An Ex Vivo Tissue Culture Model for Fibrovascular Complications in Proliferative Diabetic Retinopathy
Summary
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.
Abstract
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.
Introduction
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.
Protocol
Representative Results
Discussion
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…
Offenlegungen
The authors have nothing to disclose.
Acknowledgements
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).
Materials
| Material | |||
| Microforceps | Medicon | 07.60.03 | Used for handling the FTs |
| Disposable Scalpels – Sterile | Swann-Morton | 0513 | Used for FT dissection |
| Culture dish, vented, 28 ml (60mm) | Greiner Bio-One | 391-3210 | Used for dissection and for testing fibrin gel formation |
| Cell culture plates, 12-well | Greiner Bio-One | 392-0049 | Used for FT dissection and whole-mount immunofluorescence |
| Reagent/centrifuge tube with screw cap, 15 mL | Greiner Bio-One | 391-3477 | |
| Reagent/centrifuge tube with screw cap, 50 mL | Greiner Bio-One | 525-0384 | |
| Millex-GV Syringe Filter Unit, 0.22 µm, PVDF | Millipore | SLGV033RS | Used to sterile-filter the fibrinogen solution |
| Syringe, 10 mL | Braun | 4606108V | Used to sterile-filter the fibrinogen solution |
| Polypropylene Microcentrifuge Tubes, 1.5 mL | Fisher | FB74031 | |
| Cell-Culture Treated Multidishes, 24-well | Nunc | 142475 | Used for casting the FT/fibrin gels for native FT characterization and ex vivo culture |
| Cell culture plates, 96-well, U-bottom | Greiner Bio-One | 392-0019 | Used for whole-mount immunofluorescence |
| Round/Flat Spatulas, Stainless Steel | VWR | 82027-528 | Used for whole-mount immunofluorescence |
| Coverslips 22x22mm #1 | Menzel/Fisher | 15727582 | Used for mounting |
| Microscope slides | Fisher | Kindler K102 | Used for mounting |
| Absorbent paper | VWR | 115-0202 | Used for mounting |
| Name | Company | Catalog Number | Comments |
| Reagents | |||
| PBS tablets | Medicago | 09-9400-100 | Used for preparing 1x PBS |
| Fibrinogen, Plasminogen-Depleted, Human Plasma | Calbiochem | 341578 | |
| Hanks Balanced Salt Solution | Sigma-Aldrich | H9394-500ML | Used for preparing the fibrinogen and TA solution |
| Fetal bovine serum | Gibco | 10270106 | Used for preparing the blocking solution |
| Human Serum | Sigma-Aldrich | H4522 | Aliquoted in -20 °C, thaw before preparing the ex vivo culture media |
| Gentamicin Sulfate 10mg/ml | Biowest | L0011-100 | |
| Endothelial cell media MV Kit | Promocell | C-22120 | Contains 500 ml of Endothelial Cell Growth Medium MV, 25 mL of fetal calf serum, 2 mL of endothelial cell growth supplement, 500 μL of recombinant human epidermal growth factor (10 μg/ mL) and 500 μL of hydrocortisone (1 g/ mL) |
| Sodium azide | Sigma-Aldrich | S2002 | 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. |
| Acetone | Sigma-Aldrich | 32201-2.5L-M | Used to prepare the post-fixation solution. HARMFUL: wear protective gloves and/or clothing. Use in fume hood. |
| Methanol | Sigma-Aldrich | 32213 | Used to prepare the post-fixation solution. TOXIC: wear protective gloves and/or clothing. Use in fume hood. |
| Triton X-100 (octyl phenol ethoxylate) | Sigma-Aldrich | T9284 | Used for whole-mount immunofluorescence. HARMFUL: wear protective gloves and/or clothing. |
| Hoechst 33342, 20mM | Life Technologies | 62249 | For nuclei counterstaining. HARMFUL: wear protective gloves and/or clothing, and eye and/or face protection. |
| VECTASHIELD Antifade Mounting Medium | Vector Laboratories | H-1000 | Wear protective gloves and/or clothing, and eye protection. Use in fume hood. |
| VECTASHIELD Antifade Mounting Medium with DAPI | Vector Laboratories | H-1200 | Mounting medium with nuclei counterstaining. Wear protective gloves and/or clothing, and eye protection. Use in fume hood. |
| Eukitt Quick-hardening mounting medium | Sigma-Aldrich | 03989-100ml | TOXIC: Wear protective gloves and/or clothing, and eye protection. Use in fume hood. |
| Thrombin from bovine plasma, lyophilized powder | Sigma-Aldrich | T9549-500UN | Dissolve at 100 units/ mL, aliquote and store at -20 °C, avoid repeated freeze/ thaw |
| Aprotinin from bovine lung, lyophilized powder | Sigma | A3428 | Dissolve at 50 mg/ mL, aliquote and store at -20 °C, avoid repeated freeze/ thaw |
| Name | Company | Catalog Number | Comments |
| Growth factors | |||
| Recombinant human VEGFA | R&D Systems | 293-VE-010 | 50 ng/ mL final concentration |
| Recombinant human VEGFC | R&D Systems | 752-VC-025 | 200 ng/ mL final concentration |
| Recombinant human TGFβ | Millipore | GF346 | 1 ng/ mL final concentration |
| Recombinant human bFGF | Millipore | 01-106 | 50 ng/ mL final concentration |
| Name | Company | Catalog Number | Comments |
| Primary antibodies | |||
| CD31 (JC70A) | Dako | M0823 | Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab |
| CD34 (QBEND10) | Dako | M716501-2 | Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab |
| CD45 (2B11+PD7/26) | Dako | M070129-2 | Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab |
| CD68 | ImmunoWay | RLM3161 | Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab |
| Cleaved caspase-3 (5A1E) | Cell Signalling | 9664 | Used at 1:200 dilution, Goat anti Rabbit Alexa 594 Secondary Ab |
| ERG (EP111) | Dako | M731429-2 | Used at 1:100 dilution, Goat anti Rabbit Alexa 594 Secondary Ab |
| GFAP | Dako | Z0334 | Used at 1:100 dilution, Goat anti Rabbit Alexa 594 Secondary Ab |
| Ki67 | Leica Microsystems | NCL-Ki67p | Used at 1:1500 dilution, Goat anti Rabbit Alexa 594 Secondary Ab |
| Lyve1 | R&D Systems | AF2089 | Used at 1:100 dilution, Donkey anti Goat Alexa 568 Secondary Ab |
| NG2 | Millipore | AB5320 | Used at 1:100 dilution, Goat anti Rabbit Alexa 594 Secondary Ab |
| Prox1 | ReliaTech | 102-PA32 | Used at 1:200 dilution, Goat anti Rabbit Alexa 568 Secondary Ab |
| Prox1 | R&D Systems | AF2727 | Used at 1:40 dilution, Chicken anti Goat Alexa 594 Secondary Ab |
| VEGFR3 (9D9F9) | Millipore | MAB3757 | Used at 1:100 dilution, Donkey anti Mouse Alexa 488 Secondary Ab |
| α-SMA (1A4) | Sigma | C6198 | Used at 1:400 dilution, Cy3 conjugated |
| Name | Company | Catalog Number | Comments |
| Secondary antibodies | |||
| Alexa Fluor488 Donkey Anti-Mouse IgG | Life Technologies | A-21202 | Used at 1:500 dilution |
| Alexa Fluor594 Goat Anti-Rabbit IgG | Invitrogen | A-11012 | Used at 1:500 dilution |
| Alexa Fluor568 Donkey anti-Goat IgG | Thermo Scientific | A-11057 | Used at 1:500 dilution |
| Alexa Fluor568 Goat anti-Rabbit IgG | Thermo Scientific | A-11036 | Used at 1:500 dilution |
| Alexa Fluor594 Chicken Anti-Goat IgG | Molecular Probes | A-21468 | Used at 1:500 dilution |
| Name | Company | Catalog Number | Comments |
| Microscopes | |||
| Axiovert 200 inverted epifluorescence microscope | Zeiss | For imaging of the fresh and fibrin-embedded FT | |
| SZX9 upright dissection stereomicroscope | Olympus | For FT dissection | |
| LSM 780 confocal microscope | Zeiss | For imaging of whole-mount immunostained FT | |
| AxioImager.Z1 upright epifluorescence microscope with Apotome | Zeiss | For imaging of whole-mount immunostained FT |
Referenzen
- Cho, N. H., et al. IDF Diabetes Atlas: Global estimates of diabetes prevalence for 2017 and projections for 2045. Diabetes Research and Clinical Practice. 138, 271-281 (2018).
- Liew, G., Wong, V. W., Ho, I. V. Mini Review: Changes in the Incidence of and Progression to Proliferative and Sight-Threatening Diabetic Retinopathy Over the Last 30 Years. Ophthalmic Epidemiology. 24 (2), 73-80 (2017).
- Loukovaara, S., et al. Indications of lymphatic endothelial differentiation and endothelial progenitor cell activation in the pathology of proliferative diabetic retinopathy. Acta Ophthalmologica. 93 (6), 512-523 (2015).
- Stitt, A. W., et al. The progress in understanding and treatment of diabetic retinopathy. Progress in Retinal and Eye Research. 51, 156-186 (2016).
- Duh, E. J., Sun, J. K., Stitt, A. W. Diabetic retinopathy: current understanding, mechanisms, and treatment strategies. JCI Insight. 2 (14), (2017).
- Gross, J. G., et al. Five-Year Outcomes of Panretinal Photocoagulation vs Intravitreous Ranibizumab for Proliferative Diabetic Retinopathy: A Randomized Clinical Trial. JAMA Ophthalmology. 136 (10), 1138-1148 (2018).
- Robinson, R., Barathi, V. A., Chaurasia, S. S., Wong, T. Y., Kern, T. S. Update on animal models of diabetic retinopathy: from molecular approaches to mice and higher mammals. Disease Models, Mechanisms. 5 (4), 444-456 (2012).
- Villacampa, P., Haurigot, V., Bosch, F. Proliferative retinopathies: animal models and therapeutic opportunities. Current Neurovascular Research. 12 (2), 189-198 (2015).
- Cox, T. R., Erler, J. T. Remodeling and homeostasis of the extracellular matrix: implications for fibrotic diseases and cancer. Disease Models, Mechanisms. 4 (2), 165-178 (2011).
- Sharma, T., et al. Surgical treatment for diabetic vitreoretinal diseases: a review. Clinical, Experimental Ophthalmology. 44 (4), 340-354 (2016).
- Gucciardo, E., et al. The microenvironment of proliferative diabetic retinopathy supports lymphatic neovascularization. The Journal of Pathology. 245 (2), 172-185 (2018).
- Rezzola, S., et al. 3D endothelial cell spheroid/human vitreous humor assay for the characterization of anti-angiogenic inhibitors for the treatment of proliferative diabetic retinopathy. Angiogenesis. 20 (4), 629-640 (2017).
- Pepper, M. S., Montesano, R., Mandriota, S. J., Orci, L., Vassalli, J. D. Angiogenesis: a paradigm for balanced extracellular proteolysis during cell migration and morphogenesis. Enzyme, Protein. 49 (1-3), 138-162 (1996).
- Lafleur, M. A., Handsley, M. M., Knauper, V., Murphy, G., Edwards, D. R. Endothelial tubulogenesis within fibrin gels specifically requires the activity of membrane-type-matrix metalloproteinases (MT-MMPs). Journal of Cell Science. 115 (Pt 17), 3427-3438 (2002).
- Loukovaara, S., et al. Quantitative Proteomics Analysis of Vitreous Humor from Diabetic Retinopathy Patients. Journal of Proteome Research. 14 (12), 5131-5143 (2015).
- Abu El-Asrar, A. M., Struyf, S., Opdenakker, G., Van Damme, J., Geboes, K. Expression of stem cell factor/c-kit signaling pathway components in diabetic fibrovascular epiretinal membranes. Molecular Vision. 16, 1098-1107 (2010).
- Loukovaara, S., et al. Ang-2 upregulation correlates with increased levels of MMP-9, VEGF, EPO and TGFbeta1 in diabetic eyes undergoing vitrectomy. Acta Ophthalmologica. 91 (6), 531-539 (2013).
- Sugiyama, N., et al. EphA2 cleavage by MT1-MMP triggers single cancer cell invasion via homotypic cell repulsion. Journal of Cell Biology. 201 (3), 467-484 (2013).
- Tatti, O., et al. MMP16 Mediates a Proteolytic Switch to Promote Cell-Cell Adhesion, Collagen Alignment, and Lymphatic Invasion in Melanoma. Krebsforschung. 75 (10), 2083-2094 (2015).
- Zudaire, E., Gambardella, L., Kurcz, C., Vermeren, S. A computational tool for quantitative analysis of vascular networks. PLoS One. 6 (11), e27385 (2011).
- Senger, D. R. Molecular framework for angiogenesis: a complex web of interactions between extravasated plasma proteins and endothelial cell proteins induced by angiogenic cytokines. American Journal of Pathology. 149 (1), 1-7 (1996).
- Senger, D. R., Davis, G. E. Angiogenesis. Cold Spring Harbor Perspectives in Biology. 3 (8), a005090 (2011).
- Bishop, P. N. Structural macromolecules and supramolecular organisation of the vitreous gel. Progress in Retinal and Eye Research. 19 (3), 323-344 (2000).
- Marmorstein, A. D., Marmorstein, L. Y. The challenge of modeling macular degeneration in mice. Trends in Genetics. 23 (5), 225-231 (2007).
- Kim, L. A., et al. Characterization of cells from patient-derived fibrovascular membranes in proliferative diabetic retinopathy. Molecular Vision. 21, 673-687 (2015).
- Avery, R. L., et al. Intravitreal bevacizumab (Avastin) in the treatment of proliferative diabetic retinopathy. Ophthalmology. 113 (10), e1691-e1615 (2006).
- Zhao, L. Q., Zhu, H., Zhao, P. Q., Hu, Y. Q. A systematic review and meta-analysis of clinical outcomes of vitrectomy with or without intravitreal bevacizumab pretreatment for severe diabetic retinopathy. The British Journal of Ophthalmology. 95 (9), 1216-1222 (2011).
- Carrion, B., Janson, I. A., Kong, Y. P., Putnam, A. J. A safe and efficient method to retrieve mesenchymal stem cells from three-dimensional fibrin gels. Tissue Engineering. Part C, Methods. 20 (3), 252-263 (2014).
