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Ramos SA, Armitage LH, Morton JJ, Alzofon N, Handler D, Kelly G, Homann D, Jimeno A, Russ HA. Generation of functional thymic organoids from human pluripotent stem cells. Stem Cell Reports 2023; 18:829-840. [PMID: 36963390 PMCID: PMC10147832 DOI: 10.1016/j.stemcr.2023.02.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 02/25/2023] [Accepted: 02/26/2023] [Indexed: 03/26/2023] Open
Abstract
The thymus is critical for the establishment of a functional and self-tolerant adaptive immune system but involutes with age, resulting in reduced naive T cell output. Generation of a functional human thymus from human pluripotent stem cells (hPSCs) is an attractive regenerative strategy. Direct differentiation of thymic epithelial progenitors (TEPs) from hPSCs has been demonstrated in vitro, but functional thymic epithelial cells (TECs) only form months after transplantation of TEPs in vivo. We show the generation of TECs in vitro in isogenic stem cell-derived thymic organoids (sTOs) consisting of TEPs, hematopoietic progenitor cells, and mesenchymal cells, differentiated from the same hPSC line. sTOs support T cell development, express key markers of negative selection, including the autoimmune regulator (AIRE) protein, and facilitate regulatory T cell development. sTOs provide the basis for functional patient-specific thymic organoid models, allowing for the study of human thymus function, T cell development, and transplant immunity.
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Affiliation(s)
- Stephan A Ramos
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Lucas H Armitage
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - John J Morton
- Division of Medical Oncology, Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Nathaniel Alzofon
- Division of Medical Oncology, Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Diana Handler
- Human Immune Monitoring Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Geoffrey Kelly
- Human Immune Monitoring Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Dirk Homann
- Diabetes, Metabolism and Obesity Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Antonio Jimeno
- Division of Medical Oncology, Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA; Charles C. Gates Center for Regenerative Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Holger A Russ
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Charles C. Gates Center for Regenerative Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA; Diabetes Institute, University of Florida, Gainesville, FL 32610, USA; Department of Pathology and Therapeutics, University of Florida, Gainesville, FL 32610, USA.
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Abstract
This review briefly describes the last decades of experimental work on the thymus. Given the histological complexity of this organ, the multiple embryological origins of its cellular components and its role in carefully regulating T lymphocyte maturation and function, methods to dissect and understand this complexity have been developed through the years. The possibility to study ex vivo the thymus organ function has been achieved by developing Fetal Thymus Organ Cultures (FTOC). Subsequently, the combination of organ disaggregation and reaggregation in vitro represented by Reaggregate Thymus Organ cultures (RTOC) allowed mixing cellular components from different genetic backgrounds. Moreover, RTOC allowed dissecting the different stromal and hematological components to study the interactions between Major Histocompatibility Complex (MHC) molecules and the T-cell receptors during thymocytes selection. In more recent years, prospective isolation of stromal cells and thymocytes at different stages of development made it possible to explore and elucidate the molecular and cellular players in both the developing and adult thymus. Finally, the appearance of novel cell sources such as embryonic stem (ES) cells and more recently induced pluripotent stem (iPS) cells has opened new scenarios in modelling thymus development and regeneration strategies. Most of the work described was carried out in rodents and the current challenge is to develop equivalent or even more informative assays and tools in entirely human model systems.
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Intrathymic injection of hematopoietic progenitor cells establishes functional T cell development in a mouse model of severe combined immunodeficiency. J Hematol Oncol 2017; 10:109. [PMID: 28511686 PMCID: PMC5432974 DOI: 10.1186/s13045-017-0478-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 05/05/2017] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Even though hematopoietic stem cell transplantation can be curative in patients with severe combined immunodeficiency, there is a need for additional strategies boosting T cell immunity in individuals suffering from genetic disorders of lymphoid development. Here we show that image-guided intrathymic injection of hematopoietic stem and progenitor cells in NOD-scid IL2rγnull mice is feasible and facilitates the generation of functional T cells conferring protective immunity. METHODS Hematopoietic stem and progenitor cells were isolated from the bone marrow of healthy C57BL/6 mice (wild-type, Luciferase+, CD45.1+) and injected intravenously or intrathymically into both male and female, young or aged NOD-scid IL2rγnull recipients. The in vivo fate of injected cells was analyzed by bioluminescence imaging and flow cytometry of thymus- and spleen-derived T cell populations. In addition to T cell reconstitution, we evaluated mice for evidence of immune dysregulation based on diabetes development and graft-versus-host disease. T cell immunity following intrathymic injection of hematopoietic stem and progenitor cells in NOD-scid IL2rγnull mice was assessed in a B cell lymphoma model. RESULTS Despite the small size of the thymic remnant in NOD-scid IL2rγnull mice, we were able to accomplish precise intrathymic delivery of hematopoietic stem and progenitor cells by ultrasound-guided injection. Thymic reconstitution following intrathymic injection of healthy allogeneic hematopoietic cells was most effective in young male recipients, indicating that even in the setting of severe immunodeficiency, sex and age are important variables for thymic function. Allogeneic T cells generated in intrathymically injected NOD-scid IL2rγnull mice displayed anti-lymphoma activity in vivo, but we found no evidence for severe auto/alloreactivity in T cell-producing NOD-scid IL2rγnull mice, suggesting that immune dysregulation is not a major concern. CONCLUSIONS Our findings suggest that intrathymic injection of donor hematopoietic stem and progenitor cells is a safe and effective strategy to establish protective T cell immunity in a mouse model of severe combined immunodeficiency.
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Satoh R, Kakugawa K, Yasuda T, Yoshida H, Sibilia M, Katsura Y, Levi B, Abramson J, Koseki Y, Koseki H, van Ewijk W, Hollander GA, Kawamoto H. Requirement of Stat3 Signaling in the Postnatal Development of Thymic Medullary Epithelial Cells. PLoS Genet 2016; 12:e1005776. [PMID: 26789017 PMCID: PMC4720355 DOI: 10.1371/journal.pgen.1005776] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 12/08/2015] [Indexed: 01/20/2023] Open
Abstract
Thymic medullary regions are formed in neonatal mice as islet-like structures, which increase in size over time and eventually fuse a few weeks after birth into a continuous structure. The development of medullary thymic epithelial cells (TEC) is dependent on NF-κB associated signaling though other signaling pathways may contribute. Here, we demonstrate that Stat3-mediated signals determine medullary TEC cellularity, architectural organization and hence the size of the medulla. Deleting Stat3 expression selectively in thymic epithelia precludes the postnatal enlargement of the medulla retaining a neonatal architecture of small separate medullary islets. In contrast, loss of Stat3 expression in cortical TEC neither affects the cellularity or organization of the epithelia. Activation of Stat3 is mainly positioned downstream of EGF-R as its ablation in TEC phenocopies the loss of Stat3 expression in these cells. These results indicate that Stat3 meditated signal via EGF-R is required for the postnatal development of thymic medullary regions. Thymic medulla is known to be an essential site for the deletion of auto-reactive T cells. Whereas it has been well documented that the development of medullary thymic epithelial cells (mTECs) depends on NF-κB associated signaling, it remained unclear whether other signaling pathways are also involved. In this context, it had been reported that conditional deletion of Stat3 alleles in TECs using cytokeratin-5 (CK5) promoter controlled Cre expression results in a profound impairment in TEC development. However, a detailed analysis of phenotypes in mTECs remained unstudied. In the present study, we show that thymic medullary regions remain as small islets when Stat3 is conditionally deleted in thymic epithelial cells, while they normal fuse to form continuous structures during postnatal development. Furthermore, we identified EGF-R mediated signal to be placed upstream of Stat3 activation, as its ablation phenocopied the loss of Stat3 expression in TECs. Thus, the present study revealed that Stat3 is required for the postnatal development of medullary regions.
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Affiliation(s)
- Rumi Satoh
- Laboratory for Lymphocyte Development, RIKEN Research Center for Allergy and Immunology, Yokohama, Japan
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Kiyokazu Kakugawa
- Laboratory for Lymphocyte Development, RIKEN Research Center for Allergy and Immunology, Yokohama, Japan
- Laboratory for Immune Crosstalk, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Takuwa Yasuda
- Laboratory for Immunogenetics, RIKEN Center for Integrative Medical Sciences, Yokoham, Japan
| | - Hisahiro Yoshida
- Laboratory for Immunogenetics, RIKEN Center for Integrative Medical Sciences, Yokoham, Japan
| | - Maria Sibilia
- Department of Medicine I, Institute of Cancer Research, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
| | - Yoshimoto Katsura
- Division of Cell Regeneration and Transplantation, Advanced Medical Research Center, Nihon University School of Medicine, Tokyo, Japan
| | - Ben Levi
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Jakub Abramson
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Yoko Koseki
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Haruhiko Koseki
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan
| | - Willem van Ewijk
- Department of Molecular Cell Biology and Department of Immunology, Leiden University Medical Center, RA Leiden, the Netherlands
| | - Georg A. Hollander
- Laboratory of Pediatric Immunology, Center for Biomedicine, University of Basel, and the University Children’s Hospital, Basel, Switzerland
- Laboratory of Developmental Immunology Weatherall Institute of Molecular Medicine and Department of Paediatrics, University of Oxford, Oxford, United Kingdom
| | - Hiroshi Kawamoto
- Laboratory for Lymphocyte Development, RIKEN Research Center for Allergy and Immunology, Yokohama, Japan
- Department of Immunology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan
- * E-mail:
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Hamazaki Y. Adult thymic epithelial cell (TEC) progenitors and TEC stem cells: Models and mechanisms for TEC development and maintenance. Eur J Immunol 2015; 45:2985-93. [PMID: 26362014 DOI: 10.1002/eji.201545844] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 08/06/2015] [Accepted: 09/10/2015] [Indexed: 01/06/2023]
Abstract
The thymus is the primary lymphoid organ for generating self-restricted and self-tolerant functional T cells. Its two distinct anatomical regions, the cortex and the medulla, are involved in positive and negative selection, respectively. Thymic epithelial cells (TECs) constitute the framework of this tissue and function as major stromal components. Extensive studies for more than a decade have revealed how TECs are generated during organogenesis; progenitors specific for medullary TECs (mTECs) and cortical TECs (cTECs) as well as bipotent progenitors for both lineages have been identified, and the signaling pathways required for the development and maturation of mTECs have been elucidated. However, little is known about the initial commitment of mTECs and cTECs during ontogeny, and how regeneration of both lineages is sustained in the postnatal/adult thymus. Recently, stem cell activities in TECs have been demonstrated, and TEC progenitors have been identified in the postnatal thymus. In this review, recent advances in studying the development and maintenance of TECs are summarized, and the possible mechanisms of thymic regeneration and involution are discussed.
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Affiliation(s)
- Yoko Hamazaki
- Department of Immunology and Cell Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
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Jurberg AD, Vasconcelos-Fontes L, Cotta-de-Almeida V. A Tale from TGF-β Superfamily for Thymus Ontogeny and Function. Front Immunol 2015; 6:442. [PMID: 26441956 PMCID: PMC4564722 DOI: 10.3389/fimmu.2015.00442] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 08/14/2015] [Indexed: 12/16/2022] Open
Abstract
Multiple signaling pathways control every aspect of cell behavior, organ formation, and tissue homeostasis throughout the lifespan of any individual. This review takes an ontogenetic view focused on the large superfamily of TGF-β/bone morphogenetic protein ligands to address thymus morphogenesis and function in T cell differentiation. Recent findings on a role of GDF11 for reversing aging-related phenotypes are also discussed.
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Affiliation(s)
- Arnon Dias Jurberg
- Laboratory on Thymus Research, Oswaldo Cruz Institute, Oswaldo Cruz Foundation (Fiocruz) , Rio de Janeiro , Brazil ; Graduate Program in Cell and Developmental Biology, Institute of Biomedical Sciences, Federal University of Rio de Janeiro , Rio de Janeiro , Brazil
| | - Larissa Vasconcelos-Fontes
- Laboratory on Thymus Research, Oswaldo Cruz Institute, Oswaldo Cruz Foundation (Fiocruz) , Rio de Janeiro , Brazil
| | - Vinícius Cotta-de-Almeida
- Laboratory on Thymus Research, Oswaldo Cruz Institute, Oswaldo Cruz Foundation (Fiocruz) , Rio de Janeiro , Brazil
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Inghirami G, Chan WC, Pileri S. Peripheral T-cell and NK cell lymphoproliferative disorders: cell of origin, clinical and pathological implications. Immunol Rev 2015; 263:124-59. [PMID: 25510275 DOI: 10.1111/imr.12248] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
T-cell lymphoproliferative disorders are a heterogeneous group of neoplasms with distinct clinical-biological properties. The normal cellular counterpart of these processes has been postulated based on functional and immunophenotypic analyses. However, T lymphocytes have been proven to be remarkably capable of modulating their properties, adapting their function in relationship with multiple stimuli and to the microenvironment. This impressive plasticity is determined by the equilibrium among a pool of transcription factors and by DNA chromatin regulators. It is now proven that the acquisition of specific genomic defects leads to the enforcement/activation of distinct pathways, which ultimately alter the preferential activation of defined regulators, forcing the neoplastic cells to acquire features and phenotypes distant from their original fate. Thus, dissecting the landscape of the genetic defects and their functional consequences in T-cell neoplasms is critical not only to pinpoint the origin of these tumors but also to define innovative mechanisms to re-adjust an unbalanced state to which the tumor cells have become addicted and make them vulnerable to therapies and targetable by the immune system. In our review, we briefly describe the pathological and clinical aspects of the T-cell lymphoma subtypes as well as NK-cell lymphomas and then focus on the current understanding of their pathogenesis and the implications on diagnosis and treatment.
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Affiliation(s)
- Giorgio Inghirami
- Department of Molecular Biotechnology and Health Science and Center for Experimental Research and Medical Studies (CeRMS), University of Torino, Torino, Italy; Department of Pathology, and NYU Cancer Center, New York University School of Medicine, New York, NY, USA; Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, NY, USA
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8
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Ferrero I, Koch U, Claudinot S, Favre S, Radtke F, Luther SA, MacDonald HR. DL4-mediated Notch signaling is required for the development of fetal αβ and γδ T cells. Eur J Immunol 2013; 43:2845-53. [PMID: 23881845 DOI: 10.1002/eji.201343527] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 06/13/2013] [Accepted: 07/18/2013] [Indexed: 11/09/2022]
Abstract
T-cell development depends upon interactions between thymocytes and thymic epithelial cells (TECs). The engagement of delta-like 4 (DL4) on TECs by Notch1 expressed by blood-borne BM-derived precursors is essential for T-cell commitment in the adult thymus. In contrast to the adult, the earliest T-cell progenitors in the embryo originate in the fetal liver and migrate to the nonvascularized fetal thymus via chemokine signals. Within the fetal thymus, some T-cell precursors undergo programmed TCRγ and TCRδ rearrangement and selection, giving rise to unique γδ T cells. Despite these fundamental differences between fetal and adult T-cell lymphopoiesis, we show here that DL4-mediated Notch signaling is essential for the development of both αβ and γδ T-cell lineages in the embryo. Deletion of the DL4 gene in fetal TECs results in an early block in αβ T-cell development and a dramatic reduction of all γδ T-cell subsets in the fetal thymus. In contrast to the adult, no dramatic deviation of T-cell precursors to alternative fates was observed in the fetal thymus in the absence of Notch signaling. Taken together, our data reveal a common requirement for DL4-mediated Notch signaling in fetal and adult thymopoiesis.
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Affiliation(s)
- Isabel Ferrero
- Ludwig Center for Cancer Research of the University of Lausanne, Epalinges, Switzerland
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Dudakov JA, van den Brink MRM. Greater than the sum of their parts: combination strategies for immune regeneration following allogeneic hematopoietic stem cell transplantation. Best Pract Res Clin Haematol 2011; 24:467-76. [PMID: 21925100 DOI: 10.1016/j.beha.2011.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cytoreductive conditioning regimes designed to allow for successful allogeneic hematopoietic stem cell transplantation (allo-HSCT) paradoxically are also detrimental to recovery of the immune system in general but lymphopoiesis in particular. Post-transplant immune depletion is particularly striking within the T cell compartment which is exquisitely sensitive to negative regulation, evidenced by the profound decline in thymic function with age. As a consequence, regeneration of the immune system remains a significant unmet clinical need. Over the past decade studies have revealed several promising therapeutic strategies to address ineffective lymphopoiesis and post-transplant immune deficiency. These include the use of cytokines such as IL-7, IL-12 and IL-15; growth factors and hormones like keratinocyte growth factor (KGF), insulin-like growth factor (IGF)-1 and growth hormone (GH); adoptive transfer of ex vivo-generated precursor T cells (pre-T) and sex steroid ablation (SSA). Moreover, recently several novel approaches have been proposed to generate whole thymii ex vivo using stem cell technologies and bioscaffolds. Increasingly, however, when transferred to the clinic, these strategies alone are not sufficient to restore thymopoiesis in all patients leading to the potential of combination strategies as a way to reign in non-responders. Synergistic enhancement in combination may be due to differential targets may therefore be effective in improving clinical outcomes in the transplant settings as well as in other lymphopenic states induced by high dose chemotherapy/radiation therapy or HIV, and may also be useful in improving responses to vaccination and augmenting anti-tumor immunotherapy.
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Affiliation(s)
- Jarrod A Dudakov
- Department of Immunology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
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10
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Abstract
Control points of normal thymopoiesis may provide insights into strategies for interrupting cell interactions in thymomas which appear to maintain active T cell production. Thymus production of T cells represents one of two pathways by which peripheral T cell populations are maintained or, if lost, regenerated. The production of T cells by the thymus results from a series of thymus epithelial cell (TEC) - thymocyte interactions from entry of thymocyte precursors into the thymus to release of mature naïve single positive T cells into the periphery. Within this series of interactions, certain control points have been identified, all of which act through TEC to modulate thymopoiesis.
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Affiliation(s)
- Diana K Lee
- Experimental Transplantation and Immunology Branch, Center for Cancer Research, NCI, Bethesda, Maryland 20892, USA
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11
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Roberts NA, Desanti GE, Withers DR, Scott HR, Jenkinson WE, Lane PJL, Jenkinson EJ, Anderson G. Absence of thymus crosstalk in the fetus does not preclude hematopoietic induction of a functional thymus in the adult. Eur J Immunol 2009; 39:2395-402. [DOI: 10.1002/eji.200939501] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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12
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Anderson G, Jenkinson EJ, Rodewald HR. A roadmap for thymic epithelial cell development. Eur J Immunol 2009; 39:1694-9. [DOI: 10.1002/eji.200939379] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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13
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Abstract
A pool of immature T cells with a seemingly unrestricted repertoire of antigen specificities is generated life-long in the thymus. Amongst these cells are, however, thymocytes that express a strongly self-reactive antigen receptor and hence hold the potential to trigger autoimmunity. To prevent such an outcome, the thymus employs several independent but functionally related strategies that act in parallel to enforce self-tolerance. The deletion of strongly self-reactive thymocytes and the generation of regulatory T cells constitute the two most efficient mechanisms to induce and maintain immunological tolerance. Thymic epithelial cells of the medulla express for this purpose tissue-restricted self-antigens. This review will focus on the cellular and molecular mechanisms operative in the thymus to shape a repertoire of mature T cells tolerant to self-antigens.
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Affiliation(s)
- G A Holländer
- Department of Clinical-Biological Sciences, Laboratory of Pediatric Immunology, Center for Biomedicine, University of Basel and The University Children's Hospital, Switzerland.
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Jenkinson WE, Bacon A, White AJ, Anderson G, Jenkinson EJ. An epithelial progenitor pool regulates thymus growth. THE JOURNAL OF IMMUNOLOGY 2009; 181:6101-8. [PMID: 18941199 DOI: 10.4049/jimmunol.181.9.6101] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Thymic epithelium provides an essential cellular substrate for T cell development and selection. Gradual age-associated thymic atrophy leads to a reduction in functional thymic tissue and a decline in de novo T cell generation. Development of strategies tailored toward regeneration of thymic tissue provides an important possibility to improve immune function in elderly individuals and increase the capacity for immune recovery in patients having undergone bone marrow transfer following immunoablative therapies. In this study we show that restriction of the size of the functional thymic epithelial progenitor pool affects the number of mature thymic epithelial cells. Using an embryo fusion chimera-based approach, we demonstrate a reduction in the total number of both embryonic and adult thymic epithelium, which relates to the initial size of the progenitor cell pool. The inability of thymic epithelial progenitor cells to undergo sufficient compensatory proliferation to rescue the deficit in progenitor numbers suggests that in addition to extrinsic regulation of thymus growth by provision of growth factors, intrinsic factors such as a proliferative restriction of thymic epithelial progenitors and availability of progenitor cell niches may limit thymic epithelial recovery. Collectively, our data demonstrate an important level of regulation of thymic growth and recovery at the thymic epithelial progenitor level, providing an important consideration for developing methods targeted toward inducing thymic regeneration.
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Affiliation(s)
- William E Jenkinson
- Medical Research Council Centre for Immune Regulation, Institute for Biomedical Research, Medical School, University of Birmingham, Birmingham, United Kingdom.
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15
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Strategies for reconstituting and boosting T cell-based immunity following haematopoietic stem cell transplantation: pre-clinical and clinical approaches. Semin Immunopathol 2008; 30:457-77. [PMID: 18982327 DOI: 10.1007/s00281-008-0140-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 10/14/2008] [Indexed: 12/14/2022]
Abstract
Poor immune recovery is characteristic of bone marrow transplantation and leads to high levels of morbidity and mortality. The primary underlying cause is a compromised thymic function, resulting from age-induced atrophy and further compounded by the damaging effects of cytoablative conditioning regimes on thymic epithelial cells (TEC). Several strategies have been proposed to enhance T cell reconstitution. Some, such as the use of single biological agents, are currently being tested in clinical trials. However, a more rational approach to immune restoration will be to leverage the evolving repertoire of new technologies. Specifically, the combined targeting of TEC, thymocytes and peripheral T cells, together with the bone marrow niches, promises a more strategic clinical therapeutic platform.
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Krenger W, Holländer GA. The immunopathology of thymic GVHD. Semin Immunopathol 2008; 30:439-56. [PMID: 18974988 DOI: 10.1007/s00281-008-0131-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Accepted: 09/30/2008] [Indexed: 12/11/2022]
Abstract
The clinical success of allogeneic hematopoietic stem cell transplantation (HSCT) depends on the appropriate reconstitution of the host's immune system. While recovery of T-cell immunity may occur in transplant recipients via both thymus-dependent and thymus-independent pathways, the regeneration of a population of phenotypically naive T cells with a broad receptor repertoire relies entirely on the de novo generation of T-cells in the thymus. Preclinical models and clinical studies of allogeneic HSCT have identified the thymus as a target of graft-versus-host disease (GVHD), thus limiting T-cell regeneration. The present review focuses on recent insight into how GVHD affects thymic structure and function and how this knowledge may aid in the design of new strategies to improve T-cell reconstitution following allogeneic HSCT.
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Affiliation(s)
- Werner Krenger
- Department of Biomedicine, University of Basel, Basel, 4005, Switzerland.
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Abstract
The epithelial architecture of the thymus fosters growth, differentiation, and T cell receptor repertoire selection of large numbers of immature T cells that continuously feed the mature peripheral T cell pool. Failure to build or to maintain a proper thymus structure can lead to defects ranging from immunodeficiency to autoimmunity. There has been long-standing interest in unraveling the cellular and molecular basis of thymus organogenesis. Earlier studies gave important morphological clues on thymus development. More recent cell biological and genetic approaches yielded new and conclusive insights regarding the germ layer origin of the epithelium and the composition of the medulla as a mosaic of clonally derived islets. The existence of epithelial progenitors common for cortex and medulla with the capacity for forming functional thymus after birth has been uncovered. In addition to the thymus in the chest, mice can have a cervical thymus that is small, but functional, and produces T cells only after birth. It will be important to elucidate the pathways from putative thymus stem cells to mature thymus epithelial cells, and the properties and regulation of these pathways from ontogeny to thymus involution.
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Boehm T. Thymus development and function. Curr Opin Immunol 2008; 20:178-84. [DOI: 10.1016/j.coi.2008.03.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Accepted: 03/11/2008] [Indexed: 12/27/2022]
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Kont V, Laan M, Kisand K, Merits A, Scott HS, Peterson P. Modulation of Aire regulates the expression of tissue-restricted antigens. Mol Immunol 2008; 45:25-33. [PMID: 17599412 PMCID: PMC1994210 DOI: 10.1016/j.molimm.2007.05.014] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Accepted: 05/15/2007] [Indexed: 12/17/2022]
Abstract
Intrathymic expression of tissue-restricted antigens (TRAs) has been viewed as the key element in the induction of central tolerance and recently, a central role for the autoimmune regulator (Aire) has been suggested in this process. The aim of this study was to establish whether down or up-regulation of Aire leads to alterations in TRA expression and whether this is limited to thymic epithelial cells. This study also characterized whether TRAs follow Aire expression during normal development, and whether thymic microenvironment plays a role in the expression of Aire and TRAs. We did several in vivo and in vitro experiments to manipulate Aire expression and measured expression of four TRAs (Trefoil factor-3, Insulin-2, Major urinary protein-1 and Salivary protein-1) by real-time RT-PCR. Aire had an allele dose-dependent effect on TRA expression in the thymuses of mice from two strains, C57BL/6J and Balb/c, but had no effect on TRA expression in the lymph nodes. In the thymus, Aire and TRAs were both localized in the medulla and were co-expressed during normal development and involution. In the primary stromal cells as well as thymic epithelial cell line, the adenoviral over-expression of Aire resulted in an increase in TRA expression. By manipulating in vitro organ-cultures we showed that thymic microenvironment plays a dominant role in Aire expression whereas TRAs follow the same pattern. The data underline a direct role for Aire in TRA expression and suggest that modulation of Aire has a potential to control central tolerance and autoimmunity.
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Affiliation(s)
- Vivian Kont
- Molecular Pathology, Biomedicum, Tartu University, Ravila 19, 50411 Tartu, Estonia
| | - Martti Laan
- Molecular Pathology, Biomedicum, Tartu University, Ravila 19, 50411 Tartu, Estonia
| | - Kai Kisand
- Molecular Pathology, Biomedicum, Tartu University, Ravila 19, 50411 Tartu, Estonia
| | - Andres Merits
- Institute of Technology, Tartu University, Tartu, Estonia
| | - Hamish S. Scott
- Division of Molecular Medicine, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Pärt Peterson
- Molecular Pathology, Biomedicum, Tartu University, Ravila 19, 50411 Tartu, Estonia
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20
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Abstract
Alphabeta T cells pass through a series of lymphoid tissue stromal microenvironments to acquire self tolerance and functional competence. In the thymus, positive selection of the developing T-cell receptor repertoire occurs in the cortex, whereas events in the medulla purge the system of self reactivity. T cells that survive are exported to secondary lymphoid organs where they direct first primary and then memory immune responses. This Review focuses on the microenvironments that nurture T-cell development rather than on T cells themselves. We summarize current knowledge on the formation of thymic epithelial-cell microenvironments, and highlight similarities between the environments that produce T cells and those that select and maintain them during immune responses.
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21
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White A, Carragher D, Parnell S, Msaki A, Perkins N, Lane P, Jenkinson E, Anderson G, Caamaño JH. Lymphotoxin a-dependent and -independent signals regulate stromal organizer cell homeostasis during lymph node organogenesis. Blood 2007; 110:1950-9. [PMID: 17526859 DOI: 10.1182/blood-2007-01-070003] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Lymph nodes provide specialized stromal microenvironments that support the recruitment and organization of T cells and B cells, enabling them to effectively participate in immune responses. While CD4(+)3(-) lymphoid tissue inducer cells (LTic's) are known to play a key role in influencing lymph node (LN) development, the mechanisms that regulate the development of stromal organizer cells are unclear. Here, we define an ontogenetic program of lymph node stromal cell maturation in relation to the requirement for LTic's. We also describe a lymph node reaggregation assay to study cell-cell interactions and lymphocyte recruitment to these organs that reproduces the in vivo events during lymph node development. In addition, analysis of the lymph node anlagen in normal and lymphotoxin a (LTa)-deficient embryos shows that LTa-mediated signaling is required to sustain proliferation and survival of stromal cells in vivo. Our data identify LTa-independent and LTa-dependent stages of lymph node development, and provide direct evidence for the role of LTic's during LN organogenesis.
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Affiliation(s)
- Andrea White
- Division of Immunity and Infection, Instiute for BioMedical Research-Medical Research Council Centre for Immune Regulation, University of Birmingham Medical School, Birmingham, United Kingdom
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22
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Abstract
T-cell development occurs principally in the thymus. Here, immature progenitor cells are guided through the differentiation and selection steps required to generate a complex T-cell repertoire that is both self-tolerant and has propensity to bind self major histocompatibility complex. These processes depend on an array of functionally distinct epithelial cell types within the thymic stroma, which have a common developmental origin in the pharyngeal endoderm. Here, we describe the structural and phenotypic attributes of the thymic stroma, and review current cellular and molecular understanding of thymus organogenesis.
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Affiliation(s)
- Craig S Nowell
- Institute for Stem Cell Research, University of Edinburgh, UK
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23
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Jenkinson WE, Rossi SW, Parnell SM, Jenkinson EJ, Anderson G. PDGFRα-expressing mesenchyme regulates thymus growth and the availability of intrathymic niches. Blood 2006; 109:954-60. [PMID: 17008543 DOI: 10.1182/blood-2006-05-023143] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
AbstractThe thymus provides a specialized site for the production of T cells capable of recognizing foreign antigens in the context of self–major histocompatibility complex (MHC) molecules. During development, the thymus arises from an epithelial rudiment containing bipotent progenitors that differentiate into distinct cortical and medullary epithelial cells to regulate the maturation and selection of self-tolerant CD4+ and CD8+ T cells. In addition to their differentiation, thymic epithelial cells undergo cellular expansion to ensure that sufficient intrathymic cellular niches are available to support the large number of immature thymocytes required to form a self-tolerant T-cell pool. Thus, intrathymic T-cell production is intimately linked to the formation and availability of niches within thymic microenvironments. Here, we show the increase in intrathymic niches caused by the proliferation of the epithelium in the developing thymus is temporally regulated, and correlates with the presence of a population of fetal thymic mesenchyme defined by platelet-derived growth factor receptor α (PDGFRα) expression. Depletion of PDGFRα+ mesenchyme from embryonic thymi prior to their transplantation to ectopic sites results in the formation of functional yet hypoplastic thymic tissue. In summary, we highlight a specialized role for PDGFRα+ fetal mesenchyme in the thymus by determining availability of thymic niches through the regulation of thymic epithelial proliferation.
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Affiliation(s)
- William E Jenkinson
- MRC Centre for Immune Regulation, Institute for Biomedical Research, University of Birmingham Medical School, UK
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24
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Gray DHD, Seach N, Ueno T, Milton MK, Liston A, Lew AM, Goodnow CC, Boyd RL. Developmental kinetics, turnover, and stimulatory capacity of thymic epithelial cells. Blood 2006; 108:3777-85. [PMID: 16896157 DOI: 10.1182/blood-2006-02-004531] [Citation(s) in RCA: 323] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Despite the importance of thymic stromal cells to T-cell development, relatively little is known about their biology. Here, we use single-cell analysis of stromal cells to analyze extensive changes in the number and composition of thymic stroma throughout life, revealing a surprisingly dynamic population. Phenotypic progression of thymic epithelial subsets was assessed at high resolution in young mice to provide a developmental framework. The cellular and molecular requirements of adult epithelium were studied, using various mutant mice to demonstrate new cross talk checkpoints dependent on RelB in the cortex and CD40 in the medulla. With the use of Ki67 and BrdU labeling, the turnover of thymic epithelium was found to be rapid, but then diminished on thymic involution. The various defects in stromal turnover and composition that accompanied involution were rapidly reversed following sex steroid ablation. Unexpectedly, mature cortical and medullary epithelium showed a potent capacity to stimulate naive T cells, comparable to that of thymic dendritic cells. Overall, these studies show that the thymic stroma is a surprisingly dynamic population and may have a more direct role in negative selection than previously thought.
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Affiliation(s)
- Daniel H D Gray
- Monash Immunology and Stem Cell Laboratories (MISCL), Level 3, STRIP, Building 75, Monash University, Wellington Road, Clayton, Victoria, 3800, Australia
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25
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Rossi SW, Jenkinson WE, Anderson G, Jenkinson EJ. Clonal analysis reveals a common progenitor for thymic cortical and medullary epithelium. Nature 2006; 441:988-91. [PMID: 16791197 DOI: 10.1038/nature04813] [Citation(s) in RCA: 240] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 04/10/2006] [Indexed: 01/12/2023]
Abstract
The thymus provides an essential environment for the development of T cells from haemopoietic progenitors. This environment is separated into cortical and medullary regions, each containing functionally distinct epithelial populations that are important at successive stages of T-cell development and selection. However, the developmental origin and lineage relationships between cortical and medullary epithelial cell types remain controversial. Here we describe a clonal assay to investigate the developmental potential of single, individually selected, thymic epithelial progenitors (marked with enhanced yellow fluorescent protein) developing within the normal architecture of the thymus. Using this approach, we show that cortical and medullary epithelial cells share a common origin in bipotent precursors, providing definitive evidence that they have a single rather than dual germ layer origin during embryogenesis. Our findings resolve a long-standing issue in thymus development, and are important in relation to the development of cell-based strategies for thymus disorders and the possibility of restoring function of the atrophied adult thymus.
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Affiliation(s)
- Simona W Rossi
- MRC Centre For Immune Regulation, Division of Immunity and Infection, Institute for Biomedical Research, Medical School, University of Birmingham, Birmingham B15 2TT, UK
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