Name: adult zebrafish injury models to study the effects of prednisolone in regenerating bone tissue
Uploaded: 2018-10-18T14:30:00
Description: Watch this Scientific Journal Video about Adult Zebrafish Injury Models to Study the Effects of Prednisolone in Regenerating Bone Tissue at JoVE.com

This study was supported by a grant of the Center of Regenerative Therapies Dresden (&#34;Zebrafish as a model to unravel the mechanisms of glucocorticoid-induced bone loss&#34;) and additionally by a grant of the Deutsche Forschungsgemeinschaft (Transregio 67, project 387653785) to FK. We are very grateful to Jan Kaslin and Avinash Chekuru for their guidance and assistance on performing trepanation of the calvariae and fractures in bony fin rays. Experiments were designed, performed and analyzed by KG and FK. FK wrote the manuscript. We would also like to thank Katrin Lambert,&#160;Nicole Cudak, and other members of the Knopf and Brand labs for technical assistance and discussion. Our thanks also goes to Marika Fischer and Jitka Michling for excellent fish care and to Henriette Knopf and Josh Currie for proofreading the manuscript.

All methods described here were approved by the Landesdirektion Dresden (Permit numbers: AZ 24D-9168.11-1/2008-1, AZ 24-9168.11-1/2011-52, AZ 24-9168.11-1/2013-5, AZ 24-9168.11-1/2013-14, AZ DD24.1- 5131/354/87).
1. Preparation of Materials and Solutions
NOTE: Prednisolone, like other glucocorticoids, leads to immunosuppression. Thus, precaution must be taken to prevent infection in treated animals during the experiment. To this end, autoclave glass ware and &#39;fish...

<ol>
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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=Mutations+affecting+somite+formation+and+patterning+in+the+zebrafish,+Danio+rerio.">Mutations affecting somite formation and patterning in the zebrafish, Danio rerio.</a> Development. 123, 153-164 (1996).</li><li>Walker, M. B., Kimmel, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+two-color+acid-free+cartilage+and+bone+stain+for+zebrafish+larvae.">A two-color acid-free cartilage and bone stain for zebrafish larvae.</a> Biotechnic &amp; Histochemistry. 82 (1), 23-28 (2007).</li><li>Kyritsis, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acute+inflammation+initiates+the+regenerative+response+in+the+adult+zebrafish+brain.">Acute inflammation initiates the regenerative response in the adult zebrafish brain.</a> Science. 338 (6112), 1353-1356 (2012).</li><li>Oppedal, D., Goldsmith, M. 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+chemical+screen+to+identify+novel+inhibitors+of+fin+regeneration+in+zebrafish.">A chemical screen to identify novel inhibitors of fin regeneration in zebrafish.</a> Zebrafish. 7 (1), 53-60 (2010).</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>Spoorendonk, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinoic+acid+and+Cyp26b1+are+critical+regulators+of+osteogenesis+in+the+axial+skeleton.">Retinoic acid and Cyp26b1 are critical regulators of osteogenesis in the axial skeleton.</a> Development. 135 (22), 3765-3774 (2008).</li><li>Gioia, 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=The+chaperone+activity+of+4PBA+ameliorates+the+skeletal+phenotype+of+Chihuahua,+a+zebrafish+model+for+dominant+osteogenesis+imperfecta.">The chaperone activity of 4PBA ameliorates the skeletal phenotype of Chihuahua, a zebrafish model for dominant osteogenesis imperfecta.</a> Human Molecular Genetics. 26 (15), 2897-2911 (2017).</li><li>Fiedler, I. A. K., 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=Severely+impaired+bone+material+quality+in+Chihuahua+zebrafish+resembles+classical+dominant+human+osteogenesis+imperfecta.">Severely impaired bone material quality in Chihuahua zebrafish resembles classical dominant human osteogenesis imperfecta.</a> Journal of Bone and Mineral Research. , (2018).</li><li>Fisher, S., Jagadeeswaran, P., Halpern, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiographic+analysis+of+zebrafish+skeletal+defects.">Radiographic analysis of zebrafish skeletal defects.</a> Developmental Biology. 264 (1), 64-76 (2003).</li><li>Hayes, A. 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=Spinal+deformity+in+aged+zebrafish+is+accompanied+by+degenerative+changes+to+their+vertebrae+that+resemble+osteoarthritis.">Spinal deformity in aged zebrafish is accompanied by degenerative changes to their vertebrae that resemble osteoarthritis.</a> PLoS One. 8 (9), e75787 (2013).</li><li>Mitchell, R. 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=New+tools+for+studying+osteoarthritis+genetics+in+zebrafish.">New tools for studying osteoarthritis genetics in zebrafish.</a> Osteoarthritis Cartilage. 21 (2), 269-278 (2013).</li><li>Fleming, A., Sato, M., Goldsmith, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+in+vivo+screening+for+bone+anabolic+compounds+with+zebrafish.">High-throughput in vivo screening for bone anabolic compounds with zebrafish.</a> Journal of Biomolecular Screening. 10 (8), 823-831 (2005).</li><li>de Vrieze, E., Zethof, J., Schulte-Merker, S., Flik, G., Metz, J. 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Zebrafish have proven useful in skeletal research in many regards. Selected mutants mimic aspects of human disease such as osteogenesis imperfecta or osteoarthritis23,24,25,26,27, and larvae as well as scales are being used to identify bone anabolic compounds in small molecule screens7,28,<s...

Zebrafish represent a powerful animal model to study vertebrate development and disease. This is due to the fact that they are small animals that breed extremely well and that their genome is fully sequenced and amenable to manipulation1. Other advantages include the option to perform continued live imaging at different stages, including in vivo imaging of adult zebrafish2, and the ability to perform high throughput drug screens in zebrafish larvae3. Additionally, zebrafish possess a high regenerative capacity in a variety of organs and tissues including bone, and thus serve as a useful system to study skeletal disease and repair4,5.
Glucocorticoid-induced osteoporosis (GIO) is a disease that results from long term treatment with glucocorticoids, for example in the course of autoimmune disease treatment such as of asthma or rheumatoid arthritis. GIO develops in about 30% of glucocorticoid-treated patients and represents a major health issue6; therefore, it is important to investigate the impact of immunosuppression on bone tissue in great detail. In recent years a variety of zebrafish models dealing with the pathogenesis of GIO have been developed. Glucocorticoid-mediated bone loss has been induced in zebrafish larvae, for example, which led to the identification of counteractive compounds increasing bone mass in a drug screen7. Furthermore, glucocorticoid-induced bone inhibitory effects have been mimicked in zebrafish scales both in vitro and in vivo8,9. These assays are very convincing approaches, especially when it comes to the identification of novel immunosuppressive and bone anabolic drugs. However, they only partly take into account the endoskeleton and have not been performed in a regenerative context. Thus, they do not allow the investigation of glucocorticoid-mediated effects during rapid modes of adult, regenerative bone formation.
Here, we present a protocol enabling researchers to study glucocorticoid-mediated effects on adult zebrafish bones undergoing regeneration. Injury models include partial amputation of the zebrafish caudal fin, trepanation of the skull, as well as the creation of fin ray fractures (Figure 1A-1C), and are combined with glucocorticoid exposure via incubation (Figure 1E). We have recently used a portion of this protocol to describe the consequences of exposure to prednisolone, one of the commonly prescribed corticosteroid drugs, on adult zebrafish regenerating fin and skull bone10. In zebrafish, prednisolone administration leads to decreased osteoblast proliferation, incomplete osteoblast differentiation and rapid induction of apoptosis in the monocyte/macrophage lineage10. In this protocol, we also describe how fractures can be introduced into single bony fin ray segments11, as this approach may be useful when studying glucocorticoid-mediated effects on bone occuring during fracture repair. The methods presented here will help to further address underlying mechanisms of glucocorticoid action in rapidly regenerating bone and may also be employed in other settings of systemic drug administration in the context of zebrafish tissue regeneration.

<table>
	<tbody>
		<tr>
			<td>Prednisolone</td>
			<td>Sigma-Aldrich</td>
			<td>P6004</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylsulfoxid (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>D8418</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl-3-aminobenzoate methanesulfonate (MS-222)</td>
			<td>Sigma-Aldrich</td>
			<td>A5040</td>
			<td></td>
		</tr>
		<tr>
			<td>Blunt forceps</td>
			<td>Aesculap</td>
			<td>BD027R</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine forceps</td>
			<td>Dumont</td>
			<td>91150-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>Braun</td>
			<td>5518059</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Biozym</td>
			<td>840004</td>
			<td></td>
		</tr>
		<tr>
			<td>Injection needle (0.3x13 mm)</td>
			<td>BD Beckton Dickinson</td>
			<td>30400</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro drill</td>
			<td>Cell Point Scientific</td>
			<td>67-1000</td>
			<td>distributed e.g. by Harvard Apparatus</td>
		</tr>
		<tr>
			<td>Steel burrs (0.5 &#181;m diameter)</td>
			<td>Fine Science tools</td>
			<td>19007-05</td>
			<td></td>
		</tr>
		<tr>
			<td>Artemia ssp.</td>
			<td>Sanders</td>
			<td>425GR</td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur pipette (plastic, Pastette)</td>
			<td>Alpha Labs</td>
			<td>LW4111</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>Alizarin red S powder</td>
			<td>Sigma-Aldrich</td>
			<td>A5533</td>
			<td></td>
		</tr>
		<tr>
			<td>Alcian blue 8 GX</td>
			<td>Sigma-Aldrich</td>
			<td>A5268</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcein</td>
			<td>Sigma-Aldrich</td>
			<td>C0875</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Sigma-Aldrich</td>
			<td>T7409</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Leica</td>
			<td>MZ16 FA</td>
			<td>with QIMAGING RETIGA-SRV camera</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Olympus</td>
			<td>MVX10</td>
			<td>with Olympus DP71 or DP80 camera</td>
		</tr>
	</tbody>
</table>

adult zebrafish injury models to study the effects of prednisolone in regenerating bone tissue

Zebrafish are able to regenerate various organs, including appendages (fins) after amputation. This involves the regeneration of bone, which regrows within roughly two weeks after injury. Furthermore, zebrafish are able to heal bone rapidly after trepanation of the skull, and repair fractures that can be easily introduced into zebrafish bony fin rays. These injury assays represent feasible experimental paradigms to test the effect of administered drugs on rapidly forming bone. Here, we describe the use of these 3 injury models and their combined use with systemic glucocorticoid treatment, which exerts bone inhibitory and immunosuppressive effects. We provide a workflow on how to prepare for immunosuppressive treatment in adult zebrafish, illustrate how to perform fin amputation, trepanation of calvarial bones, and fin fractures, and describe how the use of glucocorticoids affects both bone forming osteoblasts and cells of the monocyte/macrophage lineage as part of innate immunity in bone tissue.

The protocol presented here has been used repeatedly to induce rapid bone formation in the course of regeneration of the zebrafish fin and skull10,11,16. In combination with the presented method of prednisolone administration, studies on prednisolone&#39;s effects during bone regeneration can be pursued. For example, studies on bone formation and mineralization in the regenerate can be performed....

Watch this Scientific Journal Video about Adult Zebrafish Injury Models to Study the Effects of Prednisolone in Regenerating Bone Tissue at JoVE.com

Adult Zebrafish Injury Models to Study the Effects of Prednisolone in Regenerating Bone Tissue

Here, we describe 3 adult zebrafish injury models and their combined use with immunosuppressive drug treatment. We provide guidance on imaging of regenerating tissues and on detecting bone mineralization therein.

Zebrafish are able to regenerate various organs, including appendages (fins) after amputation. This involves the regeneration of bone, which regrows ...

This method can help answer key questions in the field of immunosuppressive therapeutic intervention for studying the adverse effects of drugs on tissue regeneration, in particular, in bones. The main advantage of this technique is that it combines past models of Zebrafish bone regeneration with systemic drug exposure by immersion of the injured Zebrafish in drug supplemented fish water. Before beginning the procedure, autoclave one aluminum foil covered 600 milliliter beaker per Zebrafish and an appropriate number of glass bottles of fish water for the experiment and prepare the immunosuppressive drug in experimental control solutions of interest.For an amputation injury, use blunt forceps to carefully place an anesthetized Zebrafish on its lateral side on the inversed lid of a 100 millimeter Petri dish and use a scalpel to resect 50%of the fin. Then place the fish into an autoclaved beaker containing 300 milliliters of fish water supplemented with appropriate experimental agent and cover the beaker with foil to prevent Zebrafish escape. To induce a fin fracture injury, place an anesthetized Zebrafish on its lateral side in a 100 millimeter agarose coated Petri dish under a dissecting microscope and push an injection needle slightly into a bony fin ray segment until a crack appears.It is important to introduce not too many fractures into the fin because this might greatly impair stability. Then transfer the fish into an autoclaved beaker containing 300 milliliters of fish water supplemented with the appropriate experimental agent. To generate a calvarial skull injury, hold an anesthetized Zebrafish in the upright position so the calvarial bones are easily visualized under a dissection microscope.Place a rotating micro drill equipped with a 500 micrometer drill bit over the center of the frontal bone and gently touch the bone to produce a hole the size of the micro drill burr. It is critical to not move the drill laterally while producing the injury and to stop immediately once the resistance of the tissue drops. Otherwise, the brain will be damaged.Then place the fish into an autoclaved beaker containing 300 milliliters of fish water supplemented with the appropriate experimental agent. Change the water in the beakers daily by transferring the Zebrafish and the fish water into an appropriate temporary container and refilling the beaker with fresh drug supplemented fish water. Then use a fish net to return the Zebrafish to its beaker.For treatments lasting up to two days total, do not feed the Zebrafish. During longer experiments, feed the Zebrafish with 0.5 to one milliliter of hatched Artemia SSP every second day. For fin injury analysis, harvest the fine and use fine forceps to grasp the fin at one edge of the stump.Use a second pair of forceps to grab the opposite stump edge and slightly press the tissue onto the bottom of the dish which contains cold 4%PFA for 10 to 20 seconds. Repeat fin flattening as necessary. The fin should now lay flat without curling.For long term sample storage after fixation, wash the tissue with three 20 minute PBS washes and an ascending methanol series. The samples can then be stored in 100%methanol at minus 20 degrees Celsius. For Alizarin Red staining, rehydrate methanol stored samples in a descending methanol series followed by two 20 minute washes in PBS and one five minute wash in deionized water.After the last wash, add Alizarin Red solution to the sample tissue and incubate the sample at room temperature with rocking for the appropriate staining period. To clear the samples, treat the tissue with the decreasing 1%potassium hydroxide glycerol series. Then store the samples in a one to one 0.1%potassium hydroxide to 80%glycerol solution and mount the tissues with 80%glycerol for imagining.For Calcein staining, incubate up to three Zebrafish simultaneously in 100 millimeters of Calcein solution for 20 minutes in a glass beaker covered with aluminum foil. At the end of the incubation, transfer the Zebrafish to a container of fish water and let the fish swim briefly before transferring them to a new container of fish water. After 20 minutes in the second beaker to acquire live images of fin regenerates, place an anesthetized Zebrafish onto an agarose coated Petri dish and image the fin by stereo microscopy.To acquire images of the regenerating skull bones, place the Zebrafish upright in a sponge and image the skull by fluorescence microscopy. Treatment with Prednisolone, similar to other glucocorticoids, leads to an overall inhibition of fin regeneration including bone formation as detected by Alizarin Red staining of fixed caudal fin tissue. Similarly, the drug has delaying effect on calvarial skull injury closure.Due to immunosuppression, reduced macrophage numbers can also be detected by immunohistochemistry on frozen tissue sections as evidenced by using anti-mCherry and anti-GFP antibody staining and transgenic MPEG-1 mCherry crossed with Osterix NGFP Zebrafish on Zebrafish skull tissue samples from Prednisolone treated animals. While attempting these procedures it is important to minimize the variability in the bone regeneration speed by carrying out the injury essays in a highly reproducible manner. It is also crucial to single house Zebrafish in autoclaved beakers containing autoclaved fish water in order to avoid microbial infection.This protocol will help to further address the underlying mechanisms of glucocorticoid action. For instance, in the context of glucocorticoid induced osteoporosis and may also be adapted for the use of other drugs and other Zebrafish bone.

adult-zebrafish-injury-models-to-study-effects-prednisolone

Research

JoVE Journal

Developmental Biology

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 ...

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.

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 ...

Use of the TetON System to Study Molecular Mechanisms of Zebrafish Regeneration

The zebrafish has become a very important model organism for studying vertebrate development, physiology, disease, and tissue regeneration. A thorough understanding of the molecular and cellular mechanisms involved requires experimental tools that allow for inducible, tissue-specific manipulation of gene expression or signaling pathways. Therefore, we and others have recently adapted the TetON system for use in zebrafish. The TetON system facilitates temporally and spatially-controlled gene expression and we have recently used this tool to probe for tissue-specific functions of Wnt/beta&#8211;catenin signaling during zebrafish tail fin regeneration. Here we describe the workflow for using the TetON system to achieve inducible, tissue-specific gene expression in the adult regenerating zebrafish tail fin. This includes the generation of stable transgenic TetActivator and TetResponder lines, transgene induction and techniques for verification of tissue-specific gene expression in the fin regenerate. Thus, this protocol serves as blueprint for setting up a functional TetON system in zebrafish and its subsequent use, in particular for studying fin regeneration.

Here we outline the workflow for using the TetON system to achieve tissue-specific gene expression in the adult regenerating zebrafish tail fin.

The zebrafish has become a very important model organism for studying vertebrate development, physiology, disease, and tissue regeneration. A thorough ...

Protocols for Analyzing the Role of Paneth Cells in Regenerating the Murine Intestine using Conditional Cre-lox Mouse Models

The epithelial surface of the mammalian intestine is a dynamic tissue that renews every 3 - 7 days. Understanding this renewal process identified a population of rapidly cycling intestinal stem cells (ISCs) characterized by their expression of the Lgr5 gene. These are supported by a quiescent stem cell population, marked by Bmi-1 expression, capable of replacing them in the event of injury. Investigating the interactions between these populations is crucial to understanding their roles in disease and cancer. The ISCs exist within crypts on the intestinal surface, these niches support the ISC in replenishing the epithelia. The interaction between active and quiescent ISCs likely involves other differentiated cells within the niche, as it has previously been demonstrated that the &#8216;&#8216;stemness&#8217;&#8217; of the Lgr5 ISC is closely tied to the presence of their neighboring Paneth cells. Using conditional cre-lox mouse models we tested the effect of deleting the majority of active ISCs in the presence or absence of the Paneth cells. Here we describe the techniques and analysis undertaken to characterize the intestine and demonstrate that the Paneth cells play a crucial role within the ISC niche in aiding recovery following substantial insult.

Protocols for Analyzing the Role of Paneth Cells in Regenerating the Murine Intestine using Conditional Cre-lox Mouse Models

Intestinal epithelial stem cells (ISCs) are intermingled with Paneth cells. These cells are differentiated progeny of the ISC, which support the ISCs and provide antibacterial protection. Here we demonstrate how we used transgenic conditional mouse models to establish that Paneth cells play a crucial role in maintaining the intestinal epithelia.

The epithelial surface of the mammalian intestine is a dynamic tissue that renews every 3 - 7 days. Understanding this renewal process identified a ...

Combining Intravital Fluorescent Microscopy (IVFM) with Genetic Models to Study Engraftment Dynamics of Hematopoietic Cells to Bone Marrow Niches

Increasing evidence indicates that normal hematopoiesis is regulated by distinct microenvironmental cues in the BM, which include specialized cellular niches modulating critical hematopoietic stem cell (HSC) functions1,2. Indeed, a more detailed picture of the hematopoietic microenvironment is now emerging, in which the endosteal and the endothelial niches form functional units for the regulation of normal HSC and their progeny3,4,5. New studies have revealed the importance of perivascular cells, adipocytes and neuronal cells in maintaining and regulating HSC function6,7,8. Furthermore, there is evidence that cells from different lineages, i.e. myeloid and lymphoid cells, home and reside in specific niches within the BM microenvironment. However, a complete mapping of the BM microenvironment and its occupants is still in progress.
Transgenic mouse strains expressing lineage specific fluorescent markers or mice genetically engineered to lack selected molecules in specific cells of the BM niche are now available. Knock-out and lineage tracking models, in combination with transplantation approaches, provide the opportunity to refine the knowledge on the role of specific &#34;niche&#34; cells for defined hematopoietic populations, such as HSC, B-cells, T-cells, myeloid cells and erythroid cells. This strategy can be further potentiated by merging the use of two-photon microscopy of the calvarium. By providing in vivo high resolution imaging and 3-D rendering of the BM calvarium, we can now determine precisely the location where specific hematopoietic subsets home in the BM and evaluate the kinetics of their expansion over time. Here, Lys-GFP transgenic mice (marking myeloid cells)9 and RBPJ knock-out mice (lacking canonical Notch signaling)10 are used in combination with IVFM to determine the engraftment of myeloid cells to a Notch defective BM microenvironment.

Combining Intravital Fluorescent Microscopy IVFM with Genetic Models to Study Engraftment Dynamics of Hematopoietic Cells to Bone Marrow Niches

Intravital fluorescence microscopy (IVFM) of the calvarium is applied in combination with genetic animal models to study the homing and engraftment of hematopoietic cells into bone marrow (BM) niches.

Increasing evidence indicates that normal hematopoiesis is regulated by distinct microenvironmental cues in the BM, which include specialized cellular ...

Building Finite Element Models to Investigate Zebrafish Jaw Biomechanics

Skeletal morphogenesis occurs through tightly regulated cell behaviors during development; many cell types alter their behavior in response to mechanical strain. Skeletal joints are subjected to dynamic mechanical loading. Finite element analysis (FEA) is a computational method, frequently used in engineering that can predict how a material or structure will respond to mechanical input. By dividing a whole system (in this case the zebrafish jaw skeleton) into a mesh of smaller 'finite elements', FEA can be used to calculate the mechanical response of the structure to external loads. The results can be visualized in many ways including as a 'heat map' showing the position of maximum and minimum principal strains (a positive principal strain indicates tension while a negative indicates compression. The maximum and minimum refer the largest and smallest strain). These can be used to identify which regions of the jaw and therefore which cells are likely to be under particularly high tensional or compressional loads during jaw movement and can therefore be used to identify relationships between mechanical strain and cell behavior. This protocol describes the steps to generate Finite Element models from confocal image data on the musculoskeletal system, using the zebrafish lower jaw as a practical example. The protocol leads the reader through a series of steps: 1) staining of the musculoskeletal components, 2) imaging the musculoskeletal components, 3) building a 3 dimensional (3D) surface, 4) generating a mesh of Finite Elements, 5) solving the FEA and finally 6) validating the results by comparison to real displacements seen in movements of the fish jaw.

Finite Element Analysis is a frequently used tool to investigate the mechanical performance of structures under load. Here we apply its use to modeling the biomechanics of the zebrafish jaw.

Skeletal morphogenesis occurs through tightly regulated cell behaviors during development; many cell types alter their behavior in response to mechanical ...

In Vivo Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

The genetic and technical strengths have made the zebrafish vertebrate a key model organism in which the consequences of gene manipulations can be traced in vivo throughout the rapid developmental period. Multiple processes can be studied including cell proliferation, gene expression, cell migration and morphogenesis. Importantly, the generation of chimeras through transplantations can be easily performed, allowing mosaic labeling and tracking of individual cells under the influence of the host environment. For example, by combining functional gene manipulations of the host embryo (e.g., through morpholino microinjection) and live imaging, the effects of extrinsic, cell nonautonomous signals (provided by the genetically modified environment) on individual transplanted donor cells can be assessed. Here we demonstrate how this approach is used to compare the onset of fluorescent transgene expression as a proxy for the timing of cell fate determination in different genetic host environments.
In this article, we provide the protocol for microinjecting zebrafish embryos to mark donor cells and to cause gene knockdown in host embryos, a description of the transplantation technique used to generate chimeric embryos, and the protocol for preparing and running in vivo time-lapse confocal imaging of multiple embryos. In particular, performing multiposition imaging is crucial when comparing timing of events such as the onset of gene expression. This requires data collection from multiple control and experimental embryos processed simultaneously. Such an approach can easily be extended for studies of extrinsic influences in any organ or tissue of choice accessible to live imaging, provided that transplantations can be targeted easily according to established embryonic fate maps.

In Vivo Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

Live tracking of individual WT retinal progenitors in distinct genetic backgrounds allows for the assessment of the contribution of cell non-autonomous signaling during neurogenesis. Here, a combination of gene knockdown, chimera generation via embryo transplantation and in vivo time-lapse confocal imaging was utilized for this purpose.

The genetic and technical strengths have made the zebrafish vertebrate a key model organism in which the consequences of gene manipulations can be traced ...

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 ...

Live Imaging of Mouse Secondary Palate Fusion

The fusion of the secondary palatal shelves to form the intact secondary palate is a key process in mammalian development and its disruption can lead to cleft secondary palate, a common congenital anomaly in humans. Secondary palate fusion has been extensively studied leading to several proposed cellular mechanisms that may mediate this process. However, these studies have been mostly performed on fixed embryonic tissues at progressive timepoints during development or in fixed explant cultures analyzed at static timepoints. Static analysis is limited for the analysis of dynamic morphogenetic processes such a palate fusion and what types of dynamic cellular behaviors mediate palatal fusion is incompletely understood. Here we describe a protocol for live imaging of ex vivo secondary palate fusion in mouse embryos. To examine cellular behaviors of palate fusion, epithelial-specific Keratin14-cre was used to label palate epithelial cells in ROSA26-mTmGflox reporter embryos. To visualize filamentous actin, Lifeact-mRFPruby reporter mice were used. Live imaging of secondary palate fusion was performed by dissecting recently-adhered secondary palatal shelves of embryonic day (E) 14.5 stage embryos and culturing in agarose-containing media on a glass bottom dish to enable imaging with an inverted confocal microscope. Using this method, we have detected a variety of novel cellular behaviors during secondary palate fusion. An appreciation of how distinct cell behaviors are coordinated in space and time greatly contributes to our understanding of this dynamic morphogenetic process. This protocol can be applied to mutant mouse lines, or cultures treated with pharmacological inhibitors to further advance understanding of how secondary palate fusion is controlled.

Here, we present a protocol for live imaging of mouse secondary palate fusion using confocal microscopy. This protocol can be used in combination with a variety of fluorescent reporter mouse lines, and with pathway inhibitors for mechanistic insight. This protocol can be adapted for live imaging in other developmental systems.

The fusion of the secondary palatal shelves to form the intact secondary palate is a key process in mammalian development and its disruption can lead to ...

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the proteins involved in these pathways are evolutionarily conserved between mammals and other eukaryotes, such as the fruit fly Drosophila melanogaster, suggesting that similar organizing principles exist during the development of these organisms. Importantly, Drosophila has been used extensively to identify cellular and molecular mechanisms regulating processes that are required in mammals including neurogenesis, differentiation, axonal guidance, and synaptogenesis. Flies have also been used successfully to model a variety of human neurodevelopmental diseases. Here we describe a protocol for the step-by-step microdissection, fixation, and immunofluorescent localization of proteins within the adult Drosophila brain. This protocol focuses on two example neuronal populations, mushroom body neurons and retinal photoreceptors, and includes optional steps to trace individual mushroom body neurons using Mosaic Analysis with a Repressible Cell Marker (MARCM) technique. Example data from both wild-type and mutant brains are shown along with a brief description of a scoring criteria for axonal guidance defects. While this protocol highlights two well-established antibodies for investigating the morphology of mushroom body and photoreceptor neurons, other Drosophila brain regions and the localization of proteins within other brain regions can also be investigated using this protocol.

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

This protocol describes the dissection and immunostaining of adult Drosophila melanogaster brain tissues. Specifically, this protocol highlights the use of Drosophila mushroom body and photoreceptor neurons as example neuronal subsets that can be accurately used to uncover general principles underlying many aspects of neuronal development.

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the ...