We thank Erika Mileti for excellent technical support and Dr. Antonio Di Sabatino for providing the oxygen chambers.
Funding: This work was supported by grants from the 7th EU framework program (IBDase, ERC: Dendroworld) and Fondazione Cariplo to MR and support by a Marie Curie international training mobility network (Cross-Talk, grant agreement No: 21553-2) to KT.

1. Obtaining and Preparing the Tissue
<ol>
	<li>Tissue (healthy or IBD mucosa) is obtained during surgery. Once the specimen is excised transfer to the lab as soon as possible, keeping it in Ca++/Mg++-free HBSS buffer supplemented with Pen/Strep at 4 &deg;C or on ice.</li>
</ol>
*The size of the specimen depends on the availability of the tissue: the part of the tissue obtained, is strictly what is not needed for diagnosis and can vary greatly between healthy and IBD su...

<ol>
	<li>Schuller, S., Lucas, M., Kaper, J. B., Giron, J. A., Phillips, A. 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+ex+vivo+response+of+human+intestinal+mucosa+to+enteropathogenic+Escherichia+coli+infection.">The ex vivo response of human intestinal mucosa to enteropathogenic Escherichia coli infection.</a> Cell. Microbiol. 11, 521-530 (2009).</li><li>Tsilingiri, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probiotic+and+postbiotic+activity+in+health+and+disease:+comparison+on+a+novel+polarised+ex-vivo+organ+culture+model.">Probiotic and postbiotic activity in health and disease: comparison on a novel polarised ex-vivo organ culture model.</a> Gut. , (2012).</li><li>Tsilingiri, K., Rescigno, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Should+probiotics+be+tested+on+ex+vivo+organ+culture+models?.">Should probiotics be tested on ex vivo organ culture models?.</a> Gut Microbes. , (2012).</li><li>Mileti, E., Matteoli, G., Iliev, I. D., Rescigno, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+the+immunomodulatory+properties+of+three+probiotic+strains+of+Lactobacilli+using+complex+culture+systems:+prediction+for+in+vivo+efficacy.">Comparison of the immunomodulatory properties of three probiotic strains of Lactobacilli using complex culture systems: prediction for in vivo efficacy.</a> PLoS One. 4, e7056 (2009).</li><li>Cencic, A., Langerholc, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+cell+models+of+the+gut+and+their+applications+in+food+microbiology--a+review.">Functional cell models of the gut and their applications in food microbiology--a review.</a> Int. J. Food Microbiol. 141, S4-S14 (2010).</li><li>te Velde, A. A., Verstege, M. A., Hommes, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Critical+appraisal+of+the+current+practice+in+murine+TNBS-induced+colitis.">Critical appraisal of the current practice in murine TNBS-induced colitis.</a> Inflamm. Bowel Dis. 12, 995-999 (2006).</li><li>Senior, P. V., Pritchett, C. J., Sunter, J. P., Appleton, D. R., Watson, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crypt+regeneration+in+adult+human+colonic+mucosa+during+prolonged+organ+culture.">Crypt regeneration in adult human colonic mucosa during prolonged organ culture.</a> J. Anat. 134, 459-469 (1982).</li><li>Browning, T. H., Trier, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organ+culture+of+mucosal+biopsies+of+human+small+intestine.">Organ culture of mucosal biopsies of human small intestine.</a> J. Clin. Invest. 48, 1423-1432 (1969).</li><li>Besselink, M. G., 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=Probiotic+prophylaxis+in+predicted+severe+acute+pancreatitis:+a+randomised,+double-blind,+placebo-controlled+trial.">Probiotic prophylaxis in predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial.</a> Lancet. 371, 651-659 (2008).</li><li>Lakhdari, O., 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=Identification+of+NF-kappaB+modulation+capabilities+within+human+intestinal+commensal+bacteria.">Identification of NF-kappaB modulation capabilities within human intestinal commensal bacteria.</a> J. Biomed. Biotechnol. 2011, 282356 (2011).</li></ol>

No conflicts of interest declared.

The need for physiologically relevant models on which treatments for human intestinal mucosa can be validly tested has long been emphasized. Many researchers have identified potential artifacts and defects in both cell 5 and mouse models 6 used so far for that purpose. Indeed, even though promising preclinical data is often obtained, these rarely translate to significant clinical benefit.
The method described in this work, presents a relatively simple, yet effective and n...

<table border="1">
	<tbody>
		<tr>
			<td>Regeant</td>
			<td>Company</td>
			<td>Catalog No.</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Reagents</td>
		</tr>
		<tr>
			<td>10X HBSS</td>
			<td>Eurocalne</td>
			<td>ECM4006XL</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Peni/Strepto</td>
			<td>Lonza</td>
			<td>DE17602E</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Gentamycin</td>
			<td>Gibco</td>
			<td>15750-037</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Lonza</td>
			<td>BE12614</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>FBS-Na</td>
			<td>Gibco</td>
			<td>16000-044</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>100X ITS-X</td>
			<td>Gibco</td>
			<td>51500-056</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>EGF</td>
			<td>Tebu-bio</td>
			<td>100-15</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Lonza</td>
			<td>BE17605E</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Non essential aminoacids 100X</td>
			<td>Gibco</td>
			<td>11140-035</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NaPyr</td>
			<td>Gibco</td>
			<td>11360-039</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Materials</td>
		</tr>
		<tr>
			<td>Cloning cylinders 6x8 mm</td>
			<td>BellCo</td>
			<td>2090-00608</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cloning cylinders 8x8 mm</td>
			<td>BellCo</td>
			<td>2090-0080</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cloning cylinders 10x10 mm</td>
			<td>BellCo</td>
			<td>2090-01010</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Metal grids</td>
			<td>Home made</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Centre well organ culture plate</td>
			<td>BD Falcon</td>
			<td>353037</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Surgical glue (Vetbond)</td>
			<td>3M</td>
			<td>1469SB</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Oxygen Jars</td>
			<td>Home made</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Oxygen tanks</td>
			<td>Air Liquid Sanit&agrave;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

a novel method for the culture and polarized stimulation of human intestinal mucosa explants

Few models currently exist to realistically simulate the complex human intestine's micro-environment, where a variety of interactions take place. Proper homeostasis directly depends on these interactions, as they shape an entire immunological response inducing tolerance against food antigens while at the same time mounting effective immune responses against pathogenic microbes accidentally ingested with food.
Intestinal homeostasis is preserved also through various complex interactions between the microbiota (including food-associated beneficial bacterial strains) and the host, that regulate the attachment/degradation of mucus, the production of antimicrobial peptides by the epithelial barrier, and the "education" of epithelial cells' that controls the tolerogenic or immunogenic phenotype of unique, gut-resident lymphoid cells' populations. These interactions have been so far very difficult to reproduce with in vitro assays using either cultured cell lines or peripheral blood mononuclear cells. In addition, mouse models differ substantially in components of the intestinal mucosa (mucus layer organization, commensal bacteria community) with respect to the human gut. Thus, studies of a variety of treatments to be brought in the clinics for important stress-related or pathological conditions such as irritable bowel syndrome, inflammatory bowel disease or colorectal cancer have been difficult to carry out.
To address these issues, we developed a novel system that enables us to stimulate explants of human intestinal mucosa that retain their in situ conditioning by the host microbiota and immune response, in a polarized fashion. Polarized apical stimulation is of great importance for the outcome of the elicited immune response. It has been repeatedly shown that the same stimuli can produce completely different responses when they bypass the apical face of the intestinal epithelium, stimulating epithelial cells basolaterally or coming into direct contact with lamina propria components, switching the phenotype from tolerogenic to immunogenic and causing unnecessary and excessive inflammation in the area.
We achieved polarized stimulation by gluing a cave cylinder which delimited the area of stimulation on the apical face of the mucosa as will be described in the protocol. We used this model to examine, among others, differential effects of three different Lactobacilli strains. We show that this model system is very powerful to assess the immunomodulatory properties of probiotics in healthy and disease conditions.

We succeeded in maintaining healthy and IBD human intestinal mucosa in culture for at least 24 hr preserving the wellbeing of the tissue. In accordance with previous observations 1, this was only possible if the majority of the culture time (at least 85% of total) took place in O2, as the tissue did not survive for 24 hr in conventional incubators (Figure 2). We have also shown that different responses of the explants can be observed on this model depending on the polarity of the st...

Watch this Scientific Journal Video about A Novel Method for the Culture and Polarized Stimulation of Human Intestinal Mucosa Explants at JoVE.com

A Novel Method for the Culture and Polarized Stimulation of Human Intestinal Mucosa Explants

We introduce a novel method for the maintenance of human intestinal mucosa in culture and monitoring of the response to various types of stimuli over at least 24 hrs. With our method, the polarity of the tissue is maintained, allowing for a physiological stimulation via the apical route.

Few models currently exist to realistically simulate the complex human intestine's micro-environment, where a variety of interactions take place. Proper ...

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