We thank Dr. Jerrold R. Turner, from Brigham and Women&#39;s Hospital, Harvard Medical School, for his generous help in completing this study. This work is supported by the National Natural Science Foundation of China (grant number&#160;81470804,&#160;31401229, and 81200620), the Natural Science Foundation of Jiangsu Province (grant number&#160;BK20180838, and BK20140319), The Research Innovation Program for College Graduates of Jiangsu Province (grant number KYLX16-0116), Advanced Research Projects of Soochow University (grant number SDY2015_06), and Crohn&#39;s &#38; Colitis Foundation Research Fellowship Award (grant number 310801).

This study was approved by the Animal Care and Use Protocol of Cambridge-Suda Genomic Resource Center (CAM-SU), Soochow University.
1. Plating and Maintenance of Caco-2bbe on Porous Polycarbonate Membranes
<ol>
	<li>Grow cells in a T75 flask with media (DMEM containing 10% FBS). Flasks should be fed regularly, depending on the cell density. 
	NOTE: For optimal plating, cells should divide rapidly and have a flat &#34;fried-egg&#34; shape, which indicates that cells are in the growth pha...

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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=Myosin+light+chain+kinase+is+central+to+smooth+muscle+contraction+and+required+for+gastrointestinal+motility+in+mice.">Myosin light chain kinase is central to smooth muscle contraction and required for gastrointestinal motility in mice.</a> Gastroenterology. 135, 610-620 (2008).</li><li>Li, H. 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=Myosin+regulatory+light+chain+phosphorylation+is+associated+with+leiomyosarcoma+development.">Myosin regulatory light chain phosphorylation is associated with leiomyosarcoma development.</a> Biomed. Pharmacother. 92, 810-818 (2017).</li><li>Clayburgh, D. 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Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+molecular+mechanisms+that+mediate+basal+and+tumour+necrosis+factor-alpha-induced+regulation+of+myosin+light+chain+kinase+gene+activity.">Cellular and molecular mechanisms that mediate basal and tumour necrosis factor-alpha-induced regulation of myosin light chain kinase gene activity.</a> J. Cell Mol. Med. 12, 1331-1346 (2008).</li><li>Turner, J. R., Buschmann, M. M., Romero-Calvo, I., Sailer, A., Shen, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+molecular+remodeling+in+differential+regulation+of+tight+junction+300+permeability.">The role of molecular remodeling in differential regulation of tight junction 300 permeability.</a> Semin. Cell Dev. Biol. 36, 204-212 (2014).</li><li>Srinivasan, B., 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=TEER+measurement+techniques+for+in+vitro+barrier+model+systems.">TEER measurement techniques for in vitro barrier model systems.</a> J. Lab. Autom. 20 (2), 107-126 (2015).</li><li>Wang, F., 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=IFN-gamma-induced+TNFR2+expression+is+required+for+TNF-dependent+intestinal+epithelial+barrier+dysfunction.">IFN-gamma-induced TNFR2 expression is required for TNF-dependent intestinal epithelial barrier dysfunction.</a> Gastroenterology. 131, 1153-1163 (2006).</li><li>Peterson, M. D., Mooseker, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+enterocyte-like+brush+border+cytoskeleton+of+the+C2BBe+clones+of+the+human+intestinal+cell+line+Caco-2.">Characterization of the enterocyte-like brush border cytoskeleton of the C2BBe clones of the human intestinal cell line Caco-2.</a> J. Cell Sci. 102 (Pt 3), 581-600 (1992).</li><li>Wang, 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=Methods+to+determine+intestinal+permeability+and+bacterial+translocation+during+liver+disease.">Methods to determine intestinal permeability and bacterial translocation during liver disease.</a> J. Immunol. Methods. 421, 44-53 (2015).</li></ol>

There are several critical steps in the protocol. Caco-2BBe (brush border-expressing) cells are always used for TER measurement, selected from the Caco-2 cell line for expression of brush-border proteins. Caco-2BBe cells have a villus absorptive phenotype when fully-differentiated (after about 3 weeks of culture post-confluence)17. It is necessary to avoid contamination during the measurement, and to sterilize the electrode. Because the procedure is non-sterile, measurements can only be performed ...

Intestinal epithelial cells are not only responsible for the absorption of nutrients, but also form an important barrier to defend against pathogenic microorganisms and microbial toxins. This intestinal barrier function is regulated by tight junction permeability and epithelial cell integrity1,2,3, and dysfunction of the epithelial barrier function is associated with inflammatory bowel disease (IBD). The perijunctional actomyosin ring (PAMR) lies within the cell that is closely contiguous to the tight junctions. The contraction of the PAMR, which is regulated by the myosin light chain (MLC), is crucial for the regulation of tight junction permeability4,5,6,7,8,9,10. Tumor necrosis factor (TNF) is central to intestinal barrier loss by upregulating intestinal epithelial MLC kinase (MLCK) expression and inducing occludin internalization11,12,13.
Ions such as Na+ and Cl- can cross the paracellular space by either the pore or leak pathway14. In a &#34;leaky&#34; epithelium, changes in TER primarily reflect altered tight junction permeability. TER measurement is a commonly used electrophysiological approach to quantify tight junction permeability, primarily to Na+ and Cl-, based on the impedance of cell monolayers. Diverse cell types, including intestinal epithelial cells, pulmonary epithelial cells, and vascular endothelial cells, have been reported for TER measurements. Advantages of this method are that TER measurements are non-invasive and can be used to monitor live cells in real-time. In addition, the TER measurement technique is useful for drug toxicity studies15.
Caco-2BBe cells are human epithelial colorectal adenocarcinoma cells with a structure and function similar to the differentiated small intestinal epithelial cells: for example, these cells have microvilli and enzymes associated with small intestinal brush border. Therefore, cultured Caco-2BBe monolayers are utilized as an in vitro model for testing barrier function.
In mice, one way to study intestinal paracellular permeability is by measuring the ability of FITC-dextran to cross from the lumen into the blood. Thus, the intestinal permeability can be assessed by gavaging FITC-dextran directly into mice and measuring the fluorescence within the blood. The following protocol describes two simple methods to assess intestinal epithelium permeability both in vitro and in vivo.

<table>
	<tbody>
		<tr>
			<td>22G gavage needle</td>
			<td>VWR</td>
			<td>20068-608</td>
			<td></td>
		</tr>
		<tr>
			<td>4 kDa FITC-dextran</td>
			<td>Sigma</td>
			<td>46944</td>
			<td></td>
		</tr>
		<tr>
			<td>Avertin</td>
			<td>Sigma</td>
			<td>T48402</td>
			<td></td>
		</tr>
		<tr>
			<td>Black 96-well plates for fluorescence</td>
			<td>Fisher</td>
			<td>14-245-197A</td>
			<td></td>
		</tr>
		<tr>
			<td>C57/B6 mice</td>
			<td>Nanjing Biomedical Research Institute of Nanjing University</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Caco-2BBe cells</td>
			<td>ATCC</td>
			<td>CRL-2102</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran sulphate sodium</td>
			<td>MP Biomedicals</td>
			<td>2160110</td>
			<td></td>
		</tr>
		<tr>
			<td>DMED with high glucose and sodium pyruvate&#160;</td>
			<td>Hyclone</td>
			<td>SH30243.01B</td>
			<td></td>
		</tr>
		<tr>
			<td>Epithelial (Volt/Ohm) Meter&#160;</td>
			<td>Millicell-ERS</td>
			<td>MERS00002</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sinopharm ChemicalReagent</td>
			<td>10009218</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon tube (15 mL)</td>
			<td>Corning</td>
			<td>430791</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Gibco</td>
			<td>10437-028</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence microscope</td>
			<td>Olympus&#160;</td>
			<td>FV1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorometer</td>
			<td>Biotek</td>
			<td>Synergy 2</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS</td>
			<td></td>
			<td></td>
			<td>138 mM NaCl, 0.3 mM Na2HPO4, 0.4 mM MgSO4, 0.5 mM MgCl2, 5.0 mM KCl, 0.3 mM KH2PO4, 15.0 mM HEPES, 1.3 mM CaCl2, 25 mM glucose&#160;</td>
		</tr>
		<tr>
			<td>IFNg</td>
			<td>PeproTech</td>
			<td>315-05-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Modular Tissue Embedding Center&#160;</td>
			<td>Leica</td>
			<td>EG1150H</td>
			<td></td>
		</tr>
		<tr>
			<td>Serum collection tubes</td>
			<td>Sarstedt</td>
			<td>41.1378.005</td>
			<td></td>
		</tr>
		<tr>
			<td>T75 flask&#160;</td>
			<td>corning</td>
			<td>430641</td>
			<td></td>
		</tr>
		<tr>
			<td>TNF</td>
			<td>PeproTech</td>
			<td>315-01A</td>
			<td></td>
		</tr>
		<tr>
			<td>Parraffin</td>
			<td>Sigma</td>
			<td>A6330-1CS</td>
			<td></td>
		</tr>
		<tr>
			<td>Polycarbonate membranes (Transwell)</td>
			<td>Costar</td>
			<td>3413</td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure pump</td>
			<td>AUTOSCIENCE</td>
			<td>AP-9925</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotary Microtomy</td>
			<td>Leica</td>
			<td>RM2235</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA</td>
			<td>Gibco</td>
			<td>25200-056</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylene</td>
			<td>Sinopharm ChemicalReagent</td>
			<td>10023418</td>
			<td></td>
		</tr>
	</tbody>
</table>

in vitro and in vivo approaches to determine intestinal epithelial cell permeability

The intestinal barrier defends against pathogenic microorganism and microbial toxin. Its function is regulated by tight junction permeability and epithelial cell integrity, and disruption of the intestinal barrier function contributes to progression of gastrointestinal and systemic disease. Two simple methods are described here to measure the permeability of intestinal epithelium. In vitro, Caco-2BBe cells are plated in tissue culture wells as a monolayer and transepithelial electrical resistance (TER) can be measured by an epithelial (volt/ohm) meter. This method is convincing because of its user-friendly operation and repeatability. In vivo, mice are gavaged with 4 kDa fluorescein isothiocyanate (FITC)-dextran, and the FITC-dextran concentrations are measured in collected serum samples from mice to determine the epithelial permeability. Oral gavage provides an accurate dose, and therefore is the preferred method to measure the intestinal permeability in vivo. Taken together, these two methods can measure the permeability of the intestinal epithelium in vitro and in vivo, and hence be used to study the connection between diseases and barrier function.

In culture, Caco-2BBe cells grow as a monolayer and slowly differentiate into mature absorptive enterocytes that have brush borders. In this protocol, Caco-2BBe cells were plated with a high density on polycarbonate membranes, and cells reached 100% confluency one day after seeding. However, cells are undifferentiated at this stage: To fully differentiate the cells, the media is changed every 2-3 days for 3 weeks. Cells were stained with nuclei and F-actin stains to show the differences b...

Watch this Scientific Journal Video about In Vitro and In Vivo Approaches to Determine Intestinal Epithelial Cell Permeability at JoVE.com

In Vitro and In Vivo Approaches to Determine Intestinal Epithelial Cell Permeability

Two methods are presented here to determine intestinal barrier function. An epithelial meter (volt/ohm) is used for measurements of transepithelial electrical resistance of cultured epithelia directly in tissue culture wells. In mice, the FITC-dextran gavage method is used to determine the intestinal permeability in vivo.

In Vitro and In Vivo Approaches to Determine Intestinal Epithelial Cell Permeability

The intestinal barrier defends against pathogenic microorganism and microbial toxin. Its function is regulated by tight junction permeability and ...

The overall goal of this experiment is to study the diseases caused by epithelial barrier dysfunction by measuring the intestinal epithelial cell permeability in vitro and in vivo. This method can help answer key questions in the intestinal barrier function field, such as those related to the inflammatory bowel disease. The main advantage of this technique is that intestinal epithelial cell permeability can be assessed both in vitro and in vivo.The implications of this technique extends towards therapy or diagnosis of gastrointestinal diseases, because intestinal epithelial barrier dysfunction contributes to those diseases. Though this method can provide insight into the intestinal barrier function, it can also be applied to other systems, such as drug toxicity studies and barrier integrity of other cell types. Visual demonstration of this method is critical, as some steps are difficult to learn.An accurate operation of this method can now be understood by textual description. To begin, grow Caco-2bbe cells in a T75 flask with medium. Feed the flasks regularly, depending on the cell density.When the cells are 80%confluent, remove the medium and use 1-2 milliliters of sterile PBS without calcium to rinse them. Add 1.5 milliliters of Trypsin-EDTA, and gently rock the flask. Then, place it in the 37 degree Celsius incubator for 20 minutes, without rocking.While the cells are trypsinizing, place inserts containing porous polycarbonate membranes into 24 well plates. Then add 1 milliliter of culture medium into the basal chamber which is the lower space of the membrane. Add 5 milliliters of medium to the flask, and vigorously pipette the cells against the inside of the flask 5 to 10 times, to separate the culture into loose individual cells, or two to three cell clumps.Plate 0.166 milliliters of the cells into the apical chamber which is the upper space of the membrane. Then incubate the plates at 37 degrees Celsius for up to three weeks. Feed the cells three times weekly, by using a pressure pump to carefully aspirate the medium from the basal compartment of each well.Then gently drip one milliliter of medium into the apical chamber of each insert. For cytokine studies, one day before transepithelial electrical resistance or TER measurements, replace the basal medium with medium, containing 10 nanograms per milliliter of interferon gamma. On the day of the experiment, replace the medium with HBSS containing 2.5 or 7.5 nanograms per milliliter of TNF.To correct the meter, insert the correction electrode into the input port and choose Ohm mode. Then use a screwdriver to adjust the R Adjustment screw until the meter displays a reading of 1, 000 ohms. Sterilize the electrodes in 70%ethanol for 15 to 30 minutes and allow them to air dry for 15 seconds.Then rinse the electrodes in experimental cell culture medium. Next, turn on the power and choose Ohm mode. While keeping the electrodes vertical, carefully place the long ends of electrode bridges into the basal chamber, ensuring that they touch the dish.Then place the short ends into the apical chamber, ensuring that they stay below the surface of the medium, but above the tissue culture inserts. Measure the resistance of the sample and blank inserts at 0, 1, 2, 3 and 4 hours after cytokine treatment. Then record the resistance.To achieve consistency across different plate formats, calculate the product of the resistance and the effective membrane area as shown here. For 24 well inserts, the effective membrane area is 0.33 square centimeters. To induce colitis, add DSS to autoclaved water to a final concentration of 3.5%weight per volume.Then use the DSS solution to replace the drinking water in the cages of 8-week-old male C57 black six mice for a total of seven days. Give regular drinking water without DSS to control mice. After day seven, switch the DSS water to regular drinking water.Each day, weigh the mice and assess the clinical scores as defined according to the disease severity by four parameters:rectal prolapse, stool consistency, bleeding, and activity. Sum the scores from these parameters for a final clinical score. To analyze the histopathological condition of colon tissues seven days post DSS treatment, after euthanizing mice according to the text protocol, isolate the colon and cecum, and measure the length of the colon.Cut 0.5 centimeter segments from the distal colon, and fix the tissue in a 15 milliliter falcon tube containing 10 milliliters of 10%formalin overnight. Wash the fixed tissues with graded ethanol and xylene. Then embed the tissues in paraffin and cut six millimeter sections for the hematoxylin and eosin staining.To measure epithelial barrier permeability in DSS-induced mice, seven days after the start of DSS administration, fast the mice for three hours. Autoclave a gavage needle to ensure sterility, then use 150 microliters of 80 milligrams per milliliter four kilodalton FITC dextran in sterile water to gavage the mice, and keep the unused FITC dextran to measure the standard curve after serum collection. Next, weight the mice for the permeability calculation.Four hours later, after anesthetizing the mice by IP injection, confirm proper anesthetization by the lack of reflexes and whisker movement. Then place the mice on a heat block for five minutes. Using a pair of scissors, clip a one centimeter piece of the tail and collect 100 microliters of blood from the tail into a serum collection tube.Spin the collected blood at 10, 000 times g and room temperature for ten minutes. With water, dilute the serum one to four. Then, to make a standard curve, use water to prepare the dilutions of the unused FITC dextran.Add 100 microliters per well of the serum and the standard curve samples into 96 well plates. Using a plate reader, read the fluorescence at an excitation of 485 and an emission of 528. Calculate the permeability values based on the standard curve, and multiply by four to correct for the dilution.Divide the concentration of FITC dextran by the weight to normalize the values. This helps to normalize the difference in FITC dextran delivery if mice are sick, and have lost weight. The Caco-2bbe cells shown here were labeled with nuclei and F-actin stains to show the difference between undifferentiated and differentiated cells.Stress fibers are clearly seen in undifferentiated cells. Differentiated cells have a smaller volume, larger nuclei, and fewer stress fibers than undifferentiated cells. TNF is central to intestinal barrier loss through MLCK-dependent tight junction regulation.As seen in this figure, TNF significantly decreases the TER of the Caco-2bbe monolayer in a dose-dependent manner, suggesting that TNF increases epithelial permeability. Compared to their initial body weight, mice treated with DSS lose a significant amount of weight. The severity of colitis is scored by rectal prolapse, stool consistency, bleeding, and activity.Cross-sections of colonic tissues stained with hematoxylin and eosin show colonic mucosal damage in DSS-treated mice. In addition, the length of colon crypt, as well as the colon itself, is decreased in DSS-treated mice. Finally, there is an approximately two-fold increase in the levels of FITC dextran staining in DSS-treated mice, compared to control mice.While attempting this procedure, it's important to remember to minimize error, by standardizing operational procedures and utilizing statistical methods. After its development, this technique paved the way to researchers in the field of intestinal barrier function to explore gastrointestinal diseases in both model organisms and cell lines. After watching this video, you should have a good understanding of how to determine intestinal epithelial permeability by measuring the TER, gavaging FITC dextran, and observing morphological and histochemical changes.

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24.7K vistas.  Soochow University. El objetivo general de este experimento es estudiar las enfermedades causadas por la disfunción de la barrera epitelial midiendo la permeabilidad de las células epiteliales intestinales in vitro e in vivo. Este método puede ayudar a responder preguntas clave en el campo de la función de barrera intestinal, como las relacionadas con la enfermedad inflamatoria intestinal. La principal ventaja de esta técnica es que la permeabilidad de las células epiteliales intestinales se puede evaluar ...