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Human stem cell-derived thymic epithelial cells enhance human T-cell development in a xenogeneic thymus

  • Rafael Gras-Peña
    Correspondence
    Corresponding author: Rafael Gras-Peña, PhD, Columbia Center for Human Development, Department of Medicine, College of Physicians and Surgeons, Columbia University, 650 West 168th Street, Black Building, New York, NY 10032.
    Affiliations
    Columbia Center for Human Development, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY

    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Author Footnotes
    ∗ These authors contributed equally to this work.
    Nichole M. Danzl
    Footnotes
    ∗ These authors contributed equally to this work.
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Author Footnotes
    ∗ These authors contributed equally to this work.
    Mohsen Khosravi-Maharlooei
    Footnotes
    ∗ These authors contributed equally to this work.
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Sean R. Campbell
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Amanda E. Ruiz
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Christopher A. Parks
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • William Meng Suen Savage
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Markus A. Holzl
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Debanjana Chatterjee
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY
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  • Megan Sykes
    Correspondence
    Megan Sykes, MD, Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, 650 West 168th Street, Black Building 1512, Mailbox 127, New York, NY 10032.
    Affiliations
    Columbia Center for Translational Immunology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY

    Department of Surgery and Department of Microbiology and Immunology, Columbia University, New York, NY
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  • Author Footnotes
    ∗ These authors contributed equally to this work.
Published:October 21, 2021DOI:https://doi.org/10.1016/j.jaci.2021.09.038

      Background

      Generation of thymic tissue from pluripotent stem cells would provide therapies for acquired and congenital thymic insufficiency states.

      Objectives

      This study aimed to generate human thymic epithelial progenitors from human embryonic stem cells (hES-TEPs) and to assess their thymopoietic function in vivo.

      Methods

      This study differentiated hES-TEPs by mimicking developmental queues with FGF8, retinoic acid, SHH, Noggin, and BMP4. Their function was assessed in reaggregate cellular grafts under the kidney capsule and in hybrid thymi by incorporating them into swine thymus (SwTHY) grafts implanted under the kidney capsules of immunodeficient mice that received human hematopoietic stem and progenitor cells (hHSPCs) intravenously.

      Results

      Cultured hES-TEPs expressed FOXN1 and formed colonies expressing EPCAM and both cortical and medullary thymic epithelial cell markers. In thymectomized immunodeficient mice receiving hHSPCs, hES-TEPs mixed with human thymic mesenchymal cells supported human T-cell development. Hypothesizing that support from non–epithelial thymic cells might allow long-term function of hES-TEPs, the investigators injected them into SwTHY tissue, which supports human thymopoiesis in NOD severe combined immunodeficiency IL2Rγnull mice receiving hHSPCs. hES-TEPs integrated into SwTHY grafts, enhanced human thymopoiesis, and increased peripheral CD4+ naive T-cell reconstitution.

      Conclusions

      This study has developed and demonstrated in vivo thymopoietic function of hES-TEPs generated with a novel differentiation protocol. The SwTHY hybrid thymus model demonstrates beneficial effects on human thymocyte development of hES-TEPs maturing in the context of a supportive thymic structure.

      Graphical abstract

      Key words

      Abbreviations used:

      3rdPP (Third pharyngeal pouch), AFE (Anterior foregut endoderm), APC (Antigen-presenting cell), cTEC (Cortical thymic epithelial cell), d0 (Day 0), DE (Definitive endoderm), DP (Double positive), E1 (Embryonic day 1), hES (Human embryonic stem cell), hES-TEP (Human embryonic stem cell derived-thymic epithelial progenitor), hHSPC (Human hematopoietic stem and progenitor cell), HuTHY (Human thymus), K5 (Keratin 5), NS (Noggin+SB431542), NSG (NOD severe combined immunodeficiency IL2Rγnull), PE (Pharyngeal endoderm), PP (Pharyngeal pouch), PSC (Pluripotent stem cell), RA (Retinoic acid), SP (Single positive), SwTHY (Fetal swine thymus), TEC (Thymic epithelial cell), TEP (Thymic epithelial progenitor), TMC (Thymic mesenchymal cell), Treg (Regulatory T), YM155 (Sepantronium bromide)
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      References

        • Miller J.F.A.P.
        Immunological function of the thymus.
        Lancet. 1961; 278: 748-749
        • Abramson J.
        • Anderson G.
        Thymic epithelial cells.
        Annu Rev Immunol. 2017; 35: 85-118
        • Skogberg G.
        • Lundberg V.
        • Berglund M.
        • Gudmundsdottir J.
        • Telemo E.
        • Lindgren S.
        • et al.
        Human thymic epithelial primary cells produce exosomes carrying tissue-restricted antigens.
        Immunol Cell Biol. 2015; 93: 727-734
        • Villegas J.A.
        • Gradolatto A.
        • Truffault F.
        • Roussin R.
        • Berrih-Aknin S.
        • Le Panse R.
        • et al.
        Cultured human thymic-derived cells display medullary thymic epithelial cell phenotype and functionality.
        Front Immunol. 2018; 9: 1663
        • Parent A.V.
        • Russ H.A.
        • Khan I.S.
        • LaFlam T.N.
        • Metzger T.C.
        • Anderson M.S.
        • et al.
        Generation of functional thymic epithelium from human embryonic stem cells that supports host T cell development.
        Cell Stem Cell. 2013; 13https://doi.org/10.1016/j.stem.2013.04.004
        • Sun X.
        • Xu J.
        • Lu H.
        • Liu W.
        • Miao Z.
        • Sui X.
        • et al.
        Directed differentiation of human embryonic stem cells into thymic epithelial progenitor-like cells reconstitutes the thymic microenvironment in vivo.
        Cell Stem Cell. 2013; 13: 230-236
        • Soh C.-L.
        • Giudice A.
        • Jenny R.A.
        • Elliott D.A.
        • Hatzistavrou T.
        • Micallef S.J.
        • et al.
        FOXN1(GFP/w) reporter hESCs enable identification of integrin-β4, HLA-DR, and EPCAM as markers of human PSC-derived FOXN1(+) thymic epithelial progenitors.
        Stem Cell Reports. 2014; 2: 925-937
        • Su M.
        • Hu R.
        • Jin J.
        • Yan Y.
        • Song Y.
        • Sullivan R.
        • et al.
        Efficient in vitro generation of functional thymic epithelial progenitors from human embryonic stem cells.
        Sci Rep. 2015; 5: 9882
        • Bredenkamp N.
        • Ulyanchenko S.
        • O’Neill K.E.
        • Manley N.R.
        • Vaidya H.J.
        • Blackburn C.C.
        An organized and functional thymus generated from FOXN1-reprogrammed fibroblasts.
        Nat Cell Biol. 2014; 16: 902-908
        • Chhatta A.R.
        • Cordes M.
        • Hanegraaf M.A.J.
        • Vloemans S.
        • Cupedo T.
        • Cornelissen J.J.
        • et al.
        De novo generation of a functional human thymus from induced pluripotent stem cells.
        J Allergy Clin Immunol. 2019; 144: 1416-1419.e7
        • Yamazaki Y.
        • Urrutia R.
        • Franco L.M.
        • Giliani S.
        • Zhang K.
        • Alazami A.M.
        • et al.
        PAX1 is essential for development and function of the human thymus.
        Sci Immunol. 2020; 5eaax1036
        • Khosravi-Maharlooei M.
        • Hoelzl M.
        • Li H.W.
        • Madley R.C.
        • Waffarn E.E.
        • Danzl N.M.
        • et al.
        Rapid thymectomy of NSG mice to analyze the role of native and grafted thymi in humanized mice.
        Eur J Immunol. 2020; 50: 138-141
        • Kalscheuer H.
        • Onoe T.
        • Dahmani A.
        • Li H.W.
        • Holzl M.
        • Yamada K.
        • et al.
        Xenograft tolerance and immune function of human T cells developing in pig thymus xenografts.
        J Immunol. 2014; 192: 3442-3450
        • Nikolic B.
        • Sykes M.
        Porcine thymus supports development of human T cells that are tolerant to porcine xenoantigens.
        Transplant Proc. 1999; 31: 924
        • Nauman G.
        • Borsotti C.
        • Danzl N.
        • Khosravi-Maharlooei M.
        • Li H.W.
        • Chavez E.
        • et al.
        Reduced positive selection of a human TCR in a swine thymus using a humanized mouse model for xenotolerance induction.
        Xenotransplantation. 2019; 27e12558
        • Siepe M.
        • Thomsen A.R.
        • Duerkopp N.
        • Krause U.
        • Forster K.
        • Hezel P.
        • et al.
        Human neonatal thymus-derived mesenchymal stromal cells: characterization, differentiation, and immunomodulatory properties.
        Tissue Eng Part A. 2009; 15: 1787-1796
        • Khosravi-Maharlooei M.
        • Obradovic A.
        • Misra A.
        • Motwani K.
        • Holzl M.
        • Seay H.R.
        • et al.
        Crossreactive public TCR sequences undergo positive selection in the human thymic repertoire.
        J Clin Invest. 2019; 129: 2446-2462
        • Haddadi M.H.
        • Hajizadeh-Saffar E.
        • Khosravi-Maharlooei M.
        • Basiri M.
        • Negahdari B.
        • Baharvand H.
        Autoimmunity as a target for chimeric immune receptor therapy: a new vision to therapeutic potential.
        Blood Rev. 2020; 41100645
        • Gordon J.
        • Wilson V.A.
        • Blair N.F.
        • Sheridan J.
        • Farley A.
        • Wilson L.
        • et al.
        Functional evidence for a single endodermal origin for the thymic epithelium.
        Nat Immunol. 2004; 5: 546
        • Gordon J.
        • Manley N.R.
        Mechanisms of thymus organogenesis and morphogenesis.
        Development. 2011; 138: 3865-3878
        • D'Amour K.A.
        • Agulnick A.D.
        • Eliazer S.
        • Kelly O.G.
        • Kroon E.
        • Baetge E.E.
        Efficient differentiation of human embryonic stem cells to definitive endoderm.
        Nat Biotechnol. 2005; 23: 1534-1541
        • Green M.D.
        • Chen A.
        • Nostro M.-C.
        • d'Souza S.L.
        • Schaniel C.
        • Lemischka I.R.
        • et al.
        Generation of anterior foregut endoderm from human embryonic and induced pluripotent stem cells.
        Nat Biotechnol. 2011; 29: 267-272
        • Manley N.R.
        • Condie B.G.
        Transcriptional regulation of thymus organogenesis and thymic epithelial cell differentiation.
        in: Liston A. Progress in molecular biology and translational science 92. Academic Press, Waltham, Mass2010: 103-120
        • Farley A.M.
        • Morris L.X.
        • Vroegindeweij E.
        • Depreter M.L.G.
        • Vaidya H.
        • Stenhouse F.H.
        • et al.
        Dynamics of thymus organogenesis and colonization in early human development.
        Development. 2013; 140: 2015-2026
        • Diman N.Y.S.G.
        • Remacle S.
        • Bertrand N.
        • Picard J.J.
        • Zaffran S.
        • Rezsohazy R.
        A retinoic acid responsive hoxa3 transgene expressed in embryonic pharyngeal endoderm, cardiac neural crest and a subdomain of the second heart field.
        PLoS One. 2011; 6e27624
        • Vitelli F.
        • Taddei I.
        • Morishima M.
        • Meyers E.N.
        • Lindsay E.A.
        • Baldini A.
        A genetic link between Tbx1 and fibroblast growth factor signaling.
        Development. 2002; 129: 4605
        • Romano R.
        • Palamaro L.
        • Fusco A.
        • Giardino G.
        • Gallo V.
        • Del Vecchio L.
        • et al.
        FOXN1: a master regulator gene of thymic epithelial development program.
        Front Immunol. 2013; 4: 187
        • Wallin J.
        • Eibel H.
        • Neubuser A.
        • Wilting J.
        • Koseki H.
        • Balling R.
        Pax1 is expressed during development of the thymus epithelium and is required for normal T-cell maturation.
        Development. 1996; 122: 23
        • Hetzer-Egger C.
        • Schorpp M.
        • Haas-Assenbaum A.
        • Balling R.
        • Peters H.
        • Boehm T.
        Thymopoiesis requires Pax9 function in thymic epithelial cells.
        Eur J Immunol. 2002; 32: 1175-1181
        • Furumoto T.-a.
        • Miura N.
        • Akasaka T.
        • Mizutani-Koseki Y.
        • Sudo H.
        • Fukuda K.
        • et al.
        Notochord-dependent expression of MFH1 and PAX1 cooperates to maintain the proliferation of sclerotome cells during the vertebral column development.
        Dev Biol. 1999; 210: 15-29
        • Saldaña J.I.
        • Solanki A.
        • Lau C.-I.
        • Sahni H.
        • Ross S.
        • Furmanski A.L.
        • et al.
        Sonic hedgehog regulates thymic epithelial cell differentiation.
        J Autoimmun. 2016; 68: 86-97
        • Sacedón R.
        • Varas A.
        • Hernández-López C.
        • Gutiérrez-deFrías C.
        • Crompton T.
        • Zapata A.G.
        • et al.
        Expression of hedgehog proteins in the human thymus.
        J Histochem Cytochem. 2003; 51: 1557-1566
        • Probst S.
        • Kraemer C.
        • Demougin P.
        • Sheth R.
        • Martin G.R.
        • Shiratori H.
        • et al.
        SHH propagates distal limb bud development by enhancing CYP26B1-mediated retinoic acid clearance via AER-FGF signalling.
        Development. 2011; 138: 1913-1923
        • Garg V.
        • Yamagishi C.
        • Hu T.
        • Kathiriya I.S.
        • Yamagishi H.
        • Srivastava D.
        Tbx1, a DiGeorge syndrome candidate gene, is regulated by sonic hedgehog during pharyngeal arch development.
        Dev Biol. 2001; 235: 62-73
        • Moore-Scott B.A.
        • Manley N.R.
        Differential expression of sonic hedgehog along the anterior–posterior axis regulates patterning of pharyngeal pouch endoderm and pharyngeal endoderm-derived organs.
        Dev Biol. 2005; 278: 323-335
        • Bleul C.C.
        • Boehm T.
        BMP signaling is required for normal thymus development.
        J Immunol. 2005; 175: 5213
        • Patel S.R.
        • Gordon J.
        • Mahbub F.
        • Blackburn C.C.
        • Manley N.R.
        Bmp4 and Noggin expression during early thymus and parathyroid organogenesis.
        Gene Expr Patterns. 2006; 6: 794-799
        • Bain V.E.
        • Gordon J.
        • O'Neil J.D.
        • Ramos I.
        • Richie E.R.
        • Manley N.R.
        Tissue-specific roles for sonic hedgehog signaling in establishing thymus and parathyroid organ fate.
        Development. 2016; 143: 4027-4037
        • Chambers S.M.
        • Fasano C.A.
        • Papapetrou E.P.
        • Tomishima M.
        • Sadelain M.
        • Studer L.
        Highly efficient neural conversion of human ES and iPS cells by dual inhibition of SMAD signaling.
        Nat Biotechnol. 2009; 27: 275-280
        • Huang S.X.
        • Islam M.N.
        • O'Neill J.
        • Hu Z.
        • Yang Y.G.
        • Chen Y.W.
        • et al.
        Efficient generation of lung and airway epithelial cells from human pluripotent stem cells.
        Nat Biotechnol. 2014; 32: 84-91
        • Park J.-E.
        • Botting R.A.
        • Domínguez Conde C.
        • Popescu D.-M.
        • Lavaert M.
        • Kunz D.J.
        • et al.
        A cell atlas of human thymic development defines T cell repertoire formation.
        Science. 2020; 367eaay3224
        • Gordon J.
        • Bennett A.R.
        • Blackburn C.C.
        • Manley N.R.
        Gcm2 and Foxn1 mark early parathyroid- and thymus-specific domains in the developing third pharyngeal pouch.
        Mech Dev. 2001; 103: 141-143
        • Zamisch M.
        • Moore-Scott B.
        • Su D.-M.
        • Lucas P.J.
        • Manley N.
        • Richie E.R.
        Ontogeny and regulation of IL-7-expressing thymic epithelial cells.
        J Immunol. 2005; 174: 60
        • Pan G.J.
        • Chang Z.Y.
        • Schöler H.R.
        • Pei D.
        Stem cell pluripotency and transcription factor Oct4.
        Cell Res. 2002; 12: 321-329
        • Lee M.-O.
        • Moon S.H.
        • Jeong H.-C.
        • Yi J.-Y.
        • Lee T.-H.
        • Shim S.H.
        • et al.
        Inhibition of pluripotent stem cell-derived teratoma formation by small molecules.
        Proc Natl Acad Sci U S A. 2013; 110: E3281-E3290
        • Onoe T.
        • Kalscheuer H.
        • Chittenden M.
        • Zhao G.
        • Yang Y.-G.
        • Sykes M.
        Homeostatic expansion and phenotypic conversion of human T cells depend on peripheral interactions with APCs.
        J Immunol. 2010; 184: 6756-6765
        • Thome J.J.
        • Yudanin N.
        • Ohmura Y.
        • Kubota M.
        • Grinshpun B.
        • Sathaliyawala T.
        • et al.
        Spatial map of human T cell compartmentalization and maintenance over decades of life.
        Cell. 2014; 159: 814-828
        • Kimmig S.
        • Przybylski G.K.
        • Schmidt C.A.
        • Laurisch K.
        • Möwes B.
        • Radbruch A.
        • et al.
        Two subsets of naive T helper cells with distinct T cell receptor excision circle content in human adult peripheral blood.
        J Exp Med. 2002; 195: 789-794
        • DeWolf S.
        • Grinshpun B.
        • Savage T.
        • Lau S.P.
        • Obradovic A.
        • Shonts B.
        • et al.
        Quantifying size and diversity of the human T cell alloresponse.
        JCI Insight. 2018; 3e121256
        • Gapin L.
        Check MAIT.
        J Immunol. 2014; 192: 4475-4480
        • Vitelli F.
        • Lania G.
        • Huynh T.
        • Baldini A.
        Partial rescue of the Tbx1 mutant heart phenotype by Fgf8: genetic evidence of impaired tissue response to Fgf8.
        J Mol Cell Cardiol. 2010; 49: 836-840
        • Albazerchi A.
        • Stern C.D.
        A role for the hypoblast (AVE) in the initiation of neural induction, independent of its ability to position the primitive streak.
        Dev Biol. 2007; 301: 489-503
        • Crossley P.H.
        • Martin G.R.
        The mouse Fgf8 gene encodes a family of polypeptides and is expressed in regions that direct outgrowth and patterning in the developing embryo.
        Development. 1995; 121: 439
        • Guo Q.
        • Li J.Y.H.
        Distinct functions of the major Fgf8 spliceform, Fgf8b, before and during mouse gastrulation.
        Development. 2007; 134: 2251-2260
        • Sun X.
        • Meyers E.N.
        • Lewandoski M.
        • Martin G.R.
        Targeted disruption of Fgf8 causes failure of cell migration in the gastrulating mouse embryo.
        Genes Dev. 1999; 13: 1834-1846
        • Stuckey D.W.
        • Di Gregorio A.
        • Clements M.
        • Rodriguez T.A.
        Correct patterning of the primitive streak requires the anterior visceral endoderm.
        PLoS One. 2011; 6e17620
        • Jerome L.A.
        • Papaioannou V.E.
        DiGeorge syndrome phenotype in mice mutant for the T-box gene, Tbx1.
        Nat Genet. 2001; 27: 286-291
        • Yamagishi H.
        • Maeda J.
        • Hu T.
        • McAnally J.
        • Conway S.J.
        • Kume T.
        • et al.
        Tbx1 is regulated by tissue-specific forkhead proteins through a common sonic hedgehog-responsive enhancer.
        Genes Dev. 2003; 17: 269-281
        • Lewandoski M.
        • Sun X.
        • Martin G.R.
        Fgf8 signalling from the AER is essential for normal limb development.
        Nat Genet. 2000; 26: 460
        • Bonnin M.-A.
        • Laclef C.
        • Blaise R.
        • Eloy-Trinquet S.
        • Relaix F.
        • Maire P.
        • et al.
        Six1 is not involved in limb tendon development, but is expressed in limb connective tissue under Shh regulation.
        Mech Dev. 2005; 122: 573-585
        • Peters H.
        • Neubüser A.
        • Kratochwil K.
        • Balling R.
        Pax9-deficient mice lack pharyngeal pouch derivatives and teeth and exhibit craniofacial and limb abnormalities.
        Genes Dev. 1998; 12: 2735-2747
        • McGlinn E.
        • van Bueren K.L.
        • Fiorenza S.
        • Mo R.
        • Poh A.M.
        • Forrest A.
        • et al.
        Pax9 and Jagged1 act downstream of Gli3 in vertebrate limb development.
        Mech Dev. 2005; 122: 1218-1233
        • Xu P.-X.
        • Cheng J.
        • Epstein J.A.
        • Maas R.L.
        Mouse Eya genes are expressed during limb tendon development and encode a transcriptional activationfunction.
        Proc Natl Acad Sci. 1997; 94: 11974-11979
        • Gordon J.
        Hox genes in the pharyngeal region: how Hoxa3 controls early embryonic development of the pharyngeal organs.
        Int J Dev Biol. 2018; 62: 775-783
        • Driskell R.R.
        • Clavel C.
        • Rendl M.
        • Watt F.M.
        Hair follicle dermal papilla cells at a glance.
        J Cell Sci. 2011; 124: 1179-1182
        • Hu B.
        • Lefort K.
        • Qiu W.
        • Nguyen B.-C.
        • Rajaram R.D.
        • Castillo E.
        • et al.
        Control of hair follicle cell fate by underlying mesenchyme through a CSL–Wnt5a–FoxN1 regulatory axis.
        Genes Dev. 2010; 24: 1519-1532
        • Botchkarev V.A.
        • Botchkareva N.V.
        • Roth W.
        • Nakamura M.
        • Chen L.-H.
        • Herzog W.
        • et al.
        Noggin is a mesenchymally derived stimulator of hair-follicle induction.
        Nat Cell Biol. 1999; 1: 158
        • Kulessa H.
        • Turk G.
        • Hogan B.L.
        Inhibition of Bmp signaling affects growth and differentiation in the anagen hair follicle.
        EMBO J. 2000; 19: 6664-6674
        • Bonfanti P.
        • Claudinot S.
        • Amici A.W.
        • Farley A.
        • Blackburn C.C.
        • Barrandon Y.
        Microenvironmental reprogramming of thymic epithelial cells to skin multipotent stem cells.
        Nature. 2010; 466: 978
        • Gillard G.O.
        • Farr A.G.
        Features of medullary thymic epithelium implicate postnatal development in maintaining epithelial heterogeneity and tissue-restricted antigen expression.
        J Immunol. 2006; 176: 5815
        • Gillard G.O.
        • Dooley J.
        • Erickson M.
        • Peltonen L.
        • Farr A.G.
        Aire-dependent alterations in medullary thymic epithelium indicate a role for Aire in thymic epithelial differentiation.
        J Immunol. 2007; 178: 3007
        • Bohr S.
        • Patel S.J.
        • Vasko R.
        • Shen K.
        • Huang G.
        • Yarmush M.L.
        • et al.
        Highly upregulated Lhx2 in the Foxn1(−/−) nude mouse phenotype reflects a dysregulated and expanded epidermal stem cell niche.
        PLoS One. 2013; 8e64223
        • Lai L.
        • Jin J.
        Generation of thymic epithelial cell progenitors by mouse embryonic stem cells.
        Stem Cells. 2009; 27: 3012-3020
        • Shimizu I.
        • Fudaba Y.
        • Shimizu A.
        • Yang Y.G.
        • Sykes M.
        Comparison of human T cell repertoire generated in xenogeneic porcine and human thymus grafts.
        Transplantation. 2008; 86: 601-610
        • Fink P.J.
        • Hendricks D.W.
        Post-thymic maturation: young T cells assert their individuality.
        Nat Rev Immunol. 2011; 11: 544-549
        • Sykes M.
        • Sachs D.H.
        Transplanting organs from pigs to humans.
        Sci Immunol. 2019; 4eaau6298
        • Tanabe T.
        • Watanabe H.
        • Shah J.A.
        • Sahara H.
        • Shimizu A.
        • Nomura S.
        • et al.
        Role of intrinsic (graft) versus extrinsic (host) factors in the growth of transplanted organs following allogeneic and xenogeneic transplantation.
        Am J Transplant. 2017; 17: 1778-1790
        • Yamada K.
        • Yazawa K.
        • Shimizu A.
        • Iwanaga T.
        • Hisashi Y.
        • Nuhn M.
        • et al.
        Marked prolongation of porcine renal xenograft survival in baboons through the use of alpha1,3-galactosyltransferase gene-knockout donors and the cotransplantation of vascularized thymic tissue.
        Nat Med. 2005; 11: 32-34
        • Hongo D.
        • Hadidi S.
        • Damrauer S.
        • Garrigue V.
        • Kraft D.
        • Sachs D.H.
        • et al.
        Porcine thymic grafts protect human thymocytes from HIV-1-induced destruction.
        J Infect Dis. 2007; 196: 900-910