The work was supported by Grants from the Manpei Suzuki Diabetic Foundation (YT), Boston Children&#39;s Hospital OFD/BTREC/CTREC Faculty Career Development Grant, Boston Children&#39;s Hospital Ophthalmology Foundation, BCH Pilot Award, BCH Manton Center Fellowship, and Little Giraffe Foundation (ZF), The German Research Foundation (DFG; to BC [CA1940/1-1]), NIH R24EY024868, EY017017, R01EY01717-13S1, EY030904-01, BCH IDDRC (1U54HD090255), Massachusetts Lions Eye Foundation (LEHS).

All animal experiments described were approved by the Institutional Animal Care and Use Committee at Boston Children&#8217;s Hospital (ARCH protocol number 19-04-3913R).
1. Preparation
<ol>
	<li>Add 5 mL of Penicillin/Streptomycin (10000 U/mL) and 5 mL and 10 mL of commercially available supplements to 500 mL of complete classic medium with serum. Aliquot 50 mL of the medium initially. 
	NOTE: Do not return any medium back to the stock to avoid contamination.</li>
	<li>Put an aliquot of complete classic medium on ice.</li>
	<li>Use 70% ethanol to clean the dissecting microscope, forceps, and scissors.</li>
	<li>Prepare two cell culture dishes (10 cm), one on the dissection microscope, one on ice; put 10 mL of complete classic medium in each dish.</li>
</ol>
2. Experimental steps (Figure 1)
<ol>
	<li>Sacrifice C57BL/6J mice around postnatal (P) 20 using 75-100 mg/kg ketamine and 7.5 -10 mg/kg xylazine injected intraperitoneally. Keep the eyes in complete classic medium on ice before dissection.</li>
	<li>Remove the connective tissue (muscle and fatty tissue) and optic nerve on the eye.</li>
	<li>Use a micro-scissor to circumferentially cut 0.5 mm posterior to the corneal limbus. Remove the cornea/iris complex, vitreous and the lens.</li>
	<li>Make a 1 mm incision perpendicular to the cut edge towards the optic nerve and cut a circumferential band of 1 mm width. Separate the central and peripheral regions of the complex. Use forceps to peel off the retina from RPE/choroid/sclera complex.&#160;</li>
	<li>Keep the peripheral choroid band in complete classic medium on ice; isolate the other eye and repeat the process to cut a second band.</li>
	<li>Cut the circular band into 6 ~equal square pieces (~1 mm x 1 mm). 
	NOTE: Never touch any edge.</li>
	<li>Thaw the basal membrane extract (BME) per manufacture&#8217;s instruction. Add 30 &#181;L/well of BME into the center of each well of a 24 well tissue culture plate. Make sure the droplet of BME forms a convex dome at the bottom of the plate without touching the edges. 
	NOTE: Thaw the BME overnight in a refrigerator. BME should be on the ice any time after thawing.</li>
	<li>Place the tissue in the middle of the BME. 
	NOTE: Do not flatten the choroid explant; generally, let the tissue expand within the BME. The orientation of the tissue (scleral side up or down) does not impact the experimental outcome.</li>
	<li>Incubate the plate at 37 &#176;C for 10 min to let the gel solidify.</li>
	<li>Add 500 &#181;L of the complete classic medium/well.</li>
	<li>Change the classic medium every other day (500 &#181;L). Choroid sprouting can be observed after 3 days with a microscope. 
	NOTE: For growth factor treatment, starve the tissue for 4 h. Dilute a trial compound in growth factor-reduced medium (1:200 boost instead of 1:50).</li>
</ol>
3. SWIFT-Choroid computerized quantification method17 (Figure 2)
NOTE: A computerized method to measure the area covered by growing vessels was used. A macro plugin to ImageJ software is needed prior to quantification (see Supplemental Information for further detail).
<ol>
	<li>Open the choroid sprouting image with ImageJ and check &#8220;Image | Type| 8-bit&#8221; with gray scale.</li>
	<li>Go to &#8220;Image | Adjust | Brightness/Contrast (Ctrl/shift/C)&#8221; and optimize the contrast.</li>
	<li>Use the magic wand function to outline and remove from the image the choroid tissue which are present in the center of the sprouts (using shortcut key &#8220;F1&#8221;) (Figure 2A,B). 
	NOTE: Set the tolerance rate of the magic wand to 20-30%.</li>
	<li>Remove the background of the image with the free selection tools (Figure 2C). Go to &#8220;Image | Adjust | Threshold (Ctrl/shift/T)&#8221;. Use the threshold function to define the microvascular sprouts against the background and periphery (Figure 2D).</li>
	<li>Click &#8220;F2&#8221; and a summary will appear. Save an image of the selected area by clicking &#8220;Save&#8221;. Save in the same folder as the original image for future reference.</li>
	<li>After a group of samples is measured, copy the recorded for data analysis. 
	NOTE: It is also possible to measure the area (&#181;m&#178;) by &#8220;Analyze | Set Scale&#8221; using images with scale bars.</li>
</ol>

<ol>
	<li>Zarbin, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+concepts+in+the+pathogenesis+of+age-related+macular+degeneration.">Current concepts in the pathogenesis of age-related macular degeneration.</a> Arch Ophthalmol. 122 (4), 598-614 (2004).</li><li>Pemp, B., Schmetterer, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ocular+blood+flow+in+diabetes+and+age-related+macular+degeneration.">Ocular blood flow in diabetes and age-related macular degeneration.</a> Canadian Journal of Ophthalmology. 43 (3), 295-301 (2008).</li><li>Murakami, Y., Ishikawa, K., Nakao, S., Sonoda, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Innate+immune+response+in+retinal+homeostasis+and+inflammatory+disorders.">Innate immune response in retinal homeostasis and inflammatory disorders.</a> Progress in Retinal and Eye Research. 74, 100778 (2020).</li><li>Fu, 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=Dyslipidemia+in+retinal+metabolic+disorders.">Dyslipidemia in retinal metabolic disorders.</a> EMBO Molecular Medicine. 11 (10), 10473 (2019).</li><li>Daruich, 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=Mechanisms+of+macular+edema:+Beyond+the+surface.">Mechanisms of macular edema: Beyond the surface.</a> Progress in Retinal and Eye Research. 63, 20-68 (2018).</li><li>Tomita, Y., 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=Long-Acting+FGF21+Inhibits+Retinal+Vascular+Leakage+in+In+Vivo+and+In+Vitro+Models.">Long-Acting FGF21 Inhibits Retinal Vascular Leakage in In Vivo and In Vitro Models.</a> International Journal of Molecular Sciences. 21 (4), 21041188 (2020).</li><li>Maisto, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ARPE-19-derived+VEGF-containing+exosomes+promote+neovascularization+in+HUVEC:+the+role+of+the+melanocortin+receptor+5.">ARPE-19-derived VEGF-containing exosomes promote neovascularization in HUVEC: the role of the melanocortin receptor 5.</a> Cell Cycle. 18 (4), 413-424 (2019).</li><li>Mazzoni, J., 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+Wnt+Inhibitor+Apcdd1+Coordinates+Vascular+Remodeling+and+Barrier+Maturation+of+Retinal+Blood+Vessels.">The Wnt Inhibitor Apcdd1 Coordinates Vascular Remodeling and Barrier Maturation of Retinal Blood Vessels.</a> Neuron. 96 (5), 1055-1069 (2017).</li><li>Fu, 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=Adiponectin+Mediates+Dietary+Omega-3+Long-Chain+Polyunsaturated+Fatty+Acid+Protection+Against+Choroidal+Neovascularization+in+Mice.">Adiponectin Mediates Dietary Omega-3 Long-Chain Polyunsaturated Fatty Acid Protection Against Choroidal Neovascularization in Mice.</a> Investigative Ophthalmology and Visual Sciences. 58 (10), 3862-3870 (2017).</li><li>Gong, Y., 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=Cytochrome+P450+Oxidase+2C+Inhibition+Adds+to+omega-3+Long-Chain+Polyunsaturated+Fatty+Acids+Protection+Against+Retinal+and+Choroidal+Neovascularization.">Cytochrome P450 Oxidase 2C Inhibition Adds to omega-3 Long-Chain Polyunsaturated Fatty Acids Protection Against Retinal and Choroidal Neovascularization.</a> Arteriosclerosis, Thrombosis and Vascular Biology. 36 (9), 1919-1927 (2016).</li><li>Nicosia, R. 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V., 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=Mouse+Aortic+Ring+Assay:+A+New+Approach+of+the+Molecular+Genetics+of+Angiogenesis.">Mouse Aortic Ring Assay: A New Approach of the Molecular Genetics of Angiogenesis.</a> Biological Procedures Online. 4, 24-31 (2002).</li><li>Katakia, Y. T., 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=Ex+vivo+model+for+studying+endothelial+tip+cells:+Revisiting+the+classical+aortic-ring+assay.">Ex vivo model for studying endothelial tip cells: Revisiting the classical aortic-ring assay.</a> Microvascular Research. 128, 103939 (2020).</li><li>Rezzola, 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=In+vitro+and+ex+vivo+retina+angiogenesis+assays.">In vitro and ex vivo retina angiogenesis assays.</a> Angiogenesis. 17 (3), 429-442 (2014).</li><li>Rezzola, 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=A+novel+ex+vivo+murine+retina+angiogenesis+(EMRA)+assay.">A novel ex vivo murine retina angiogenesis (EMRA) assay.</a> Experimental Eye Research. 112, 51-56 (2013).</li><li>Shao, 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=Choroid+sprouting+assay:+an+ex+vivo+model+of+microvascular+angiogenesis.">Choroid sprouting assay: an ex vivo model of microvascular angiogenesis.</a> PLoS One. 8 (7), 69552 (2013).</li><li>Tomita, Y., 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=Free+fatty+acid+receptor+4+activation+protects+against+choroidal+neovascularization+in+mice.">Free fatty acid receptor 4 activation protects against choroidal neovascularization in mice.</a> Angiogenesis. 23, 385-394 (2020).</li><li>Li, J., 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=Endothelial+TWIST1+promotes+pathological+ocular+angiogenesis.">Endothelial TWIST1 promotes pathological ocular angiogenesis.</a> Investigative Ophthalmology and Vision Science. 55 (12), 8267-8277 (2014).</li><li>Liu, C. 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=Endothelial+microRNA-150+is+an+intrinsic+suppressor+of+pathologic+ocular+neovascularization.">Endothelial microRNA-150 is an intrinsic suppressor of pathologic ocular neovascularization.</a> Proceedings of the National Academy of Science U. S. A. 112 (39), 12163-12168 (2015).</li><li>Zhou, 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=LncEGFL7OS+regulates+human+angiogenesis+by+interacting+with+MAX+at+the+EGFL7/miR-126+locus.">LncEGFL7OS regulates human angiogenesis by interacting with MAX at the EGFL7/miR-126 locus.</a> Elife. 8, 40470 (2019).</li><li>Kobayashi, S., Fukuta, M., Kontani, H., Yanagita, S., Kimura, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+assay+for+angiogenesis+of+cultured+choroidal+tissues+in+streptozotocin-diabetic+Wistar+and+spontaneously+diabetic+GK+rats.">A quantitative assay for angiogenesis of cultured choroidal tissues in streptozotocin-diabetic Wistar and spontaneously diabetic GK rats.</a> Japanese Journal of Pharmacology. 78 (4), 471-478 (1998).</li><li>Kobayashi, 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=Inhibitory+effects+of+tetrandrine+and+related+synthetic+compounds+on+angiogenesis+in+streptozotocin-diabetic+rodents.">Inhibitory effects of tetrandrine and related synthetic compounds on angiogenesis in streptozotocin-diabetic rodents.</a> Biological and Pharmaceutical Bulletin. 22 (4), 360-365 (1999).</li><li>Kobayashi, S., Shinohara, H., Tsuneki, H., Nagai, R., Horiuchi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N(epsilon)-(carboxymethyl)lysine+proliferated+CD34(+)+cells+from+rat+choroidal+explant+in+culture.">N(epsilon)-(carboxymethyl)lysine proliferated CD34(+) cells from rat choroidal explant in culture.</a> Biological and Pharmaceutical Bulletin. 27 (9), 1382-1387 (2004).</li><li>Kobayashi, 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=Overproduction+of+N(epsilon)-(carboxymethyl)lysine-induced+neovascularization+in+cultured+choroidal+explant+of+streptozotocin-diabetic+rat.">Overproduction of N(epsilon)-(carboxymethyl)lysine-induced neovascularization in cultured choroidal explant of streptozotocin-diabetic rat.</a> Biological and Pharmaceutical Bulletin. 27 (10), 1565-1571 (2004).</li><li>Bergers, G., Song, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+pericytes+in+blood-vessel+formation+and+maintenance.">The role of pericytes in blood-vessel formation and maintenance.</a> Neuro-Oncology. 7 (4), 452-464 (2005).</li><li>Browning, A. 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The authors have no financial disclosures. The computerized method is available free of charge to academic institutions through the authors.

The choroidal sprouting assay aids research in neovascular AMD9,10,18,19,20. Choroid explants can be isolated from mice as well as rats and humans17,21. The choroid explant includes ECs, macrophages, and pericytes17. In this assay the interaction between choroidal ECs and adjace...

Choroidal angiogenesis dysregulation is associated with neovascular age-related macular degeneration (AMD)1. The choroid is a microvascular bed present underneath the retinal pigment epithelium (RPE). It has been shown that reduced blood flow in the choroid is associated with progression of AMD2. The intricate relationship between vascular endothelium, RPE, macrophages, pericytes and other cells is responsible for the homeostasis of the tissue3,4,5. Therefore, a reproducible assay modeling choroidal microenvironment is critical for the study of neovascular AMD.
Ex vivo angiogenesis assays and in vitro endothelial cell cultures can complement studies of microvascular behavior in vivo, for testing new drugs and for studies of pathogenesis. Endothelial cells such as human retinal microvascular endothelial cells (HRMECs), Human Umbilical Vein Endothelial Cells (HUVEC), isolated primary animal brain or retinal ECs are often used in in vitro studies for ocular angiogenesis research6,7,8. HRMECs in particular have been widely used as a model of in vitro choroidal neovascularization (CNV)9 by assessing endothelial proliferation, migration, tubular formation, and vascular leakage to evaluate interventions6,10. However, ECs in culture are limited as a model of CNV because of the lack of interactions with other cell types found in the choroid and because most EC used in these assays do not originate from choroid. Mouse choroidal ECs are difficult to isolate and maintain in culture.
The aortic ring assay is widely used as a model of macro vascular proliferation. Vascular sprouts from aortic explants include ECs, pericytes and macrophages11. The aortic ring assay models large vessel angiogenesis well12,13,14. However, it has limitations as a model of choroidal neovascularization as aortic rings are a macrovascular tissue lacking the characteristic choroidal microvascular environment, and sprouts from large vessels may differ from sprouts from capillary networks involved in microvascular pathology. Recently a group published an ex-vivo retinal assay15,16. Although, it is suitable for retinal neovascular disease, it is not as appropriate for choroidal neovascularization as seen in AMD.
The choroidal sprouting assay using mouse RPE, choroid, and scleral explanted tissue was developed to better model CNV. The tissue can easily be isolated from mouse (or other species) eyes17. This assay allows reproducible evaluation of pro- and anti-angiogenic potential of pharmacologic compounds and evaluation of the role of specific pathways in choroidal neovascularization using tissue from genetically modified mice and controls18. This choroidal sprouting assay has been referenced in many subsequent publications9,10,18,19,20. Here, the method involved in the use of this assay are demonstrated.

<table><tbody><tr><td>AnaSed (Xylazine)</td><td>AKORN</td><td>59339-110-20</td><td></td></tr><tr><td>Basal membrane extract (BME) Matrigel</td><td>BD Biosciences</td><td>354230</td><td></td></tr><tr><td>Cell culture dish</td><td>NEST</td><td>704001</td><td>10cm</td></tr><tr><td>Complete classic medium with serum and CultureBoost</td><td>Cell systems</td><td>4Z0-500</td><td></td></tr><tr><td>Ethyl alcohol 200 Proof</td><td>Pharmco</td><td>111000200</td><td>use for 70%</td></tr><tr><td>Kimwipes</td><td>Kimberly-Clark</td><td>06-666</td><td></td></tr><tr><td>Microscope</td><td>ZEISS</td><td>Axio Observer Z1</td><td></td></tr><tr><td>Penicillin/Streptomycin</td><td>GIBCO</td><td>15140</td><td>10000 U/mL</td></tr><tr><td>Tissue culture plate (24-well)</td><td>Olympus</td><td>25-107</td><td></td></tr><tr><td>VetaKet CIII (Ketamine)</td><td>AKORN</td><td>59399-114-10</td><td></td></tr></tbody></table>

an ex vivo choroid sprouting assay of ocular microvascular angiogenesis

Pathological choroidal angiogenesis, a salient feature of age-related macular degeneration, leads to vision impairment and blindness. Endothelial cell (EC) proliferation assays using human retinal microvascular endothelial cells (HRMECs) or isolated primary retinal ECs are widely used in vitro models to study retinal angiogenesis. However, isolating pure murine retinal endothelial cells is technically challenging and retinal ECs may have different proliferation responses than choroidal endothelial cells and different cell/cell interactions. A highly reproducible ex vivo choroidal sprouting assay as a model of choroidal microvascular proliferation was developed. This model includes the interaction between choroid vasculature (EC, macrophages, pericytes) and retinal pigment epithelium (RPE). Mouse RPE/choroid/scleral explants are isolated and incubated in growth-factor-reduced basal membrane extract (BME) (day 0). Medium is changed every other day and choroid sprouting is quantified at day 6. The images of individual choroid explant are taken with an inverted phase microscope and the sprouting area is quantified using a semi-automated macro plug-in to the ImageJ software developed in this lab. This reproducible ex vivo choroidal sprouting assay can be used to assess compounds for potential treatment and for microvascular disease research to assess pathways involved in choroidal micro vessel proliferation using wild type and genetically modified mouse tissue.

Comparison of choroid sprouting growth per day
We dissected the choroid with sclera, embedded in BME and cultured them for 6 days (Figure 1). The choroid sprouting in C57BL/6J mice from day 3 to day 6 were examined with a microscope and quantified with SWIFT-Choroid a semi-automated quantification method in ImageJ. In a representative case, the choroidal sprouting area (the vessels extending from the explant, excluding the explant itself) was 0.38...

Watch this Scientific Journal Video about An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis at JoVE.com

An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis

This protocol presents choroid sprouting assay, an ex vivo model of microvascular proliferation. This assay can be used to assess pathways involved in proliferating choroidal micro vessels and assess drug treatments using wild type and genetically modified mouse tissue.

Pathological choroidal angiogenesis, a salient feature of age-related macular degeneration, leads to vision impairment and blindness. Endothelial cell ...

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Research

JoVE Journal

Biology

5.6K Views.  Boston Children's Hospital, Harvard Medical School. Dit protocol presenteert choroïde kiemen test, een ex vivo model van microvasculaire proliferatie. Deze test kan worden gebruikt om trajecten die betrokken zijn bij het verspreiden van choroidale microvaten te beoordelen en te beoordelen drug behandelingen met behulp van wilde type en genetisch gemodificeerd muisweefsel.

Video: An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis

A Mouse Model of the Cornea Pocket Assay for Angiogenesis Study

A normal cornea is clear of vascular tissues. However, blood vessels can be induced to grow and survive in the cornea when potent angiogenic factors are administered 1. This uniqueness has made the cornea pocket assay one of the most used models for angiogenesis studies. The cornea composes multiple layers of cells. It is therefore possible to embed a pellet containing the angiogenic factor of interest in the cornea to investigate its angiogenic effect 2,3. Here, we provide a step by step demonstration of how to (I) produce the angiogenic factor-containing pellet (II) embed the pellet into the cornea (III) analyze the angiogenesis induced by the angiogenic factor of interest. Since the basic fibroblast growth factor (bFGF) is known as one of the most potent angiogenic factors 4, it is used here to induce angiogenesis in the cornea.

The cornea is unique in that it lacks vascular tissues. However, robust blood vessel growth and survival can be induced in the cornea by potent angiogenic factors. Therefore, the cornea can provide with us a valuable tool for angiogenic studies. This protocol demonstrates how to perform the mouse model of cornea pocket assay and how to assess the angiogenesis induced by angiogenic factors using this model.

A normal cornea is clear of vascular tissues. However, blood vessels can be induced to grow and survive in the cornea when potent angiogenic factors are ...

Medicine

An Ex Vivo Method for Time-Lapse Imaging of Cultured Rat Mesenteric Microvascular Networks

Angiogenesis, defined as the growth of new blood vessels from pre-existing vessels, involves endothelial cells, pericytes, smooth muscle cells, immune cells, and the coordination with lymphatic vessels and nerves. The multi-cell, multi-system interactions necessitate the investigation of angiogenesis in a physiologically relevant environment. Thus, while the use of in vitro cell-culture models have provided mechanistic insights, a common critique is that they do not recapitulate the complexity associated with a microvascular network. The objective of this protocol is to demonstrate the ability to make time-lapse comparisons of intact microvascular networks before and after angiogenesis stimulation in cultured rat mesentery tissues. Cultured tissues contain microvascular networks that maintain their hierarchy. Immunohistochemical labeling confirms the presence of endothelial cells, smooth muscle cells, pericytes, blood vessels and lymphatic vessels. In addition, labeling tissues with BSI-lectin enables time-lapse comparison of local network regions before and after serum or growth factor stimulation characterized by increased capillary sprouting and vessel density. In comparison to common cell culture models, this method provides a tool for endothelial cell lineage studies and tissue specific angiogenic drug evaluation in physiologically relevant microvascular networks.

An Ex Vivo Method for Time-Lapse Imaging of Cultured Rat Mesenteric Microvascular Networks

Angiogenesis involves multi-cell, multi-system interactions that need to be investigated in a physiologically relevant environment. The objective of this study is to demonstrate the ability of the rat mesentery culture model to make time-lapse comparisons of intact microvascular networks during angiogenesis.

Angiogenesis, defined as the growth of new blood vessels from pre-existing vessels, involves endothelial cells, pericytes, smooth muscle cells, immune ...

Developmental Biology

Whole Mount Immunofluorescent Staining of the Neonatal Mouse Retina to Investigate Angiogenesis In vivo

Angiogenesis is the complex process of new blood vessel formation defined by the sprouting of new blood vessels from a pre-existing vessel network. Angiogenesis plays a key role not only in normal development of organs and tissues, but also in many diseases in which blood vessel formation is dysregulated, such as cancer, blindness and ischemic diseases. In adult life, blood vessels are generally quiescent so angiogenesis is an important target for novel drug development to try and regulate new vessel formation specifically in disease. In order to better understand angiogenesis and to develop appropriate strategies to regulate it, models are required that accurately reflect the different biological steps that are involved. The mouse neonatal retina provides an excellent model of angiogenesis because arteries, veins and capillaries develop to form a vascular plexus during the first week after birth. This model also has the advantage of having a two-dimensional (2D) structure making analysis straightforward compared with the complex 3D anatomy of other vascular networks. By analyzing the retinal vascular plexus at different times after birth, it is possible to observe the various stages of angiogenesis under the microscope. This article demonstrates a straightforward procedure for analyzing the vasculature of a mouse retina using fluorescent staining with isolectin and vascular specific antibodies.

Whole Mount Immunofluorescent Staining of the Neonatal Mouse Retina to Investigate Angiogenesis In vivo

The neonatal murine retina provides a well characterized physiological model of angiogenesis, which permits investigations of the roles of different genes or drugs that modulate angiogenesis in an in vivo context. Immunofluorescent staining to accurately visualize the vascular plexus is pivotal to the success of these types of studies.

Angiogenesis  is the complex process of new blood vessel formation defined by the sprouting  of new blood vessels from a pre-existing vessel network. ...

Neuroscience

The Corneal Micropocket Assay: A Model of Angiogenesis in the Mouse Eye

The mouse corneal micropocket assay is a robust and quantitative in vivo assay for evaluating angiogenesis. By using standardized slow-release pellets containing specific growth factors that trigger blood vessel growth throughout the naturally avascular cornea, angiogenesis can be measured and quantified. In this assay the angiogenic response is generated over the course of several days, depending on the type and dose of growth factor used. The induction of neovascularization is commonly triggered by either basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF). By combining these growth factors with sucralfate and hydron (poly-HEMA (poly(2-hydroxyethyl methacrylate))) and casting the mixture into pellets, they can be surgically implanted in the mouse eye. These uniform pellets slowly-release the growth factors over five or six days (bFGF or VEGF respectively) enabling sufficient angiogenic response required for vessel area quantification using a slit lamp. This assay can be used for different applications, including the evaluation of angiogenic modulator drugs or treatments as well as comparison between different genetic backgrounds affecting angiogenesis. A skilled investigator after practicing this assay can implant a pellet in less than 5 min per eye.

The protocol describes the corneal micropocket assay as developed in mice.

The mouse corneal micropocket assay is a robust and quantitative in vivo assay for evaluating angiogenesis. By using standardized slow-release pellets ...

Standardized and Scalable Assay to Study Perfused 3D Angiogenic Sprouting of iPSC-derived Endothelial Cells In Vitro

Pre-clinical drug research of vascular diseases requires in vitro models of vasculature that are amendable to high-throughput screening. However, current in vitro screening models that have sufficient throughput only have limited physiological relevance, which hinders the translation of findings from in vitro to in vivo. On the other hand, microfluidic cell culture platforms have shown unparalleled physiological relevancy in vitro, but often lack the required throughput, scalability and standardization. We demonstrate a robust platform to study angiogenesis of endothelial cells derived from human induced pluripotent stem cells (iPSC-ECs) in a physiological relevant cellular microenvironment, including perfusion and gradients. The iPSC-ECs are cultured as 40 perfused 3D microvessels against a patterned collagen-1 scaffold. Upon the application of a gradient of angiogenic factors, important hallmarks of angiogenesis can be studied, including the differentiation into tip- and stalk cell and the formation of perfusable lumen. Perfusion with fluorescent tracer dyes enables the study of permeability during and after anastomosis of the angiogenic sprouts. In conclusion, this method shows the feasibility of iPSC-derived ECs in a standardized and scalable 3D angiogenic assay that combines physiological relevant culture conditions in a platform that has the required robustness and scalability to be integrated within the drug screening infrastructure.

This method describes the culture of iPSC-derived endothelial cells as 40 perfused 3D microvessels in a standardized microfluidic platform. This platform enables the study of gradient-driven angiogenic sprouting in 3D, including anastomosis and stabilization of the angiogenic sprouts in a scalable and high-throughput manner.

Pre-clinical drug research of vascular diseases requires in vitro models of vasculature that are amendable to high-throughput screening. However, current ...

Bioengineering

Retinal Explant of the Adult Mouse Retina as an Ex Vivo Model for Studying Retinal Neurovascular Diseases

One of the challenges in retina research is studying the cross-talk between different retinal cells such as retinal neurons, glial cells, and vascular cells. Isolating, culturing, and sustaining retinal neurons in vitro have technical and biological limitations. Culturing retinal explants may overcome these limitations and offer a unique ex vivo model to study the cross-talk between various retinal cells with well-controlled biochemical parameters and independent of the vascular system. Moreover, retinal explants are an effective screening tool for studying novel pharmacological interventions in various retinal vascular and neurodegenerative diseases such as diabetic retinopathy. Here, we describe a detailed protocol for retinal explants' isolation and culture for an extended period. The manuscript also presents some of the technical problems during this procedure that may affect the desired outcomes and reproducibility of the retinal explant culture. The immunostaining of the retinal vessels, glial cells, and neurons demonstrated intact retinal capillaries and neuroglial cells after 2 weeks from the beginning of the retinal explant culture. This establishes retinal explants as a reliable tool for studying changes in the retinal vasculature and neuroglial cells under conditions that mimic retinal diseases such as diabetic retinopathy.

Retinal Explant of the Adult Mouse Retina as an Ex Vivo Model for Studying Retinal Neurovascular Diseases

This protocol presents and describes steps for the isolation, dissection, culturing, and staining of retinal explants obtained from an adult mouse. This method is beneficial as an ex vivo model for studying different retinal neurovascular diseases such as diabetic retinopathy.

One of the challenges in retina research is studying the cross-talk between different retinal cells such as retinal neurons, glial cells, and vascular ...

Study of Angiogenesis Using Scratch Wound Migration and Spheroid Sprouting Assays

Investigating Angiogenesis on a Functional and Molecular Level by Leveraging the Scratch Wound Migration Assay and the Spheroid Sprouting Assay

Angiogenesis plays a crucial role in both physiological and pathological processes within the body including tumor growth or neovascular eye disease. A detailed understanding of the underlying molecular mechanisms and reliable screening models are essential for targeting diseases effectively and developing new therapeutic options. Several in vitro assays have been developed to model angiogenesis, capitalizing on the opportunities a controlled environment provides to elucidate angiogenic drivers at a molecular level and screen for therapeutic targets.
This study presents workflows for investigating angiogenesis in vitro using human umbilical vein endothelial cells (HUVECs). We detail a scratch wound migration assay utilizing a live cell imaging system measuring endothelial cell migration in a 2D setting and the spheroid sprouting assay assessing endothelial cell sprouting in a 3D setting provided by a collagen matrix. Additionally, we outline strategies for sample preparation to enable further molecular analyses such as transcriptomics, particularly in the 3D setting, including RNA extraction as well as immunocytochemistry. Altogether, this framework offers scientists a reliable and versatile toolset to pursue their scientific inquiries in in vitro angiogenesis assays.

Author Spotlight: Investigating Angiogenesis Through Challenges and Innovations in Assay Development

This study presents the two-dimensional (2D) scratch wound migration assay and the three-dimensional (3D) spheroid sprouting assay, along with their respective downstream analysis methods, including RNA extraction and immunocytochemistry, as suitable assays to study angiogenesis in vitro.

Angiogenesis plays a crucial role in both physiological and pathological processes within the body including tumor growth or neovascular eye disease. A ...

In Vitro Three-Dimensional Sprouting Assay of Angiogenesis Using Mouse Embryonic Stem Cells for Vascular Disease Modeling and Drug Testing

Recent advances in induced pluripotent stem cells (iPSC) and gene editing technologies enable the development of novel human cell-based disease models for phenotypic drug discovery (PDD) programs. Although these novel devices could predict the safety and efficacy of investigational drugs in humans more accurately, their development to the clinic still strongly rely on mammalian data, notably the use of mouse disease models. In parallel to human organoid or organ-on-chip disease models, the development of relevant in vitro mouse models is therefore an unmet need for evaluating direct drug efficacy and safety comparisons between species and in vivo and in vitro conditions. Here, a vascular sprouting assay that utilizes mouse embryonic stem cells differentiated into embryoid bodies (EBs) is described. Vascularized EBs cultured onto 3D-collagen gel develop new blood vessels that expand, a process called sprouting angiogenesis. This model recapitulates key features of in vivo sprouting angiogenesis-formation of blood vessels from a pre-existing vascular network-including endothelial tip cell selection, endothelial cell migration and proliferation, cell guidance, tube formation, and mural cell recruitment. It is amenable to screening for drugs and genes modulating angiogenesis and shows similarities with recently described three-dimensional (3D) vascular assays based on human iPSC technologies.

In Vitro Three-Dimensional Sprouting Assay of Angiogenesis Using Mouse Embryonic Stem Cells for Vascular Disease Modeling and Drug Testing

This assay utilizes mouse embryonic stem cells differentiated into embryoid bodies cultured in 3D-collagen gel to analyze the biological processes that control sprouting angiogenesis in vitro. The technique can be applied for testing drugs, modeling diseases, and for studying specific genes in the context of deletions that are embryonically lethal.

Recent advances in induced pluripotent stem cells (iPSC) and gene editing technologies enable the development of novel human cell-based disease models for ...

Versatile 2.5D Model for Analyzing Cellular Sprouting in Porcine Arteries

2.5D Model for Ex Vivo Mechanical Characterization of Sprouting Angiogenesis in Living Tissue

Sprouting angiogenesis is the formation of new blood vessels from pre-existing vasculature and is of great importance for physiological such as tissue growth and repair and pathological processes, including cancer and metastasis. The multistep process of sprouting angiogenesis is a molecularly and mechanically driven process. It consists of induction of cellular sprout by vascular endothelial growth factor, leader/follower cell selection through Notch signaling, directed migration of endothelial cells, and vessel fusion and stabilization. A variety of sprouting angiogenesis models have been developed over the years to better understand the underlying mechanisms of cellular sprouting. Despite advancements in understanding the molecular drivers of sprouting angiogenesis, the role of mechanical cues and the mechanical driver of sprouting angiogenesis remains underexplored due to limitations in existing models. In this study, we designed a 2.5D ex vivo model that enables us to mechanically characterize cellular sprouting from a porcine carotid artery using traction force microscopy. The model identifies distinct force patterns within the sprout, where leader cells exert pulling forces and follower cells exert pushing forces on the matrix. The model's versatility allows for the manipulation of both chemical and mechanical cues, such as matrix stiffness, enhancing its relevance to various microenvironments. Here, we demonstrate that the onset of sprouting angiogenesis is stiffness-dependent. The presented 2.5D model for quantifying cellular traction forces in sprouting angiogenesis offers a simplified yet physiologically relevant method, enhancing our understanding of cellular responses to mechanical cues, which could advance tissue engineering and therapeutic strategies against tumor angiogenesis.

Sprouting angiogenesis, fundamental for development and disease, involves complex molecular and mechanical processes. We present a versatile 2.5D ex vivo model that analyzes cellular sprouting from porcine carotid arteries, revealing stiffness-dependent angiogenesis and distinct leader-follower cell mechanics. This model aids in advancing tissue engineering strategies and cancer therapy approaches.

Sprouting angiogenesis is the formation of new blood vessels from pre-existing vasculature and is of great importance for physiological such as tissue ...

Choroid Sprouting Assay to Study Ocular Microvascular Proliferation Ex Vivo

Source: Tomita, Y., et al. <a href="https://app.jove.com/v/61677">An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis.</a> J. Vis. Exp. (2020)
This video demonstrates the development of an ex vivo model of choroidal sprouting to study ocular microvascular angiogenesis. The assay involves culturing mouse eye explants containing the choroid tissue attached to the sclera and retinal pigment epithelium under specific conditions that promote choroidal microvascular sprouting.

Source: Tomita, Y., et al. An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis. J. Vis. Exp. (2020)
This video demonstrates the ...

An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis

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