The authors would like to thank Drs. Stephen Wilson and Lisa Wilsbacher for helpful discussions. This work was supported in part by NIH HL054737.

NOTE: Procedures using zebrafish were approved by UCSF&#39;s Institutional Animal Care and Use Committee.
1. Preparation of Tools
<ol>
	<li>Insert minutia pin into a pin holder and clamp the pin.</li>
	<li>Using fine tip forceps, carefully bend the tip of the pin to create a slight hook.</li>
	<li>For manipulation and stabilization of the embryo during injury, bend the end of a 28 guage &#189; inch needle mounted on an insulin syringe using needle-nose pliers.</li>
</ol>
2. Preparation of Zebrafish Embryos for Injury
<ol>
	<li>Set up zebrafish breeding pairs and collect eggs in egg water (60ug/mL aquarium salts) as shown previously22.</li>
	<li>Add 0.003% N-Phenylthiourea (PTU) to the egg water when the embryos are approximately 8 hr post fertilization (hpf) to prevent melanization.</li>
	<li>Dechorionate two day post fertilization (dpf) embryos prior to the experiment using fine tip forceps. 
	NOTE: Embryos can be injured anytime after circulation begins. The data presented here is for 2 dpf embryos, but the technique has been successfully applied in embryos up to 5 dpf.</li>
	<li>Anesthetize the embryos with 0.02% buffered 3-aminobenzoic acid (Tricaine) approximately 10 min prior to manipulations.</li>
</ol>
3. Mechanical Vessel Injury of Embryos
<ol>
	<li>Transfer anesthetized embryos to a depression slide on a dissecting stereomicroscope using a transfer pipet.</li>
	<li>Using the short flat side of the syringe needle to manipulate the embryo with the dominant hand, position the embryo on its side with the ventral surface facing away from the needle.</li>
	<li>Position the minutia pin with the tip pointed directly against the ventral surface of the fish posterior to the urogenital opening. Position the minutia pin at a slight angle such that the curved tip is able to pierce through the periderm directly into the caudal vein (Figure 1).</li>
	<li>Using the syringe needle to manipulate the embryo, pierce the caudal vein with the minutia pin by tapping the embryo into the pin to slightly hook the pin into the vein.</li>
	<li>Using the syringe needle, pull the embryo away from the minutia pin to create a small tear in the vessel. 
	NOTE: A successful injury will result in immediate bleeding from the vein.</li>
</ol>
4. Analysis of Hemostasis
<ol>
	<li>Choose only embryos with visibly circulating blood cells for this procedure.</li>
	<li>Prepare to begin the timer as soon as the minutia pin is pulled from the vessel.</li>
	<li>Start the timer as soon as blood loss can be visualized from the wound. When blood loss from the wound ceases, stop the timer and record total time as Bleeding Time. If coagulation is inhibited, record the time to when there are no longer visibly circulating blood cells.</li>
</ol>
5. Analysis of Wound Healing
<ol>
	<li>Transfer post-injury animals onto glass-bottom imaging dishes for microscopy.</li>
	<li>Remove the majority of the egg water.</li>
	<li>Cover the embryos in 0.3-1.2% low melting agarose dissolved in egg water, heated to between 42 and 45 &#186;C and supplemented with 0.02% Tricaine.</li>
	<li>Position embryos on their sides using forceps.</li>
	<li>After the agarose cools, fill the dish with 0.02% Tricaine in egg water.</li>
	<li>Acquire images using brightfield, epifluorescence, or confocal microscopy.</li>
	<li>Remove embryo from the agarose using forceps and transfer back to egg water.</li>
</ol>

<ol>
	<li>Gore, A. V., Monzo, K., Cha, Y. R., Pan, W., Weinstein, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+development+in+the+zebrafish.">Vascular development in the zebrafish.</a> Cold Spring Harb Perspect Med. 2 (5), a006684 (2012).</li><li>Boatman, 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=Assaying+hematopoiesis+using+zebrafish.">Assaying hematopoiesis using zebrafish.</a> Blood Cells Mol Dis. 51 (4), 271-276 (2013).</li><li>Ellett, F., Lieschke, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+as+a+model+for+vertebrate+hematopoiesis.">Zebrafish as a model for vertebrate hematopoiesis.</a> Curr Opin Pharmacol. 10 (5), 563-570 (2010).</li><li>Liu, J., Stainier, D. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+in+the+study+of+early+cardiac+development.">Zebrafish in the study of early cardiac development.</a> Circ Res. 110 (6), 870-874 (2012).</li><li>Traver, D., 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+zebrafish+as+a+model+organism+to+study+development+of+the+immune+system.">The zebrafish as a model organism to study development of the immune system.</a> Adv Immunol. 81, 253-330 (2003).</li><li>Lieschke, G. J., Trede, N. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fish+immunology.">Fish immunology.</a> Curr Biol. 19 (16), R678-R682 (2009).</li><li>Lesley, R., Ramakrishnan, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+into+early+mycobacterial+pathogenesis+from+the+zebrafish.">Insights into early mycobacterial pathogenesis from the zebrafish.</a> Curr Opin Microbiol. 11 (3), 277-283 (2008).</li><li>Oehlers, S. 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=A+chemical+enterocolitis+model+in+zebrafish+larvae+that+is+dependent+on+microbiota+and+responsive+to+pharmacological+agents.">A chemical enterocolitis model in zebrafish larvae that is dependent on microbiota and responsive to pharmacological agents.</a> Dev Dyn. 240 (1), 288-298 (2011).</li><li>Gemberling, M., Bailey, T. J., Hyde, D. R., Poss, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+zebrafish+as+a+model+for+complex+tissue+regeneration.">The zebrafish as a model for complex tissue regeneration.</a> Trends Genet. 29 (11), 611-620 (2013).</li><li>LeBert, D. C., Huttenlocher, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+and+wound+repair.">Inflammation and wound repair.</a> Semin Immunol. , (2014).</li><li>Henry, K. M., Loynes, C. A., Whyte, M. K., Renshaw, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+as+a+model+for+the+study+of+neutrophil+biology.">Zebrafish as a model for the study of neutrophil biology.</a> J Leukoc Biol. 94 (4), 633-642 (2013).</li><li>Niethammer, P., Grabher, C., Look, A. T., Mitchison, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+tissue-scale+gradient+of+hydrogen+peroxide+mediates+rapid+wound+detection+in+zebrafish.">A tissue-scale gradient of hydrogen peroxide mediates rapid wound detection in zebrafish.</a> Nature. 459 (7249), 996-999 (2009).</li><li>Rosenberg, A. F., Wolman, M. A., Franzini-Armstrong, C., Granato, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+nerve-macrophage+interactions+following+peripheral+nerve+injury.">In vivo nerve-macrophage interactions following peripheral nerve injury.</a> J Neurosci. 32 (11), 3898-3909 (2012).</li><li>Otten, C., Abdelilah-Seyfried, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-inflicted+injury+of+zebrafish+embryonic+skeletal+muscle.">Laser-inflicted injury of zebrafish embryonic skeletal muscle.</a> J Vis Exp. (71), e4351 (2013).</li><li>Matrone, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-targeted+ablation+of+the+zebrafish+embryonic+ventricle:+a+novel+model+of+cardiac+injury+and+repair.">Laser-targeted ablation of the zebrafish embryonic ventricle: a novel model of cardiac injury and repair.</a> Int J Cardiol. 168 (4), 3913-3919 (2013).</li><li>Jagadeeswaran, P., Carrillo, M., Radhakrishnan, U. P., Rajpurohit, S. K., Kim, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-induced+thrombosis+in+zebrafish.">Laser-induced thrombosis in zebrafish.</a> Methods Cell Biol. 101, 197-203 (2011).</li><li>Vo, A. H., Swaroop, A., Liu, Y., Norris, Z. G., Shavit, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+fibrinogen+in+zebrafish+results+in+symptoms+consistent+with+human+hypofibrinogenemia.">Loss of fibrinogen in zebrafish results in symptoms consistent with human hypofibrinogenemia.</a> PLoS One. 8 (9), e74682 (2013).</li><li>Liu, 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=Targeted+mutagenesis+of+zebrafish+antithrombin+III+triggers+disseminated+intravascular+coagulation+and+thrombosis,+revealing+insight+into+function.">Targeted mutagenesis of zebrafish antithrombin III triggers disseminated intravascular coagulation and thrombosis, revealing insight into function.</a> Blood. , (2014).</li><li>Jagadeeswaran, P., Liu, Y. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+hemophilia+model+in+zebrafish:+analysis+of+hemostasis.">A hemophilia model in zebrafish: analysis of hemostasis.</a> Blood Cells Mol Dis. 23 (1), 52-57 (1997).</li><li>Jagadeeswaran, P., Gregory, M., Day, K., Cykowski, M., Thattaliyath, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish:+a+genetic+model+for+hemostasis+and+thrombosis.">Zebrafish: a genetic model for hemostasis and thrombosis.</a> J Thromb Haemost. 3 (1), 46-53 (2005).</li><li>Lin, H. F., 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=Analysis+of+thrombocyte+development+in+CD41-GFP+transgenic+zebrafish.">Analysis of thrombocyte development in CD41-GFP transgenic zebrafish.</a> Blood. 106 (12), 3803-3810 (2005).</li><li>Rosen, J. N., Sweeney, M. F., Mably, 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=Microinjection+of+zebrafish+embryos+to+analyze+gene+function.">Microinjection of zebrafish embryos to analyze gene function.</a> J Vis Exp. (25), (2009).</li><li>Benard, E. L., 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=Infection+of+zebrafish+embryos+with+intracellular+bacterial+pathogens.">Infection of zebrafish embryos with intracellular bacterial pathogens.</a> J Vis Exp. (61), (2012).</li><li>Jagadeeswaran, P., Sheehan, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+blood+coagulation+in+the+zebrafish.">Analysis of blood coagulation in the zebrafish.</a> Blood Cells Mol Dis. 25 (3-4), 3-4 (1999).</li><li>Jin, S. W., Beis, D., Mitchell, T., Chen, J. N., Stainier, D. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+molecular+analyses+of+vascular+tube+and+lumen+formation+in+zebrafish.">Cellular and molecular analyses of vascular tube and lumen formation in zebrafish.</a> Development. 132 (23), 5199-5209 (2005).</li><li>Traver, D., 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=Transplantation+and+in+vivo+imaging+of+multilineage+engraftment+in+zebrafish+bloodless+mutants.">Transplantation and in vivo imaging of multilineage engraftment in zebrafish bloodless mutants.</a> Nat Immunol. 4 (12), 1238-1246 (2003).</li><li>Lawson, N. D., Weinstein, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+embryonic+vascular+development+using+transgenic+zebrafish.">In vivo imaging of embryonic vascular development using transgenic zebrafish.</a> Dev Biol. 248 (2), 307-318 (2002).</li><li>Renshaw, S. 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=A+transgenic+zebrafish+model+of+neutrophilic+inflammation.">A transgenic zebrafish model of neutrophilic inflammation.</a> Blood. 108 (13), 3976-3978 (2006).</li><li>Hall, C., Flores, M. V., Storm, T., Crosier, K., Crosier, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+zebrafish+lysozyme+C+promoter+drives+myeloid-specific+expression+in+transgenic+fish.">The zebrafish lysozyme C promoter drives myeloid-specific expression in transgenic fish.</a> BMC Dev Biol. 7, 48 (2007).</li><li>Ellett, F., Pase, L., Hayman, J. W., Andrianopoulos, A., Lieschke, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=mpeg1+promoter+transgenes+direct+macrophage-lineage+expression+in+zebrafish.">mpeg1 promoter transgenes direct macrophage-lineage expression in zebrafish.</a> Blood. 117 (4), e49-e56 (2011).</li><li>Gray, C., 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=Simultaneous+intravital+imaging+of+macrophage+and+neutrophil+behaviour+during+inflammation+using+a+novel+transgenic+zebrafish.">Simultaneous intravital imaging of macrophage and neutrophil behaviour during inflammation using a novel transgenic zebrafish.</a> Thromb Haemost. 105 (5), 811-819 (2011).</li><li>Bellido-Martin, L., Chen, V., Jasuja, R., Furie, B., Furie, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+fibrin+formation+and+platelet+and+endothelial+cell+activation+in+vivo.">Imaging fibrin formation and platelet and endothelial cell activation in vivo.</a> Thromb Haemost. 105 (5), 776-782 (2011).</li><li>Bielczyk-Maczynska, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+loss+of+function+screen+of+identified+genome-wide+association+study+Loci+reveals+new+genes+controlling+hematopoiesis.">A loss of function screen of identified genome-wide association study Loci reveals new genes controlling hematopoiesis.</a> PLoS Genet. 10 (7), e1004450 (2014).</li></ol>

The authors declare that they have no competing financial interests.

Zebrafish have been used successfully as a model for different types of wounds including laser injury13-15, laser-induced thrombosis16, and epithelial wounding10. We report a method of mechanical wounding that is simple to execute and produces a controlled injury in an in vivo model that is highly amenable to real-time microscopy. Injury results in a rapid and measurable hemostatic response and a reproducible wound repair program that can be monitored using video and timelapse microscopy.
Their simple and stereotyped vascular anatomy, which permits reproducible injury at a defined and microscopically accessible site, and the presence of most vascular and hematopoietic cell types make zebrafish embryos particularly useful for studying responses to injury. However, zebrafish embryos do not have functional lymphocytes during the first weeks of development5,6, making this system most appropriate for studying the contribution of innate immunity in inflammation and repair. At present, a wide variety of transgenic zebrafish exist with markers for cells and proteins that participate in thrombus formation, coagulation, inflammation, and wound repair, including lines that label thrombocytes, fibrinogen, erythrocytes, leukocytes and vascular endothelium17,21,25-31. These and other tools should make it possible to follow processes involved in hemostasis and repair in significant detail.
Mechanical injury complements laser injury for the study of hemostasis in zebrafish. While laser-induced injury has been used for years to trigger thrombus formation in zebrafish embryos and mouse models, the mechanisms by which laser injury triggers coagulation and thrombocyte/platelet activation are not fully known16,32. Mechanical injury provides a physiologically relevant method for inducing coagulation by vascular breach and, presumably, tissue-factor-dependent initiation of coagulation cascade. The finding that hirudin treatment significantly increased bleeding times after injury suggests that this model is thrombin-dependent. Mechanical injury additionally complements laser injury by providing sufficient disruption of a blood vessel to provide an opportunity to follow vessel repair. Previous studies have successfully used mechanical injury by scalpel incision and needle puncture to show differences in bleeding times in conditions of pharmacological and genetic manipulation19,33. The minutia pin injury used in the current model may complement other injury models by providing a more reproducible injury due to the small and defined size of the wound it produces and by providing an opportunity to better study vessel recanalization and repair.
Epithelial wounding in the zebrafish has proven to be a powerful model for studying inflammation and wound repair10. The ability to introduce a vascular injury provides an opportunity to assess repair of more complex wounds in settings where fibrin provides a provisional matrix, thrombi and debris are cleared, and vessels regenerate. As these processes participate in normal tissue repair and in acute and chronic inflammation and vascular pathology, this method should help to model aspects of human disease in a system where cellular behaviors can be monitored in real time in a whole animal model.

Zebrafish have been used extensively to study a variety of topics in vascular biology, including vascular development, angiogenesis, and hematopoietic development and pathology1-3. Embryos develop a functional circulation as well as leukocytes and other components of the innate immune system by 1 day post fertilization (dpf) 1,4,5. The conservation of the inflammatory and leukocyte response to injury has made the zebrafish embryo an informative model for such diverse inflammatory processes as tuberculous infection, enterocolitis, and tissue regeneration6-9. Zebrafish embryos have been used to study injury-related inflammation particularly in the context of epithelial wounding and the neutrophil response10,11. Injury to the embryo results in a highly conserved cellular response from cells at the injury site and the innate immune cells recruited to respond to the injury and regulate its resolution11,12. Other injury models have used focused laser pulses to spatially localize injury to specific cell types including neurons, muscle cells, and cardiomyocytes13-15. 
Zebrafish embryos have been used as a model to study hemostasis and thrombosis in conditions of pharmacological and genetic manipulation, using both mechanical and laser-induced thrombus formation16-19. Components of the coagulation cascade appear to be well-conserved and transgenics have allowed for detailed studies of thrombocyte and fibrin deposition at the site of coagulation17,20,21. The procedure presented in this paper complements these methods by providing a system for studying mechanical vessel injury resulting in vessel breach, thrombus formation and resolution, and vessel repair.

<table border="0" cellpadding="0" cellspacing="0" width="867">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Name of Material/ Equipment</td>
			<td style="width:159px;">Company</td>
			<td style="width:159px;">Catalog Number</td>
			<td style="width:303px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Minutia Pins</td>
			<td style="width:159px;">Fine Science Tools</td>
			<td>26002-10</td>
			<td>Tip diameter 0.0125 mm, rod diameter 0.1 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Pin Holder</td>
			<td style="width:159px;">Fine Science Tools</td>
			<td>26016-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dumont #5 Fine Tip Forceps</td>
			<td style="width:159px;">Fine Science Tools</td>
			<td>11254-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Glass Depression Slide</td>
			<td>Aquatic Eco-Systems</td>
			<td style="width:159px;">M30</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Low Melting Agarose</td>
			<td>Lonza&#160;</td>
			<td style="width:159px;">50081</td>
			<td>Preheated to 42 &#186; C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">N-Phenylthiourea (PTU)</td>
			<td style="width:159px;">Sigma Aldrich</td>
			<td style="width:159px;">P7629</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">3-aminobenzoic acid (Tricaine)</td>
			<td style="width:159px;">Sigma Aldrich</td>
			<td style="width:159px;">E10521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Hirudin</td>
			<td style="width:159px;">Sigma Aldrich</td>
			<td style="width:159px;">H7016</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass bottom imaging dishes</td>
			<td style="width:159px;">Mattek</td>
			<td>P35G-1.5-14-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dissecting microscope</td>
			<td style="width:159px;">Olympus</td>
			<td style="width:159px;">SZH10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Fluorescence microscope</td>
			<td style="width:159px;">Zeiss</td>
			<td>Axio Observer</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Aquarium salts</td>
			<td style="width:159px;">Instant Ocean</td>
			<td style="width:159px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Insulin syringe with 28G1/2 needle</td>
			<td style="width:159px;">Becton Dickinson&#160;</td>
			<td style="width:159px;">329461</td>
			<td></td>
		</tr>
	</tbody>
</table>

mechanical vessel injury in zebrafish embryos

Zebrafish (Danio rerio) embryos have proven to be a powerful model for studying a variety of developmental and disease processes. External development and optical transparency make these embryos especially amenable to microscopy, and numerous transgenic lines that label specific cell types with fluorescent proteins are available, making the zebrafish embryo an ideal system for visualizing the interaction of vascular, hematopoietic, and other cell types during injury and repair in vivo. Forward and reverse genetics in zebrafish are well developed, and pharmacological manipulation is possible. We describe a mechanical vascular injury model using micromanipulation techniques that exploits several of these features to study responses to vascular injury including hemostasis and blood vessel repair. Using a combination of video and timelapse microscopy, we demonstrate that this method of vascular injury results in measurable and reproducible responses during hemostasis and wound repair. This method provides a system for studying vascular injury and repair in detail in a whole animal model.

Mechanical vessel injury was performed on 2 dpf embryos (Figure 2A-C). Injury results in a rapid and reliable coagulation response as measured by time to cessation of bleeding (Figure 2D). To determine whether or not differences in the coagulation response could be measured, the anticoagulant hirudin was administered to the embryos by injection into the Duct of Cuvier immediately prior to wounding (5-10 nl of 1 unit per &#181;l hirudin dissolved in water)(for demonstration of injections into the Duct of Cuvier, see previous JoVE article23)24. The administration of hirudin prior to injury resulted in significantly increased bleeding times versus vehicle control (Figure 2D).
Evidence of vessel damage and coagulation can be seen immediately post-injury using transgenic lines for endothelial (kdrl:egfp) and red blood cell (gata1a:dsred) markers25,26. Images were acquired sequentially every 5 min for a 12 hr period using epifluorescence. Representative still images are shown throughout different stages of wound repair (Figure 3). Using a combination of differential interference contrast (DIC) and fluorescence microscopy, it is possible to measure distinct parameters of wound repair. In order to determine whether or not wound repair followed a reproducible pattern across experiments, the time to reestablished blood flow was measured in 4 groups of fish. Vessel injury resulted in a reliable stereotypical response of 253 &#177; 16 min to the reestablishment of blood flow through the wounded vessel (n = 4-5 fish per experiment, average &#177; SEM).
<img alt="Figure 1" src="/files/ftp_upload/52460/52460fig1highres.jpg" /> 
Figure 1: Diagram of 2 dpf embryo showing placement of minutia pin for performing mechanical injury of the caudal vein (CV). Vascular compartment is shaded in grey.
<img alt="Figure 2" src="/files/ftp_upload/52460/52460fig2highres.jpg" /> 
Figure 2: Bleeding times can be visually measured after mechanical injury. Stills from real-time video of zebrafish vessel injury on 2 dpf embryos. Images are shown at the time of injury (A), during active blood loss from the wound (B), and after cessation of blood loss (C). All times indicated are in seconds. Embryos are oriented laterally with anterior at top and ventral surface facing to the left. Scale bar 100 &#181;m. Administration of the anticoagulant hirudin led to significantly increased bleeding times versus vehicle control (D) (p &#60;0.0001, Student&#8217;s t-test).<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52460/52460fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/52460/52460fig3highres.jpg" /> 
Figure 3: Visualizing mechanical injury and repair using transgenic markers. Stills from timelapse DIC and fluorescence microscopy after vessel injury using markers for vascular endothelium (kdrl:egfp) and red blood cells (gata1a:dsred) in 2 dpf embryos. Images showed a gap in vessels and local red blood cell accumulation (t = 25), partial repair with re-established blood flow (t = 210), and apparently complete restoration of normal vessel structure (t = 615). Time is indicated in minutes. Embryos are oriented laterally with anterior at top and ventral surface facing to the left. * indicates the position of the dorsal aorta. The injury (arrowhead) disrupted the caudal vein and part of the caudal plexus. Scale bar 25 &#181;m.

Watch this Scientific Journal Video about Mechanical Vessel Injury in Zebrafish Embryos at JoVE.com

Mechanical Vessel Injury in Zebrafish Embryos

This article describes a method for creating a mechanical vessel injury in zebrafish embryos. This injury model provides a platform for studying hemostasis, injury-related inflammation, and wound healing in an organism ideally suited for real-time microscopy.

Zebrafish (Danio rerio) embryos have proven to be a powerful model for studying a variety of developmental and disease processes.  External development ...

mechanical-vessel-injury-in-zebrafish-embryos

Nanyang Technological University

Research

JoVE Journal

Developmental Biology

7.2K Views.  University of California. This article describes a method for creating a mechanical vessel injury in zebrafish embryos. This injury model provides a platform for studying hemostasis, injury-related inflammation, and wound healing in an organism ideally suited for real-time microscopy. 

Video: Mechanical Vessel Injury in Zebrafish Embryos

Kidney Regeneration in Adult Zebrafish by Gentamicin Induced Injury

The kidney is essential for fluid homeostasis, blood pressure regulation and filtration of waste from the body. The fundamental unit of kidney function is the nephron. Mammals are able to repair existing nephrons after injury, but lose the ability to form new nephrons soon after birth. In contrast to mammals, adult fish produce new nephrons (neonephrogenesis) throughout their lives in response to growth requirements or injury. Recently, lhx1a has been shown to mark nephron progenitor cells in the adult zebrafish kidney, however mechanisms controlling the formation of new nephrons after injury remain unknown. Here we show our method for robust and reproducible injury in the adult zebrafish kidney by intraperitoneal (i.p.) injection of gentamicin, which uses a noninvasive visual screening process to select for fish with strong but nonlethal injury. Using this method, we can determine optimal gentamicin dosages for injury and go on to demonstrate the effect of higher temperatures on kidney regeneration in zebrafish.

Here we present a reliable method to study adult kidney regeneration by inducing acute kidney injury by gentamicin injection. We show that injury is dependent on gentamicin dosage and environmental temperature using in situ hybridization to label lhx1a+ developing new nephrons.

The kidney is essential for fluid homeostasis, blood pressure regulation and filtration of waste from the body. The fundamental unit of kidney function is ...

Isolation and Characterization of Single Cells from Zebrafish Embryos

The zebrafish (Danio rerio) is a powerful model organism to study vertebrate development. Though many aspects of zebrafish embryonic development have been described at the morphological level, little is known about the molecular basis of cellular changes that occur as the organism develops. With recent advancements in microfluidics and multiplexing technologies, it is now possible to characterize gene expression in single cells. This allows for investigation of heterogeneity between individual cells of specific cell populations to identify and classify cell subtypes, characterize intermediate states that occur during cell differentiation, and explore differential cellular responses to stimuli. This study describes a protocol to isolate viable, single cells from zebrafish embryos for high throughput multiplexing assays. This method may be rapidly applied to any zebrafish embryonic cell type with fluorescent markers. An extension of this method may also be used in combination with high throughput sequencing technologies to fully characterize the transcriptome of single cells. As proof of principle, the relative abundance of cardiac differentiation markers was assessed in isolated, single cells derived from nkx2.5 positive cardiac progenitors. By evaluation of gene expression at the single cell level and at a single time point, the data support a model in which cardiac progenitors coexist with differentiating progeny. The method and work flow described here is broadly applicable to the zebrafish research community, requiring only a labeled transgenic fish line and access to microfluidics technologies.

This protocol describes a method for isolating single cells from zebrafish embryos, enriching for cells of interest, capturing zebrafish cells in microfluidic based single cell multiplex systems, and assessing gene expression from single cells.

The zebrafish (Danio rerio) is a powerful model organism to study vertebrate development. Though many aspects of zebrafish embryonic development have been ...

Affinity Labeling Detection of Endogenous Receptors from Zebrafish Embryos

By combining the powers of Affinity Labeling and Immunoprecipitation (AFLIP), a technique for the detection of low abundance receptors in zebrafish embryos has been implemented. This technique takes advantage of the selectivity and sensitivity conferred by affinity labeling of a given receptor by its ligand with the specificity of the immunoprecipitation. We have used AFLIP to detect the type III TGF-&#946; receptor (TGFBR3), also know as betaglycan, during early zebrafish development. AFLIP was instrumental in validating the efficacy of a TGFBR3 morphant zebrafish phenotype. In the first step, embryo protein extracts are prepared and used to generate 125I-TGF-&#946;2-TGFBR3 complexes that are purified by immunoprecipitation. Later, these complexes are covalently cross-linked and revealed using SDS-PAGE separation and autoradiography detection. This technique requires the availability of a labeled ligand for, and a specific antibody against, the receptor to be detected, and shall be easily adapted to identify any growth factor or cytokine receptor that meets these requirements.

A novel technique for the detection of low abundance endogenous receptors present in zebrafish embryos is described. We have named it AFLIP because it consists of affinity labeling of the receptor by its ligand linked to immunoprecipitation.

By combining the powers of Affinity Labeling and Immunoprecipitation (AFLIP), a technique for the detection of low abundance receptors in zebrafish ...

Ploidy Manipulation of Zebrafish Embryos with Heat Shock 2 Treatment

Manipulation of ploidy allows for useful transformations, such as diploids to tetraploids, or haploids to diploids. In the zebrafish Danio rerio, specifically the generation of homozygous gynogenetic diploids is useful in genetic analysis because it allows the direct production of homozygotes from a single heterozygous mother. This article describes a modified protocol for ploidy duplication based on a heat pulse during the first cell cycle, Heat Shock 2 (HS2). Through inhibition of centriole duplication, this method results in a precise cell division stall during the second cell cycle. The precise one-cycle division stall, coupled to unaffected DNA duplication, results in whole genome duplication. Protocols associated with this method include egg and sperm collection, UV treatment of sperm, in vitro fertilization and heat pulse to cause a one-cell cycle division delay and ploidy duplication. A modified version of this protocol could be applied to induce ploidy changes in other animal species.

A modified protocol for ploidy manipulation uses a heat shock to induce a one-cycle stall in cytokinesis in the early embryo. This protocol is demonstrated in the zebrafish but may be applicable to other species.

Manipulation of ploidy allows for useful transformations, such as diploids to tetraploids, or haploids to diploids. In the zebrafish Danio rerio, ...

Biosensing Motor Neuron Membrane Potential in Live Zebrafish Embryos

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the cells are located. Specifically, they have been developed to analyze the electrical activity of excitable cells, such as spinal neurons. In such a scenario, it is crucial to preserve the integrity of the spinal cell, but it is also important to preserve the anatomy and physiological shape of the systems involved. Indeed, the comprehension of the manner in which the nervous system-and other complex systems-works must be based on a systemic approach. For this reason, the live zebrafish embryo was chosen as a model system, and the spinal neuron membrane voltage changes were evaluated without interfering with the physiological conditions of the embryos. 
Here, an approach combining the employment of zebrafish embryos with a FRET-based biosensor is described. Zebrafish embryos are characterized by a very simplified nervous system and are particularly suited for imaging applications thanks to their transparency, allowing for the employment of fluorescence-based voltage indicators at the plasma membrane during zebrafish development. The synergy between these two components makes it possible to analyze the electrical activity of the cells in intact living organisms, without perturbing the physiological state. Finally, this non-invasive approach can co-exist with other analyses (e.g., spontaneous movement recordings, as shown here).

Protocols described here allow for the study of the electrical properties of excitable cells in the most non-invasive physiological conditions by employing zebrafish embryos in an in vivo system together with a fluorescence resonance energy transfer (FRET)-based genetically encoded voltage indicator (GEVI) selectively expressed in the cell type of interest.

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the ...

Precise Cellular Ablation Approach for Modeling Acute Kidney Injury in Developing Zebrafish

Acute Kidney Injury (AKI) is a common medical condition with a high mortality rate. With the repair abilities of the kidney, it is possible to restore adequate kidney function after supportive treatment. However, a better understanding of how nephron cell death and repair occur on the cellular level is required to minimize cell death and to enhance the regenerative process. The zebrafish pronephros is a good model system to accomplish this goal because it contains anatomical segments that are similar to the mammalian nephron. Previously, the most common model used to study kidney injury in fish was the pharmacological gentamicin model. However, this model does not allow for precise spatiotemporal control of injury, and hence it is difficult to study cellular and molecular processes involved in kidney repair. To overcome this limitation, this work presents a method through which, in contrast to the gentamicin approach, a specific Green Fuorescent Protein (GFP)-expressing nephron segment can be photoablated using a violet laser light (405 nm). This novel model of AKI provides many advantages that other methods of epithelial injury lack. Its main advantages are the ability to &#34;dial&#34; the level of injury and the precise spatiotemporal control in the robust in vivo animal model. This new method has the potential to significantly advance the level of understanding of kidney injury and repair mechanisms.

This work presents a new in vivo model of segmental kidney injury using kidney GFP transgenic zebrafish. The model allows for the induction of the targeted ablation of kidney epithelial cells to show the cellular mechanisms of nephron injury and repair.

Acute Kidney Injury (AKI) is a common medical condition with a high mortality rate. With the repair abilities of the kidney, it is possible to restore ...

Histological Analyses of Acute Alcoholic Liver Injury in Zebrafish

Alcoholic Liver Disease (ALD) refers to damage to the liver due to acute or chronic alcohol abuse. It is among the leading causes of alcohol-related morbidity and mortality and affects more than 2 million people in the United States. A better understanding of the cellular and molecular mechanisms underlying alcohol-induced liver injury is crucial for developing effective treatment for ALD. Zebrafish larvae exhibit hepatic steatosis and fibrogenesis after just 24 h of exposure to 2% ethanol, making them useful for the study of acute alcoholic liver injury. This work describes the procedure for acute ethanol treatment in zebrafish larvae and shows that it causes steatosis and swelling of the hepatic blood vessels. A detailed protocol for Hematoxylin and Eosin (H&#38;E) staining that is optimized for the histological analysis of the zebrafish larval liver, is also described. H&#38;E staining has several unique advantages over immunofluorescence, as it marks all liver cells and extracellular components simultaneously and can readily detect hepatic injury, such as steatosis and fibrosis. Given the increasing usage of zebrafish in modeling toxin and virus-induced liver injury, as well as inherited liver diseases, this protocol serves as a reference for the histological analyses performed in all these studies.

This protocol describes histological analyses of the livers from zebrafish larvae that have been treated with 2% ethanol for 24 h. Such acute ethanol treatment results in hepatic steatosis and swelling of the hepatic vasculature.

Alcoholic Liver Disease (ALD) refers to damage to the liver due to acute or chronic alcohol abuse. It is among the leading causes of alcohol-related ...

Induction of Hypoxia in Living Frog and Zebrafish Embryos

Here, we introduce a novel system for hypoxia induction, which we developed to study the effects of hypoxia in aquatic organisms such as frog and zebrafish embryos. Our system comprises a chamber featuring a simple setup that is nevertheless robust to induce and maintain a specific oxygen concentration and temperature in any experimental solution of choice. The presented system is very cost-effective but highly functional, it allows induction and sustainment of hypoxia for direct experiments in vivo and for various time periods up to 48 h.
To monitor and study the effects of hypoxia, we have employed two methods - measurement of levels of hypoxia-inducible factor 1alpha (HIF-1&#945;) in whole embryos or specific tissues and determination of retinal stem cell proliferation by 5-ethynyl-2&#8242;-deoxyuridine (EdU) incorporation into the DNA. HIF-1&#945; levels can serve as a general hypoxia marker in the whole embryo or tissue of choice, here embryonic retina. EdU incorporation into the proliferating cells of embryonic retina is a specific output of hypoxia induction. Thus, we have shown that hypoxic embryonic retinal progenitors decrease proliferation within 1 h of incubation under 5% oxygen of both frog and zebrafish embryos.
Once mastered, our setup can be employed for use with small aquatic model organisms, for direct in vivo experiments, any given time period and under normal, hypoxic or hyperoxic oxygen concentration or under any other given gas mixture.

We introduce a novel hypoxic chamber system for use with aquatic organisms such as frog and zebrafish embryos. Our system is simple, robust, cost-effective and allows the induction and sustainment of hypoxia in vivo and for up to 48 h. We present 2 reproducible methods to monitor the effectiveness of hypoxia.

Here, we introduce a novel system for hypoxia induction, which we developed to study the effects of hypoxia in aquatic organisms such as frog and ...

Visualization of Cellular Electrical Activity in Zebrafish Early Embryos and Tumors

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling processes of excitable neuronal and muscular cells and many other biological processes, such as embryonic developmental patterning. However, there is a need for in vivo electrical activity monitoring in vertebrate embryogenesis. The advances of genetically encoded fluorescent voltage indicators (GEVIs) have made it possible to provide a solution for this challenge. Here, we describe how to create a transgenic voltage indicator zebrafish using the established voltage indicator, ASAP1 (Accelerated Sensor of Action Potentials 1), as an example. The Tol2 kit and a ubiquitous zebrafish promoter, ubi, were chosen in this study. We also explain&#160;the processes of Gateway site-specific cloning, Tol2 transposon-based zebrafish transgenesis, and the imaging process for early-stage fish embryos and fish tumors using regular epifluorescent microscopes. Using this fish line, we found that there are cellular electric voltage changes during zebrafish embryogenesis, and fish larval movement. Furthermore, it was observed that in a few zebrafish malignant peripheral nerve sheath tumors, the tumor cells were generally polarized compared to the surrounding normal tissues.

Here, we show the process of creating a cellular electric voltage reporter zebrafish line to visualize embryonic development, movement, and fish tumor cells in vivo.

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling ...

Whole Mount Immunohistochemistry in Zebrafish Embryos and Larvae

Immunohistochemistry is a widely used technique to explore protein expression and localization during both normal developmental and disease states. Although many immunohistochemistry protocols have been optimized for mammalian tissue and tissue sections, these protocols often require modification and optimization for non-mammalian model organisms. Zebrafish are increasingly used as a model system in basic, biomedical, and translational research to investigate the molecular, genetic, and cell biological mechanisms of developmental processes. Zebrafish offer many advantages as a model system but also require modified techniques for optimal protein detection. Here, we provide our protocol for whole-mount fluorescence immunohistochemistry in zebrafish embryos and larvae. This protocol additionally describes several different mounting strategies that can be employed and an overview of the advantages and disadvantages each strategy provides. We also describe modifications to this protocol to allow detection of chromogenic substrates in whole mount tissue and fluorescence detection in sectioned larval tissue. This protocol is broadly applicable to the study of many developmental stages and embryonic structures.

Here, we present a protocol for fluorescent antibody-mediated detection of proteins in whole preparations of zebrafish embryos and larvae.

Immunohistochemistry is a widely used technique to explore protein expression and localization during both normal developmental and disease states. ...