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 (Figure 1A). Test and adjust the settings depending on the capillary puller machine that is being used.</li>
		<li>Break the pipette tips with forceps to use to obtain capillaries of a 50-&#181;m diameter at the tip. 
		Note: The tips may be too long to penetrate the testis.</li>
		<li>Sharpen the tip in a 30&#176; angle by using a micropipette beveler (Figure 1C).</li>
	</ol>
	</li>
	<li>Reagents
	<ol>
		<li>Prepare 1% pentobarbital sodium: dissolve pentobarbital sodium 100 mg in 10 mL of phosphate-buffered saline (PBS) (step 2.3.3).</li>
		<li>Prepare 10 mg/mL inulin-FITC: dissolve inulin-FITC 1 mg in 100 &#956;L of PBS (step 2.1.6).</li>
		<li>Prepare 4% paraformaldehyde: dissolve paraformaldehyde (PFA) 4 g in 100 mL of PBS (step 2.3.3).</li>
		<li>Prepare 30% sucrose: dissolve sucrose 3 g in 10 mL of PBS (step 2.3.4).</li>
		<li>Prepare 0.1% cadmium chloride: dissolve cadmium chloride 10 mg in 10 mL of PBS (step 2.1.1).</li>
	</ol>
	</li>
</ol>
2. Methods
<ol>
	<li>Anesthesia and presurgery preparation
	<ol>
		<li>Weigh 8-week-old C57BL/6 male mice and calculate the required dose of CdCl2. Treat a group of mice (n = 3) with CdCl2 (5 mg/kg b.w., i.p.) for 3 d before surgery. Treat another group of 8-week-old C57BL/6 male mice (n = 3) with PBS as control.</li>
		<li>Perform surgery under aseptic conditions by using sterile syringe, needle, scissors, and forceps.</li>
		<li>Prepare anesthesia working solution freshly. The required dose of anesthesia is 70 mg of pentobarbital sodium/kg of body weight. On average, an adult C57BL/6 mouse at 8 weeks of age weighs ~25 g, which corresponds to 175 &#956;L of 1% pentobarbital sodium (1.75 mg per mouse). 
		NOTE:&#160;The pentobarbital sodium is dissolved in sterile phosphate-buffered saline (PBS). The solution is filtered by 0.22 um filter unit before being used.</li>
		<li>Clean the area for surgery with 75% ethanol and cover the area with a clean tissue towel.</li>
		<li>Turn on the thermostatic heater and adjust the temperature to 37 &#176;C.</li>
		<li>Prepare inulin-FITC working solution (10 mg/mL) on the day of the surgery.</li>
	</ol>
	</li>
	<li>Surgical procedure
	<ol>
		<li>Weigh 8-week-old C57BL/6 male mice and calculate the required dose of anesthesia.</li>
		<li>Perform an intraperitoneal injection of pentobarbital sodium using the 1-mL sterile syringe. Keep the mouse in a clean cage.</li>
		<li>Observe the eye reflex response and breathing pattern of the mouse to confirm that it is under complete anesthesia. 
		NOTE: Usually, 10 - 15 min are needed until the mouse is deeply anesthetized, with a total lack of toe pinch response and maintenance of slow, steady breathing.</li>
		<li>Move the mouse to the operation area and cover its eye area with a moist tissue paper to avoid dryness during anesthesia (Figure 2A).</li>
		<li>Shave its abdominal hair with a&#160;shaver and disinfect the surgery area with 75% ethanol.</li>
		<li>With sharp scissors, make a 1-cm skin incision above the preputial glands to expose the abdominal wall. Lift the abdominal wall with small forceps and make a 0.5-cm incision to expose the peritoneal cavity (Figure 2B).</li>
		<li>Use forceps to search for fat pads around the epididymis and testis. Carefully pull the fat pads out to expose the attached testis clearly (Figure 2C and 2D). Usually, operate on one testis at a time. 
		NOTE: Avoid touching the fat pads and testis with hands.</li>
		<li>Place a paper (9 cm in diameter) underneath the fat pads and testis (Figure 2C).</li>
		<li>Inject inulin-FITC into a microinjection pipette and connect it to the micromanipulator unit (Figure 1D). Gently insert the microinjection pipette under the tunica albuginea and load a total of 20 &#956;L of inulin-FITC into the interstitium of the testis (Figure 2E and 2F). 
		NOTE: Carefully depress the microinjection pipette to avoid moving it.</li>
		<li>Monitor the movement of inulin-FITC in the testis (Figure 2G).</li>
		<li>Immediately put the testis back into the abdominal cavity after the completion of the injection.</li>
		<li>Repeat the procedure on the contralateral testis. This testis is injected with 20 &#956;L of PBS as a control.</li>
		<li>Close the skin with a surgical suture and move the mouse to a heat pad of a thermostatic heater (Figure 1B).&#160;Administer a dose of 1 mg of analgesic (buprenorphine) per 1 kg of body weight via subcutaneous injection.</li>
	</ol>
	</li>
	<li>Harvesting the testes and frozen sections preparation
	<ol>
		<li>40 min after the injection, euthanize the recipient mouse by cervical dislocation according to animal care and use guidelines.</li>
		<li>Use a pair of sharp scissors to collect the testes. Place the testes into 1 mL of ice-cold PBS to remove any blood contamination.</li>
		<li>Fix the testes in 4% paraformaldehyde (PFA) at 4 &#176;C for 12 - 24 h. Discard the 4% PFA and wash the tissue 3x with 1.5 mL of 1% PBS at room temperature.</li>
		<li>Dehydrate the tissue in 30% sucrose overnight. Put the testis in the embedding frame and cover the tissue with optimal cutting temperature compound (OCT). After the OCT is frozen, fill the embedding frame with OCT so that the whole testis can be covered with OCT.</li>
		<li>Cut 5-&#956;m-thick, frozen cross sections of the testes in a cryostat at -20 &#176;C and let them adhere to microscope slides. 
		NOTE: Refreezing embedded tissues in dry ice may increase the rigidity for cutting.</li>
	</ol>
	</li>
	<li>Image requisition
	<ol>
		<li>Place the slides in a humidified box. Warm the slides at room temperature for 10 min.</li>
		<li>Wash the sections 3x with Tris-buffered saline (TBS) at room temperature.</li>
		<li>Air-dry for 5 min in the dark. Wipe off any residual TBS with dust-free paper.</li>
		<li>Cover the cross sections with 4&#8217;,6-diamidino-2-phenylindole (DAPI). Place the inverted coverslip on a microscope slide.</li>
		<li>Acquire images using a confocal microscope. A total of 20X magnification is generally sufficient for detecting the brightly fluorescent signal.</li>
	</ol>
	</li>
</ol>

<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>

The authors have nothing to disclose.

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.
<s...

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 ...

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

Research

JoVE Journal

Developmental Biology

10.8K Views.  Nanjing Medical University. 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.

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

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 ...

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 ...

Assessment of Oxidative Damage in the Primary Mouse Ocular Surface Cells/Stem Cells in Response to Ultraviolet-C (UV-C) Damage

The ocular surface is subjected to regular wear and tear due to various environmental factors. Exposure to UV-C radiation constitutes an occupational health hazard. Here, we demonstrate the exposure of primary stem cells from the mouse ocular surface to UV-C radiation. Reactive oxygen species (ROS) formation is the readout of the extent of oxidative stress/damage. In an experimental in vitro setting, it is also essential to assess the percentage of dead cells generated due to oxidative stress. In this article, we will demonstrate the 2&#39;,7&#39;-Dichlorofluoresceindiacetate (DCFDA) staining of UV-C exposed mouse primary ocular surface stem cells and their quantification based on the fluorescent images of DCFDA staining. DCFDA staining directly corresponds to ROS generation. We also demonstrate the quantification of dead and live cells by simultaneous staining with propidium iodide (PI) and Hoechst 3332 respectively and the percentage of DCFDA (ROS positive) and PI positive cells.

Assessment of Oxidative Damage in the Primary Mouse Ocular Surface Cells/Stem Cells in Response to Ultraviolet-C UV-C Damage

This protocol demonstrates the simultaneous detection of reactive oxygen species (ROS), live cells, and dead cells in live primary cultures from mouse ocular surface cells. 2&#39;,7&#39;-Dichlorofluoresceindiacetate, propidium iodide, and Hoechst staining are used to assess the ROS, dead cells, and live cells, respectively, followed by imaging and analysis.

The ocular surface is subjected to regular wear and tear due to various environmental factors. Exposure to UV-C radiation constitutes an occupational ...