for cell culture 2. The assessment of tissue viability using the metabolic dye alamar blue 3. Ex vivo infection of cultured tissues with vaccinia virus expressing either GFP or firefly luciferase 4. Detection of transgene expression by fluorescence microscopy or using an In Vivo Imaging System (IVIS) 5. Quantification of virus by plaque assay. This comprehensive method presents several advantages including ease of tissue processing, compensation for tissue heterogeneity, control of tissue viability, and discrimination between abortive infection and bone fide viral replication.

Ex Vivo Infection of Live Tissue with Oncolytic Viruses

Oncolytic viruses are promising for cancer therapeutics. The ability to ascertain the infectability of live tissue specimens obtained from patients prior to treatment is a unique advantage of this therapeutic approach. This protocol describes how to process tissues for ex vivo infection with oncolytic virus and subsequent viral quantification.

Oncolytic Viruses (OVs) are novel therapeutics that selectively replicate in and kill tumor cells1. Several clinical trials evaluating the effectiveness ...

An Ex vivo Model to Study Hormone Action in the Human Breast

The study of hormone action in the human breast has been hampered by lack of adequate model systems. Upon in vitro culture, primary mammary epithelial cells tend to lose hormone receptor expression. Widely used hormone receptor positive breast cancer cell lines are of limited relevance to the in vivo situation. Here, we describe an ex vivo model to study hormone action in the human breast. Fresh human breast tissue specimens from surgical discard material such as reduction mammoplasties or mammectomies are mechanically and enzymatically digested to obtain tissue fragments containing ducts and lobules and multiple stromal cell types. These tissue microstructures kept in basal medium without growth factors preserve their intercellular contacts, the tissue architecture, and remain hormone responsive for several days. They are readily processed for RNA and protein extraction, histological analysis or stored in freezing medium. Fluorescence activated cell sorting (FACS) can be used to enrich for specific cell populations. This protocol provides a straightforward, standard approach for translational studies with highly complex, varied human specimens.

An Ex vivo Model to Study Hormone Action in the Human Breast

We have developed a novel ex vivo model to study hormone action in the human breast. It is based on tissue microstructures isolated from surgical breast tissue specimens which preserve tissue architecture, intercellular interactions, and paracrine signaling.

The study of hormone action in the human breast has been hampered by lack of adequate model systems. Upon in vitro culture, primary mammary epithelial ...

Human Dupuytren's Ex Vivo Culture for the Study of Myofibroblasts and Extracellular Matrix Interactions

Organ fibrosis or &#8220;scarring&#8221; is known to account for a high death toll due to the extensive amount of disorders and organs affected (from cirrhosis to cardiovascular diseases). There is no effective treatment and the in vitro tools available do not mimic the in vivo situation rendering the progress of the out of control wound healing process still enigmatic.
To date, 2D and 3D cultures of fibroblasts derived from DD patients are the main experimental models available. Primary cell cultures have many limitations; the fibroblasts derived from DD are altered by the culture conditions, lack cellular context and interactions, which are crucial for the development of fibrosis and weakly represent the derived tissue. Real-time PCR analysis of fibroblasts derived from control and DD samples show that little difference is detectable. 3D cultures of fibroblasts include addition of extracellular matrix that alters the native conditions of these cells. 
As a way to characterize the fibrotic, proliferative properties of these resection specimens we have developed a 3D culture system, using intact human resections of the nodule part of the cord. The system is based on transwell plates with an attached nitrocellulose membrane that allows contact of the tissue with the medium but not with the plastic, thus, preventing the alteration of the tissue. No collagen gel or other extracellular matrix protein substrate is required. The tissue resection specimens maintain their viability and proliferative properties for 7 days. This is the first &#8220;organ&#8221; culture system that allows human resection specimens from DD patients to be grown ex vivo and functionally tested, recapitulating the in vivo situation.

Human Dupuytren&#039;s Ex Vivo Culture for the Study of Myofibroblasts and Extracellular Matrix Interactions

Dupuytren&#8217;s disease (DD) is a fibroproliferative disease of the palm of the hand. Here, we present a protocol to culture resection specimens from DD in a three-dimensional (3D) culture system. Such short-term culture system allows preservation of the 3D structure and molecular properties of the fibrotic tissue.

Organ fibrosis or &#8220;scarring&#8221; is known to account for a high death toll due to the extensive amount of disorders and organs affected (from ...

Creation and Transplantation of an Adipose-derived Stem Cell (ASC) Sheet in a Diabetic Wound-healing Model

Artificial skin has achieved considerable therapeutic results in clinical practice. However, artificial skin treatments for wounds in diabetic patients with impeded blood flow or with large wounds might be prolonged. Cell-based therapies have appeared as a new technique for the treatment of diabetic ulcers, and cell-sheet engineering has improved the efficacy of cell transplantation. A number of reports have suggested that adipose-derived stem cells (ASCs), a type of mesenchymal stromal cell (MSC), exhibit therapeutic potential due to their relative abundance in adipose tissue and their accessibility for collection when compared to MSCs from other tissues. Therefore, ASCs appear to be a good source of stem cells for therapeutic use. In this study, ASC sheets from the epididymal adipose fat of normal Lewis rats were successfully created using temperature-responsive culture dishes and normal culture medium containing ascorbic acid. The ASC sheets were transplanted into Zucker diabetic fatty (ZDF) rats, a rat model of type 2 diabetes and obesity, that exhibit diminished wound healing. A wound was created on the posterior cranial surface, ASC sheets were transplanted into the wound, and a bilayer artificial skin was used to cover the sheets. ZDF rats that received ASC sheets had better wound healing than ZDF rats without the transplantation of ASC sheets. This approach was limited because ASC sheets are sensitive to dry conditions, requiring the maintenance of a moist wound environment. Therefore, artificial skin was used to cover the ASC sheet to prevent drying. The allogenic transplantation of ASC sheets in combination with artificial skin might also be applicable to other intractable ulcers or burns, such as those observed with peripheral arterial disease and collagen disease, and might be administered to patients who are undernourished or are using steroids. Thus, this treatment might be the first step towards improving the therapeutic options for diabetic wound healing.

Creation and Transplantation of an Adipose-derived Stem Cell ASC Sheet in a Diabetic Wound-healing Model

Adipose-derived stem cells (ASCs) are easily isolated and harvested from the fat of normal rats. ASC sheets can be created using cell-sheet engineering and can be transplanted into Zucker diabetic fatty rats exhibiting full-thickness skin defects with exposed bone and then covered with a bilayer of artificial skin.

Artificial skin has achieved considerable therapeutic results in clinical practice. However, artificial skin treatments for wounds in diabetic patients ...

Breast Milk Enhances Growth of Enteroids: An Ex Vivo Model of Cell Proliferation

Human small intestinal enteroids are derived from the crypts and when grown in a stem cell niche contain all of the epithelial cell types. The ability to establish human enteroid ex vivo culture systems are important to model intestinal pathophysiology and to study the particular cellular responses involved. In recent years, enteroids from mice and humans are being cultured, passaged, and banked away for future use in several laboratories across the world. This enteroid platform can be used to test the effects of various treatments and drugs and what effects are exerted on different cell types in the intestine. Here, a protocol for establishing primary stem cell-derived small intestinal enteroids derived from neonatal mice and premature human intestine is provided. Moreover, this enteroid culture system was utilized to test the effects of species-specific breast milk. Mouse breast milk can be obtained efficiently using a modified human breast pump and expressed mouse milk can then be used for further research experiments. We now demonstrate the effects of expressed mouse, human, and donor breast milk on the growth and proliferation of enteroids derived from neonatal mice or premature human small intestine.

Breast Milk Enhances Growth of Enteroids: An Ex Vivo Model of Cell Proliferation

This protocol describes how to establish an enteroid culture system from neonatal mouse or premature human intestine as well as an efficient method to collect milk from mice.

Human small intestinal enteroids are derived from the crypts and when grown in a stem cell niche contain all of the epithelial cell types. The ability to ...

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, normothermic ex vivo liver perfusion (NEVLP) has been introduced as a method to evaluate and modify organ function. NEVLP has many advantages in comparison to hypothermic and subnormothermic perfusion including reduced preservation injury, restoration of normal organ function under physiologic conditions, assessment of organ performance, and as a platform for organ repair, remodeling, and modification. Both murine and porcine NEVLP models have been described. We demonstrate a rat model of NEVLP and use this model to show one of its important applications &#8212; the use of a therapeutic molecule added to liver perfusate. Catalase is an endogenous reactive oxygen species (ROS) scavenger and has been demonstrated to decrease ischemia-reperfusion in the eye, brain, and lung. Pegylation has been shown to target catalase to the endothelium. Here, we added pegylated-catalase (PEG-CAT) to the base perfusate and demonstrated its ability to mitigate liver preservation injury. An advantage of our rodent NEVLP model is that it is inexpensive in comparison to larger animal models. A limitation of this study is that it does not currently include post-perfusion liver transplantation. Therefore, prediction of the function of the organ post-transplantation cannot be made with certainty. However, the rat liver transplant model is well established and certainly could be used in conjunction with this model. In conclusion, we have demonstrated an inexpensive, simple, easily replicable NEVLP model using rats. Applications of this model can include testing novel perfusates and perfusate additives, testing software designed for organ evaluation, and experiments designed to repair organs.

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant liver donor shortage, and criteria for liver donors have been expanded. Normothermic ex vivo liver perfusion (NEVLP) has been developed to evaluate and modify organ function. This study demonstrates a rat model of NEVLP and tests the ability of pegylated-catalase, to mitigate liver preservation injury.

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, ...

Ex Vivo Corneal Organ Culture Model for Wound Healing Studies

The cornea has been used extensively as a model system to study wound healing. The ability to generate and utilize primary mammalian cells in two dimensional (2D) and three dimensional (3D) culture has generated a wealth of information not only about corneal biology but also about wound healing, myofibroblast biology, and scarring in general. The goal of the protocol is an assay system for quantifying myofibroblast development, which characterizes scarring. We demonstrate a corneal organ culture ex vivo model using pig eyes. In this anterior keratectomy wound, corneas still in the globe are wounded with a circular blade called a trephine. A plug of approximately 1/3 of the anterior cornea is removed including the epithelium, the basement membrane, and the anterior part of the stroma. After wounding, corneas are cut from the globe, mounted on a collagen/agar base, and cultured for two weeks in supplemented-serum free medium with stabilized vitamin C to augment cell proliferation and extracellular matrix secretion by resident fibroblasts. Activation of myofibroblasts in the anterior stroma is evident in the healed cornea. This model can be used to assay wound closure, the development of myofibroblasts and fibrotic markers, and for toxicology studies. In addition, the effects of small molecule inhibitors as well as lipid-mediated siRNA transfection for gene knockdown can be tested in this system.

A protocol for an ex vivo corneal organ culture model useful for wound healing studies is described. This model system can be used to assess the effects of agents to promote regenerative healing or drug toxicity in an organized 3D multicellular environment.

The cornea has been used extensively as a model system to study wound healing. The ability to generate and utilize primary mammalian cells in two ...

Preclinical Model of Hind Limb Ischemia in Diabetic Rabbits

Peripheral vascular disease is a widespread clinical problem that affects millions of patients worldwide. A major consequence of peripheral vascular disease is the development of ischemia. In severe cases, patients can develop critical limb ischemia in which they experience constant pain and an increased risk of limb amputation. Current therapies for peripheral ischemia include bypass surgery or percutaneous interventions such as angioplasty with stenting or atherectomy to restore blood flow. However, these treatments often fail to the continued progression of vascular disease or restenosis or are contraindicated due to the overall poor health of the patient. A promising potential approach to treat peripheral ischemia involves the induction of therapeutic neovascularization to allow the patient to develop collateral vasculature. This newly formed network alleviates peripheral ischemia by restoring perfusion to the affected area. The most frequently employed preclinical model for peripheral ischemia utilizes the creation of hind limb ischemia in healthy rabbits through femoral artery ligation. In the past, however, there has been a strong disconnect between the success of preclinical studies and the failure of clinical trials regarding treatments for peripheral ischemia. Healthy animals typically have robust vascular regeneration in response to surgically induced ischemia, in contrast to the reduced vascularity and regeneration in patients with chronic peripheral ischemia. Here, we describe an optimized animal model for peripheral ischemia in rabbits that includes hyperlipidemia and diabetes. This model has reduced collateral formation and blood pressure recovery in comparison to a model with a higher cholesterol diet. Thus, the model may provide better correlation with human patients with compromised angiogenesis from the common co-morbidities that accompany peripheral vascular disease.

We describe a surgical procedure used to induce peripheral ischemia in rabbits with hyperlipidemia and diabetes. This surgery acts as a preclinical model for conditions experienced in peripheral artery disease in patients. Angiography is also described as a means to measure the extent of introduced ischemia and recovery of perfusion.

Peripheral vascular disease is a widespread clinical problem that affects millions of patients worldwide. A major consequence of peripheral vascular ...

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.

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