This work has been supported by the German Cancer Research Center (DKFZ), the EU-consortium &#8220;Tolerage&#8221;, the Deutsche Forschungsgemeinschaft (SFB 938) and the Landesstiftung Baden-W&#252;rttemberg.

This study has been approved by the ethics committee of the Regierungspr&#228;sidium Karlsruhe. All animals were housed under specific pathogen-free conditions at the German Cancer Research Center (DKFZ). For all culture experiments mouse pups ranging from 1 to 7 days of age were used.
1. Isolation of mTECs from Thymus
NOTE: The following digestion steps were performed as described previously1 under sterile conditions with some modifications as follows....

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	<li>Derbinski, J., Schulte, A., Kyewski, B., Klein, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Promiscuous+gene+expression+in+medullary+thymic+epithelial+cells+mirrors+the+peripheral+self.">Promiscuous gene expression in medullary thymic epithelial cells mirrors the peripheral self.</a> Nat Immunol. 2, 1032-1039 (2001).</li><li>Kyewski, B., Klein, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+central+role+for+central+tolerance.">A central role for central tolerance.</a> Annual review of immunology. 24, 571-606 (2006).</li><li>Bonfanti, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microenvironmental+reprogramming+of+thymic+epithelial+cells+to+skin+multipotent+stem+cells.">Microenvironmental reprogramming of thymic epithelial cells to skin multipotent stem cells.</a> Nature. 466, 978-982 (2010).</li><li>Kont, V., 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=Modulation+of+Aire+regulates+the+expression+of+tissue-restricted+antigens.">Modulation of Aire regulates the expression of tissue-restricted antigens.</a> Molecular Immunology. 45, 25-33 (2008).</li><li>Mohtashami, M., Zuniga-Pflucker, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+architecture+of+the+thymus+is+required+to+maintain+delta-like+expression+necessary+for+inducing+T+cell+development.">Three-dimensional architecture of the thymus is required to maintain delta-like expression necessary for inducing T cell development.</a> J Immunol. 176, 730-734 (2006).</li><li>Palumbo, M. O., Levi, D., Chentoufi, A. A., Polychronakos, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+proinsulin-producing+medullary+thymic+epithelial+cell+clones.">Isolation and characterization of proinsulin-producing medullary thymic epithelial cell clones.</a> Diabetes. 55, 2595-2601 (2006).</li><li>White, A., Jenkinson, E., Anderson, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reaggregate+thymus+cultures.">Reaggregate thymus cultures.</a> Journal of visualized experiments : JoVE. , (2008).</li><li>Stark, H. 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=Epidermal+homeostasis+in+long-term+scaffold-enforced+skin+equivalents.">Epidermal homeostasis in long-term scaffold-enforced skin equivalents.</a> J Investig Dermatol Symp Proc. 11, 93-105 (2006).</li><li>Boehnke, 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=Effects+of+fibroblasts+and+microenvironment+on+epidermal+regeneration+and+tissue+function+in+long-term+skin+equivalents.">Effects of fibroblasts and microenvironment on epidermal regeneration and tissue function in long-term skin equivalents.</a> Eur J Cell Biol. 86, 731-746 (2007).</li><li>Pinto, 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=An+organotypic+coculture+model+supporting+proliferation+and+differentiation+of+medullary+thymic+epithelial+cells+and+promiscuous+gene+expression.">An organotypic coculture model supporting proliferation and differentiation of medullary thymic epithelial cells and promiscuous gene expression.</a> J Immunol. 190, 1085-1093 (2013).</li><li>Gabler, J., Arnold, J., Kyewski, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Promiscuous+gene+expression+and+the+developmental+dynamics+of+medullary+thymic+epithelial+cells.">Promiscuous gene expression and the developmental dynamics of medullary thymic epithelial cells.</a> Eur J Immunol. 37, 3363-3372 (2007).</li><li>Farr, A., Nelson, A., Truex, J., Hosier, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epithelial+heterogeneity+in+the+murine+thymus:+a+cell+surface+glycoprotein+expressed+by+subcapsular+and+medullary+epithelium.">Epithelial heterogeneity in the murine thymus: a cell surface glycoprotein expressed by subcapsular and medullary epithelium.</a> The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society. 39, 645-653 (1991).</li><li>Stark, H. 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Alongside RTOCs, the 3D OTCs have been by far superior in terms of TEC differentiation and pGE maintenance/induction (Table 1) compared to other (i) &#8216;simplified 3D cultures&#8217; using - fibroblasts alone without the scaffold; (ii) 2D systems using - fibroblasts/feeder cells co-cultured with TECs10, (iii) 3T3-J2 cells wherein TEC clones develop, but pGE is lost, (iv) matrigel or (v) ECM components (unpublished data). PGE was maintained for up to 7 days in the 3D OTCs, 4 days being the o...

Developing thymocytes make up about 98 % of the thymus, while the remaining 2 % consists of a variety of cells that collectively compose the thymic stroma (i.e., epithelial cells, dendritic cells, macrophages, B cells, fibroblasts, endothelial cells). The outer cortical epithelial cells (cTECs) procure immigration of pro-T cells from the bone marrow, T cell lineage induction in multipotent pre-T cells and positive selection of self-MHC restricted immature thymocytes. The inner medullary thymic epithelial cells (mTECs) are involved in tolerance induction of those thymocytes with a high-affinity TCR for self-peptide/MHC complexes by either inducing negative selection or their deviation into the T regulatory cell lineage. In the context of central tolerance induction, mTECs are unique in that they express a wide spectrum of tissue-restricted self-antigens (TRAs) thus mirroring the peripheral self. This phenomenon is called promiscuous gene expression (pGE)1,2.
Most current studies on this fascinating cell type rely on ex vivo isolated cells, as various short-term 2D culture systems invariably resulted in the loss of pGE and key regulator molecules like MHC class II, FoxN1 and Aire within the first 2 days3-6. It remained however unclear, which particular components and features of the intact 3D meshwork of the thymus were missing in 2D models. The re-aggregation thymic organ culture (RTOC) has been so far the only 3D system that allows the study of T cell development, on the one hand, and stromal cell biology, on the other hand, in an intact thymic microenvironment7. Yet, RTOCs have certain limitations, i.e., they already contain a complex mixture of cells, require the input of fetal stromal cells and endure a maximal culture period of 5 to 10 days.
The lack of reductionist in vitro culture systems has hampered the study of several aspects of T cell development and thymic organogenesis not least the molecular regulation of pGE and its relationship to the developmental biology of mTECs.
Owing to the close-relatedness of the structured organization of the epithelial cells of skin and thymus, we opted for a 3D organotypic culture (OTC) system that had been developed originally to emulate the differentiation of keratinocytes in vitro and thus create a dermal equivalent. The OTC system consists of an inert scaffold matrix overlaid with dermal fibroblasts that are trapped in a fibrin gel, onto which keratinocytes are seeded8,9. Here, we replaced keratinocytes with purified mTECs. While keeping the basic features of this model, we optimized certain parameters.
In the adopted OTC model mTECs proliferated, underwent terminal differentiation and maintained mTEC identity and pGE, thus closely mimicking in vivo mTECs development10. This technical note provides a detailed protocol allowing the stepwise set-up of thymus OTCs.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Pregnant C57BL/6 mice&#160;</td>
			<td>Charles River WIGA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LS columns</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>MS columns</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-201</td>
			<td></td>
		</tr>
		<tr>
			<td>CD45 Microbeads, mouse</td>
			<td>Miltenyi Biotec</td>
			<td>130-052-301</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-PE Microbeads</td>
			<td>Miltenyi Biotec</td>
			<td>130-048-801</td>
			<td></td>
		</tr>
		<tr>
			<td>Streptavidin Microbeads</td>
			<td>Miltenyi Biotec</td>
			<td>130-048-101</td>
			<td></td>
		</tr>
		<tr>
			<td>EpCAM (G8.8 -Alexa 647 and -biotin)</td>
			<td>Ref. 12</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CD80-PE antibody</td>
			<td>BD Pharmingen</td>
			<td>553769</td>
			<td></td>
		</tr>
		<tr>
			<td>CD45-PerCP antibody</td>
			<td>BD Pharmingen</td>
			<td>557235</td>
			<td></td>
		</tr>
		<tr>
			<td>Ly51-FITC antibody</td>
			<td>BD Pharmingen</td>
			<td>553160</td>
			<td></td>
		</tr>
		<tr>
			<td>CDR1-Pacific Blue</td>
			<td>Ref. 15</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Keratin 14 antibody</td>
			<td>Covance</td>
			<td>PRB-155P</td>
			<td></td>
		</tr>
		<tr>
			<td>Vimentin antibody</td>
			<td>Progen</td>
			<td>GP58</td>
			<td></td>
		</tr>
		<tr>
			<td>Cy3-conjugated AffiniPure Goat anti-Rabbit IgG (H+L)</td>
			<td>Jackson ImmunoResearch&#160;</td>
			<td>111-165-003</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa 488-conjugated AffiniPure F(ab&#39;)2 Fragment Goat anti-Guinea Pig IgG (H+L)</td>
			<td>Jackson ImmunoResearch&#160;</td>
			<td>106-546-003</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG (H+L) Secondary Antibody, Alexa Fluor 488 conjugate</td>
			<td>Molecular Probes (Invitrogen GmbH)</td>
			<td>A-11008</td>
			<td></td>
		</tr>
		<tr>
			<td><a href="https://www.lifetechnologies.com/order/catalog/product/C10339">Click-iT EdU Alexa Fluor 594 Imaging Kit</a></td>
			<td>Invitrogen</td>
			<td><a href="https://www.lifetechnologies.com/order/catalog/product/C10339">C10339</a></td>
			<td></td>
		</tr>
		<tr>
			<td><a href="https://www.lifetechnologies.com/order/catalog/product/C10425">Click-iT EdU Alexa Fluor 488 Flow Cytometry Assay Kit</a></td>
			<td>Invitrogen</td>
			<td><a href="https://www.lifetechnologies.com/order/catalog/product/C10425">C10425</a></td>
			<td></td>
		</tr>
		<tr>
			<td>12-well filter inserts (thincerts)</td>
			<td>Greiner bio-one</td>
			<td>657631</td>
			<td></td>
		</tr>
		<tr>
			<td>12-well plate</td>
			<td>Greiner</td>
			<td>665180-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Jettex 2005/45</td>
			<td>ORSA, Giorla Minore, Italy</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fibrinogen TISSUECOL-Kit Immuno</td>
			<td>Baxter</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Thrombin TISSUECOL-Kit Immuno</td>
			<td>Baxter</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Serva</td>
			<td>47302.03</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Lonza</td>
			<td>BE12-604F</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/F12</td>
			<td>Lonza</td>
			<td>BE12-719F</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Gibco</td>
			<td>15630-049&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS Gold</td>
			<td>GE Healthcare</td>
			<td>A11-151</td>
			<td></td>
		</tr>
		<tr>
			<td>Aprotinin (Trasylol)</td>
			<td>Bayer</td>
			<td>4032037</td>
			<td></td>
		</tr>
		<tr>
			<td>Cholera toxin</td>
			<td>Biomol</td>
			<td>G117</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrocortisone</td>
			<td>Seromed (Biochrom)</td>
			<td>K3520</td>
			<td></td>
		</tr>
		<tr>
			<td>L-ascorbic acid</td>
			<td>Sigma</td>
			<td>A4034</td>
			<td></td>
		</tr>
		<tr>
			<td>TGF-&#223;1</td>
			<td>Invitrogen</td>
			<td>PHG9214</td>
			<td></td>
		</tr>
		<tr>
			<td>RANKL</td>
			<td>R&#38;D systems</td>
			<td>462-TR-010</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermolysin</td>
			<td>Sigma Aldrich</td>
			<td>&#160;T-7902</td>
			<td></td>
		</tr>
		<tr>
			<td>OCT Compound</td>
			<td>TissueTek</td>
			<td>4583</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizol (aka. Denaturing solution - Acid guanidinium thiocyanate-phenol-chloroform extraction)</td>
			<td>Invitrogen</td>
			<td>10296028</td>
			<td></td>
		</tr>
		<tr>
			<td>FastPrep FP120</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase Type IV&#160;</td>
			<td>CellSystems</td>
			<td>LS004189</td>
			<td>0.2 mg/ml and 57U/ml final conc.</td>
		</tr>
		<tr>
			<td>Neutrale Protease (Dispase)</td>
			<td>CellSystems</td>
			<td>LS002104</td>
			<td>0.2 mg/ml and 1.2U/ml final conc.</td>
		</tr>
		<tr>
			<td>DNase I&#160;</td>
			<td>Roche</td>
			<td>11 284 932 001</td>
			<td>25 &#181;g/ml final conc.</td>
		</tr>
	</tbody>
</table>

3d organotypic co-culture model supporting medullary thymic epithelial cell proliferation, differentiation and promiscuous gene expression

Intra-thymic T cell development requires an intricate three-dimensional meshwork composed of various stromal cells, i.e., non-T cells. Thymocytes traverse this scaffold in a highly coordinated temporal and spatial order while sequentially passing obligatory check points, i.e., T cell lineage commitment, followed by T cell receptor repertoire generation and selection prior to their export into the periphery. The two major resident cell types forming this scaffold are cortical (cTECs) and medullary thymic epithelial cells (mTECs). A key feature of mTECs is the so-called promiscuous expression of numerous tissue-restricted antigens. These tissue-restricted antigens are presented to immature thymocytes directly or indirectly by mTECs or thymic dendritic cells, respectively resulting in self-tolerance.
Suitable in vitro models emulating the developmental pathways and functions of cTECs and mTECs are currently lacking. This lack of adequate experimental models has for instance hampered the analysis of promiscuous gene expression, which is still poorly understood at the cellular and molecular level. We adapted a 3D organotypic co-culture model to culture ex vivo isolated mTECs. This model was originally devised to cultivate keratinocytes in such a way as to generate a skin equivalent in vitro. The 3D model preserved key functional features of mTEC biology: (i) proliferation and terminal differentiation of CD80lo, Aire-negative into CD80hi, Aire-positive mTECs, (ii) responsiveness to RANKL, and (iii) sustained expression of FoxN1, Aire and tissue-restricted genes in CD80hi mTECs.

We adopted a 3D organotypic co-culture model (3D OTC) which had been originally developed for in vitro long term culture of keratinocytes9. MACS-enriched mTECs (see MACS enrichment scheme Figure 1) were seeded onto a scaffold comprising of a fibrin gel and entrapped fibroblasts. The fibroblasts provide the essential extracellular matrix (ECM) supporting mTECs in vitro. MTECs were cultivated in OTCs for 4-14 days in the presence of RANKL in submerged cultures unlike keratinocy...

Watch this Scientific Journal Video about 3D Organotypic Co-culture Model Supporting Medullary Thymic Epithelial Cell Proliferation, Differentiation and Promiscuous Gene Expression at JoVE.com

3D Organotypic Co-culture Model Supporting Medullary Thymic Epithelial Cell Proliferation, Differentiation and Promiscuous Gene Expression

Studying medullary thymic epithelial cells in vitro has been largely unsuccessful, as current 2D culture systems do not mimic the in vivo scenario. The 3D culture system described herein - a modified skin organotypic culture model - has proven superior in recapitulating mTEC proliferation, differentiation and maintenance of promiscuous gene expression.

Intra-thymic T cell development requires an intricate three-dimensional meshwork composed of various stromal cells, i.e., non-T cells. Thymocytes traverse ...

3d-organotypic-co-culture-model-supporting-medullary-thymic

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JoVE Journal

Developmental Biology

10.5K vistas.  German Cancer Research Center (DKFZ). Studying medullary thymic epithelial cells in vitro has been largely unsuccessful, as current 2D culture systems do not mimic the in vivo scenario. The 3D culture system described herein - a modified skin organotypic culture model - has proven superior in recapitulating mTEC proliferation, differentiation and maintenance of promiscuous gene expression. 