Thymus: the next (re)generation

Integrating cuproptosis and immunosenescence: A novel therapeutic strategy in cancer treatment

Recent advancements in our understanding of cell death mechanisms have progressed beyond traditional apoptosis to encompass various forms of regulated cell death, notably cuproptosis. This copper-dependent cell death occurs when copper interacts with lipoylated enzymes in the tricarboxylic acid cycle, leading to protein aggregation and subsequent cell death. Alongside this, immunosenescence the gradual decline in immune function due to aging has emerged as a significant factor in cancer progression and response to treatment. Innovative strategies that integrate cuproptosis and immunosenescence are showing considerable promise in cancer therapy. By leveraging the altered copper metabolism in cancer cells, cuproptosis can selectively induce cell death, effectively targeting and eliminating tumors. Simultaneously, addressing immunosenescence can rejuvenate the aging immune system, enhancing its capacity to identify and destroy cancer cells. This dual approach creates a synergistic effect, optimizing therapeutic efficacy by directly attacking tumor cells while revitalizing the immune response. Such integration bolsters the defense against cancer progression and recurrence and holds great potential for advancing cancer treatment modalities and improving patient outcomes. This paper delves into the interactions between cuproptosis and immunosenescence, emphasizing their implications for developing innovative cancer therapies.

The Cellular and Molecular Characteristics of Postnatal Human Thymus Stromal Stem Cells

Background: The thymus is the central hub of T-cell differentiation, where epithelial cells guide the process of their maturation. Objective: Our goal was to identify and describe progenitor cells within the human thymus that can differentiate into epithelial cells. Methods: When we plated enriched thymic cells in 3D culture conditions, rare individual cells capable of self-renewal and differentiation formed spheroids. Results: Both neonatal and adult thymuses produced similar numbers of spheroids, suggesting that progenitor potential remains consistent across age groups. Some cells within the spheres express genes typical of mature epithelial cells, while others express genes associated with the immature compartment active during thymic organogenesis. However, there were also cells expressing PDGFRβ. We treated the tissues with 2-deoxyguanosine before digestion, which improved the yield of progenitor cells. We also cultured the enriched stromal thymocytes with Cyr61 and Interleukin-22, which affected the spheroid size. Conclusions: Our efforts towards thymic reconstitution are ongoing, but our research uncovers previously unknown characteristics of the elusive epithelial progenitor population.

Polydatin Alleviates Cyclophosphamide-Induced Mouse Immunosuppression by Promoting Splenic Lymphocyte Proliferation and Thymic T Cell Development and Differentiation

Immunosuppression increases disease risk, and the natural compound polydatin (PD) has been reported to modulate immune-related disorders. In cyclophosphamide-induced immunosuppressed mice, PD was evaluated for its immunomodulatory effects. Immune organ indices were measured, while H&E staining and ELISA assessed spleen pathology and serum cytokine levels. The proliferation of splenic lymphocytes, both total and subpopulation, was determined using concanavalin A or lipopolysaccharide stimulation, with flow cytometry analyzing peripheral blood and splenic lymphocytes, thymic T cell subtypes, cell cycling, and bromodeoxyuridine incorporation. Western blotting was used to assess Ki67, PCNA expression, and MAPK activation. PD significantly alleviated cyclophosphamide-induced reductions in spleen and thymus indices, improved the organization of red and white pulp in the spleen, and restored TNF-α and IFN-γ levels. It reversed cyclophosphamide-induced cell cycle arrest, characterized by increased PCNA and decreased Ki67, and corrected the diminished numbers of B and T cells and the reduced CD4+/CD8+ ratio in the thymus. In vitro, PD directly promoted splenic lymphocyte proliferation and cell cycling via MAPK activation. Overall, our findings demonstrated that PD alleviated mouse immunosuppression by activating splenic lymphocyte proliferation and re-organizing thymic T cell development and differentiation.

Effect of sakuranetin against cyclophosphamide-induced immunodeficiency mice: role of IFN-γ/TNF-α/IgG/IgM/interleukins

Cyclophosphamide is a widely used chemotherapeutic agent known for its effectiveness in treating various cancers; however, it is associated with significant immunosuppressive side effects. This study investigates the potential of sakuranetin, a natural flavonoid, in mice under cyclophosphamide-induced immunosuppressive conditions. Mice were grouped into four groups: one control group, two treated with cyclophosphamide and two sakuranetin-treated groups receiving different doses (10 and 20 mg/kg). Immune organ indices, lymphocyte proliferation, hematological parameters, nitric oxide levels, cytokines (tumor necrosis factor alpha-TNF-α, interferon γ-IFN-γ), interleukins (interleukin-1β-IL-1β, IL-4, IL-6), immunoglobulin G (IgG), IgM levels, plague-forming cells quantification, qualitative hemolysis, and delayed-type hypersensitivity were assessed. Cyclophosphamide significantly (P < 0.05) reduced immune organ indices, lymphocyte proliferation, changes in hematological parameters, and nitric oxide levels. Treatment with both sakuranetin doses restored these parameters and normalized cytokine, IgG, and IgM levels (P < 0.05). Sakuranetin significantly (P < 0.05) improved the immunomodulatory action with elevated immune response with downregulation in immune response mediated by cells. Sakuranetin effectively counteracts cyclophosphamide-induced immunosuppression by modulating the IFN-γ, TNF-α, IgG, and interleukin pathway, suggesting its potential as a protective agent.

Morphological characteristics of microenvironment in the human thymus during fetal development

BACKGROUND

The thymus is a key organ for the development of T cells. T cell precursors first migrate from the bone marrow to the thymus. During maturation, these precursors require interactions with various types of cells that form the thymic microenvironment, such as epithelial, mesenchymal, and other immune cells not belonging to the T lineage. The aim of this study was to examine the changes in the number and diameter of Hassall's corpuscles, as well as the density and distribution of epithelial cells (p63+) and macrophages (CD68+).

METHODS

Twenty-five fetal thymus samples were examined, divided into five groups according to gestational age. The samples were processed using standard histological methods and immunohistochemical staining.

RESULTS

The study showed that the number and diameter of Hassall's corpuscles gradually increased during fetal development, with a significant increase from the 14th to the 38th gestational week. The average diameter of Hassall's corpuscles was largest in the age group of 34-38 weeks. The density of p63 + epithelial cells decreased in correlation with gestational week, while the density of CD68 + macrophages significantly increased, particularly in the thymic medulla, towards the end of the fetal period.

CONCLUSIONS

An increase in the number and size of Hassall's corpuscles during fetal development was recorded, while the density of epithelial cells decreased and the density of macrophages increased.

Recirculating regulatory T cells mediate thymic regeneration through amphiregulin following damage

Thymic injury associated with disease or cancer treatment reduces T cell production and makes patients more vulnerable to infections and cancers. Here, we examined the role of regulatory T (Treg) cells on thymic regeneration. Treg cell frequencies increased in the thymus in various acute injury models. Depletion of Treg cells impaired thymic regeneration, impacting both the thymocyte compartment and the stromal cell compartment; adoptive transfer of Treg cells enhanced regeneration. Expansion of circulating Treg cells, as opposed to that of tissue resident or recent thymic emigrants, explained this increase, as seen using parabiotic and adoptive transfer models. Single-cell analyses of recirculating Treg cells revealed expression of various regenerative factors, including the cytokine amphiregulin. Deletion of amphiregulin in these Treg cells impaired regeneration in the injured thymus. We identified an analogous population of CD39+ICOS+ Treg cells in the human thymus. Our findings point to potential therapeutic avenues to address aging- and treatment-induced immunosuppression.

The immunosenescence clock: A new method for evaluating biological age and predicting mortality risk

Precisely assessing an individual's immune age is critical for developing targeted aging interventions. Although traditional methods for evaluating biological age, such as the use of cellular senescence markers and physiological indicators, have been widely applied, these methods inherently struggle to capture the full complexity of biological aging. We propose the concept of an 'immunosenescence clock' that evaluates immune system changes on the basis of changes in immune cell abundance and omics data (including transcriptome and proteome data), providing a complementary indicator for understanding age-related physiological transformations. Rather than claiming to definitively measure biological age, this approach can be divided into a biological age prediction clock and a mortality prediction clock. The main function of the biological age prediction clock is to reflect the physiological state through the transcriptome data of peripheral blood mononuclear cells (PBMCs), whereas the mortality prediction clock emphasizes the ability to identify people at high risk of mortality and disease. We hereby present nearly all of the immunosenescence clocks developed to date, as well as their functional differences. Critically, we explicitly acknowledge that no single diagnostic test can exhaustively capture the intricate changes associated with biological aging. Furthermore, as these biological functions are based on the acceleration or delay of immunosenescence, we also summarize the factors that accelerate immunosenescence and the methods for delaying it. A deep understanding of the regulatory mechanisms of immunosenescence can help establish more accurate immune-age models, providing support for personalized longevity interventions and improving quality of life in old age.

Thymic microenvironment's impact on immunosenescence

Age-related thymic involution is characterized by the loss of T cell development and the supporting epithelial network, which are replaced by adipose tissue. We previously showed that aging functionally impairs lymphohematopoietic progenitor cells, including thymic early T cell progenitors (ETPs), contributing to thymic involution. Considering that the thymic microenvironment is essential for thymocyte incubation, we aimed to investigate its role in age-related thymic involution and the mechanisms underlying these changes. The challenge in studying these processes led us to transplant T cell-depleted fetal thymus tissue into the kidney capsule of aged mice. This model allowed us to identify the mechanisms driving age-related changes in the thymic microenvironment and to assess whether these changes could be reversed. Flow cytometry was used to detect naïve T cells (CD62L+CD44-), including CD4 CD8 double-negative, double-positive, and single-positive T cells. Real-time PCR was used to detect and quantify signal-joint T cell receptor excision circles. We rearranged δRec-ΨJα in murine peripheral blood leukocytes to evaluate the thymic output of newly developed naïve T cells in the mice and gene expression in the thymus. Age-related thymic involution decreased naïve T cells and increased memory T cells, while fetal thymus transplantation improved thymic output and T cell production and reversed the impairment of thymopoiesis due to thymic involution in aged mice. Furthermore, the expression of key cytokines was restored and ETPs in the aged mice showed normal thymic T cell development. Our study suggests that degenerative changes in the thymic microenvironment are the primary cause of thymic dysfunction, leading to immunosenescence associated with age-related thymic involution.

Thymic epithelial organoids mediate T-cell development

Although the advent of organoids has opened unprecedented perspectives for basic and translational research, immune system-related organoids remain largely underdeveloped. Here, we established organoids from the thymus, the lymphoid organ responsible for T-cell development. We identified conditions enabling mouse thymic epithelial progenitor cell proliferation and development into organoids with diverse cell populations and transcriptional profiles resembling in vivo thymic epithelial cells (TECs) more closely than traditional TEC cultures. In contrast to these two-dimensional cultures, thymic epithelial organoids maintained thymus functionality in vitro and mediated physiological T-cell development upon reaggregation with T-cell progenitors. The reaggregates showed in vivo-like epithelial diversity and the ability to attract T-cell progenitors. Thymic epithelial organoids are the first organoids originating from the stromal compartment of a lymphoid organ. They provide new opportunities to study TEC biology and T-cell development in vitro, paving the way for future thymic regeneration strategies in ageing or acute injuries.

Thymus transplantation as immunotherapy for the enhancement and/or correction of T cell function

The thymus is where T cells, among the most important immune cells involved in biological defense and homeostasis, are produced and developed. The thymus plays an important role in the defense against infection and cancer as well as the prevention of autoimmune diseases. However, the thymus gland atrophies with age, which might have pathological functions, and in some circumstances, there is a congenital defect in the thymus. These can be the cause of many diseases related to the dysregulation of T cell functions. Thus, the enhancement and/or normalization of thymic function may lead to protection against and treatment of a wide variety of diseases. Therefore, thymus transplantation is considered a strong candidate for permanent treatment. The status and issues related to thymus transplantation for possible immunotherapy are discussed although it is still at an early stage of development.

Intravital two-photon microscopy of the native mouse thymus

The thymus, a key organ in the adaptive immune system, is sensitive to a variety of insults including cytotoxic preconditioning, which leads to atrophy, compression of the blood vascular system, and alterations in hemodynamics. Although the thymus has innate regenerative capabilities, the production of T cells relies on the trafficking of lymphoid progenitors from the bone marrow through the altered thymic blood vascular system. Our understanding of thymic blood vascular hemodynamics is limited due to technical challenges associated with accessing the native thymus in live mice. To overcome this challenge, we developed an intravital two-photon imaging method to visualize the native thymus in vivo and investigated functional changes to the vascular system following sublethal irradiation. We quantified blood flow velocity and shear rate in cortical blood vessels and identified a subtle but significant increase in vessel leakage and diameter ~24 hrs post-sublethal irradiation. Ex vivo whole organ imaging of optically cleared thymus lobes confirmed a disruption of the thymus vascular structure, resulting in an increase in blood vessel diameter and vessel area, and concurrent thymic atrophy. This novel two-photon intravital imaging method enables a new paradigm for directly investigating the thymic microenvironment in vivo.

Epigallocatechin-3-gallate ameliorates lipopolysaccharide-induced acute thymus involution in mice via AMPK/Sirt1 pathway

The thymus, a site to culture the naïve T lymphocytes, is susceptible to atrophy or involution due to aging, inflammation, and oxidation. Epigallocatechin-3-gallate (EGCG) has been proven to possess anti-inflammatory, antioxidant, and antitumor activity. Here, we investigate the effects of EGCG on thymic involution induced by lipopolysaccharide (LPS), an endotoxin derived from Gram-negative bacteria. The methodology included an in vivo experiment on female Kunming mice exposed to LPS and EGCG. Morphological assessment of thymic involution, immunohistochemical detection, and thymocyte subsets analysis by flow cytometry were further carried out to evaluate the potential role of EGCG on the thymus. As a result, we found that EGCG alleviated LPS-induced thymic atrophy, increased mitochondrial membrane potential and superoxide dismutase levels, and decreased malondialdehyde and reactive oxygen species levels. In addition, EGCG pre-supplement restored the ratio of thymocyte subsets, the expression of autoimmune regulator, sex-determining region Y-box 2, and Nanog homebox, and reduced the number of senescent cells and collagen fiber deposition. Western blotting results indicated that EGCG treatment elevated LPS-induced decrease in pAMPK, Sirt1 protein expression. Collectively, EGCG relieved thymus architecture and function damaged by LPS via regulation of AMPK/Sirt1 signaling pathway. Our findings may provide a new strategy on protection of thymus from involution caused by LPS by using EGCG. And EGCG might be considered as a potential agent for the prevention and treatment of thymic involution.

Shape of the art: TCR-repertoire after allogeneic hematopoietic cell transplantation

The human adaptive immune repertoire is characterized by specificity and diversity to provide immunity against past and future tasks. Such tasks are mainly infections but also malignant transformations of cells. With its multiple lines of defense, the human immune system contains both, rapid reaction forces and the potential to capture, disassemble and analyze strange structures in order to teach the adaptive immune system and mount a specific immune response. Prevention and mitigation of autoimmunity is of equal importance. In the context of allogeneic hematopoietic cell transplantation (HCT) specific challenges exist with the transfer of cells from the adapted donor immune system to the immunosuppressed recipient. Those challenges are immunogenetic disparity between donor and host, reconstitution of immunity early after HCT by expansion of mature immune effector cells, and impaired thymic function, if the recipient is an adult (as it is the case in most HCTs). The possibility to characterize the adaptive immune repertoire by massively parallel sequencing of T-cell receptor gene rearrangements allows for a much more detailed characterization of the T-cell repertoire. In addition, high-dimensional characterization of immune effector cells based on their immunophenotype and single cell RNA sequencing allow for much deeper insights in adaptive immune responses. We here review, existing - still incomplete - information on immune reconstitution after allogeneic HCT. Building on the technological advances much deeper insights into immune recovery after HCT and adaptive immune responses and can be expected in the coming years.

CD4+ T-Cell Senescence in Neurodegenerative Disease: Pathogenesis and Potential Therapeutic Targets

With the increasing proportion of the aging population, neurodegenerative diseases have become one of the major health issues in society. Neurodegenerative diseases (NDs), including multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), are characterized by progressive neurodegeneration associated with aging, leading to a gradual decline in cognitive, emotional, and motor functions in patients. The process of aging is a normal physiological process in human life and is accompanied by the aging of the immune system, which is known as immunosenescence. T-cells are an important part of the immune system, and their senescence is the main feature of immunosenescence. The appearance of senescent T-cells has been shown to potentially lead to chronic inflammation and tissue damage, with some studies indicating a direct link between T-cell senescence, inflammation, and neuronal damage. The role of these subsets with different functions in NDs is still under debate. A growing body of evidence suggests that in people with a ND, there is a prevalence of CD4+ T-cell subsets exhibiting characteristics that are linked to senescence. This underscores the significance of CD4+ T-cells in NDs. In this review, we summarize the classification and function of CD4+ T-cell subpopulations, the characteristics of CD4+ T-cell senescence, the potential roles of these cells in animal models and human studies of NDs, and therapeutic strategies targeting CD4+ T-cell senescence.

Derivation of functional thymic epithelial organoid lines from adult murine thymus

Thymic epithelial cells (TECs) orchestrate T cell development by imposing positive and negative selection on thymocytes. Current studies on TEC biology are hampered by the absence of long-term ex vivo culture platforms, while the cells driving TEC self-renewal remain to be identified. Here, we generate long-term (>2 years) expandable 3D TEC organoids from the adult mouse thymus. For further analysis, we generated single and double FoxN1-P2A-Clover, Aire-P2A-tdTomato, and Cldn4-P2A-tdTomato reporter lines by CRISPR knockin. Single-cell analyses of expanding clonal organoids reveal cells with bipotent stem/progenitor phenotypes. These clonal organoids can be induced to express Foxn1 and to generate functional cortical- and Aire-expressing medullary-like TECs upon RANK ligand + retinoic acid treatment. TEC organoids support T cell development from immature thymocytes in vitro as well as in vivo upon transplantation into athymic nude mice. This organoid-based platform allows in vitro study of TEC biology and offers a potential strategy for ex vivo T cell development.

Morphometric Analysis of the Thymic Epithelial Cell (TEC) Network Using Integrated and Orthogonal Digital Pathology Approaches

The thymus, a central primary lymphoid organ of the immune system, plays a key role in T cell development. Surprisingly, the thymus is quite neglected with regards to standardized pathology approaches and practices for assessing structure and function. Most studies use multispectral flow cytometry to define the dynamic composition of the thymus at the cell population level, but they are limited by lack of contextual insight. This knowledge gap hinders our understanding of various thymic conditions and pathologies, particularly how they affect thymic architecture, and subsequently, immune competence. Here, we introduce a digital pathology pipeline to address these challenges. Our approach can be coupled to analytical algorithms and utilizes rationalized morphometric assessments of thymic tissue, ranging from tissue-wide down to microanatomical and ultrastructural levels. This pipeline enables the quantitative assessment of putative changes and adaptations of thymic structure to stimuli, offering valuable insights into the pathophysiology of thymic disorders. This versatile pipeline can be applied to a wide range of conditions that may directly or indirectly affect thymic structure, ranging from various cytotoxic stimuli inducing acute thymic involution to autoimmune diseases, such as myasthenia gravis. Here, we demonstrate applicability of the method in a mouse model of age-dependent thymic involution, both by confirming established knowledge, and by providing novel insights on intrathymic remodeling in the aged thymus. Our orthogonal pipeline, with its high versatility and depth of analysis, promises to be a valuable and practical toolset for both basic and translational immunology laboratories investigating thymic function and disease.

Primary and secondary defects of the thymus

The thymus is the primary site of T-cell development, enabling generation, and selection of a diverse repertoire of T cells that recognize non-self, whilst remaining tolerant to self- antigens. Severe congenital disorders of thymic development (athymia) can be fatal if left untreated due to infections, and thymic tissue implantation is the only cure. While newborn screening for severe combined immune deficiency has allowed improved detection at birth of congenital athymia, thymic disorders acquired later in life are still underrecognized and assessing the quality of thymic function in such conditions remains a challenge. The thymus is sensitive to injury elicited from a variety of endogenous and exogenous factors, and its self-renewal capacity decreases with age. Secondary and age-related forms of thymic dysfunction may lead to an increased risk of infections, malignancy, and autoimmunity. Promising results have been obtained in preclinical models and clinical trials upon administration of soluble factors promoting thymic regeneration, but to date no therapy is approved for clinical use. In this review we provide a background on thymus development, function, and age-related involution. We discuss disease mechanisms, diagnostic, and therapeutic approaches for primary and secondary thymic defects.

An integrative mechanistic model of thymocyte dynamics

Background

The thymus plays a central role in shaping human immune function. A mechanistic, quantitative description of immune cell dynamics and thymic output under homeostatic conditions and various patho-physiological scenarios are of particular interest in drug development applications, e.g., in the identification of potential therapeutic targets and selection of lead drug candidates against infectious diseases.

Methods

We here developed an integrative mathematical model of thymocyte dynamics in human. It incorporates mechanistic features of thymocyte homeostasis as well as spatial constraints of the thymus and considerations of age-dependent involution. All model parameter estimates were obtained based on published physiological data of thymocyte dynamics and thymus properties in mouse and human. We performed model sensitivity analyses to reveal potential therapeutic targets through an identification of processes critically affecting thymic function; we further explored differences in thymic function across healthy subjects, multiple sclerosis patients, and patients on fingolimod treatment.

Results

We found thymic function to be most impacted by the egress, proliferation, differentiation and death rates of those thymocytes which are most differentiated. Model predictions also showed that the clinically observed decrease in relapse risk with age, in multiple sclerosis patients who would have discontinued fingolimod therapy, can be explained mechanistically by decreased thymic output with age. Moreover, we quantified the effects of fingolimod treatment duration on thymic output.

Conclusions

In summary, the proposed model accurately describes, in mechanistic terms, thymic output as a function of age. It may be further used to perform predictive simulations of clinically relevant scenarios which combine specific patho-physiological conditions and pharmacological interventions of interest.

Transcriptional profile of human thymus reveals IGFBP5 is correlated with age-related thymic involution

Thymus is the main immune organ which is responsible for the production of self-tolerant and functional T cells, but it shrinks rapidly with age after birth. Although studies have researched thymus development and involution in mouse, the critical regulators that arise with age in human thymus remain unclear. We collected public human single-cell transcriptomic sequencing (scRNA-seq) datasets containing 350,678 cells from 36 samples, integrated them as a cell atlas of human thymus. Clinical samples were collected and experiments were performed for validation. We found early thymocyte-specific signaling and regulons which played roles in thymocyte migration, proliferation, apoptosis and differentiation. Nevertheless, signaling patterns including number, strength and path completely changed during aging, Transcription factors (FOXC1, MXI1, KLF9, NFIL3) and their target gene, IGFBP5, were resolved and up-regulated in aging thymus and involved in promoting epithelial-mesenchymal transition (EMT), responding to steroid and adipogenesis process of thymic epithelial cell (TECs). Furthermore, we validated that IGFBP5 protein increased at TECs and Hassall's corpuscle in both human and mouse aging thymus and knockdown of IGFBP5 significantly increased the expression of proliferation-related genes in thymocytes. Collectively, we systematically explored cell-cell communications and regulons of early thymocytes as well as age-related differences in human thymus by using both bioinformatic and experimental verification, indicating IGFBP5 as a functional marker of thymic involution and providing new insights into the mechanisms of thymus involution.

Tuft cells and fibroblasts promote thymus regeneration through ILC2-mediated type 2 immune response

The thymus is a primary lymphoid organ that is essential for the establishment of adaptive immunity through generation of immunocompetent T cells. In response to various stress signals, the thymus undergoes acute but reversible involution. However, the mechanisms governing its recovery are incompletely understood. Here, we used a dexamethasone-induced acute thymic involution mouse model to investigate how thymic hematopoietic cells (excluding T cells) contribute to thymic regeneration. scRNA-seq analysis revealed marked transcriptional and cellular changes in various thymic populations and highlighted thymus-resident innate lymphoid cells type 2 (ILC2) as a key cell type involved in the response to damage. We identified that ILC2 are activated by the alarmins IL-25 and IL-33 produced in response to tissue damage by thymic tuft cells and fibroblasts, respectively. Moreover, using mouse models deficient in either tuft cells and/or IL-33, we found that these alarmins are required for effective thymus regeneration after dexamethasone-induced damage. We also demonstrate that upon their damage-dependent activation, thymic ILC2 produce several effector molecules linked to tissue regeneration, such as amphiregulin and IL-13, which in turn promote thymic epithelial cell differentiation. Collectively, our study elucidates a previously undescribed role for thymic tuft cells and fibroblasts in thymus regeneration through activation of the type 2 immune response.

Characteristics of immune cells and causal relationship with chondromalacia: A two-sample, bidirectional mendelian randomization study

Chondromalacia, characterized by the softening of cartilage, is a prevalent condition affecting joint health with complex etiology. The immune system's role in its pathogenesis has been implicated but remains to be fully elucidated. To address a critical knowledge gap, we conducted a two-sample Mendelian randomization analysis of 731 immune cell phenotypes, assessing parameters like fluorescence, cell count, and morphology. After sensitivity and pleiotropy checks, and applying a false discovery rate correction, our study linked 17 phenotypes to chondromalacia (p < .05). Among them, seven immune cell phenotypes were found to have a protective effect against chondromalacia (IVW: p < .05, OR <1), while 10 were considered risk factors (IVW:p < .05, OR >1). Despite the constraints of sample size and possible genetic differences among populations, our research has identified a notable genetic correlation between specific immune cell indicators and chondromalacia. This breakthrough sheds light on the pathophysiological mechanisms of the condition. The identification of protective and risk-associated immune cell phenotypes provides a foundation for further exploration of immunological mechanisms in chondromalacia and may pave the way for targeted interventions. Future research is warranted to validate these findings and explore their clinical implications.

Thymus as Incontrovertible Target of Future Immune Modulatory Therapeutics

Thymus plays a crucial role in cellular immunity by acting as a warehouse for proliferating and differentiating lymphocytes. Thymic stromal cells educate T-cells to differentiate self from non-self antigens while nurse cells and thymoproteasome play a major role in the maturation and differentiation of T-cells. The thymic conditions dictate T-cells to cope with the risk of cancer development. A study was designed to demonstrate potential mechanisms behind the failure to eliminate tumors and impaired immune surveillance as well as the impact of delay in thymus regression on cancer and autoimmune disorders. Scientific literature from Pubmed; Scopus; WOS; JSTOR; National Library of Medicine Bethesda, Maryland; The New York Academy of Medicine; Library of Speech Rehabilitation, NY; St. Thomas' Hospital Library; The Wills Library of Guys Hospital; Repository of Kings College London; and Oxford Academic repository was explored for pathological, physiological, immunological and toxicological studies of thymus. Studies have shown that systemic chemotherapy may lead to micro inflammatory environment within thymus where conventionally and dynamically metastasized dormant cells seek refuge. The malfunctioning of the thymus and defective T and Treg cells, bypassing negative selection, contributes to autoimmune disorders, while AIRE and Fezf2 play significant roles in thymic epithelial cell solidity. Different vitamins, TCM, and live cell therapy are effective therapeutics. Vitamin A, C, D, and E, selenium and zinc, cinobufagin and dietary polysaccharides, and glandular extracts and live cell injections have strong potential to restore immune system function and thymus health. Moreover, the relationship between different ages/ stages of thymus and their corresponding T-cell mediated anti-tumor immune response needs further exploration.

Modeling frameworks for radiation induced lymphopenia: A critical review

Radiation-induced lymphopenia (RIL) is a frequent, and often considered unavoidable, side effect of radiation therapy (RT), whether or not chemotherapy is included. However, in the last few years several studies have demonstrated the detrimental effect of RIL on therapeutic outcomes, with conflicting findings concerning possible inferior patient survival. In addition, since immunotherapeutic treatment has become an integral part of cancer therapy, preserving the immune system is recognized as crucial. Given this background, various research groups have reported on different frameworks for modelling RIL, frequently based on different definitions of RIL itself, and discordant results have been reported. Our aim is to critically review the current literature on RIL modelling and summarize the different approaches recently proposed to improve the prediction of RIL after RT and aimed at immunity-sparing RT. A detailed description of these approaches will be outlined and illustrated through their applications as found in the literature from the last five years. Such a critical analysis represents the necessary starting step to develop an effective strategy that ultimately could harmonize the diverse modelling methods.

The alarmin IL33 orchestrates type 2 immune-mediated control of thymus regeneration

As the primary site of T-cell development, the thymus dictates immune competency of the host. The rates of thymus function are not constant, and thymus regeneration is essential to restore new T-cell production following tissue damage from environmental factors and therapeutic interventions. Here, we show the alarmin interleukin (IL) 33 is a product of Sca1+ thymic mesenchyme both necessary and sufficient for thymus regeneration via a type 2 innate immune network. IL33 stimulates expansion of IL5-producing type 2 innate lymphoid cells (ILC2), which triggers a cellular switch in the intrathymic availability of IL4. This enables eosinophil production of IL4 to re-establish thymic mesenchyme prior to recovery of thymopoiesis-inducing epithelial compartments. Collectively, we identify a positive feedback mechanism of type 2 innate immunity that regulates the recovery of thymus function following tissue injury.

Aryl hydrocarbon receptor regulates IL-22 receptor expression on thymic epithelial cell and accelerates thymus regeneration

Improving regeneration of damaged thymus is important for reconstituting T-cell immunity. Interleukin-22 (IL-22) was proved to improve thymus regeneration through recovering thymic epithelial cells (TECs). The IL-22 receptor IL-22RA1 is crucial for mediating IL-22 functions. Mechanism that regulates IL-22RA1 expression is unknown. Through using TECs-conditional knockout mice, we found aryl hydrocarbon receptor (AHR) is important for thymus regeneration, because Foxn1-cre-mediated AHR knockout (AhrKO) significantly blocks recovery of thymus cells. Giving mice the AHR inhibitor CH-223191 or the AHR agonist FICZ blocks or accelerates thymus regeneration, respectively. AhrKO-mediated blockade of thymus regeneration could not be rescued by giving exogenous IL-22. Mechanistically, AhrKO mice shows decreased IL-22RA1 expression. In the murine TECs cell line mTEC1 cells, targeting AHR shows an impact on IL-22RA1 mRNA levels. Using chromatin immunoprecipitation and luciferase reporter assays, we find AHR co-operates with STAT3, binds the promotor region of IL-22RA1 gene and transcriptionally increases IL-22RA1 expression in mTEC1 cells. Foxn1-cre-mediated IL-22RA1 knockout (Il22ra1KO) blocks thymus regeneration after irradiation. Furthermore, targeting AHR or IL-22RA1 has significant impacts on severity of murine chronic graft-versus-host disease (cGVHD), which is an autoimmune-like complication following allogeneic hematopoietic cell transplantation. Giving FICZ decreases cGVHD, whereas Il22ra1KO exacerbates cGVHD. The impacts on cGVHD are associated with thymus regeneration and T-cell immune reconstitution. In conclusion, we report an unrecognized function of TECs-expressed AHR in thymus regeneration and AHR transcriptionally regulates IL-22RA1 expression, which have implications for improving thymus regeneration and controlling cGVHD.

Disorganization of secondary lymphoid organs and dyscoordination of chemokine secretion as key contributors to immune aging

Aging is characterized by progressive loss of organ and tissue function, and the immune system is no exception to that inevitable principle. Of all the age-related changes in the body, reduction of the size of, and naïve T (Tn) cell output from, the thymus occurs earliest, being prominent already before or by the time of puberty. Therefore, to preserve immunity against new infections, over much of their lives, vertebrates dominantly rely on peripheral maintenance of the Tn cell pool in the secondary lymphoid organs (SLO). However, SLO structure and function subsequently also deteriorate with aging. Several recent studies have made a convincing case that this deterioration is of major importance to the erosion of protective immunity in the last third of life. Specifically, the SLO were found to accumulate multiple degenerative changes with aging. Importantly, the results from adoptive transfer and parabiosis studies teach us that the old microenvironment is the limiting factor for protective immunity in old mice. In this review, we discuss the extent, mechanisms, and potential role of stromal cell aging in the age-related alteration of T cell homeostatic maintenance and immune function decline. We use that discussion to frame the potential strategies to correct the SLO stromal aging defects - in the context of other immune rejuvenation approaches, - to improve functional immune responses and protective immunity in older adults.

Fish Collagen Peptides Enhance Thymopoietic Gene Expression, Cell Proliferation, Thymocyte Adherence, and Cytoprotection in Thymic Epithelial Cells via Activation of the Nuclear Factor-κB Pathway, Leading to Thymus Regeneration after Cyclophosphamide-Induced Injury

Prolonged thymic involution results in decreased thymopoiesis and thymic output, leading to peripheral T-cell deficiency. Since the thymic-dependent pathway is the only means of generating fully mature T cells, the identification of strategies to enhance thymic regeneration is crucial in developing therapeutic interventions to revert immune suppression in immunocompromised patients. The present study clearly shows that fish collagen peptides (FCPs) stimulate activities of thymic epithelial cells (TECs), including cell proliferation, thymocyte adhesion, and the gene expression of thymopoietic factors such as FGF-7, IGF-1, BMP-4, VEGF-A, IL-7, IL-21, RANKL, LTβ, IL-22R, RANK, LTβR, SDF-1, CCL21, CCL25, CXCL5, Dll1, Dll4, Wnt4, CD40, CD80, CD86, ICAM-1, VCAM-1, FoxN1, leptin, cathepsin L, CK5, and CK8 through the NF-κB signal transduction pathway. Furthermore, our study also revealed the cytoprotective effects of FCPs on TECs against cyclophosphamide-induced cellular injury through the NF-κB signaling pathway. Importantly, FCPs exhibited a significant capability to facilitate thymic regeneration in mice after cyclophosphamide-induced damage via the NF-κB pathway. Taken together, this study sheds light on the role of FCPs in TEC function, thymopoiesis, and thymic regeneration, providing greater insight into the development of novel therapeutic strategies for effective thymus repopulation for numerous clinical conditions in which immune reconstitution is required.

Active immunization against gonadotropin-releasing hormone affects thymic T cell production, migration, and colonization in male rat lymphoid tissue

Active immunization against gonadotropin-releasing hormone (GnRH) inhibits animal reproduction and has become a friendly alternative to surgical castration, which has been reported to affect the proportion of thymic T cell subpopulations. The effects of active immunization against GnRH on T cell migration from the thymus to the periphery and T cell distribution in lymphoid tissues remain unclear. Here, we showed that active immunization against GnRH increased thymic size and weight, enlarged the number of thymocytes, and enhanced CD4+ recent thymic emigrants (RTEs) and CD8+ RTEs migration to the blood and spleen. Active immunization against GnRH had no significant effect on naïve CD4+, naïve CD8+, CD4+ memory/activated, or CD8+ memory/activated T cells. In addition, active immunization against GnRH increased the proportion of CD3+ T cells in the spleen and lymph nodes. The percentages of CD3+CD4+ and CD3+CD8+ T cells in the blood, spleen, and lymph nodes were not significantly affected by GnRH immunization. Overall, these results enhance our understanding of thymic T cell production, migration, and colonization in rat lymphoid tissues affected by GnRH immunization.

Does the Thymus Index Predict COVID-19 Severity?

BACKGROUND

The COVID-19 (coronavirus disease 2019) pandemic is a global health emergency that is straining health care resources. Identifying patients likely to experience severe illness would allow more targeted use of resources. This study aimed to investigate the association between the thymus index (TI) on thorax computed tomography (CT) and prognosis in patients with COVID-19.

METHODS

A multicenter, cross-sectional, retrospective study was conducted between March 17 and June 30, 2020, in patients with confirmed COVID-19. The patients' clinical history and laboratory data were collected after receiving a signed consent form. Four experienced radiologists who were blinded to each other and patient data performed image evaluation. The appearance of the thymus was assessed in each patient using 2 published systems, including the TI and thymic morphology. Exclusion criteria were lack of initial diagnostic thoracic CT, previous sternotomy, pregnancy, and inappropriate images for thymic evaluation. A total of 2588 patients with confirmed COVID-19 and 1231 of these with appropriate thoracic CT imaging were included. Multivariable analysis was performed to predict the risk of severe disease and mortality.

RESULTS

The median age was 45 (interquartile range, 33-58) years; 52.2% were male. Two hundred forty-nine (20.2%) patients had severe disease, and 60 (4.9%) patients died. Thymus index was significantly associated with mortality and severe disease (odds ratios, 0.289 [95% confidence interval, 0.141-0.588; P = 0.001]; and 0.266 [95% confidence interval, 0.075-0.932; P = 0.038]), respectively. Perithymic lymphadenopathy on CT imaging had a significantly strong association with grades of TI in patients with severe disease and death ( V = 0.413 P = 0.017; and V = 0.261 P = 0.002, respectively). A morphologically assessable thymus increased the probability of survival by 17-fold and the absence of severe disease by 12-fold.

CONCLUSION

Assessment of the thymus in patients with COVID-19 may provide useful prognostic data for both disease severity and mortality.

An induced thymic epithelial cell-based high throughput screen for thymus extracellular matrix mimetics

Thymic epithelial cells (TECs) are key effectors of the thymic stroma and are critically required for T-cell development. TECs comprise a diverse set of related but functionally distinct cell types that are scarce and difficult to isolate and handle. This has precluded TEC-based screening assays. We previously described induced thymic epithelial cells (iTECs), an artificial cell type produced in vitro by direct reprogramming, raising the possibility that iTECs might provide the basis for functional screens related to TEC biology. Here, we present an iTEC-based three-stage medium/high-throughput in vitro assay for synthetic polymer mimics of thymic extracellular matrix (ECM). Using this assay, we identified, from a complex library, four polymers that bind iTEC as well as or better than gelatin but do not bind mesenchymal cells. We show that these four polymers also bind and maintain native mouse fetal TECs and native human fetal TECs. Finally, we show that the selected polymers do not interfere with iTEC function or T-cell development. Collectively, our data establish that iTECs can be used to screen for TEC-relevant compounds in at least some medium/high-throughput assays and identify synthetic polymer ECM mimics that can replace gelatin or ECM components in TEC culture protocols.

Aging and CMV Infection Affect Pre-existing SARS-CoV-2-Reactive CD8+ T Cells in Unexposed Individuals

Age is a major risk factor for COVID-19 severity, and T cells play a central role in anti-SARS-CoV-2 immunity. Because SARS-CoV-2-cross-reactive T cells have been detected in unexposed individuals, we investigated the age-related differences in pre-existing SARS-CoV-2-reactive T cells. SARS-CoV-2-reactive CD4⁺ T cells from young and elderly individuals were mainly detected in the central memory fraction and exhibited similar functionalities and numbers. Naïve-phenotype SARS-CoV-2-reactive CD8⁺ T cell populations decreased markedly in the elderly, while those with terminally differentiated and senescent phenotypes increased. Furthermore, senescent SARS-CoV-2-reactive CD8⁺ T cell populations were higher in cytomegalovirus seropositive young individuals compared to seronegative ones. Our findings suggest that age-related differences in pre-existing SARS-CoV-2-reactive CD8⁺ T cells may explain the poor outcomes in elderly patients and that cytomegalovirus infection is a potential factor affecting CD8⁺ T cell immunity against SARS-CoV-2. Thus, this study provides insights for developing effective therapeutic and vaccination strategies for the elderly.

Age-related thymic involution: Mechanisms and functional impact

The thymus is the primary immune organ responsible for generating self‐tolerant and immunocompetent T cells. However, the thymus gradually involutes during early life resulting in declined naïve T‐cell production, a process known as age‐related thymic involution. Thymic involution has many negative impacts on immune function including reduced pathogen resistance, high autoimmunity incidence, and attenuated tumor immunosurveillance. Age‐related thymic involution leads to a gradual reduction in thymic cellularity and thymic stromal microenvironment disruption, including loss of definite cortical‐medullary junctions, reduction of cortical thymic epithelial cells and medullary thymic epithelial cells, fibroblast expansion, and an increase in perivascular space. The compromised thymic microenvironment in aged individuals substantially disturbs thymocyte development and differentiation. Age‐related thymic involution is regulated by many transcription factors, micro RNAs, growth factors, cytokines, and other factors. In this review, we summarize the current understanding of age‐related thymic involution mechanisms and effects.

A Proposed Link Between Acute Thymic Involution and Late Adverse Effects of Chemotherapy

Epidemiologic data suggest that cancer survivors tend to develop a protuberant number of adverse late effects, including second primary malignancies (SPM), as a result of cytotoxic chemotherapy. Besides the genotoxic potential of these drugs that directly inflict mutational burden on genomic DNA, the precise mechanisms contributing to SPM development are poorly understood. Cancer is nowadays perceived as a complex process that goes beyond the concept of genetic disease and includes tumor cell interactions with complex stromal and immune cell microenvironments. The cancer immunoediting theory offers an explanation for the development of nascent neoplastic cells. Briefly, the theory suggests that newly emerging tumor cells are mostly eliminated by an effective tissue immunosurveillance, but certain tumor variants may occasionally escape innate and adaptive mechanisms of immunological destruction, entering an equilibrium phase, where immunologic tumor cell death "equals" new tumor cell birth. Subsequent microenvironmental pressures and accumulation of helpful mutations in certain variants may lead to escape from the equilibrium phase, and eventually cause an overt neoplasm. Cancer immunoediting functions as a dedicated sentinel under the auspice of a highly competent immune system. This perspective offers the fresh insight that chemotherapy-induced thymic involution, which is characterized by the extensive obliteration of the sensitive thymic epithelial cell (TEC) compartment, can cause long-term defects in thymopoiesis and in establishment of diverse T cell receptor repertoires and peripheral T cell pools of cancer survivors. Such delayed recovery of T cell adaptive immunity may result in prolonged hijacking of the cancer immunoediting mechanisms, and lead to development of persistent and mortal infections, inflammatory disorders, organ-specific autoimmunity lesions, and SPMs. Acknowledging that chemotherapy-induced thymic involution is a potential risk factor for the emergence of SPM demarcates new avenues for the rationalized development of pharmacologic interventions to promote thymic regeneration in patients receiving cytoreductive chemotherapies.

The determination of the effect of in ovo administered monosodium glutamate on the embryonic development of thymus and bursa of Fabricius and percentages of alpha-naphthyl acetate esterase positive lymphocyte in chicken

Monosodium glutamate (MSG) is a flavor enhancer commonly used in modern nutrition. In this study, it was aimed to determine the effect of in ovo administered MSG on the embryonic development of thymus, bursa of Fabricius, and percentages of alpha-naphthyl acetate esterase (ANAE) positive lymphocyte by using histological, histometrical, and enzyme histochemical methods in chickens. For this purpose, 410 fertile eggs were used. The eggs were then divided into five groups: group 1 (control group, n = 40 eggs), group 2 (distilled water-injected group, n = 62 eggs), group 3 (0.12 mg/g egg MSG-injected group, n = 80 eggs), group 4 (0.6 mg/g egg MSG-injected group, n = 90 eggs), and group 5 (1.2 mg/g egg MSG-injected group, n = 138 eggs), and injections were performed via the egg yolk. On the 18th and 21st days of the incubation, the eggs were randomly opened from each group until six live embryos were obtained. The embryos of each group were sacrificed by decapitation, and blood, thymus, and bursa of Fabricius tissue samples were taken from the obtained embryos. The MSG-treated groups were found to be retarded embryonic development of thymus and bursa of Fabricius tissue compared to the control and distilled water groups. MSG treatment also resulted in reduced lymphoid follicles count and follicle diameters in bursa of Fabricius (P < 0.05). The percentage of peripheral blood ANAE positive lymphocytes was significantly lower in the MSG-treated groups than in the control and distilled water groups (P < 0.05). In conclusion, it has been found that in ovo administered MSG can adversely affect the embryonic development of thymus and bursa of Fabricius and decrease percentage of ANAE positive lymphocyte.

Metformin ameliorates thymus degeneration of mice by regulating mitochondrial function

As the main lymphoid organ, the thymus degenerates with age. The loss of thymic epithelial cells is mainly related to thymus degeneration and reduced T cells development. As an insulin sensitizer, metformin is a first-line drug for the treatment of diabetes and has been shown to prolong the lifespan of mice, but the mechanism is still unclear. In this study, we explored the therapeutic effect of metformin on thymus degeneration in the accelerated aging mice, which was established by intraperitoneal injection D-galactose (120 mg/kg/day) for eight weeks. Metformin was intragastrically given with 100 or 300 mg/kg body weight per day, respectively, for six weeks. Histological examination showed that metformin administration could alleviate thymus atrophy caused by D-galactose. In addition, metformin therapy increased mitochondrial membrane potential, with a reduction in mitochondrial reactive oxygen species, MDA and SOD levels, and restored mitochondrial balance through enhanced expression of dynamin-related protein 1 (Drp1). Furthermore, metformin altered T lymphocyte subsets and cellular senescent cells; the expression of FoxN1, Aire and Sox2 of thymic epithelial cells also increased. Thus, metformin presented a positive effect on thymic degeneration through improving mitochondrial function. Taken together, these findings revealed an unexpected complexity in the anti-aging of this widely used drug.

Peptides Regulating Proliferative Activity and Inflammatory Pathways in the Monocyte/Macrophage THP-1 Cell Line

This study evaluates the effects of five different peptides, the Epitalon^® tetrapeptide, the Vilon^® dipeptide, the Thymogen^® dipeptide, the Thymalin^® peptide complex, and the Chonluten^® tripeptide, as regulators of inflammatory and proliferative processes in the human monocytic THP-1, which is a human leukemia monocytic cell line capable of differentiating into macrophages by PMA in vitro. These peptides (Khavinson Peptides^®), characterized by Prof. Khavinson from 1973 onwards, were initially isolated from animal tissues and found to be organ specific. We tested the capacity of the five peptides to influence cell cultures in vitro by incubating THP-1 cells with peptides at certain concentrations known for being effective on recipient cells in culture. We found that all five peptides can modulate key proliferative patterns, increasing tyrosine phosphorylation of mitogen-activated cytoplasmic kinases. In addition, the Chonluten tripeptide, derived from bronchial epithelial cells, inhibited in vitro tumor necrosis factor (TNF) production of monocytes exposed to pro-inflammatory bacterial lipopolysaccharide (LPS). The low TNF release by monocytes is linked to a documented mechanism of TNF tolerance, promoting attenuation of inflammatory action. Therefore, all peptides inhibited the expression of TNF and pro-inflammatory IL-6 cytokine stimulated by LPS on terminally differentiated THP-1 cells. Lastly, by incubating the THP1 cells, treated with the peptides, on a layer of activated endothelial cells (HUVECs activated by LPS), we observed a reduction in cell adhesion, a typical pro-inflammatory mechanism. Overall, the results suggest that the Khavinson Peptides^® cooperate as natural inducers of TNF tolerance in monocyte, and act on macrophages as anti-inflammatory molecules during inflammatory and microbial-mediated activity.

Eosinophils are an essential element of a type 2 immune axis that controls thymus regeneration

Therapeutic interventions used for cancer treatment provoke thymus damage and limit the recovery of protective immunity. Here, we show that eosinophils are an essential part of an intrathymic type 2 immune network that enables thymus recovery after ablative therapy. Within hours of damage, the thymus undergoes CCR3-dependent colonization by peripheral eosinophils, which reestablishes the epithelial microenvironments that control thymopoiesis. Eosinophil regulation of thymus regeneration occurs via the concerted action of NKT cells that trigger CCL11 production via IL4 receptor signaling in thymic stroma, and ILC2 that represent an intrathymic source of IL5, a cytokine that therapeutically boosts thymus regeneration after damage. Collectively, our findings identify an intrathymic network composed of multiple innate immune cells that restores thymus function during reestablishment of the adaptive immune system.

Thymic Polypeptide Fraction Biomodulina T Decreases Exhausted and Terminally Differentiated EMRA T Cells in Advanced Lung Cancer Patients Treated With Platinum-Based Chemotherapy

Lung cancer is the second cause of cancer related deaths worldwide. Chemotherapy and immunotherapy represent the current standard of care for advanced NSCLC. Platinum-based chemotherapy expands late-differentiated T cell populations. Therefore, immune restoration after chemotherapy to adjuvate the immunotherapeutic potential could be crucial. The aim of this study was to evaluate the effect of Biomodulina T (BT), a thymic polypeptide fraction, on peripheral lymphocytes subpopulations in the context of cancer disease. Additionally, whether these effects might induce a better response to CIMAvax-EGF, an epidermal growth factor (EGF) depleting immunotherapy. Eighteen advanced NSCLC patients were evaluated after being treated with platinum-based chemotherapy. We found that the frequency of terminally differentiated effector T cells re-expressing CD45RA (EMRA) CD4+ (p=0.0031) and CD8+ (p=0.0372) T cells decreased with the administration of BT, whereas CD4+ naive T cells increase in more than 70% of the patients. Remarkably, CD4+ and CD8+ T lymphocytes expressing programmed cell death receptor-1 (PD1) significantly decreased after BT administration (p=0.0005 and p<0.0001, respectively). We also found an enhancement of the anti-EGF antibody response with a large percentage of patients treated with CIMAvax-EGF reaching the good antibody response condition after four vaccine doses. Moreover, the median overall survival of patients treated with CIMAvax-EGF was 16.09 months. In conclusion, our results suggest that the immunorestoration generated by the administration of BT after first-line chemotherapy may induce a better immune response to CIMAvax-EGF that could translate into the clinical benefit of patients diagnosed with advanced NSCLC.

Redox regulation of age-associated defects in generation and maintenance of T cell self-tolerance and immunity to foreign antigens

Thymic atrophy reduces naive T cell production and contributes to increased susceptibility to viral infection with age. Expression of tissue-restricted antigen (TRA) genes also declines with age and has been thought to increase autoimmune disease susceptibility. We find that diminished expression of a model TRA gene in aged thymic stromal cells correlates with impaired clonal deletion of cognate T cells recognizing an autoantigen involved in atherosclerosis. Clonal deletion in the polyclonal thymocyte population is also perturbed. Distinct age-associated defects in the generation of antigen-specific T cells include a conspicuous decline in generation of T cells recognizing an immunodominant influenza epitope. Increased catalase activity delays thymic atrophy, and here, we show that it mitigates declining production of influenza-specific T cells and their frequency in lung after infection, but does not reverse declines in TRA expression or efficient negative selection. These results reveal important considerations for strategies to restore thymic function.

Effectiveness of interleukin-4 administration or zinc supplementation in improving zinc deficiency-associated thymic atrophy and fatty degeneration and in normalizing T cell maturation process

Nutritional zinc deficiency induces thymic atrophy, but the underlying mechanisms remain unknown. In this study, we investigated the mechanism of thymic atrophy and fatty degeneration associated with zinc deficiency, and its effect on T cell maturation. Building on previous research demonstrating the beneficial effect of IL-4 administration or zinc supplementation on the spleen in zinc deficiency rats, we further examined whether these supplements also improve thymic atrophy. Five-week-old male Sprague-Dawley rats were fed a standard diet, zinc-deficient diet (n = 16 each) with either saline or IL-4, or a zinc-deficient diet for 6 weeks followed by a standard diet for 4 weeks. Relative thymus weights, serum thymulin concentrations, and the number of cytokeratin-8-positive cells, AIRE-positive cells, IL-7-positive cells, CD8⁺ T cells, CD4⁺ T cells, pre T cells, and CD25⁺ CD44⁺ (DN3) cells in the thymus of zinc deficiency rats significantly decreased compared with those in all other groups. Conversely, PPAR-γ-positive cells, oil red O-positive areas, pro T cells, CD25^- CD44⁺ cells, TUNEL positive cells, Viobility 405/452 Fixable Dye-positive cells, CD68-, CD163- or CD169- macrophages, and IL-1β concentrations were significantly increased in the thymus of zinc deficiency rats as compared to those in the other groups. After IL-4 administration or zinc supplementation for zinc deficiency, all the measurement indices were recovered to levels in standard rats. It was demonstrated that zinc deficiency caused thymic atrophy, accompanied by fatty degeneration in the cortical regions and affected T cell maturation. IL-4 administration or zinc supplementation for zinc deficiency ameliorated thymic fatty degeneration.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Epigenetic modifications in thymic epithelial cells: an evolutionary perspective for thymus atrophy

Background

The thymic microenvironment is mainly comprised of thymic epithelial cells, the cytokines, exosomes, surface molecules, and hormones from the cells, and plays a vital role in the development, differentiation, maturation and homeostasis of T lymphocytes. However, the thymus begins to degenerate as early as the second year of life and continues through aging in human beings, leading to a decreased output of naïve T cells, the limited TCR diversity and an expansion of monoclonal memory T cells in the periphery organs. These alternations will reduce the adaptive immune response to tumors and emerging infectious diseases, such as COVID-19, also it is easier to suffer from autoimmune diseases in older people. In the context of global aging, it is important to investigate and clarify the causes and mechanisms of thymus involution.

Main body

Epigenetics include histone modification, DNA methylation, non-coding RNA effects, and chromatin remodeling. In this review, we discuss how senescent thymic epithelial cells determine and control age-related thymic atrophy, how this process is altered by epigenetic modification. How the thymus adipose influences the dysfunctions of the thymic epithelial cells, and the prospects of targeting thymic epithelial cells for the treatment of thymus atrophy.

Conclusion

Epigenetic modifications are emerging as key regulators in governing the development and senescence of thymic epithelial cells. It is beneficial to re-establish effective thymopoiesis, identify the potential therapeutic strategy and rejuvenate the immune function in the elderly.

Recapitulation of Thymic Function by Tissue Engineering Strategies

The thymus is responsible for the development and selection of T lymphocytes, which in turn also participate in the maturation of thymic epithelial cells. These events occur through the close interactions between hematopoietic stem cells and developing thymocytes with the thymic stromal cells within an intricate 3D network. The complex thymic microenvironment and function, and the current therapies to induce thymic regeneration or to overcome the lack of a functional thymus are herein reviewed. The recapitulation of the thymic function using tissue engineering strategies has been explored as a way to control the body's tolerance to external grafts and to generate ex vivo T cells for transplantation. In this review, the main advances in the thymus tissue engineering field are disclosed, including both scaffold- and cell-based strategies. In light of the current gaps and limitations of the developed systems, the design of novel biomaterials for this purpose with unique features is also discussed.

Proteomic changes in the extracellular environment of sea bass thymocytes exposed to 17α-ethinylestradiol in vitro

The thymus is an important immune organ providing the necessary microenvironment for the development of a diverse, self-tolerant T cell repertoire, which is selected to allow for the recognition of foreign antigens while avoiding self-reactivity. Thymus function and activity are known to be regulated by sex steroid hormones, such as oestrogen, leading to sexual dimorphisms in immunocompetence between males and females. The oestrogenic modulation of the thymic function provides a potential target for environmental oestrogens, such as 17α-ethynylestradiol (EE2), to interfere with the cross-talk between the endocrine and the immune system. Oestrogen receptors have been identified on thymocytes and the thymic microenvironment, but it is unclear how oestrogens regulate thymic epithelial and T cell communication including paracrine signalling. Much less is known regarding intrathymic signalling in fish. Secretomics allows for the analysis of complex mixtures of immunomodulatory signalling factors secreted by T cells. Thus, in the present study, isolated thymocytes of the European sea bass, Dicentrarchus labrax, were exposed in vitro to 30 nM EE2 for 4 h and the T cell-secretome (i.e., extracellular proteome) was analysed by quantitative label-free mass-spectrometry. Progenesis revealed a total of 111 proteins differentially displayed between EE2-treated and control thymocytes at an α-level of 5% and a 1.3-fold change cut off (n = 5-6). The EE2-treatment significantly decreased the level of 90 proteins. Gene ontology revealed the proteasome to be the most impacted pathway. In contrast, the abundance of 21 proteins was significantly increased, with cathepsins showing the highest level of induction. However, no particular molecular pathway was significantly altered for these upregulated proteins. To the best of our knowledge, this work represents the first study of the secretome of the fish thymus exposed to the environmental oestrogen EE2, highlighting the impact on putative signalling pathways linked to immune surveillance, which may be of crucial importance for fish health and defence against pathogens.

Overexpression of wild-type IL-7Rα promotes T-cell acute lymphoblastic leukemia/lymphoma

Tight regulation of IL-7Rα expression is essential for normal T-cell development. IL-7Rα gain-of-function mutations are known drivers of T-cell acute lymphoblastic leukemia (T-ALL). Although a subset of patients with T-ALL display high IL7R messenger RNA levels and cases with IL7R gains have been reported, the impact of IL-7Rα overexpression, rather than mutational activation, during leukemogenesis remains unclear. In this study, overexpressed IL-7Rα in tetracycline-inducible Il7r transgenic and Rosa26 IL7R knockin mice drove potential thymocyte self-renewal, and thymus hyperplasia related to increased proliferation of T-cell precursors, which subsequently infiltrated lymph nodes, spleen, and bone marrow, ultimately leading to fatal leukemia. The tumors mimicked key features of human T-ALL, including heterogeneity in immunophenotype and genetic subtype between cases, frequent hyperactivation of the PI3K/Akt pathway paralleled by downregulation of p27Kip1 and upregulation of Bcl-2, and gene expression signatures evidencing activation of JAK/STAT, PI3K/Akt/mTOR and Notch signaling. Notably, we also found that established tumors may no longer require high levels of IL-7R expression upon secondary transplantation and progressed in the absence of IL-7, but remain sensitive to inhibitors of IL-7R-mediated signaling ruxolitinib (Jak1), AZD1208 (Pim), dactolisib (PI3K/mTOR), palbociclib (Cdk4/6), and venetoclax (Bcl-2). The relevance of these findings for human disease are highlighted by the fact that samples from patients with T-ALL with high wild-type IL7R expression display a transcriptional signature resembling that of IL-7-stimulated pro-T cells and, critically, of IL7R-mutant cases of T-ALL. Overall, our study demonstrates that high expression of IL-7Rα can promote T-cell tumorigenesis, even in the absence of IL-7Rα mutational activation.

End-Stage Renal Disease-Related Accelerated Immune Senescence: Is Rejuvenation of the Immune System a Therapeutic Goal?

End-stage renal disease (ESRD) patients exhibit clinical features of premature ageing, including frailty, cardiovascular disease, and muscle wasting. Accelerated ageing also concerns the immune system. Patients with ESRD have both immune senescence and chronic inflammation that are resumed in the so-called inflammaging syndrome. Immune senescence is particularly characterised by premature loss of thymic function that is associated with hyporesponsiveness to vaccines, susceptibility to infections, and death. ESRD-related chronic inflammation has multiple causes and participates to accelerated cardiovascular disease. Although, both characterisation of immune senescence and its consequences are relatively well-known, mechanisms are more uncertain. However, prevention of immune senescence/inflammation or/and rejuvenation of the immune system are major goal to ameliorate clinical outcomes of ESRD patients.

DL4-μbeads induce T cell lineage differentiation from stem cells in a stromal cell-free system

T cells are pivotal effectors of the immune system and can be harnessed as therapeutics for regenerative medicine and cancer immunotherapy. An unmet challenge in the field is the development of a clinically relevant system that is readily scalable to generate large numbers of T-lineage cells from hematopoietic stem/progenitor cells (HSPCs). Here, we report a stromal cell-free, microbead-based approach that supports the efficient in vitro development of both human progenitor T (proT) cells and T-lineage cells from CD34⁺cells sourced from cord blood, GCSF-mobilized peripheral blood, and pluripotent stem cells (PSCs). DL4-μbeads, along with lymphopoietic cytokines, induce an ordered sequence of differentiation from CD34⁺ cells to CD34⁺CD7⁺CD5⁺ proT cells to CD3⁺αβ T cells. Single-cell RNA sequencing of human PSC-derived proT cells reveals a transcriptional profile similar to the earliest thymocytes found in the embryonic and fetal thymus. Furthermore, the adoptive transfer of CD34⁺CD7⁺ proT cells into immunodeficient mice demonstrates efficient thymic engraftment and functional maturation of peripheral T cells. DL4-μbeads provide a simple and robust platform to both study human T cell development and facilitate the development of engineered T cell therapies from renewable sources.

T cells derived from stem cells can be harnessed for regenerative medicine and cancer immunotherapy, but current technologies limit production and translation. Here, the authors present a serum-free, stromal-cell free DLL4-coated microbead method for the scalable production of T-lineage cells from multiple sources of stem cells.

Identification and Characterization of Non-Coding RNAs in Thymoma

BACKGROUND Thymoma is the most common tumor of the anterior mediastinum, and can be caused by infrequent malignancies arising from the epithelial cells of the thymus. Unfortunately, blood-based diagnostic markers are not currently available. High-throughput sequencing technologies, such as RNA-seq with next-generation sequencing, have facilitated the detection and characterization of both coding and non-coding RNAs (ncRNAs), which play significant roles in genomic regulation, transcriptional and post-transcriptional regulation, and imprinting and epigenetic modification. The knowledge about fusion genes and ncRNAs in thymomas is scarce. MATERIAL AND METHODS For this study, we gathered large-scale RNA-seq data belonging to samples from 25 thymomas and 25 healthy thymus specimens and analyzed them to identify fusion genes, lncRNAs, and miRNAs. RESULTS We found 21 fusion genes, including KMT2A-MAML2, HADHB-REEP1, COQ3-CGA, MCM4-SNTB1, and IFT140-ACTN4, as the most frequent and significant in thymomas. We also detected 65 differentially-expressed lncRNAs in thymomas, including AFAP1-AS1, LINC00324, ADAMTS9-AS1, VLDLR-AS1, LINC00968, and NEAT1, that have been validated with the TCGA database. Moreover, we identified 1695 miRNAs from small RNA-seq data that were overexpressed in thymomas. Our network analysis of the lncRNA-mRNA-miRNA regulation axes identified a cluster of miRNAs upregulated in thymomas, that can trigger the expression of target protein-coding genes, and lead to the disruption of several biological pathways, including the PI3K-Akt signaling pathway, FoxO signaling pathway, and HIF-1 signaling pathway. CONCLUSIONS Our results show that overexpression of this miRNA cluster activates PI3K-Akt, FoxO, HIF-1, and Rap-1 signaling pathways, suggesting pathway inhibitors may be therapeutic candidates against thymoma.

Recent Advancements in Regenerative Approaches for Thymus Rejuvenation

The thymus plays a key role in adaptive immunity by generating a diverse population of T cells that defend the body against pathogens. Various factors from disease and toxic insults contribute to the degeneration of the thymus resulting in a fewer output of T cells. Consequently, the body is prone to a wide host of diseases and infections. In this review, first, the relevance of the thymus is discussed, followed by thymic embryological organogenesis and anatomy as well as the development and functionality of T cells. Attempts to regenerate the thymus include in vitro methods, such as forming thymic organoids aided by biofabrication techniques that are transplantable. Ex vivo methods that have shown promise in enhancing thymic regeneration are also discussed. Current regenerative technologies have not yet matched the complexity and functionality of the thymus. Therefore, emerging techniques that have shown promise and the challenges that lie ahead are explored.

Radiation inducible MafB gene is required for thymic regeneration

The thymus facilitates mature T cell production by providing a suitable stromal microenvironment. This microenvironment is impaired by radiation and aging which lead to immune system disturbances known as thymic involution. Young adult thymus shows thymic recovery after such involution. Although various genes have been reported for thymocytes and thymic epithelial cells in such processes, the roles of stromal transcription factors in these remain incompletely understood. MafB (v-maf musculoaponeurotic fibrosarcoma oncogene homolog B) is a transcription factor expressed in thymic stroma and its expression was induced a day after radiation exposure. Hence, the roles of mesenchymal MafB in the process of thymic regeneration offers an intriguing research topic also for radiation biology. The current study investigated whether MafB plays roles in the adult thymus. MafB/green fluorescent protein knock-in mutant (MafB^+/GFP) mice showed impaired thymic regeneration after the sublethal irradiation, judged by reduced thymus size, total thymocyte number and medullary complexity. Furthermore, IL4 was induced after irradiation and such induction was reduced in mutant mice. The mutants also displayed signs of accelerated age-related thymic involution. Altogether, these results suggest possible functions of MafB in the processes of thymic recovery after irradiation, and maintenance during aging.