This work was supported by the National Key R&#38;D Program of China (2016YFA0500902), the National Natural Science Foundation of China (31471228, 31771653), the Jiangsu Science Foundation for Distinguished Young Scholars (BK20150047),&#160;the Natural Science Foundation of Jiangsu Province (BK20140897, 14KJA180005) and the Innovative and Entrepreneurial Program of Jiangsu Province to K.Z.

All performed animal experiments have been approved by the Nanjing Medical University committee. Male C57BL/6 mice were kept under controlled photoperiod conditions and were supplied with food and water.
1. Preparations
<ol>
	<li>Microinjection capillaries
	<ol>
		<li>Use microinjection capillaries with an outer diameter, inner dimeter, and length of 1.0 mm, 0.8 mm, and 10.0 cm, respectively.</li>
		<li>Pull glass capillaries with a capillary puller (Fig...

<ol>
	<li>Mruk, D. D., Cheng, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sertoli-Sertoli+and+Sertoli-germ+cell+interactions+and+their+significance+in+germ+cell+movement+in+the+seminiferous+epithelium+during+spermatogenesis.">Sertoli-Sertoli and Sertoli-germ cell interactions and their significance in germ cell movement in the seminiferous epithelium during spermatogenesis.</a> Endocrine Reviews. 25 (5), 747-806 (2004).</li><li>Wen, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transport+of+germ+cells+across+the+seminiferous+epithelium+during+spermatogenesis-the+involvement+of+both+actin-+and+microtubule-based+cytoskeletons.">Transport of germ cells across the seminiferous epithelium during spermatogenesis-the involvement of both actin- and microtubule-based cytoskeletons.</a> Tissue Barriers. 4 (4), e1265042 (2016).</li><li>Wang, C. Q., Cheng, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+seamless+trespass:+germ+cell+migration+across+the+seminiferous+epithelium+during+spermatogenesis.">A seamless trespass: germ cell migration across the seminiferous epithelium during spermatogenesis.</a> Journal of Cell Biology. 178 (4), 549-556 (2007).</li><li>Fijak, M., Meinhardt, 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+testis+in+immune+privilege.">The testis in immune privilege.</a> Immunological Reviews. 213, 66-81 (2006).</li><li>O'Bryan, M. K., Hedger, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammatory+Networks+in+the+Control+of+Spermatogenesis+Chronic+Inflammation+in+an+Immunologically+Privileged+Tissue?.">Inflammatory Networks in the Control of Spermatogenesis Chronic Inflammation in an Immunologically Privileged Tissue?.</a> Molecular Mechanisms In Spermatogenesis. 636, 92-114 (2008).</li><li>Li, N., Wang, T., Han, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+cellular+and+molecular+aspects+of+immune+privilege+in+the+testis.">Structural cellular and molecular aspects of immune privilege in the testis.</a> Frontiers in Immunology. 3, 152 (2012).</li><li>Mruk, D. D., Cheng, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Mammalian+Blood-Testis+Barrier:+Its+Biology+and+Regulation.">The Mammalian Blood-Testis Barrier: Its Biology and Regulation.</a> Endocrine Review. 36 (5), 564-591 (2015).</li><li>Govero, 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=Zika+virus+infection+damages+the+testes+in+mice.">Zika virus infection damages the testes in mice.</a> Nature. 540 (7633), 438-442 (2016).</li><li>Jenabian, M. 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=Immune+tolerance+properties+of+the+testicular+tissue+as+a+viral+sanctuary+site+in+ART-treated+HIV-infected+adults.">Immune tolerance properties of the testicular tissue as a viral sanctuary site in ART-treated HIV-infected adults.</a> AIDS. 30 (18), 2777-2786 (2016).</li><li>Holembowski, 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=TAp73+is+essential+for+germ+cell+adhesion+and+maturation+in+testis.">TAp73 is essential for germ cell adhesion and maturation in testis.</a> Journal Of Cell Biology. 204 (7), 1173-1190 (2014).</li><li>Legendre, 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=An+engineered+3D+blood-testis+barrier+model+for+the+assessment+of+reproductive+toxicity+potential.">An engineered 3D blood-testis barrier model for the assessment of reproductive toxicity potential.</a> Biomaterials. 31 (16), 4492-4505 (2010).</li><li>Setchell, B. P., Waites, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+the+permeability+of+the+testicular+capillaries+and+of+the+'blood-testis+barrier'+after+injection+of+cadmium+chloride+in+the+rat.">Changes in the permeability of the testicular capillaries and of the 'blood-testis barrier' after injection of cadmium chloride in the rat.</a> Journal of Endocrinology. 47 (1), 81-86 (1970).</li><li>Griswold, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+central+role+of+Sertoli+cells+in+spermatogenesis.">The central role of Sertoli cells in spermatogenesis.</a> Seminars in Cell &amp; Developmental Biology. 9 (4), 411-416 (1998).</li><li>Cheng, C. Y., Mruk, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+blood-testis+barrier+and+its+implications+for+male+contraception.">The blood-testis barrier and its implications for male contraception.</a> Pharmacological Reviews. 64 (1), 16-64 (2012).</li><li>Mruk, D. D., Cheng, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+in+vitro+system+to+study+Sertoli+cell+blood-testis+barrier+dynamics.">An in vitro system to study Sertoli cell blood-testis barrier dynamics.</a> Methods Molecular Biology. 763, 237-252 (2011).</li><li>Orth, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proliferation+of+Sertoli+cells+in+fetal+and+postnatal+rats:+a+quantitative+autoradiographic+study.">Proliferation of Sertoli cells in fetal and postnatal rats: a quantitative autoradiographic study.</a> Anatomical Record. 203 (4), 485-492 (1982).</li><li>Lee, N. P. Y., Mruk, D., Lee, W. M., Cheng, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+the+cadherin/catenin+complex+a+functional+unit+of+cell-cell+actin-based+adherens+junctions+in+the+rat+testis?.">Is the cadherin/catenin complex a functional unit of cell-cell actin-based adherens junctions in the rat testis?.</a> Biology of Reproduction. 68 (2), 489-508 (2003).</li><li>Bai, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Germline-Specific+Role+for+the+mTORC2+Component+Rictor+in+Maintaining+Spermatogonial+Differentiation+and+Intercellular+Adhesion+in+Mouse+Testis.">A Germline-Specific Role for the mTORC2 Component Rictor in Maintaining Spermatogonial Differentiation and Intercellular Adhesion in Mouse Testis.</a> Molecular Human Reproduction. 24 (5), 244-259 (2018).</li><li>Korhonen, H. 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=DICER+Regulates+the+Formation+and+Maintenance+of+Cell-Cell+Junctions+in+the+Mouse+Seminiferous+Epithelium.">DICER Regulates the Formation and Maintenance of Cell-Cell Junctions in the Mouse Seminiferous Epithelium.</a> Biology of Reproduction. 93 (6), 139 (2015).</li><li>Loir, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trout+Sertoli+cells+and+germ+cells+in+primary+culture:+I.+Morphological+and+ultrastructural+study.">Trout Sertoli cells and germ cells in primary culture: I. Morphological and ultrastructural study.</a> Gamete Research. 24 (2), 151-169 (1989).</li><li>Chen, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+the+Integrity+of+the+Blood-Testis+Barrier+(BTB):+An+In+Vivo+Assay.">Monitoring the Integrity of the Blood-Testis Barrier (BTB): An In Vivo Assay.</a> Methods in Molecular Biology. 1748, 245-252 (2018).</li></ol>

Spermatogenesis takes place in the seminiferous epithelium and is a highly ordered and dynamic process that is governed by germ cells and somatic cells (e.g., Sertoli cells)13. The BTB structure, which is constructed by Sertoli cells, divides the seminiferous epithelium into a basal and an apical compartment. The development of meiotic and haploid germ cells occurs in the apical compartment which forms an immunological barrier14.
<p class="jove_content...

Mammalian spermatogenesis is considered a highly structured process that encompasses spermatogonial self-renewal and differentiation through spermatocytes into haploid spermatozoa via mitosis, meiosis, and spermiogenesis, during which dramatic biochemical and morphological changes occur. Developing germ cells are progressively transported from the base of the seminiferous tubule toward the lumen. This process is regulated by cell-cell contacts between germ cells and Sertoli cells1,2. Adjacent Sertoli cells form the BTB that is located near the base of the seminiferous tubule. The BTB physically divides the epithelium into a basal and an adluminal compartment. During stages VIII - IX of the epithelial cycle, preleptotene/leptotene spermatocytes from the basal compartments migrate across the BTB, entering the adluminal compartments3. Therefore, the function of the BTB is to provide an immunoprivileged microenvironment for the completion of meiosis and spermiogenesis4,5,6. Unlike other blood-tissue barriers (e.g., blood-brain barrier) that are only composed of tight junctions (TJs), the BTB is formed by four different junctions (TJs, ectoplasmic specializations, gap junctions, and intermediate filament-based desmosomes) between Sertoli cells1,7.
Many studies have used genetically-modified mice, virus infections, and environmental toxicants to investigate mechanisms of BTB integrity7,8,9. The BTB disruption induces impaired spermatogenesis and subfertility or infertility. Since the BTB formation and integrity have been confirmed to be affected by contacts between Sertoli cells8, an in vitro model based on primary culture of isolated Sertoli cells has been used for BTB study. However, this model cannot accurately mimic BTB dynamics in vivo. Moreover, no such co-culture of germ cells with Sertoli cells has been established as capable of reflecting all relevant structural and functional components of the BTB10,11.
In general, in vivo BTB integrity assays are typically based on small molecules, such as EZ-Link Sulfo-NHS-LC-Biotin and FITC-conjugated inulin (inulin-FITC). Normally, the diffusion of biotin or inulin-FITC from the basal compartment is blocked by BTB structure. Therefore, we are able to use this method to assess the extent of BTB damage compared with control groups. While BTB can be compromised with certain types of stimuli, such as treatment with cadmium chloride (CdCl2)12, BTB becomes accessible to small molecules, which eventually enter the adluminal compartment as indicators.
An early in vivo BTB integrity assay involves injecting biotin or inulin-FITC into the jugular vein, which involves surgery, and is invasive, complicated, and time-consuming. Besides, as the reporter substances diffuse through the whole body via the circulation, the local concentration of biotin or inulin-FITC in the seminiferous tubules is limited. Moreover, systemic exposure may induce immune reactions. Here, we present a simple and effective in vivo BTB integrity assay enabling direct injection of a small aliquot of inulin-FITC into the interstitium of a testis. Using the fluorescent labeling method, the staining process is convenient, as secondary antibodies are not required. Here, the process of fluorescent dye entering the testis is visualized.

<table border="0" cellpadding="0" cellspacing="0" style="width:803px;" width="802">
	
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Capillary puller&#160;</td>
			<td style="width:231px;">SUTTER INSTRUMENT (USA)</td>
			<td style="width:139px;">P-97</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">10x PBS</td>
			<td style="width:231px;">Hyclone (USA)</td>
			<td style="width:139px;">SH30258.01</td>
			<td>dilution to 1&#215; in ddH2O</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4&#8217;,6-diamidino-2-phenylindole (DAPI)</td>
			<td style="width:231px;">Sigma (USA)</td>
			<td style="width:139px;">F6057</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Adhesion microscope slides</td>
			<td style="width:231px;">CITOGLAS (China)</td>
			<td style="width:139px;">80312-3161</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cadmium chloride</td>
			<td style="width:231px;">Sigma (USA)</td>
			<td style="width:139px;">655198-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Confocal microscope</td>
			<td style="width:231px;">Zeiss (Germany)</td>
			<td style="width:139px;">LSM700</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dust-free paper</td>
			<td style="width:231px;">Kimberly-Clark (USA)</td>
			<td style="width:139px;">34120</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Inulin-FITC</td>
			<td style="width:231px;">Sigma (USA)</td>
			<td style="width:139px;">F3272</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Microinjection capillaries</td>
			<td style="width:231px;">Zhengtianyi (China)</td>
			<td style="width:139px;">BJ-40</td>
			<td>1.0 mm &#215; 0.8 mm&#160; &#215; 100 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micropipette beveler</td>
			<td style="width:231px;">NARISHIGE (JAPAN)</td>
			<td style="width:139px;">EG-400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">OCT</td>
			<td style="width:231px;">SAKURA (JAPAN)</td>
			<td style="width:139px;">4583</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Paraformaldehyde</td>
			<td style="width:231px;">Sigma (USA)</td>
			<td style="width:139px;">P6148</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pentobarbital sodium</td>
			<td style="width:231px;">Merck (Germany)</td>
			<td style="width:139px;">P11011</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Shaver&#160;</td>
			<td style="width:231px;">Yashen (China)</td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Stereo microscope</td>
			<td style="width:231px;">Nikon (JAPAN)</td>
			<td style="width:139px;">SMZ1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sucrose&#160;</td>
			<td style="width:231px;">Sangon Biotech (China)</td>
			<td style="width:139px;">A610498</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">Surgical instruments</td>
			<td style="width:231px;">Stronger (China)</td>
			<td style="width:139px;"></td>
			<td>scissors, forceps, needle holder</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Syringe</td>
			<td style="width:231px;">KDL (China)</td>
			<td style="width:139px;">20163150518</td>
			<td>0.45 mm &#215; 0.16 mm RW LB</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">thermostatic heater</td>
			<td style="width:231px;">KELL (Nanjing, China)</td>
			<td style="width:139px;">KEL-2010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td >10x TBS, pH 7.6</td>
<td></td>
<td></td>
<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.2 M Tris</td>
			<td style="width:231px;">Sangon Biotech (China)</td>
			<td style="width:139px;">A600194</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:261px;">1.37 M Nacl</td>
			<td style="width:231px;">Sangon Biotech (China)</td>
			<td style="width:139px;">A610476</td>
			<td></td>
		</tr>
	</tbody>
</table>

an in vivo method to study mouse blood-testis barrier integrity

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by Sertoli cell junctions at the blood-testis barrier (BTB), which is the tightest tissue barrier in the mammalian body and segregates the seminiferous epithelium into two compartments, a basal and an adluminal. The BTB creates a unique microenvironment for germ cells in meiosis I/II and for the development of postmeiotic spermatids into spermatozoa via spermiogenesis. Here, we describe a reliable assay to monitor BTB integrity of mouse testis in vivo. An intact BTB blocks the diffusion of FITC-conjugated inulin from the basal to the apical compartment of the seminiferous tubules. This technique is suitable for studying gene candidates, viruses, or environmental toxicants that may affect BTB function or integrity, with an easy procedure and a minimal requirement of surgical skills compared to alternative methods.

The experimental set-up for performing the BTB integrity assay is shown in Figure 1. Pull and sharpen microinjection capillaries with a capillary puller and micropipette beveler, respectively (Figure 1A and 1C). The thermostatic heater and equipment for microinjection are illustrated in Figure 1B and 1D.
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Watch this Scientific Journal Video about An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity at JoVE.com

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Here, we present a protocol to assess the blood-testis barrier integrity by injecting inulin-FITC into testes. This is an efficient in vivo method to study blood-testis barrier integrity that can be compromised by genetic and environmental elements.

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by ...

This method can help answer key questions in the blood-testis barrier of biology fields about gene candidates, viruses, or environmental toxins that may affect blood-testis barrier function or integrity. Three days before the surgery, treat at least three eight-week-old C57Black/6 male mice daily with a five milligrams per kilogram body weight cadmium chloride via intraperitoneal injection. On the day of the surgery, place a clean tissue over a 75%ethanol-sterilized surgical area and set a thermostatic heater to 37 degrees Celsius.Place an anesthetized mouse onto the tissue, then confirm a lack of response to toe pinch. Shave the abdominal hair with a shaver, and disinfect the exposed skin with 75%ethanol. Make a one-centimeter skin incision above the preputial glands to expose the abdominal wall, and use small forceps to lift the skin to make a 0.5-centimeter incision in the peritoneum.Use the forceps to search for fat pads around the epididymis and testis, carefully pulling the fat pads out to expose one attached testis. Place a nine-centimeter piece of paper under the fat pads and testis, and load a microinjection pipette with freshly prepared inulin-FITC solution. Connect the pipette to a micromanipulator unit, and use a dissecting microscope to gently insert the microinjection pipette tip under the tunica albuginea.Slowly rotate the operating lever to deliver 20 microliters of the inulin-FITC into the interstitium of the testis. If the delivery is successful, the testis will turn a bright green-yellow color. Immediately return the testis to the abdominal cavity, and inject the contralateral testis with 20 microliters of PBS, then close the skin with a surgical suture.And place the mouse onto the heat pad of a thermostatic heater. 40 minutes after the injection, use sharp scissors to collect the testes from each mouse, and wash the tissues in one milliliter of ice-cold PBS. Next, fix the testes in 4%paraformaldehyde at four degrees Celsius for 12 to 24 hours followed by three washes in 1.5 milliliters of 1%PBS per wash.After 30%sucrose dehydration overnight, transfer the samples into individual embedding frames, and cover the tissues with optimal cutting temperature compound. Set the temperature of a cryostat to negative 20 degrees Celsius and place the frames in the cryostat for about 10 minutes until the OCT is frozen. Then, fill each embedding frame with fresh OCT until the whole testis is covered in each mold.When the second layer of OCT has frozen, acquire a five-micrometer-thick cross sections of each testis, capturing the tissue sections onto glass microscope slides as they are obtained. To image the samples, first warm the slides in a humidified box at room temperature. After 10 minutes, wash the slides three times in fresh Tris-buffered saline per wash and allow the sections to dry for five minutes protected from light.Use dust-free paper to remove any residual saline, and mount the samples with DAPI-supplemented mounting medium. Then, cover each sample with an inverted cover slip, and image the samples under the 20X objective of a confocal microscope. Three days of cadmium chloride treatment causes damage to the blood-testis barrier allowing inulin-FITC diffusion from the basal compartment to the apical compartment of the seminiferous epithelium.In contrast, this diffusion is blocked in control PBS-treated testes. The extent of the blood-testis barrier damage is determined by calculating the ratio of the distance of inulin-FITC diffusion to the radius of the same seminiferous tubule. Further, the intact blood-testis barrier in heterozygous Rictor floxed knockout mice blocks inulin diffusion across the barrier into the apical compartment, while conditional Rictor knockout mice possess a compromised blood-testis barrier that permits inulin diffusion.While attempting this procedure, it's important to remember to deliver inulin-FITC prepared on the day of the experiment and to keep the tissue protected from light since FITC is a light-sensitive molecule. The implications of this technique extend to the therapy of impaired spermatogenesis because the function of the blood-testis barrier is to provide an immune-privileged microenvironment for the completion of meiosis in spermatogenesis. After its development, this technique provide a way for researchers in the field of reproductive medicine to explore subfertility and infertility in mice.Don't forget that working with paraformaldehydes can be extremely hazardous and that precautions such as wearing garments and face masks should always be taken when performing this procedure.

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Video: An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

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An In Vivo Method for Evaluating the Gut-Blood Barrier and Liver Metabolism of Microbiota Products

in vivo microinjection and electroporation of mouse testis

In Vivo Microinjection and Electroporation of Mouse Testis

This article describes microinjection and electroporation of mouse testis in&#160;vivo as a&#160;transfection technique for testicular mouse cells to study unique processes of spermatogenesis. The presented protocol involves steps of glass capillary preparation, microinjection via the efferent duct, and transfection by...

In Vivo Microinjection and Electroporation of Mouse Testis

an in vivo immunofluorescence localization method to study antibody biodistribution

This video demonstrates an in vivo immunofluorescence localization (IVIL) technique to study the biodistribution of tumor-targeting antibodies in a murine model of breast cancer. Upon the intravenous injection of a tumor-specific antibody in the mouse, the tumor is surgically isolated, and the localization of the antibody within the tumor tissue is confirmed via ex vivo...

An In Vivo Immunofluorescence Localization Method to Study Antibody Biodistribution

an in vivo blood-brain barrier permeability assay in mice using fluorescently labeled tracers

An In Vivo Blood-brain Barrier Permeability Assay in Mice Using Fluorescently Labeled Tracers

Here we present a mouse brain vascular permeability assay using intraperitoneal injection of fluorescent tracers followed by perfusion that is applicable to animal models of blood-brain barrier dysfunction. One hemi-brain is used for assessing permeability quantitatively and the other for tracer visualization/immunostaining. The procedure takes 5 - 6 h for 10...

An In Vivo Blood-brain Barrier Permeability Assay in Mice Using Fluorescently Labeled Tracers

Visualize blood backflow into the catheter to ensure that the needle is properly placed so that the solutions will fully enter the animal versus being captured in the...

barrier functional integrity recording on bend.3 vascular endothelial cells via transendothelial electrical resistance detection

Author Spotlight: Applications of TEER Detection to Assess Cell Barrier Integrity 

This protocol describes a dependable and efficient in vitro model of the brain blood barrier. The method uses mouse cerebral vascular endothelial cells bEnd.3 and measures transmembrane electrical...

Transendothelial Resistance Measurement to Assess Cell Barrier Integrity

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an in vivo assessment of blood-brain barrier disruption in a rat model of ischemic stroke

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

The overall goal of this procedure is to provide a highly reproducible technique for in vivo assessment of the blood-brain barrier disruption in rat models of ischemic...

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

an in vivo assay to test blood vessel permeability

An in vivo Assay to Test Blood Vessel Permeability

We are presenting an in vivo assay to test blood vessel permeability. This assay is based on intravenous injection of a dye and subsequent visualization of its diffusion into interstitial...

An in vivo Assay to Test Blood Vessel Permeability

measuring changes in brain endothelial barrier integrity with two impedance-based biosensors in response to cancer cells and cytokines

Author Spotlight: Studying Brain Endothelial Barrier in Metastatic Cancer Using Impedance-Based Biosensors

Here we demonstrate the technique of using impedance-based biosensors: ECIS and cellZscope, for measuring brain endothelial barrier strength. We detail the preparation and technique of adding various stimuli to an in vitro model of the brain endothelium. We measure, record, and give a representative analysis of the...

Impedance-Based Biosensors in Investigating Brain Endothelial Barrier Strength

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endothelial cell transcytosis assay as an in vitro model to evaluate inner blood-retinal barrier permeability

Endothelial Cell Transcytosis Assay as an In Vitro Model to Evaluate Inner Blood-Retinal Barrier Permeability

This protocol illustrates an in vitro endothelial cell transcytosis assay as a model to evaluate inner blood-retinal barrier permeability by measuring the ability of human retinal microvascular endothelial cells to transport horseradish peroxidase across cells in caveolae-mediated transcellular transport processes.

Endothelial Cell Transcytosis Assay as an In Vitro Model to Evaluate Inner Blood-Retinal Barrier Permeability

cellzscope monitoring of brain endothelial barrier integrity in response to treatments

CellZscope Monitoring of Brain Endothelial Barrier Integrity in Response to Treatments

improved method for the establishment of an in vitro blood-brain barrier model based on porcine brain endothelial cells

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of the protocol is to present an optimized procedure for the establishment of an in vitro blood-brain barrier (BBB) model based on primary porcine brain endothelial cells (pBECs). The model shows high reproducibility, high tightness, and is suitable for studies of transport and intracellular trafficking in drug discovery.

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

focus ultrasound based microbubble mediated blood-brain barrier opening: a technique to create localized transient openings in blood-brain barrier of mouse by sonoporation

This video describes a method of temporarily disrupting the blood-brain barrier (BBB) by creating transient openings using microbubble-mediated focused ultrasound (FUS). These transient local BBB openings can eventually be used to deliver larger-sized drug molecules directly into the brain...

Focus Ultrasound Based Microbubble Mediated Blood-Brain Barrier Opening: A Technique to Create Localized Transient Openings in Blood-Brain Barrier of Mouse by Sonoporation

predicting in vivo payloads delivery using a blood-brain tumor-barrier in a dish

Predicting In Vivo Payloads Delivery using a Blood-brain Tumor-barrier in a Dish

Drug targeting to central nervous system tumors is a major challenge. Here we describe a protocol to produce an in vitro mimic of the blood-brain tumor-barrier using murine and/or human cells and discuss their relevance for the predictability of central nervous system tumor targeting in...

assessment of gut barrier integrity in mice using fluorescein-isothiocyanate-labeled dextran

Assessment of Gut Barrier Integrity in Mice Using Fluorescein-Isothiocyanate-Labeled Dextran

In the present study, fluorescein-isothiocyanate-labeled (FITC) dextran is administered to mice via oral gavage to evaluate intestinal permeability both in vivo and in plasma and fecal samples. As gut barrier function is affected in many disease processes, this direct and quantitative assay can be used in diverse research...

Place the animal on the temperature-regulated stereotactic platform to avoid hypothermia. Fix the head of the animal using a bite bar and ear bars and tape the tail and catheter to the platform. Fix the body of the mouse with a...

barrier destruction and statistical analysis after teer measurement in an in vitro blood-brain barrier model

Barrier Destruction and Statistical Analysis After TEER Measurement in an In Vitro Blood-Brain Barrier Model  

enhanced crosslinking immunoprecipitation (eclip) method for efficient identification of protein-bound rna in mouse testis

Enhanced Crosslinking Immunoprecipitation eCLIP Method for Efficient Identification of Protein-bound RNA in Mouse Testis

Here, we present an eCLIP protocol to determine major RNA targets of RBP candidates in...

Enhanced Crosslinking Immunoprecipitation (eCLIP) Method for Efficient Identification of Protein-bound RNA in Mouse Testis

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Using Ex Vivo Upright Droplet Cultures of Whole Fetal Organs to Study Developmental Processes during Mouse Organogenesis

Investigating organogenesis in utero is a technically challenging process in placental mammals due to inaccessibility of reagents to embryos that develop within the uterus. A newly developed ex vivo upright droplet culture method provides an attractive alternative to studies performed in utero. The ex vivo droplet culture provides the ability to examine and manipulate cellular interactions and diverse signaling pathways through use of various blocking and activating compounds; additionally, the effects of various pharmacological reagents on the development of specific organs can be studied without unwanted side effects of systemic drug delivery in utero. As compared to other in vitro systems, the droplet culture not only allows for the ability to study three-dimensional morphogenesis and cell-cell interactions, which cannot be reproduced in mammalian cell lines, but also requires significantly less reagents than other ex vivo and in vitro protocols. This paper demonstrates proper mouse fetal organ dissection and upright droplet culture techniques, followed by whole organ immunofluorescence to demonstrate the effectiveness of the method. The ex vivo droplet culture method allows the formation of organ architecture comparable to what is observed in vivo and can be utilized to study otherwise difficult-to-study processes due to embryonic lethality in in vivo models. As a model application system, a small-molecule inhibitor will be utilized to probe the role of vascularization in testicular morphogenesis. This ex vivo droplet culture method is expandable to other fetal organ systems, such as lung and potentially others, although each organ must be extensively studied to determine any organ-specific modifications to the protocol. This organ culture system provides flexibility in experimentation with fetal organs, and results obtained using this technique will help researchers gain insights into fetal development.

Using Ex Vivo Upright Droplet Cultures of Whole Fetal Organs to Study Developmental Processes during Mouse Organogenesis

The&#160;ex vivo&#160;upright droplet culture is an alternative to current&#160;in vitro&#160;and&#160;in vivo&#160;experimental techniques. This protocol is easy to perform and requires smaller amounts of reagent, while permitting the ability to manipulate and study fetal vascularization, morphogenesis, and organogenesis.

Investigating organogenesis in utero is a technically challenging process in placental mammals due to inaccessibility of reagents to embryos that develop ...

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

Understanding the genetic programs underlying neural development is an important goal of developmental and stem cell biology. In the amphibian blastula, cells from the roof of the blastocoel are pluripotent. These cells can be isolated, and programmed to generate various tissues through manipulation of genes expression or induction by morphogens. In this manuscript protocols are described for the use of Xenopus laevis blastocoel roof explants as an assay system to investigate key in vivo and in vitro features of early neural development. These protocols allow the investigation of fate acquisition, cell migration behaviors, and cell autonomous and non-autonomous properties. The blastocoel roof explants can be cultured in a serum-free defined medium and grafted into host embryos. This transplantation into an embryo allows the investigation of the long-term lineage commitment, the inductive properties, and the behavior of transplanted cells in vivo. These assays can be exploited to investigate molecular mechanisms, cellular processes and gene regulatory networks underlying neural development. In the context of regenerative medicine, these assays provide a means to generate neural-derived cell types in vitro that could be used in drug screening.

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

In Xenopus embryos, cells from the roof of the blastocoel are pluripotent and can be programmed to generate various tissues. Here, we describe protocols to use amphibian blastocoel roof explants as an assay system to investigate key in vivo and in vitro features of early neural development.

Understanding the genetic programs underlying neural development is an important goal of developmental and stem cell biology. In the amphibian blastula, ...

Quantitative Analysis of Protein Expression to Study Lineage Specification in Mouse Preimplantation Embryos

This protocol presents a method to perform quantitative, single-cell in situ analyses of protein expression to study lineage specification in mouse preimplantation embryos. The procedures necessary for embryo collection, immunofluorescence, imaging on a confocal microscope, and image segmentation and analysis are described. This method allows quantitation of the expression of multiple nuclear markers and the spatial (XYZ) coordinates of all cells in the embryo. It takes advantage of MINS, an image segmentation software tool specifically developed for the analysis of confocal images of preimplantation embryos and embryonic stem cell (ESC) colonies. MINS carries out unsupervised nuclear segmentation across the X, Y and Z dimensions, and produces information on cell position in three-dimensional space, as well as nuclear fluorescence levels for all channels with minimal user input. While this protocol has been optimized for the analysis of images of preimplantation stage mouse embryos, it can easily be adapted to the analysis of any other samples exhibiting a good signal-to-noise ratio and where high nuclear density poses a hurdle to image segmentation (e.g., expression analysis of embryonic stem cell (ESC) colonies, differentiating cells in culture, embryos of other species or stages, etc.).

This protocol presents a method to perform quantitative, single-cell in situ analysis of protein expression to study lineage specification in mouse preimplantation embryos. The procedures necessary for collection of blastocysts, whole-mount immunofluorescent detection of proteins, imaging of samples on a confocal microscope, and nuclear segmentation and image analysis are described.

This protocol presents a method to perform quantitative, single-cell in situ analyses of protein expression to study lineage specification in mouse ...

An Efficient Method to Obtain Dedifferentiated Fat Cells

Tissue engineering and cell therapy hold great promise clinically. In this regard, multipotent cells, such as mesenchymal stem cells (MSCs), may be used therapeutically, in the near future, to restore function to damaged organs. Nevertheless, several technical issues, including the highly invasive procedure of isolating MSCs and the inefficiency surrounding their amplification, currently hamper the potential clinical use of these therapeutic modalities. Herein, we introduce a highly efficient method for the generation of dedifferentiated fat cells (DFAT), MSC-like cells. Interestingly, DFAT cells can be differentiated into several cell types including adipogenic, osteogenic, and chondrogenic cells. Although other groups have previously presented various methods for generating DFAT cells from mature adipose tissue, our method allows us to produce DFAT cells more efficiently. In this regard, we demonstrate that DFAT culture medium (DCM), supplemented with 20% FBS, is more effective in generating DFAT cells than DMEM, supplemented with 20% FBS. Additionally, the DFAT cells produced by our cell culture method can be redifferentiated into several tissue types. As such, a very interesting and useful model for the study of tissue dedifferentiation is presented.

We have modified the conditions for DFAT cell generation and provide herein information regarding the use of an improved growth medium for the production of these cells.

Tissue engineering and cell therapy hold great promise clinically. In this regard, multipotent cells, such as mesenchymal stem cells (MSCs), may be used ...

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema and diminished visual acuity. However, human CECs are prone to compromised proliferative potential. Furthermore, stimulation of cell growth is often complicated by gradual endothelial-mesenchymal transition (EnMT). Therefore, understanding the mechanism of EnMT is necessary for facilitating the regeneration of CECs with competent function. In this study, we prepared a primary culture of bovine CECs by peeling the CECs with Descemet's membrane from the corneal button and demonstrated that bovine CECs exhibited the EnMT process, including phenotypic change, nuclear translocation of &#946;-catenin, and EMT regulators snail and slug, in the in vitro culture. Furthermore, we used a rat corneal endothelium cryoinjury model to demonstrate the EnMT process in vivo. Collectively, the in vitro primary culture of bovine CECs and in vivo rat corneal endothelium cryoinjury models offers useful platforms for investigating the mechanism of EnMT.

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

A primary culture of bovine corneal endothelial cells was used to investigate the mechanism of corneal endothelial-mesenchymal transition. Furthermore, a rat corneal endothelium cryoinjury model was used to demonstrate corneal endothelial-mesenchymal transition in vivo.

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema ...

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

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

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

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

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

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 ...

Organotypic Culture Method to Study the Development Of Embryonic Chicken Tissues

The embryonic chicken is commonly used as a reliable model organism for vertebrate development. Its accessibility and short incubation period makes it ideal for experimentation. Currently, the study of these developmental pathways in the chicken embryo is conducted by applying inhibitors and drugs at localized sites and at low concentrations using a variety of methods. In vitro tissue&#160;culturing is a technique that enables the study of tissues separated from the host organism, while simultaneously bypassing many of the physical limitations present when working with whole embryos, such as the susceptibility of embryos to high doses of potentially lethal chemicals. Here, we present an organotypic culturing protocol for culturing the embryonic chicken half head in vitro, which presents new opportunities for the examination of developmental processes beyond the currently established methods.

Here, we present an organotypic culturing protocol to grow embryonic chicken organs in vitro. Using this method, the development of embryonic chicken tissue can be studied, while maintaining a high degree of control over the culture environment.

The embryonic chicken is commonly used as a reliable model organism for vertebrate development. Its accessibility and short incubation period makes it ...

A Hyperandrogenic Mouse Model to Study Polycystic Ovary Syndrome

Hyperandrogenemia plays a critical role in reproductive and metabolic function in females and is the hallmark of polycystic ovary syndrome. Developing a lean PCOS-like mouse model that mimics women with PCOS is clinically meaningful. In this protocol, we describe such a model. By inserting a 4 mm length of DHT (dihydrotestosterone) crystal powder pellet (total length of pellet is 8 mm), and replacing it monthly, we are able to produce a PCOS-like mouse model with serum DHT levels 2 fold higher than mice not implanted with DHT (no-DHT). We observed reproductive and metabolic dysfunction without changing body weight and body composition. While exhibiting a high degree of infertility, a small subset of these PCOS-like female mice can get pregnant and their offspring show delayed puberty and increased testosterone as adults. This PCOS-like lean mouse model is a useful tool to study the pathophysiology of PCOS and the offspring from these PCOS-like dams.

We describe the development of a lean PCOS-like mouse model with&#160;dihydrotestosterone pellet to study the pathophysiology of PCOS and the offspring from these PCOS-like dams.

Hyperandrogenemia plays a critical role in reproductive and metabolic function in females and is the hallmark of polycystic ovary syndrome. Developing a ...