Name: whole-mount confocal microscopy for adult ear skin: a model system to study neuro-vascular branching morphogenesis and immune cell distribution
Uploaded: 2018-03-29T15:00:00
Description: Watch this Scientific Journal Video about Whole-mount Confocal Microscopy for Adult Ear Skin: A Model System to Study Neuro-vascular Branching Morphogenesis and Immune Cell Distribution at JoVE.com

We thank K. Gill for the laboratory management and technical support, J. Hawkins and the staff of National Institutes of Health (NIH) Building 50 animal facility for the assistance with mouse care, and R. Reed and F. Baldrey for administrative assistance. Thanks also to S. Motegi and M. Udey for sharing their ear skin dissection protocol, N. Burns for editorial help, and members of the Laboratory of Stem Cell and Neuro-Vascular Biology for technical help and thoughtful discussion. T. Yamazaki was supported by the Japan Society for the Promotion of Science (JSPS) NIH-KAITOKU. This work was supported by the Intramural Research Program of the National Heart, Lung, and Blood Institute (HL005702-11 to Y.M.)

All experiments in this section were performed under approval from the National Heart, Lung, and Blood Institute (NHLBI) Animal Care and Use Committee.
1. Adult Mouse Ear Skin Collection
<ol>
	<li>Euthanize adult mice by carbon dioxide (CO2) exposure in a closed chamber and then confirm the euthanasia by cervical dislocation. 
	NOTE: The experiment follows the National Institutes of Health (NIH) guideline for the euthanasia method.</li>
	<li>Dissect the ear from the base and ...

<ol>
	<li>Mukouyama, Y. S., Shin, D., Britsch, S., Taniguchi, M., Anderson, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensory+nerves+determine+the+pattern+of+arterial+differentiation+and+blood+vessel+branching+in+the+skin.">Sensory nerves determine the pattern of arterial differentiation and blood vessel branching in the skin.</a> Cell. 109, 693-705 (2002).</li><li>Mukouyama, Y. S., James, J., Nam, J., Uchida, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole-mount+confocal+microscopy+for+vascular+branching+morphogenesis.">Whole-mount confocal microscopy for vascular branching morphogenesis.</a> Methods Mol Biol. 843, 69-78 (2012).</li><li>Li, W., Mukouyama, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole-mount+immunohistochemical+analysis+for+embryonic+limb+skin+vasculature:+a+model+system+to+study+vascular+branching+morphogenesis+in+embryo.">Whole-mount immunohistochemical analysis for embryonic limb skin vasculature: a model system to study vascular branching morphogenesis in embryo.</a> J Vis Exp. , (2011).</li><li>Yamazaki, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue+Myeloid+Progenitors+Differentiate+into+Pericytes+through+TGF-beta+Signaling+in+Developing+Skin+Vasculature.">Tissue Myeloid Progenitors Differentiate into Pericytes through TGF-beta Signaling in Developing Skin Vasculature.</a> Cell Rep. 18, 2991-3004 (2017).</li><li>Mukouyama, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vessel-dependent+recruitment+of+sympathetic+axons:+looking+for+innervation+in+all+the+right+places.">Vessel-dependent recruitment of sympathetic axons: looking for innervation in all the right places.</a> J Clin Invest. 124, 2855-2857 (2014).</li><li>Li, W., 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=Peripheral+nerve-derived+CXCL12+and+VEGF-A+regulate+the+patterning+of+arterial+vessel+branching+in+developing+limb+skin.">Peripheral nerve-derived CXCL12 and VEGF-A regulate the patterning of arterial vessel branching in developing limb skin.</a> Dev Cell. 24, 359-371 (2013).</li><li>Chang, H., Wang, Y., Wu, H., Nathans, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flat+mount+imaging+of+mouse+skin+and+its+application+to+the+analysis+of+hair+follicle+patterning+and+sensory+axon+morphology.">Flat mount imaging of mouse skin and its application to the analysis of hair follicle patterning and sensory axon morphology.</a> J Vis Exp. , e51749 (2014).</li><li>Salz, L., Driskell, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Horizontal+Whole+Mount:+A+Novel+Processing+and+Imaging+Protocol+for+Thick,+Three-dimensional+Tissue+Cross-sections+of+Skin.">Horizontal Whole Mount: A Novel Processing and Imaging Protocol for Thick, Three-dimensional Tissue Cross-sections of Skin.</a> J Vis Exp. , (2017).</li><li>Liakath-Ali, 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=Novel+skin+phenotypes+revealed+by+a+genome-wide+mouse+reverse+genetic+screen.">Novel skin phenotypes revealed by a genome-wide mouse reverse genetic screen.</a> Nat Commun. 5, 3540 (2014).</li><li>Gunawan, 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=The+methyltransferase+Ezh2+controls+cell+adhesion+and+migration+through+direct+methylation+of+the+extranuclear+regulatory+protein+talin.">The methyltransferase Ezh2 controls cell adhesion and migration through direct methylation of the extranuclear regulatory protein talin.</a> Nat Immunol. 16, 505-516 (2015).</li><li>Avci, 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=Animal+models+of+skin+disease+for+drug+discovery.">Animal models of skin disease for drug discovery.</a> Expert Opin Drug Dis. 8, 331-355 (2013).</li><li>Jin, H., He, R., Oyoshi, M., Geha, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+atopic+dermatitis.">Animal models of atopic dermatitis.</a> J Invest Dermatol. 129, 31-40 (2009).</li><li>Wagner, E. F., Schonthaler, H. B., Guinea-Viniegra, J., Tschachler, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Psoriasis:+what+we+have+learned+from+mouse+models.">Psoriasis: what we have learned from mouse models.</a> Nat Rev Rheumatol. 6, 704-714 (2010).</li><li>Nunan, R., Harding, K. G., Martin, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+challenges+of+chronic+wounds:+searching+for+an+optimal+animal+model+to+recapitulate+their+complexity.">Clinical challenges of chronic wounds: searching for an optimal animal model to recapitulate their complexity.</a> Dis Model Mech. 7, 1205-1213 (2014).</li><li>O'Brien, P. D., Sakowski, S. A., Feldman, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+diabetic+neuropathy.">Mouse models of diabetic neuropathy.</a> ILAR J. 54, 259-272 (2014).</li><li>Yamazaki, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole-Mount+Adult+Ear+Skin+Imaging+Reveals+Defective+Neuro-Vascular++Branching+Morphogenesis+in+Obese+and+Type+2+Diabetic+Mouse+Models.">Whole-Mount Adult Ear Skin Imaging Reveals Defective Neuro-Vascular Branching Morphogenesis in Obese and Type 2 Diabetic Mouse Models.</a> Sci Rep. 8, (2018).</li></ol>

This protocol describes the whole-mount immunonohistochemical imaging of adult ear skin for the analysis of neuro-vascular structures and immune cell distribution. We believe this method has numerous experimental advantages for researchers to study branching morphogenesis and the patterning of peripheral nerves and blood vessels, as well as three-dimensional distribution of skin components including immune cells and hair follicles. The results of the imaging can be quantified using imaging softwares for further quantitat...

Skin is comprised of three layers: the epidermis, dermis and hypodermis. It has been used as a model system to study stem cell maintenance, differentiation, and morphogenesis in development as well as the regeneration, tumorigenesis, and inflammation in adult. Skin is richly vascularized and innervated such that the development of the peripheral nervous system and vascular system is well-coordinated.
We have previously demonstrated a whole-mount embryonic skin imaging technique with multiple labeling to study intact peripheral nerves and blood vessels including their cellular components1,2,3,4: sensory axons, sympathetic axons, Schwann cells in nerves, endothelial cells, pericytes, and vascular smooth muscle cells (VSMCs) in blood vessels. During the angiogenesis, a primary capillary network undergoes intensive vascular remodeling and develops into a hierarchical vascular branching network. In the developing dermis/hypodermis, arteries branch alongside peripheral sensory nerves and veins then form adjacent to the arteries. After the hierarchical vascular network is thoroughly covered with VSMCs, sympathetic nerves extend along and innervate large-diameter blood vessels1,5,6. Despite the significance in the close association between the developing nervous and vascular systems, a major question has been to address what happens to the neuro-vascular networks in various pathological situations in adults. A three-dimensional high-resolution imaging is necessary to appreciate the pathogenesis, along with anatomically recognizable branching morphogenesis and patterning.
Neuronal and vascular morphogenesis in adult mouse skin is commonly analyzed by tissue section staining. Other studies have used whole-mount imaging of the skin to visualize the peripheral nerves and blood vessels, in addition to the hair follicles, sebaceous glands, and arrector pili muscles7,8,9. However, the thickness of adult skin has made it difficult to analyze the skin over its entire depth.
In the present study, we developed a novel high-resolution whole-mount imaging of adult ear skin to overcome these challenges. Ear skin is readily accessible for dissection and subsequent whole-mount imaging of the skin over its entire depth. Thus, it is a straightforward and highly reproducible method that can be applied to compare three-dimensional architecture of peripheral nervous and vascular systems in the skin, with comprehensive quantification measurements. We demonstrated that the alignment of peripheral sensory and sympathetic nerves with large-diameter blood vessels is preserved in the adult skin. The goal of this protocol is to visualize branching morphogenesis, and the patterning of peripheral nerves and blood vessels, as well as the immune cell distribution at a cellular level in adult mouse models in various conditions such as inflammation and regeneration.

<table>
	<tbody>
		<tr>
			<td>10 x Phosphate Buffered Saline</td>
			<td>KD Medical</td>
			<td>RGE-3210</td>
			<td>PBS, without Ca2+/Mg2+</td>
		</tr>
		<tr>
			<td>Hank&#8217;s Balanced Salt Solution</td>
			<td>Gibco</td>
			<td>14025-092</td>
			<td>HBSS, with Ca2+/Mg2+</td>
		</tr>
		<tr>
			<td>16% Paraformaldehyde</td>
			<td>Electron Microscopy Sciences</td>
			<td>15710</td>
			<td>PFA, fixative, diluted in PBS</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>X100</td>
			<td>Detergent</td>
		</tr>
		<tr>
			<td>Normal goat serum</td>
			<td>Gibco</td>
			<td>16210064</td>
			<td>Component of blocking/washing buffer</td>
		</tr>
		<tr>
			<td>Normal donkey serum</td>
			<td>Jackson Immuno research</td>
			<td>017-000-121</td>
			<td>Component of blocking/washing buffer</td>
		</tr>
		<tr>
			<td>Curved fine tweezers</td>
			<td>Dumont</td>
			<td>RS-5047</td>
			<td></td>
		</tr>
		<tr>
			<td>Curved tweezers</td>
			<td>Integra Miltex Vantage</td>
			<td>V918-782, V918-784</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter Unit 0.45 mm</td>
			<td>Thermo Scientific</td>
			<td>157-0045</td>
			<td>For filtration</td>
		</tr>
		<tr>
			<td>1 mL syringe</td>
			<td>Coviden</td>
			<td>8881501400</td>
			<td>For filtration</td>
		</tr>
		<tr>
			<td>Syringe filter Unit 0.22 mm</td>
			<td>Millex-GV</td>
			<td>SLGVR04NL</td>
			<td>For filtration</td>
		</tr>
		<tr>
			<td>ProLong Gold</td>
			<td>Thermo Scientific</td>
			<td>P36934</td>
			<td>Anti-fade mounting medium</td>
		</tr>
		<tr>
			<td>Nail Polish</td>
			<td>Electron Microscopy Sciences</td>
			<td>72180</td>
			<td>For sealing</td>
		</tr>
		<tr>
			<td>Dissecting microscope</td>
			<td>Leica</td>
			<td>MZ95</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Leica</td>
			<td>TCS SP5</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoshop CC 2017</td>
			<td>Adobe</td>
			<td></td>
			<td>Graphics editor software</td>
		</tr>
		<tr>
			<td>Illustrator CC 2017</td>
			<td>Adobe</td>
			<td></td>
			<td>Graphics editor software</td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>NIH</td>
			<td></td>
			<td>Image processing software</td>
		</tr>
		<tr>
			<td>Anti-PECAM-1 (CD31) antibody</td>
			<td>Millipore</td>
			<td>MAB1398Z</td>
			<td>Hamster IgG, vascular endothelial cell marker, 1:300</td>
		</tr>
		<tr>
			<td>Anti-PECAM-1 (CD31) antibody</td>
			<td>BD Pharmingen</td>
			<td>553369</td>
			<td>Rat IgG2a kappa, vascular endothelial cell marker, 1:300</td>
		</tr>
		<tr>
			<td>Anti-aSMA antibody conjugated with cy-3</td>
			<td>Sigma</td>
			<td>C6198</td>
			<td>Mouse IgG2a, vascular smooth muscle cell marker, 1:500</td>
		</tr>
		<tr>
			<td>Anti-EphB1 antibody</td>
			<td>Santa Cruz</td>
			<td>sc-9319</td>
			<td>Goat polyclonal, venous endothelial cell marker, 1:100</td>
		</tr>
		<tr>
			<td>Anti-neuron-specific Class III b-tubulin (Tuj1)</td>
			<td>Abcam</td>
			<td>AB18207</td>
			<td>Tuj1, Rabbit polyclonal IgG, pan-axonal marker, 1:500</td>
		</tr>
		<tr>
			<td>Anti-Tuj1 antibody</td>
			<td>Covance</td>
			<td>MMS-435P</td>
			<td>Mouse IgG2a, pan-axonal marker, 1:500</td>
		</tr>
		<tr>
			<td>Anti-MBP antibody</td>
			<td>Abcam</td>
			<td>AB40390</td>
			<td>Rabbit polyclonal IgG, myelination marker, 1:200</td>
		</tr>
		<tr>
			<td>Anti-Tyrosine Hydroxylase antibody</td>
			<td>Chemicon</td>
			<td>AB152</td>
			<td>Rabbit polyclonal, sympathetic neuron marker, 1:500</td>
		</tr>
		<tr>
			<td>Anti-Peripherin antibody</td>
			<td>Chemicon</td>
			<td>AB1530</td>
			<td>Rabbit polyclonal, peripheral neuron marker, 1:1000</td>
		</tr>
		<tr>
			<td>Anti-CD11b antibody</td>
			<td>Bio-Rad</td>
			<td>MCA74G</td>
			<td>Rat IgG2b, inflammatory cell marker (macrophages), 1:50</td>
		</tr>
		<tr>
			<td>Anti-CD45 antibody</td>
			<td>Thermo Fisher Scientific</td>
			<td>14-0451-85</td>
			<td>Rat IgG2b kappa, pan-hematopoietic cell marker, 1:500</td>
		</tr>
		<tr>
			<td>Anti-CD3 antibody</td>
			<td>Bio-Rad</td>
			<td>MCA1477T</td>
			<td>Rat IgG1, immune cell marker, 1:100</td>
		</tr>
		<tr>
			<td>Anti-CD45R (B220) antibody</td>
			<td>Thermo Fisher Scientific</td>
			<td>14-0452</td>
			<td>Rat IgG2a kappa, inflammatory cell marker, 1:200</td>
		</tr>
		<tr>
			<td>Anti-GFP antibody</td>
			<td>Thermo Fisher Scientific</td>
			<td>A11122</td>
			<td>Rabbit polyclonal, 1:300</td>
		</tr>
		<tr>
			<td>Anti-GFP antibody</td>
			<td>Abcam</td>
			<td>Ab13970</td>
			<td>Chicken polyclonal, 1:500</td>
		</tr>
		<tr>
			<td>Anti-b-gal antibody</td>
			<td>Cappel</td>
			<td>55976</td>
			<td>Rabbit polyclonal, 1:5000</td>
		</tr>
		<tr>
			<td>Anti-RFP antibody</td>
			<td>Abcam</td>
			<td>Ab62341</td>
			<td>Rabbit polyclonal, 1:300</td>
		</tr>
		<tr>
			<td>Goat anti-rabbit IgG (H+L) Alexa 488</td>
			<td>Thermo Fisher Scientific</td>
			<td>A11034</td>
			<td>Rabbit polyclonal secondary antibody, 1:250</td>
		</tr>
		<tr>
			<td>Goat anti-hamster IgG (H+L) Alexa 647</td>
			<td>Jackson Immuno research</td>
			<td>127-605-160</td>
			<td>Hamster polyclonal secondary antibody, 1:250</td>
		</tr>
		<tr>
			<td>Goat anti-rat IgG (H+L) Alexa 594</td>
			<td>Jackson Immuno research</td>
			<td>112-585-167</td>
			<td>Rat polyclonal secondary antibody, 1:250</td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG2a Alexa 633</td>
			<td>Thermo Fisher Scientific</td>
			<td>A21136</td>
			<td>Mouse IgG2a secondary antibody, 1:250</td>
		</tr>
	</tbody>
</table>

whole-mount confocal microscopy for adult ear skin: a model system to study neuro-vascular branching morphogenesis and immune cell distribution

Here, we present a protocol of a whole-mount adult ear skin imaging technique to study comprehensive three-dimensional neuro-vascular branching morphogenesis and patterning, as well as immune cell distribution at a cellular level. The analysis of peripheral nerve and blood vessel anatomical structures in adult tissues provides some insights into the understanding of functional neuro-vascular wiring and neuro-vascular degeneration in pathological conditions such as wound healing. As a highly informative model system, we have focused our studies on adult ear skin, which is readily accessible for dissection. Our simple and reproducible protocol provides an accurate depiction of the cellular components in the entire skin, such as peripheral nerves (sensory axons, sympathetic axons, and Schwann cells), blood vessels (endothelial cells and vascular smooth muscle cells), and inflammatory cells. We believe this protocol will pave the way to investigate morphological abnormalities in peripheral nerves and blood vessels as well as the inflammation in the adult ear skin under different pathological conditions.

Adult mouse posterior ear skin (Figure 1A) and anterior ear skin (Figure 1B) were immunostained with antibodies to &#945;SMA (red), Tuj1 (green), and PECAM-1 (blue). Posterior skin was immunostained to study neuro-immune distribution using antibodies to CD11b (red) and MBP (green), together with Tuj1 (blue) (Figure 2A). Distribution of CD11b+ inflammatory cells, including macrophages was d...

Watch this Scientific Journal Video about Whole-mount Confocal Microscopy for Adult Ear Skin: A Model System to Study Neuro-vascular Branching Morphogenesis and Immune Cell Distribution at JoVE.com

Whole-mount Confocal Microscopy for Adult Ear Skin: A Model System to Study Neuro-vascular Branching Morphogenesis and Immune Cell Distribution

Here, we describe a high resolution whole-mount imaging method in the entire adult mouse ear skin, which enables us to visualize branching morphogenesis and patterning of peripheral nerves and blood vessels, as well as immune cell distribution.

Here, we present a protocol of a whole-mount adult ear skin imaging technique to study comprehensive three-dimensional neuro-vascular branching ...

The overall goal of this procedure is to visualize branching morphogenesis and patterning of peripheral nerves and blood vessels, as well as immune cell distribution. This method can help answer key questions in the fields of neurobiology, vascular biology, and immunology by illuminating morphological abnormalities in peripheral nerves and blood vessels, as well as inflammation. The main strength of this technique is that we can visualize the cellular components of peripheral nerves, blood vessels, and immune cells in the skin over its entire depth and can compare three-dimensional architecture on nervous and vascular systems.This method can provide insight into neuro-vasculature structures and immune cell distribution in juvenile to adult mice under normal and pathology conditions. After euthanizing adult mice according to the text protocol, dissect the ear from the base, and place it in a 35-by-10-millimeter Petri dish containing two milliliters of HBSS. Then, use scissors to briefly trim the hairs.Carefully peel the posterior and anterior skin away from the intervening cartilage. Transfer each section of skin separately to a 24-well plate containing one milliliter of ice-cold, fresh 4%PFA in PBS per well. Then, flatten the skin in the PFA.Next, fix the posterior and anterior skin with cartilage at four degrees Celsius for one hour. Then, use one milliliter of PBS to wash the skin three times for five minutes with gentle mixing at room temperature. Transfer the skin with cartilage to the bottom of a 35-by-10-millimeter Petri dish.Use fine curved forceps to peel off the cartilage from the anterior skin. Then, cut off the base region, which is folded and has adipose and connective tissues. Using the same forceps, carefully remove the hairs, adipose tissue, and connective tissue from the inside of the posterior skin.Use PBS to keep the skin wet. To carry out whole-mount immunohistochemical staining, transfer the posterior and anterior skin to a 24-well plate containing one milliliter of 10%heat-inactivated serum blocking buffer per well. Incubate the skin with gentle mixing at room temperature for 30 minutes.Dilute the primary antibodies in the blocking buffer as described in the text protocol, and add 150 microliters of primary antibodies in blocking buffer to the well. Then, transfer the posterior and anterior skin to new wells containing primary antibodies. Incubate the skin with gentle mixing at four degrees Celsius overnight.The following day, after transferring the skin to new wells or aspirating the primary antibodies, add one milliliter of 2%serum in PBS with 0.2%Triton X-100. Wash the samples with gentle mixing at room temperature for 15 minutes. Repeat the wash two more times.In the meantime, prepare secondary antibodies in 10%blocking buffer and filter the antibody solutions through a 0.22-micrometer PVDF membrane syringe filter connected to a one-milliliter syringe. Centrifuge the solution at 13, 000 times gravity for 10 minutes to remove aggregated particles of the secondary antibodies from the blocking buffer, adding 150 microliters of secondary antibodies in blocking buffer to the new well. Transfer the skin to the well containing secondary antibodies.Wrap the 24-well plate in aluminum foil to protect it from light, and incubate the skin with gentle mixing at room temperature for one hour. Add one milliliter of 2%serum washing buffer. Then, transfer the posterior and anterior skin to the wells containing washing buffer.Wrap the plate, and wash the samples with gentle mixing at room temperature for 15 minutes. Repeat the wash two more times. Place the skin on the bottom of a 35-by-10-millimeter Petri dish.Then, under a stereo microscope with low illumination to minimize photo bleaching, use fine curved forceps to carefully remove the hairs, adipose tissue, connective tissue, dust, and fibers from the inside of the skin. Use PBS to keep the skin wet. With forceps, transfer the posterior and anterior skin, with the inside facing up, on an adhesive microscope slide.Use forceps to flatten the skin. Mount the skin in a liquid anti-fade mounting medium to avoid photo-bleaching and preserve fluorescent signals. Make sure that no air bubbles are on or around the skin.Store the stained skin sample slides in the dark overnight at room temperature to allow the mounting medium to get firm. Then, use nail polish to seal the coverslip to the slide, and store it at four degrees Celsius for long-term storage. To carry out confocal microscopy, set up appropriate lasers for fluorophores.A confocal microscope with three laser sources is used in this experiment. Image the samples under a 10X objective, and use the sequential scan tool, which simultaneously excites triple-stained samples, to avoid and reduce any overlap. In this experiment, adult mouse posterior ear skin and anterior ear skin were immunostained with antibodies to alpha-SMA, Tuj1, and PECAM-1.The posterior skin was immunostained to study neuroimmune distribution using antibodies to CD11b and MBP, together with Tuj1. Finally, as shown here, distribution of CD11b-positive inflammatory cells, including macrophages, was detected at a single-cell resolution. While attempting this procedure, it's important to remember to handle your skin with care and to gently and slowly remove the hairs, adipose tissue, and connective tissue from the inside of the ear skin before mounting.This technique will pave the way for researchers to study branching morphogenesis and patterning of peripheral nerves and blood vessels, as well as three-dimensional distribution of skin components, including immune cells in juvenile to adult mouse models. Thanks for watching. Good luck with your experiments.

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Research

JoVE Journal

Developmental Biology

Live Imaging of Innate Immune and Preneoplastic Cell Interactions Using an Inducible Gal4/UAS Expression System in Larval Zebrafish Skin

Here we describe a method to conditionally induce epithelial cell transformation by the use of the 4-Hydroxytamoxifen (4-OHT) inducible KalTA4-ERT2/UAS expression system1 in zebrafish larvae, and the subsequent live imaging of innate immune cell interaction with HRASG12V expressing skin cells. The KalTA4-ERT2/UAS system is both inducible and reversible which allows us to induce cell transformation with precise temporal/spatial resolution in vivo. This provides us with a unique opportunity to live image how individual preneoplastic cells interact with host tissues as soon as they emerge, then follow their progression as well as regression. Recent studies in zebrafish larvae have shown a trophic function of innate immunity in the earliest stages of tumorigenesis2,3. Our inducible system would allow us to live image the onset of cellular transformation and the subsequent host response, which may lead to important insights on the underlying mechanisms for the regulation of oncogenic trophic inflammatory responses. We also discuss how one might adapt our protocol to achieve temporal and spatial control of ectopic gene expression in any tissue of interest.

Studying the earliest events of preneoplastic cell progression and innate immune cell interaction is pivotal to understand and treat cancer. Here we describe a method to conditionally induce epithelial cell transformations and the subsequent live imaging of innate immune cell interaction with HRASG12V expressing skin cells in zebrafish larvae.

Here we describe a method to conditionally induce epithelial cell transformation by the use of the 4-Hydroxytamoxifen (4-OHT) inducible KalTA4-ERT2/UAS ...

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 ...

Horizontal Whole Mount: A Novel Processing and Imaging Protocol for Thick, Three-dimensional Tissue Cross-sections of Skin

Processing a tissue of interest to generate a microscopic image that supports a scientific argument can be challenging. The acquisition of high-quality microscopic images is not entirely dependent upon the quality of the microscope, but also upon the methods of tissue processing, which often involve multiple critical actions or steps. Furthermore, mesenchymal cell types in the skin and other tissues represent a new challenge for tissue preparation and imaging. Here, we present a complete process, from tissue harvest to microscopy. Our technique, called &#34;horizontal whole mount,&#34; is one that novices can quickly become proficient in and that allows for antigen preservation and detection in 60-300 &#181;m-thick sections cut with a cryostat. Sections of this thickness provide enhanced visualization of tissue microarchitecture in a three-dimensional environment. In addition, the protocol preserves mesenchymal cells in a manner that enhances image quality when compared to standard cryostat or paraffin sections, thereby increasing the efficacy and reliability of immunostaining. We believe that this protocol will benefit all laboratories that visualize skin, and possibly other tissues and organs.

This work presents a novel processing and imaging protocol for thick, three-dimensional tissue cross-section analysis that enables the full exploitation of confocal imaging modalities. This protocol preserves antigenicity and represents a robust system to analyze skin histology and potentially other tissue types.

Processing a tissue of interest to generate a microscopic image that supports a scientific argument can be challenging. The acquisition of high-quality ...

Quantitative Whole-mount Immunofluorescence Analysis of Cardiac Progenitor Populations in Mouse Embryos

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development and organogenesis are two areas of research that have benefitted greatly from these advances, due to the high quality of data that can be obtained directly from imaging pre-implantation embryos or ex vivo organs. While pre-implantation embryos have yielded data with especially high spatial resolution, later stages have been less amenable to three-dimensional reconstruction. Obtaining high-quality 3D or volumetric data for known embryonic structures in combination with fate mapping or genetic lineage tracing will allow for a more comprehensive analysis of the morphogenetic events taking place during embryogenesis.
This protocol describes a whole-mount immunofluorescence approach that allows for the labeling, visualization, and quantification of progenitor cell populations within the developing cardiac crescent, a key structure formed during heart development. The approach is designed in such a way that both cell- and tissue-level information can be obtained. Using confocal microscopy and image processing, this protocol allows for three-dimensional spatial reconstruction of the cardiac crescent, thereby providing the ability to analyze the localization and organization of specific progenitor populations during this critical phase of heart development. Importantly, the use of reference antibodies allows for successive masking of the cardiac crescent and subsequent quantitative measurements of areas within the crescent. This protocol will not only enable a detailed examination of early heart development, but with adaptations should be applicable to most organ systems in the gastrula to early somite stage mouse embryo.

Here, we describe a protocol for whole mount immunofluorescence and image-based quantitative volumetric analysis of early stage mouse embryos. We present this technique as a powerful approach to qualitatively and quantitatively assess cardiac structures during development, and propose that it may be widely adaptable to other organ systems.

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development ...

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 ...

Visualizing the Node and Notochordal Plate In Gastrulating Mouse Embryos Using Scanning Electron Microscopy and Whole Mount Immunofluorescence

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is the formation of the transient organizers, the node and notochordal plate, from cells that have passed through the primitive streak. The proper formation of these signaling centers is essential for the development of the body plan and techniques to visualize them are of high interest to mouse developmental biologists. The node and notochordal plate lie on the ventral surface of gastrulating mouse embryos around embryonic day (E) 7.5 of development. The node is a cup-shaped structure whose cells possess a single slender cilium each. The proper subcellular localization and rotation of the cilia in the node pit determines left-right asymmetry. The notochordal plate cells also possess single cilia albeit shorter than those of the node cells. The notochordal plate forms the notochord which acts as an important signaling organizer for somitogenesis and neural patterning. Because the cells of the node and notochordal plate are transiently present on the surface and possess cilia, they can be visualized using scanning electron microscopy (SEM). Among other techniques used to visualize these structures at the cellular level is whole mount immunofluorescence (WMIF) using the antibodies against the proteins that are highly expressed in the node and notochordal plate. In this report, we describe our optimized protocols to perform SEM and WMIF of the node and notochordal plate in developing mouse embryos to help in the assessment of tissue shape and cellular organization in wild-type and gastrulation mutant embryos.

The node and notochordal plate are transient signaling organizers in developing mouse embryos that can be visualized using several techniques. Here, we describe in detail how to perform two of the techniques to study their structure and morphogenesis: 1) scanning electron microscopy (SEM); and 2) whole mount immunofluorescence (WMIF).

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is ...

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart disease. When using prosthetic materials however, these grafts are susceptible to bacterial infections and various host responses.
Identification of bacterial and host factors that play a vital role in endovascular adherence of microorganisms is of importance to better understand the pathophysiology of the onset of infections such as infective endocarditis (IE) and to develop preventive strategies. Therefore, the development of competent models to investigate bacterial adhesion under physiological shear conditions is necessary. Here, we describe the use of a newly designed in vitro perfusion chamber based on parallel plates that allows the study of bacterial adherence to different components of graft tissues such as exposed extracellular matrix, endothelial cells and inert areas. This method combined with colony-forming unit (CFU) counting is adequate to evaluate the propensity of graft materials towards bacterial adhesion under flow. Further on, the flow chamber system might be used to investigate the role of blood components in bacterial adhesion under shear conditions. We demonstrated that the source of tissue, their surface morphology and bacterial species specificity are not the major determining factors in bacterial adherence to graft tissues by using our in-house designed in vitro perfusion model.

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

We describe an in-house designed in vitro flow chamber model, which allows the investigation of bacterial adherence to graft tissues.

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart ...

Analysis of Cardiac Chamber Development During Mouse Embryogenesis Using Whole Mount Epifluorescence

The goal of this protocol is to describe a method for the dissection of mouse embryos and visualization of embryonic mouse ventricular chambers during heart development using ventricular specific fluorescent reporter knock-in mice (MLC-2v-tdTomato mice). Heart development involves a linear heart tube formation, the heart tube looping, and four chamber septation. These complex processes are highly conserved in all vertebrates. The mouse embryonic heart has been widely used for heart developmental studies. However, due to their extremely small size, dissecting mouse embryonic hearts is technically challenging. In addition, visualization of cardiac chamber formation often needs in situ hybridization, beta-galactosidase staining using LacZ reporter mice, or immunostaining of sectioned embryonic hearts. Here, we describe how to dissect mouse embryonic hearts and directly visualize ventricular chamber formation of MLC-2v-tdTomato mice using whole mount epifluorescent microscopy. With this method, it is possible to directly examine heart tube formation and looping, and four chamber formation without further experimental manipulation of mouse embryos. Although the MLC-2v-tdTomato reporter knock-in mouse line is used in this protocol as an example, this protocol can be applied to other heart-specific fluorescent reporter transgenic mouse lines.

We present the protocols to examine mouse heart development using whole mount epifluorescent microscopy on mouse embryos dissected from ventricular specific MLC-2v-tdTomato reporter knock-in mice. This method allows us to directly visualize each stage of the ventricular formation during mouse heart development without labor-intensive histochemical methods.

The goal of this protocol is to describe a method for the dissection of mouse embryos and visualization of embryonic mouse ventricular chambers during ...

A Layered Mounting Method for Extended Time-Lapse Confocal Microscopy of Whole Zebrafish Embryos

Dynamics of development can be followed by confocal time-lapse microscopy of live transgenic zebrafish embryos expressing fluorescence in specific tissues or cells. A difficulty with imaging whole embryo development is that zebrafish embryos grow substantially in length. When mounted as regularly done in 0.3-1% low melt agarose, the agarose imposes growth restriction, leading to distortions in the soft embryo body. Yet, to perform confocal time-lapse microscopy, the embryo must be immobilized. This article describes a layered mounting method for zebrafish embryos that restrict the motility of the embryos while allowing for the unrestricted growth. The mounting is performed in layers of agarose at different concentrations. To demonstrate the usability of this method, whole embryo vascular, neuronal and muscle development was imaged in transgenic fish for 55 consecutive hours. This mounting method can be used for easy, low-cost imaging of whole zebrafish embryos using inverted microscopes without requirements of molds or special equipment.

This article describes a method to mount fragile zebrafish embryos for extended time-lapse confocal microscopy. This low-cost method is easy to perform using regular glass-bottom microscopy dishes for imaging on any inverted microscope. The mounting is performed in layers of agarose at different concentrations.

Dynamics of development can be followed by confocal time-lapse microscopy of live transgenic zebrafish embryos expressing fluorescence in specific tissues ...

Whole-Mount In Situ Hybridization in Zebrafish Embryos and Tube Formation Assay in iPSC-ECs to Study the Role of Endoglin in Vascular Development

Vascular development is determined by the sequential expression of specific genes, which can be studied by performing in situ hybridization assays in zebrafish during different developmental stages. To investigate the role of endoglin(eng) in vessel formation during the development of hereditary hemorrhagic telangiectasia&#160;(HHT), morpholino-mediated targeted knockdown of eng in zebrafish are used to study its temporal expression and associated functions. Here, whole-mount in situ RNA hybridization (WISH) is employed for the analysis of eng and its downstream genes in zebrafish embryos. Also, tube formation assays are performed in HHT patient-derived induced pluripotent stem cell-differentiated&#160;endothelial cells (iPSC-ECs; with eng mutations). A specific signal amplifying system using the whole amount In Situ Hybridization &#8211; WISH provides higher resolution and lower background results compared to traditional methods. To obtain a better signal, the post-fixation time is adjusted to 30 min after probe hybridization. Because fluorescence staining is not sensitive in zebrafish embryos, it is replaced with diaminobezidine (DAB) staining here. In this protocol, HHT&#160;patient-derived iPSC lines containing an eng mutation are differentiated into endothelial cells. After coating a plate with basement membrane matrix for 30 min at 37 &#176;C, iPSC-ECs are seeded as a monolayer into wells and kept at 37 &#176;C for 3 h. Then, the tube length and number of branches are calculated using microscopic images. Thus, with this improved WISH protocol, it is shown that reduced eng expression affects endothelial progenitor formation in zebrafish embryos. This is further confirmed by tube formation assays using iPSC-ECs derived from a patient with HHT. These assays confirm the role for eng in early vascular development.

Presented here is a protocol for whole-mount in situ RNA hybridization analysis in zebrafish and tube formation assay in patient-derived induced pluripotent stem cell-derived endothelial cells to study the role of endoglin in vascular formation.

Vascular development is determined by the sequential expression of specific genes, which can be studied by performing in situ hybridization assays in ...