Name: adult mouse digit amputation and regeneration: a simple model to investigate mammalian blastema formation and intramembranous ossification
Uploaded: 2019-07-12T14:00:00
Description: Watch this Scientific Journal Video about Adult Mouse Digit Amputation and Regeneration: A Simple Model to Investigate Mammalian Blastema Formation and Intramembranous Ossification at JoVE.com

We thank members of the Muneoka Lab and the Texas Institute for Genomic Medicine (TIGM). This work was supported by Texas A&#38;M University.

All animal use and techniques were in compliance with the standard operating procedures of the Institutional Animal Care and Use Committee of Texas A&#38;M University.
1. Adult Mouse Hind Limb Distal P3 Amputation
<ol>
	<li>Anesthetize an 8 to 12 week-old CD-1 mouse (Table of Materials) using isoflurane gas in oxygen; initially anesthetize at 3% in a chamber, followed by 2% isoflurane supplied by a nosecone over the duration of the surgery. Apply ophthalmic ointment on eyes ...

<ol>
	<li>Douglas, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conservative+management+of+guillotine+amputation+of+the+finger+in+children.">Conservative management of guillotine amputation of the finger in children.</a> Australian Paediatric Journal. 8, 86-89 (1972).</li><li>Illingworth, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trapped+fingers+and+amputated+finger+tips+in+children.">Trapped fingers and amputated finger tips in children.</a> Journal of Pediatric Surgery. 9, 853-858 (1974).</li><li>Borgens, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mice+regrow+the+tips+of+their+foretoes.">Mice regrow the tips of their foretoes.</a> Science. 217, 747-750 (1982).</li><li>Neufeld, D. A., Zhao, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phalangeal+regrowth+in+rodents:+postamputational+bone+regrowth+depends+upon+the+level+of+amputation.">Phalangeal regrowth in rodents: postamputational bone regrowth depends upon the level of amputation.</a> Progress in Clinical and Biological Research. 383a, 243-252 (1993).</li><li>Han, M., Yang, X., Lee, J., Allan, C. H., Muneoka, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+regeneration+of+the+neonatal+digit+tip+in+mice.">Development and regeneration of the neonatal digit tip in mice.</a> Developmental Biology. 315, 125-135 (2008).</li><li>Takeo, 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=Wnt+activation+in+nail+epithelium+couples+nail+growth+to+digit+regeneration.">Wnt activation in nail epithelium couples nail growth to digit regeneration.</a> Nature. 499, 228-232 (2013).</li><li>Chamberlain, C. 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=Level-specific+amputations+and+resulting+regenerative+outcomes+in+the+mouse+distal+phalanx.">Level-specific amputations and resulting regenerative outcomes in the mouse distal phalanx.</a> Wound repair and Regeneration: Official Publication of the Wound Healing Society [and] the European Tissue Repair Society. 25, 443-453 (2017).</li><li>Dawson, L. 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=Analogous+cellular+contribution+and+healing+mechanisms+following+digit+amputation+and+phalangeal+fracture+in+mice.">Analogous cellular contribution and healing mechanisms following digit amputation and phalangeal fracture in mice.</a> Regeneration. 3, 39-51 (2016).</li><li>Seifert, A. W., Muneoka, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+blastema+and+epimorphic+regeneration+in+mammals.">The blastema and epimorphic regeneration in mammals.</a> Developmental Biology. 433, 190-199 (2018).</li><li>Carlson, 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=.">.</a> Principles of Regenerative Biology. , (2007).</li><li>Fernando, W. 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=Wound+healing+and+blastema+formation+in+regenerating+digit+tips+of+adult+mice.">Wound healing and blastema formation in regenerating digit tips of adult mice.</a> Developmental Biology. 350, 301-310 (2011).</li><li>Simkin, 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=Epidermal+closure+regulates+histolysis+during+mammalian+(Mus)+digit+regeneration.">Epidermal closure regulates histolysis during mammalian (Mus) digit regeneration.</a> Regeneration. 2, 106-119 (2015).</li><li>Yu, 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=Angiogenesis+is+inhibitory+for+mammalian+digit+regeneration.">Angiogenesis is inhibitory for mammalian digit regeneration.</a> Regeneration. 1, 33-46 (2014).</li><li>Dolan, C. P., 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=Axonal+regrowth+is+impaired+during+digit+tip+regeneration+in+mice.">Axonal regrowth is impaired during digit tip regeneration in mice.</a> Developmental Biology. 445, 237-244 (2018).</li><li>Dawson, L. 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=Blastema+formation+and+periosteal+ossification+in+the+regenerating+adult+mouse+digit.">Blastema formation and periosteal ossification in the regenerating adult mouse digit.</a> Wound Repair and Regeneration: Official Publication of the Wound Healing Society [and] the European Tissue Repair Society. 26, 263-273 (2018).</li><li>Sammarco, M. 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=Endogenous+bone+regeneration+is+dependent+upon+a+dynamic+oxygen+event.">Endogenous bone regeneration is dependent upon a dynamic oxygen event.</a> Journal of Bone and Mineral Research: The Official Journal of the American Society for Bone and Mineral Research. 29, 2336-2345 (2014).</li><li>Einhorn, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+science+of+fracture+healing.">The science of fracture healing.</a> Journal of Orthopaedic Trauma. 19, S4-S6 (2005).</li><li>Shapiro, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+development+and+its+relation+to+fracture+repair.+The+role+of+mesenchymal+osteoblasts+and+surface+osteoblasts.">Bone development and its relation to fracture repair. The role of mesenchymal osteoblasts and surface osteoblasts.</a> European Cells &amp; Materials. 15, 53-76 (2008).</li><li>Ilizarov, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+tension-stress+effect+on+the+genesis+and+growth+of+tissues.+Part+I.+The+influence+of+stability+of+fixation+and+soft-tissue+preservation.">The tension-stress effect on the genesis and growth of tissues. Part I. The influence of stability of fixation and soft-tissue preservation.</a> Clinical Orthopaedics And Related Research. (238), 249-281 (1989).</li><li>Thompson, Z., Miclau, T., Hu, D., Helms, 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=A+model+for+intramembranous+ossification+during+fracture+healing.">A model for intramembranous ossification during fracture healing.</a> Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society. 20, 1091-1098 (2002).</li><li>Dolan, C. P., Dawson, L. A., Muneoka, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Digit+Tip+Regeneration:+Merging+Regeneration+Biology+with+Regenerative+Medicine.">Digit Tip Regeneration: Merging Regeneration Biology with Regenerative Medicine.</a> Stem Cells Translational Medicine. 7, 262-270 (2018).</li><li>Lee, 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=SDF-1alpha/CXCR4+signaling+mediates+digit+tip+regeneration+promoted+by+BMP-2.">SDF-1alpha/CXCR4 signaling mediates digit tip regeneration promoted by BMP-2.</a> Developmental Biology. 382, 98-109 (2013).</li><li>Doube, 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=BoneJ:+Free+and+extensible+bone+image+analysis+in+ImageJ.">BoneJ: Free and extensible bone image analysis in ImageJ.</a> Bone. 47, 1076-1079 (2010).</li></ol>

This protocol describes a standardized procedure of adult mouse distal P3 amputation, fluorescent immunohistochemical staining to visualize and investigate blastema formation and intramembranous ossification, and sequential in-vivo &#181;CT scanning to identify bone morphological, volume, and length changes post amputation. P3 amputation is a unique, procedurally simple, and reproducible model to analyze a pro-regenerative wound environment that triggers blastema formation. Furthermore, the P3 digit model offers numerous...

Mammals, including humans and mice, have the capacity to regenerate the tips of their digits after distal amputation of the terminal phalanx (P3)1,2,3. In mice, the regeneration response is amputation-level-dependent; increasingly proximal digit amputations display a progressively attenuated regenerative response until complete regenerative failure at amputations transecting and proximal to the P3 nail matrix4,5,6,7,8. P3 regeneration is mediated by the formation of a blastema, defined as a population of proliferating cells that undergo morphogenesis to regenerate the amputated structures9. The formation of a blastema to regenerate the structures lost by amputation, a process termed epimorphic regeneration, distinguishes the multi-tissue-level P3 regeneration response from traditional tissue repair after injury6,10. P3 regeneration is a reproducible and procedurally simple model to investigate complex regenerative processes including wound healing11,12, bone histolysis11,12, revascularization13, peripheral nerve regeneration14, and blastemal conversion to bone via intramembranous ossification15.
Previous studies using immunohistochemistry have demonstrated that the blastema is heterogeneous, avascular, hypoxic, and highly proliferative11,13,15,16. Following distal P3 amputation, the early blastema is initially associated with the P3 periosteum and endosteum and is characterized by robust proliferation and nascent osteogenesis adjacent to the bone surface15. Subsequent to bone degradation and wound closure, the heterogeneous blastema is formed by the merging of periosteal and endosteal-associated cells, followed by the differentiation of blastemal components including bone via intramembranous ossification15.
Bone repair in response to injury typically occurs by endochondral ossification, i.e. via an initial cartilaginous callus that forms a template for subsequent bone formation17,18. Long bone intramembranous ossification, i.e., bone formation without a cartilaginous intermediate, is commonly induced using complex distraction devices or surgical fixation19,20. The digit regeneration response is a pre-clinical model that offers advantages over conventional intramembranous ossification models: 1) it does not require external or internal fixation post injury to stimulate intramembranous ossification, 2) it is performed using 4 digits from each animal, thus maximizing samples while minimizing animal use, and 3) sequential in vivo microcomputed tomography (&#956;CT) analysis can be performed with ease and speed.
In the present study, we show the standardized P3 amputation plane to achieve a reproducible and robust regeneration response. Additionally, we demonstrate an optimized fluorescence immunohistochemistry protocol using paraffin sections to visualize blastema formation, revascularization in the context of regeneration, and blastemal conversion to bone via intramembranous ossification. We also demonstrate the use of sequential in-vivo &#956;CT to identify changes in bone morphology, volume, and length in the same digit over the course of regeneration. The goal of this protocol is to investigate mammalian blastema formation after amputation and to demonstrate 2 techniques, fluorescence immunohistochemistry and sequential in vivo &#956;CT, for the study of intramembranous bone regeneration.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Protein Block Serum Free</td>
			<td>DAKO</td>
			<td>X0909</td>
			<td>Ready to use</td>
		</tr>
		<tr>
			<td>Mouse anti-PCNA antibody</td>
			<td>Abcam</td>
			<td>ab29</td>
			<td>1:2000 dilution</td>
		</tr>
		<tr>
			<td>Rat anti-CXCR4 antibody</td>
			<td>R&#38;D Systems</td>
			<td>MAB21651</td>
			<td>1:500 dilution</td>
		</tr>
		<tr>
			<td>Rabbit anti-human vWF XIII antibody</td>
			<td>DAKO</td>
			<td>A0082</td>
			<td>1:800 dilution</td>
		</tr>
		<tr>
			<td>Rabbit anti-osterix, SP7 antibody</td>
			<td>Abcam</td>
			<td>ab22552</td>
			<td>1:400 dilution</td>
		</tr>
		<tr>
			<td>Rabbit anti-Runx2 antibody</td>
			<td>Sigma-Aldrich Co.</td>
			<td>HPA022040</td>
			<td>1:250 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor 647-conjugated goat anti-mouse IgG (H+L)</td>
			<td>Invitrogen</td>
			<td>A21235</td>
			<td>1:500 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488-conjugated goat anti-rabbit IgG (H+L)</td>
			<td>Invitrogen</td>
			<td>A11008</td>
			<td>1:500 dilution</td>
		</tr>
		<tr>
			<td>Alexa Fluor 568-conjugated goat anti-rat IgG (H+L)</td>
			<td>Invitrogen</td>
			<td>A11077</td>
			<td>1:500 dilution</td>
		</tr>
		<tr>
			<td>Prolong Gold antifade reagent</td>
			<td>Invitrogen</td>
			<td>P36930</td>
			<td>Ready to use</td>
		</tr>
		<tr>
			<td>Surgipath Decalicifier 1</td>
			<td>Leica Biosystems</td>
			<td>3800400</td>
			<td>Ready to use</td>
		</tr>
		<tr>
			<td>Z-Fix, Aqueous buffered zinc formalin fixative</td>
			<td>Anatech LTD</td>
			<td>174</td>
			<td>Ready to use</td>
		</tr>
		<tr>
			<td>CD-1 Female Mouse</td>
			<td>Envigo</td>
			<td>ICR(CD-1)</td>
			<td>8-12-weeks-old</td>
		</tr>
		<tr>
			<td>vivaCT 40</td>
			<td>SCANCO Medical</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

adult mouse digit amputation and regeneration: a simple model to investigate mammalian blastema formation and intramembranous ossification

Here, we present a protocol of adult mouse distal terminal phalanx (P3) amputation, a procedurally simple and reproducible mammalian model of epimorphic regeneration, which involves blastema formation and intramembranous ossification analyzed by fluorescence immunohistochemistry and sequential in-vivo microcomputed tomography (&#956;CT). Mammalian regeneration is restricted to amputations transecting the distal region of the terminal phalanx (P3); digits amputated at more proximal levels fail to regenerate and undergo fibrotic healing and scar formation. The regeneration response is mediated by the formation of a proliferative blastema, followed by bone regeneration via intramembranous ossification to restore the amputated skeletal length. P3 amputation is a preclinical model to investigate epimorphic regeneration in mammals, and is a powerful tool for the design of therapeutic strategies to replace fibrotic healing with a successful regenerative response. Our protocol uses fluorescence immunohistochemistry to 1) identify early-and-late blastema cell populations, 2) study revascularization in the context of regeneration, and 3) investigate intramembranous ossification without the need for complex bone stabilization devices. We also demonstrate the use of sequential in vivo &#956;CT to create high resolution images to examine morphological changes after amputation, as well as quantify volume and length changes in the same digit over the course of regeneration. We believe this protocol offers tremendous utility to investigate both epimorphic and tissue regenerative responses in mammals.

Adult mouse regenerating P3 digits at 6/7 DPA (Figure 2A-D), 9 DPA (Figure 2E-H), and 10 DPA (Figure 2I-L) were immunostained with antibodies to Runx2, OSX, and PCNA to visualize intramembranous bone regeneration, and immunostained with antibodies to CXCR4 and vWF to visualize blastema formation. Representative &#956;CT renderings of digits scanned prior to amputation and at various...

Watch this Scientific Journal Video about Adult Mouse Digit Amputation and Regeneration: A Simple Model to Investigate Mammalian Blastema Formation and Intramembranous Ossification at JoVE.com

Adult Mouse Digit Amputation and Regeneration: A Simple Model to Investigate Mammalian Blastema Formation and Intramembranous Ossification

Here, we present a protocol of adult mouse terminal phalanx amputation to investigate mammalian blastema formation and intramembranous ossification, analyzed by fluorescent immunohistochemistry and sequential in-vivo microcomputed tomography.

Here, we present a protocol of adult mouse distal terminal phalanx (P3) amputation, a procedurally simple and reproducible mammalian model of epimorphic ...

P3 amputation is a preclinical model for investigating mammalian epimorphic regeneration and a powerful tool for identifying critical cell populations and mechanisms that control endogenous regeneration. The P3 model allows for the identification of early and late blastemal cell populations, the study of revascularization during regeneration, and the investigation of intramembranous ossification without complex bone stabilization device requirements. Demonstrating the procedure with me will be Osama Qureshi, Alyssa Falck, and Katherine Zimmel, technician, and Regina Brunaeur, a Research Assistant Professor all from our laboratory.After confirming a lack of response to toe pinch in an eight to 12-week-old CD-1 mouse, Apply ointment to the animal's eyes and place the mouse under a 10X dissection microscope. Use surgical povidone iodine and 70%ethanol to sterilize the digits of each hind limb and use microscissors to trim hair away from the surgical site. Apply one microliter of topical bupivacaine locally to anesthetize the surgical site, and gently splay one hind paw to expose the medial digit surface.Then holding the scalpel at an angle parallel to the fat pad, use a sterile number 10 scalpel to amputate the distal tip of the terminal phalanx of digits two and four. Apply one additional microliter of bupivacaine locally to each amputated digit and return the mouse to a clean cage to allow the wounds to heal without wound dressing and with monitoring until full recumbency. To assure a successful P3 amputation plane, hold the scalpel parallel to the fat pad during the amputation and perform micro-CT scanning to confirm the correct amputation length.At the appropriate experimental endpoint, use a scalpel to sever the digit midway through the middle phalanx bone at approximately the second ventral fat pad indent. Transfer the tissue to a 20-milliliter scintillation vial containing 10 milliliters of fresh buffered zinc formalin fixative for 24 to 48 hours. And use a microtome to acquire four to five micrometer thick sections of each digit, placing the slices into a 38 to 41 degrees Celsius water bath supplemented with a histological adhesive solution as they are obtained.Then capture the slices on adhesive slides and place the slides on a 37-degree Celsius slide warmer to dry. When the slides have been deparaffinized immerse the samples in a staining jar of an appropriate antigen retrieval solution, and heat the slides to 95 degrees Celsius for 25 minutes making sure that boiling does not occur. At the end of the incubation, allow the jar to come to room temperature, and lay the slides flat in a one-inch deep covered plastic slide box with moistened tissue paper at the base.Add 100 microliters of prewarmed proteinase K to each sample. Cover each slide with a small strip of parafilm to ensure the sections do not become dry. After 12 minutes at 37 degrees Celsius, carefully remove the paraffin film, and gently drain the slides on tissue paper to remove excess blocking solution.Next, add 100 to 200 microliters of the primary antibody solution of interest to each slide. Return the sites to the humidifying chamber covered with paraffin film for an overnight incubation at four degrees Celsius. The next morning after washing the slides in TRIS-buffered saline plus TWEEN or TBST label the slides with an appropriate secondary antibody solution for a 45-minute incubation at room temperature protected from light.At the end of the incubation, wash the slides in TBST and allow them to dry. Then use 100 microliters of anti-fade mounting medium to carefully place coverslips onto the dried slides and store the slides flat at room temperature overnight protected from light to allow the mounting medium to dry. For sequential in vivo micro-computed tomography or micro-CT outfit the micro-CT imager with tubing to enable oxygen flow into and out of the micro-CT animal chamber, making sure that the outflowing oxygen is equipped with an activated charcoal filter to trap the isoflurane.Set the Voxelsize to 10.5 micrometers at 55 peak kilovoltage and 145 microamps with 1, 000 projections per 180 degrees and continuous rotation with an Integration Time of 200 milliseconds, resulting in a maximum of 213 slices per scan. When the scanner is ready, gently place the anesthetized mouse in the micro-CT animal chamber with the hind limb digits arranged in flat, close association ventral side up with the left paw on the left side and the right on the right side of the scanning platform. Then apply surgical tape to gently secure the digits in place.Apply ophthalmic ointment to the animal's eyes before initiating the scan. After scanning, return animal to a clean cage with monitoring until full recumbency, and allow up to several hours for micro-CT image reconstruction. For analysis of the reconstructed 3D bone image, using the software provided with the micro-CT, convert the image files to a series of DICOM files.When all of the files have been converted, download the DICOM series in a single folder using a batch file downloader in a web browser. Load the BoneJ plug-in into the ImageJ plug-in folder. Drag-and-drop the DICOM file series folder into the ImageJ bar to open the files.A 16-bit image stack displaying all of the gray values will be opened. To display bone only, click Image Adjust and Threshold. Slide the upper threshold bar to the far right and adjust the lower threshold bar until only the bone is highlighted red.The lower threshold value will be approximately 10, 000 to 13, 000 at a maximal signal intensity of 32, 767. Click Apply and in the new dialog box, click Black background. Next, click OK.An eight-bit image displaying black and white values will be generated.With the white corresponding to bone. Draw a rectangle around the P3 bone to select it and duplicate the stack. To generate a 3D image, click Plugins and 3D Viewer and use the freehand selection tool to circle the bone to be deleted.Then right-click and select Fill selection to crop any unnecessary bone from the image. To quantify the bone volume from the 3D rendering, open the BoneJ plug-in and select Volume Fraction. A results window will appear and the bone volume displayed in millimeters cubed.To quantify the bone length from the 3D rendering, use the ImageJ multipoint tool. To capture an image of the 3D rendering, click View and take a snapshot. Then save the image as a TIF or JPEG file.In these images sections of an adult mouse regenerating P3 digit were immunostained with antibodies to visualize intramembranous bone regeneration and blastema formation at day six to seven, nine and 10 post-amputation. Here, representative micro-CT renderings of digits scanned prior to amputation and at various time points over the course of regeneration with landmarks used to identify length measurements are shown. The mouse digit model is a powerful system for analyzing a pro-regenerative wound environment that triggers blastema formation when amputated at a distal level.Conversely, proximal amputation of the digits serves as a model system for investigating regenerative failure as well a site for testing strategies for enhancing regeneration.

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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 ...

Loss- and Gain-of-function Approach to Investigate Early Cell Fate Determinants in Preimplantation Mouse Embryos

Gene silencing and overexpression techniques are instrumental for the identification of genes involved in embryonic development. Direct target gene modification in preimplantation embryos provides a means to study the underlying mechanisms of genes implicated in, for instance, cellular differentiation into the trophectoderm (TE) and the inner cell mass (ICM). Here, we describe a protocol that examines the role of neogenin as an authentic receptor for initial cell fate determination in preimplantation mouse embryos. First, we discuss the experimental manipulations that were used to produce gain and loss of neogenin function by microinjecting neogenin cDNA and shRNA; the effectiveness of this approach was confirmed by a strong correlation between the pair-wise expression levels of either red fluorescent protein (RFP) or green fluorescent protein (GFP) and the immunocytochemical quantification of neogenin expression. Secondly, overexpression of neogenin in preimplantation mouse embryos leads to normal ICM development while neogenin knockdown causes the ICM to develop abnormally, implying that neogenin could be a receptor that relays extracellular cues to drive blastomeres to early cell fates. Given the success of this detailed protocol in investigating the function of a novel embryonic developmental stage-specific receptor, we propose that it has the potential to aid in exploration and identification of other stage-specific genes during embryogenesis.

The goal of this protocol is to describe a loss- and gain-of function method that is applicable to identify neogenin as a stage-specific receptor that leads to trophectoderm and inner cell mass differentiation in preimplantation mouse embryos.

 Gene silencing and overexpression techniques are instrumental for the identification of genes involved in embryonic development. Direct target gene ...

Epigenetic Conversion as a Safe and Simple Method to Obtain Insulin-secreting Cells from Adult Skin Fibroblasts

Regenerative medicine requires new, fully functional cells that are delivered to patients in order to repair degenerated or damaged tissues. When such cells are not readily available, they can be obtained using different approaches that include, among the many, reprogramming and trans-differentiation, with advantages and limitations that are specific of the different techniques. Here a new strategy for the conversion of an adult mature fibroblast into an insulin-secreting cell, arbitrarily designated as epigenetic converted cells (EpiCC), is described. The method has been developed, based on the increasing understanding of the mechanisms controlling epigenetic regulation of cell fate and differentiation. In particular, the first step uses an epigenetic modifier, namely 5-aza-cytidine, to drive adult cells into a "highly permissive" state. It then takes advantage of this brief and reversible window of epigenetic plasticity, to re-address cells toward a different lineage. The approach is designated "epigenetic cell conversion". It is a simple and robust way to obtain an efficient, controlled and stable cellular inter-lineage switch. Since the protocol does not involve the use of any gene transfection, it is free of viral vectors and does not involve a stable pluripotent state, it is highly promising for translational medicine applications.

Here, a new method that allows the conversion of adult skin fibroblasts into insulin-secreting cells is presented. This technique is based on epigenetic conversion, does not involve the use of retroviral vectors nor the acquisition of a stable pluripotent state. It is therefore highly promising for translational medicine applications.

Regenerative medicine requires new, fully functional cells that are delivered to patients in order to repair degenerated or damaged tissues. When such ...

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 ...

Culture of Murine Embryonic Metatarsals: A Physiological Model of Endochondral Ossification

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or longitudinal bone growth. As such, it is imperative that we further our understanding of the underpinning molecular mechanisms involved in such disorders so as to provide advances towards human and animal patient benefit. The mouse metatarsal organ explant culture is a highly physiological ex vivo model for studying endochondral ossification and bone growth as the growth rate of the bones in culture mimic that observed in vivo. Uniquely, the metatarsal organ culture allows the examination of chondrocytes in different phases of chondrogenesis and maintains cell-cell and cell-matrix interactions, therefore providing conditions closer to the in vivo situation than cells in monolayer or 3D culture. This protocol describes in detail the intricate dissection of embryonic metatarsals from the hind limb of E15 murine embryos and the subsequent analyses that can be performed in order to examine endochondral ossification and longitudinal bone growth.

We present a protocol to dissect and culture embryonic day 15 (E15) murine metatarsal bones. This highly physiological ex vivo model of endochondral ossification provides conditions closer to the in vivo situation than cells in monolayer or 3D culture and is a vital tool for investigating bone growth and development.

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or ...

Establishment of Larval Zebrafish as an Animal Model to Investigate Trypanosoma cruzi Motility In Vivo

Chagas disease is a parasitic infection caused by Trypanosoma cruzi, whose motility is not only important for localization, but also for cellular binding and invasion. Current animal models for the study of T. cruzi allow limited observation of parasites in vivo, representing a challenge for understanding parasite behavior during the initial stages of infection in humans. This protozoan has a flagellar stage in both vector and mammalian hosts, but there are no studies describing its motility in vivo.The objective of this project was to establish a live vertebrate zebrafish model to evaluate T. cruzi motility in the vascular system. Transparent zebrafish larvae were injected with fluorescently labeled trypomastigotes and observed using light sheet fluorescence microscopy (LSFM), a noninvasive method to visualize live organisms with high optical resolution. The parasites could be visualized for extended periods of time due to this technique&#39;s relatively low risk of photodamage compared to confocal or epifluorescence microscopy. T. cruzi parasites were observed traveling in the circulatory system of live zebrafish in different-sized blood vessels and the yolk. They could also be seen attached to the yolk sac wall and to the atrioventricular valve despite the strong forces associated with heart contractions. LSFM of T. cruzi-inoculated zebrafish larvae is a valuable method that can be used to visualize circulating parasites and evaluate their tropism, migration patterns, and motility in the dynamic environment of the cardiovascular system of a live animal.

Establishment of Larval Zebrafish as an Animal Model to Investigate Trypanosoma cruzi Motility In Vivo

In this protocol, fluorescently labeled T. cruzi&#160;were injected into transparent zebrafish larvae, and parasite motility was observed in vivo using light sheet fluorescence microscopy.

Chagas disease is a parasitic infection caused by Trypanosoma cruzi, whose motility is not only important for localization, but also for cellular binding ...

A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result in a series of bone metabolic diseases, including osteoporosis. To develop pharmaceutical targets for the prevention of pathological bone mass loss, the mechanisms by which osteoclasts differentiate from precursors must be understood. The ability to isolate and culture a large number of osteoclasts in vitro is critical in order to determine the role of specific genes in osteoclast differentiation. Inactivation of the mammalian/mechanistic target of rapamycin complex 1 (TORC1) in osteoclasts can decrease osteoclast number and increase bone mass; however, the underlying mechanisms require further study. In the present study, a RANKL-based protocol to isolate and culture osteoclasts from mouse bone marrow and to study the influence of mTORC1 inactivation on osteoclast formation is described. This protocol successfully resulted in a large number of giant osteoclasts, typically within one week. Deletion of Raptor impaired osteoclast formation and decreased the activity of secretory tartrate-resistant acid phosphatase, indicating that mTORC1 is critical for osteoclast formation.

This manuscript describes a protocol to isolate and culture osteoclasts in vitro from mouse bone marrow, and to study the role of the mammalian/mechanistic target of rapamycin complex 1 in osteoclast formation.

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result ...

Chemical Amputation and Regeneration of the Pharynx in the Planarian Schmidtea mediterranea

Planarians are flatworms that are extremely efficient at regeneration. They owe this ability to a large number of stem cells that can rapidly respond to any type of injury. Common injury models in these animals remove large amounts of tissue, which damages multiple organs. To overcome this broad tissue damage, we describe here a method to selectively remove a single organ, the pharynx, in the planarian Schmidtea mediterranea. We achieve this by soaking animals in a solution containing the cytochrome oxidase inhibitor sodium azide. Brief exposure to sodium azide causes extrusion of the pharynx from the animal, which we call &#34;chemical amputation.&#34;&#160;Chemical amputation removes the entire pharynx, and generates a small wound where the pharynx attaches to the intestine. After extensive rinsing, all amputated animals regenerate a fully functional pharynx in approximately one week. Stem cells in the rest of the body drive regeneration of the new pharynx. Here, we provide a detailed protocol for chemical amputation, and describe both histological and behavioral methods to assess successful amputation and regeneration.

Chemical Amputation and Regeneration of the Pharynx in the Planarian Schmidtea mediterranea

The planarian Schmidtea mediterranea is an excellent model for studying stem cells and tissue regeneration. This publication describes a method to selectively remove one organ, the pharynx, by exposing animals to the chemical sodium azide. This protocol also outlines methods for monitoring pharynx regeneration.

Planarians are flatworms that are extremely efficient at regeneration. They owe this ability to a large number of stem cells that can rapidly respond to ...

Partial Lobular Hepatectomy: A Surgical Model for Morphologic Liver Regeneration

Morphological organ regeneration following acute tissue loss is common among lower vertebrates, but is rarely observed in mammalian postnatal life. Adult liver regeneration after 70% partial hepatectomy results in hepatocyte hypertrophy with some replication in remaining lobes with restoration of metabolic activity, but with permanent loss of the injured lobe&#39;s morphology and architecture. Here, we detail a new surgical method in the neonate that leaves a physiologic environment conducive to regeneration. This model involves amputation of the left lobe apex and a subsequent conservative management regimen, and lacks the necessity for ligation of major liver vessels or chemical injury, leaving a physiologic environment where regeneration may occur. We extend this protocol to amputations on juvenile (P7-14) mice, during which the injured liver transitions from organ regeneration to compensatory growth by hypertrophy. The presented, brief 30 min protocol provides a framework to study the mechanisms of regeneration, its age-associated decline in mammals, and the characterization of putative hepatic stem or progenitors.

Here, we present a new method for partial resection of the left hepatic lobe in neonatal (day 0) mice. This new protocol is suitable for studying acute liver injury and injury response in the neonatal setting.

Morphological organ regeneration following acute tissue loss is common among lower vertebrates, but is rarely observed in mammalian postnatal life. Adult ...

A Simplified and Efficient Method to Isolate Primary Human Keratinocytes from Adult Skin Tissue

Primary human keratinocytes isolated from fresh skin tissues and their expansion in vitro have been widely used for laboratory research and for clinical applications. The conventional isolation method of human keratinocytes involves a two-step sequential enzymatic digestion procedure, which has been proven to be inefficient in generating primary cells from adult tissues due to the low cell recovery rate and reduced cell viability. We recently reported an advanced method to isolate human primary epidermal progenitor cells from skin tissues that utilizes the Rho kinase inhibitor Y-27632 in the medium. Compared with the traditional protocol, this new method is simpler, easier, and less time-consuming, and increases epithelial stem cell yield and enhances their stem cell characteristics. Moreover, the new methodology does not require the separation of the epidermis from the dermis, and, therefore, is suitable for isolating cells from different types of adult tissues. This new isolation method overcomes the major shortcomings of conventional methods and is more suitable for producing large numbers of epidermal cells with high potency both for laboratory and for clinical applications. Here, we describe the new method in detail.

Here we present a protocol to efficiently isolate primary human keratinocytes from adult skin tissues. This method simplifies the conventional procedure by using the ROCK Inhibitor Y-27632 in the inoculation medium to spontaneously separate epidermal cells from dermal cells.

Primary human keratinocytes isolated from fresh skin tissues and their expansion in vitro have been widely used for laboratory research and for clinical ...