Caloric restriction in humans reveals immunometabolic regulators of health span.

The extension of life span driven by 40% caloric restriction (CR) in rodents causes trade-offs in growth, reproduction, and immune defense that make it difficult to identify therapeutically relevant CR-mimetic targets. We report that about 14% CR for 2 years in healthy humans improved thymopoiesis and was correlated with mobilization of intrathymic ectopic lipid. CR-induced transcriptional reprogramming in adipose tissue implicated pathways regulating mitochondrial bioenergetics, anti-inflammatory responses, and longevity. Expression of the gene Pla2g7 encoding platelet activating factor acetyl hydrolase (PLA2G7) is inhibited in humans undergoing CR. Deletion of Pla2g7 in mice showed decreased thymic lipoatrophy, protection against age-related inflammation, lowered NLRP3 inflammasome activation, and improved metabolic health. Therefore, the reduction of PLA2G7 may mediate the immunometabolic effects of CR and could potentially be harnessed to lower inflammation and extend the health span.

Anatomy of teleost fish immune structures and organs.

The function of a tissue is determined by its construction and cellular composition. The action of different genes can thus only be understood properly when seen in the context of the environment in which they are expressed and function. We now experience a renaissance in morphological research in fish, not only because, surprisingly enough, large structures have remained un-described until recently, but also because improved methods for studying morphological characteristics in combination with expression analysis are at hand. In this review, we address anatomical features of teleost immune tissues. There are approximately 30,000 known teleost fish species and only a minor portion of them have been studied. We aim our review at the Atlantic salmon (Salmo salar) and other salmonids, but when applicable, we also present information from other species. Our focus is the anatomy of the kidney, thymus, spleen, the interbranchial lymphoid tissue (ILT), the newly discovered salmonid cloacal bursa and the naso-pharynx associated lymphoid tissue (NALT).

Preliminar histological study of the thymus in regularly slaughtered Chianina beef cattle to improve methods for the detection of illicit treatments.

Chianina is an Italian cattle breed appreciated for its meat and resilience skills. No standard values are present in literature regarding Chianina thymic involution. A possible early physiological involution has been reported during the Italian National Residue Plan screening tests. The aim of this work was to perform an anatomo­histopathological study of the thymus in Chianina cattle to improve knowledge about thymic involution in this breed. Forty Chianina bulls (16­24 months old), never treated with corticosteroids and regularly slaughtered in the Umbria region (Italy), were enrolled. Animals aged 19­21 months which received score 3 thymic atrophy had a prevalence of 0.15 (CI 95%: 0.02­0.45%), while the prevalence was 0.29 (CI 95%: 0.10­0.56%) among animals aged 22­24 months. The thymus/carcass weight and thymic cortex/medulla ratio resulted close to those reported in cattle experimentally challenged with corticosteroids. Results suggest that the Chianina breed could be characterized by a physiological premature involution of the thymus gland in comparison to other breeds. These results represent a starting point to increase the reliability of the National Residue Plan histological screening test.

Thymus development in the zebrafish (Danio rerio) from an ecoimmunology perspective.

The thymus is present in all gnathostome vertebrates and is an essential organ for the adaptive immune system via the generation of functional mature T-cells. Over the life span of mammals, the thymus undergoes morphological and functional alterations, including an age-related involution, which in humans starts in early life. Life history tradeoffs have been suggested as possible reasons for thymus involution. While in teleost fish, only a few studies have investigated alterations of thymus structure and function over different life stages, resulting in a fragmented database. Here, we investigated the thymus growth of zebrafish (Danio rerio) from early life, throughout puberty and reproductive stage, up to 1-year-old. We assessed thymus growth by histological and morphometric analyses and thymocyte numbers. Thymus function was assessed by measuring the transcripts of the thymocyte marker genes, ikaros, tcrα, and tcrδ. Additionally, we analyzed gonad maturity and tail homogenate vitellogenin concentrations to align thymus status with the status of the reproductive system. Our results showed that the zebrafish thymus, in contrast to the human thymus, grew strongly during early life and puberty but started to undergo involution when the fish reached the reproductive age. The involution was characterized by reduced thymus area and thymocyte number, altered histoarchitecture, and decreasing thymocyte marker gene transcript levels. Our findings suggest that age-related changes of the zebrafish thymus do exist and could be partly explained in terms of resource tradeoffs, but also in terms of the ontogenetically late development of a functional adaptive immune system in teleosts.

Induced Prostanoid Synthesis Regulates the Balance between Th1- and Th2-Producing Inflammatory Cytokines in the Thymus of Diet-Restricted Mice.

Multiple external and internal factors have been reported to induce thymic involution. Involution involves dramatic reduction in size and function of the thymus, leading to various immunodeficiency-related disorders. Therefore, clarifying and manipulating molecular mechanisms governing thymic involution are clinically important, although only a few studies have dealt with this issue. In the present study, we investigated the molecular mechanisms underlying thymic involution using a murine acute diet-restriction model. Gene expression analyses indicated that the expression of T helper 1 (Th1)-producing cytokines, namely interferon-γ and interleukin (IL)-2, was down-regulated, while that of Th2-producing IL-5, IL-6, IL-10 and IL-13 was up-regulated, suggesting that acute diet-restriction regulates the polarization of naïve T cells to a Th2-like phenotype during thymic involution. mRNAs for prostanoid biosynthetic enzymes were up-regulated by acute diet-restriction. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses detected the increased production of prostanoids, particularly prostaglandin D2 and thromboxane B2, a metabolite of thromboxane A2, in the diet-restricted thymus. Administration of non-steroidal anti-inflammatory drugs, namely aspirin and etodolac, to inhibit prostanoid synthesis suppressed the biased expression of Th1- and Th2-cytokines as well as molecular markers of Th1 and Th2 cells in the diet-restricted thymus, without affecting the reduction of thymus size. In vitro stimulation of thymocytes with phorbol myristate acetate (PMA)/ionomycin confirmed the polarization of thymocytes from diet-restricted mice toward Th2 cells. These results indicated that the induced production of prostanoids during diet-restriction-induced thymic involution is involved in the polarization of naïve T cells in the thymus.

Gallic acid attenuates thymic involution in the d-galactose induced accelerated aging mice.

Senescence is an inevitable and complicated phenomenon. Age-associated thymic involution increases the risk of infectious diseases, which results in the immunosenescence and leads to a poor immune function. d-galactose (d-gal) can cause damages that resemble accelerated aging in mice. Gallic acid (GA), as one of the natural phenolic compounds, has been demonstrated to act in antioxidant and anti-tumor effects. In this study, we explored the effects of GA in preventing the age-related thymic involution and the alterations of the forkhead box protein N1 (FoxN1) in d-gal induced accelerated aging mice. The accelerated aging mice model was established by intraperitoneal injection d-gal for eight weeks and given GA with 200, 250, 500 mg/kg body weight per day, respectively, for six weeks. It showed that the d-gal-treated mice developed structural changes in the thymi compared to normal control mice. With supplement of GA, the mice restored the normal thymic anatomy, including the thickening cortex compartment and clearer cortico-medullary junction. The d-gal-treated mice showed a severe reduction in the number of thymocytes, GA mice also displayed the increased numbers of CD4 + T cells through flow cytometric analysis. GA treatment increased the proliferative cells by BrdU incorporation assay and reduced the numbers of apoptotic cells with FITC-12-dUTP labeling (TUNEL). The expression of FoxN1 was also found increased in GA treated mice by immunohistochemistry and quantitative reverse transcriptase PCR (qRT-PCR). Taken together, our results suggested that the administration of GA opposed the involution of thymus via stimulation of FoxN1 expression and proliferation of cells in a dose-dependent manner.

Variance of body and organ weights in 28-day studies in mice.

The OECD guideline 407 outlines the conduct of 28-day studies in rodents to detect systemic toxicity with focus on endocrine and immunotoxic effects. It was validated with the rat as preferred model species. Justification is required for other rodent species, as an increased variability is expected compared to the rat. We investigated the variability of organ weights in the mouse and compared this to data published for the rat in the validation report of test guideline 407. Furthermore, the influence of the immunotoxic model substance cyclophosphamide on spleen and thymus weights in the mouse in immunotoxicity studies (duration 28 days) is reported and discussed, an immunotoxic model substance was not included in the validation report. Historical control data were compiled for mouse studies performed according to OECD 407 and for immunotoxicity studies between 2008 and 2013 at BASF SE. For absolute weights, the coefficient of variation was determined for each study group and compared with the rat. Adrenal glands, ovaries and to lesser degree testes and prostate showed higher coefficients of variation in the mouse (most pronounced in adrenal glands in male animals: rat 5%-17%, CD1 mouse 20%-51%). Effects of cyclophosphamide were best detected measuring the thymus weight.

Effect of early pregnancy on the expression of prostaglandin synthases in the ovine thymus.

Thymus is a primary lymphoid organ, must adapt to the presence of fetal alloantigens. Prostaglandins (PGs) have diverse effects to activate or inhibit the immune response, but effects of early pregnancy on the expression of PG synthases in ovine maternal thymus are unclear. In this study, ovine thymic samples were obtained at day 16 of the estrous cycle, and days 13, 16 and 25 of pregnancy. The expression of PG synthases, including cyclooxygenase 1 (COX-1), COX-2, PGE2 synthase (PTGES), and a prostaglandin F2α synthase (Aldo-keto reductase family 1, member B1, AKR1B1), was evaluated using quantitative real-time PCR, Western blot and immunohistochemistry analysis. In addition, the thymus/body ratio was also calculated. Our results showed that the expression of COX-2 mRNA and protein, AKR1B1 mRNA and dimer were up-regulated on day 25 of pregnancy (P < 0.05), and expression of COX-1, PTGES mRNA and protein, AKR1B1 monomer and thymus/body ratio were similar at different stages of pregnancy and the estrous cycle. The immunohistochemistry results showed that the COX-2 and AKR1B1 proteins were located in the stromal cells, capillaries and thymic corpuscles. This is the first study to report that expression of COX-2 and AKR1B1 dimer is up-regulated in the maternal thymus during early pregnancy, suggesting that early pregnancy exerts its effects on maternal thymus, which is involved in immunomodulation during early pregnancy in sheep.

Surgical Approaches to Myasthenia Gravis: Perspective of Anatomy and Radicality in Surgery.

The effectiveness of thymectomy for nonthymomatous myasthenia gravis is analyzed with regard to extensiveness of removal of the adipose tissue of the mediastinum and the lower neck region with various techniques of thymectomy. The approach necessary to achieve maximal radicality must include access to both pleural cavity and the lower neck area up to the thyroid gland. Surgical techniques include extended transsternal approach, which might be combined with separate transcervical incision, bilateral videothoracoscopic (VATS) approach combined with transcervical incision, and extended subxiphoid approach, either uniportal or combined with bilateral VATS. Anatomic aspects of maximally extensive thymectomy are described in detail.

Is thymus size at birth associated with respiratory distress syndrome in preterm infants?

AIM: Thymus size in neonates depend on many factors. We aimed to assess the thymus size radiographically in preterm neonates and its relationship with respiratory distress syndrome (RDS) and other complications of prematurity. METHODS: Thymus size was assessed by cardiothymic: thoracic ratio (CT/T), measuring the width of the cardiothymic shadow at the level of carina and dividing it by the width of the thorax at the costophrenic angles, from the first chest radiograph in patients less than 34 weeks gestational age. RESULTS: Neonates born between 30-34 weeks of gestation with RDS had smaller CT/T than non RDS group (0.34±0.1 vs 0.36±0.05, p = 0.045). Birth weight has positive correlation with CT/T (r = 0.166, p = 0.03). CONCLUSION: Thymus involution in the perinatal period is a complex process and the response is variable in different clinical situations. Activated hypothalamic-pituitary-adrenal (HPA) axis may be responsible for thymic involution in preterm infants between 30-34 weeks of gestation with RDS.

[Structure of the thymus at the beginning of the 21th century]. / A thymus szerkezete a huszonegyedik század elején.

The classical histological features of the thymus are the cortex and medulla, the Hassall's bodies as well as the lobules. Anti-pan-cytokeratin immunocytochemistry shows that the keratin staining pattern of the cortical and medullary epithelial cells is different. The medulla is further compartmentalized: it consists of keratin-positive network and keratin-negative areas. Histology of the keratin-negative area is identical with the connective tissue of the septae. The basal lamina is continuous at the capsule and septae, but it becomes discontinuous at the border between the keratin-positive network and keratin-negative area. This immunohistochemical finding is the first histological sign, which may explain that the medulla has no blood-thymus barrier. The supporting tissue of the keratin-negative area is identical with that of the septae. The connective tissue of thymic capsule and septae develops from the cranial neural crest cells, therefore we hypothesize that the keratin-negative area has neural crest origin. Blood vessels of the thymic medulla localize in the keratin-negative area. Every emigrating or immigrating immunologically competent cells should enter the keratin-negative area, therefore this area is the transit zone of the thymus. The hematoxylin-eosin staining of the thymus shows that the thymic cortico-medullary border does not represent cellular background. However, the border between keratin-positive network and keratin-negative area is determined by cellular identity (epithelial and mesenchymal tissues). Therefore, it can be assumed that the real histological and functional border is the border between the keratin-positive network and the keratin-negative area. Orv Hetil. 2019; 160(5): 163-171.

Thymus gland size during recovery from complicated severe acute malnutrition: a prospective study of the role of probiotics.

Background: Children with severe acute malnutrition (SAM) are prone to infections due to immune dysfunction including severe thymus atrophy which recovers during nutritional rehabilitation. Aim: To investigate predictors of thymus size recovery, including probiotics during nutritional rehabilitation of children admitted with complicated SAM. Methods: In this prospective study nested in a randomized controlled trial, children 6-59 months admitted with SAM received standard care and either probiotics or placebo during hospitalization until 8 weeks post-discharge. Thymus size was measured using ultrasound at admission, discharge, 8 weeks post-discharge and among 27 community controls. Predictors of thymus size recovery were assessed using linear regression. Results: Among 388 children with SAM, mean (SD) thymus size was 1.06 cm2 (0.41), 1.24 cm2 (0.48), 2.85 cm2 (1.07) and 4.2 cm2 (0.93) at admission, discharge, follow-up and in the healthy controls respectively (p < 0.05).Probiotics did not affect thymus recovery. During both inpatient therapeutic care (ITC) and outpatient therapeutic care (OTC), thymus recovery correlated positively with anthropometry but negatively with caregiver-perceived illness severity and Haemoglobin <8 g/dl. Negative predictors of thymus recovery during ITC included grade 3 oedema (ß -0.13, 95%CI -0.25; -0.01), dermatosis (ß -0.21, 95%CI -0.41; -0.01), C-reactive protein (CRP) >15mg/L (ß -0.13, 95%CI -0.25; -0.02) and neutrophils (ß -0.01, 95%CI -0.02; -0.002). During OTC, HIV negatively predicted thymus recovery. Conclusion: Children with SAM failed to regain thymus size at 8 weeks post-discharge. Probiotics did not predict thymus recovery during nutritional rehabilitation. More research is needed to find interventions which can accelerate immune recovery. Abbreviations: ART, Antiretroviral therapy; BB-12, Bifidobacterium animalis subsp. Lactis; CRP, C-reactive protein; ITC, inpatient therapeutic care; LGG, Lactobacillus rhamnosus; MNU, Mwanamugimu Nutrition Unit; MUAC, mid-upper arm circumference; OTC, outpatient therapeutic care; PCR, Polymerised chain reaction; RUTF, ready-to-use therapeutic food; SAM, severe acute malnutrition; VAS, visual analogue score; WHO, World Health Organization; WHZ, weight-for-height score.

The androgen receptor is required for maintenance of bone mass in adult male mice.

Previous studies evaluating the role of the androgen receptor (AR) for bone mass have used mouse models with global or tissue-specific lifelong inactivation of the AR. However, these mouse models have the AR inactivated already early in life and the relative roles of the AR during development, sexual maturation and in adult mice cannot be evaluated separately. The aim of the present study was to determine the specific roles of the AR in bone during sexual maturation and in adult mice. The AR was conditionally ablated at four (pre-pubertal) or ten (post-pubertal) weeks of age in male mice using tamoxifen-inducible Cre-mediated recombination. Both the pre-pubertal and the post-pubertal AR inactivation were efficient demonstrated by substantially lower AR mRNA levels in seminal vesicle, bone and white adipose tissue as well as markedly reduced weights of reproductive tissues when comparing inducible ARKO mice and control mice at 14 weeks of age. Total body BMD, as analyzed by DXA, as well as tibia diaphyseal cortical bone thickness and proximal metaphyseal trabecular bone volume fraction, as analyzed by µCT, were significantly reduced by both pre-pubertal and post-pubertal AR inactivation. These bone effects were associated with an increased bone turnover, indicating a high bone turnover osteoporosis. Pre-pubertal but not post-pubertal AR inactivation resulted in substantially increased fat mass. In conclusion, the AR is required for maintenance of both trabecular and cortical bone in adult male mice while AR expression during puberty is crucial for normal fat mass homeostasis in adult male mice.

Age-stratified Patterns of Thymic Involution on Multidetector CT.

PURPOSE: The aim of this study was to better assess the prevalence and appearance of thymic tissue in adults stratified by age using multidetector computed tomography (MDCT) in order to prevent misinterpretation of normal thymic tissue as pathology. MATERIALS AND METHODS: This study examined the CT appearance of the thymus in 597 trauma patients aged 30 to 69 years (M=48.0 y, SD=11.3). Three body fellowship-trained attending radiologists independently reviewed the CT scans. Reviewers assigned one of 5 grades on the basis of the relative proportions of fat and soft tissue in the thymic bed: complete fatty replacement (grade 0), predominantly fat (grade 1), even mix of soft tissue and fat (grade 2), predominantly soft tissue (grade 3), and discrete confluent thymic tissue (grade 4). Objectively, fixed-area region of interest values of the thymic bed were obtained. Interrater reliability was calculated. RESULTS: Increased fatty replacement of the thymus occurred with increasing age. We found residual thymic tissue (≥grade 1) in the following age categories: 30 to 39 years (83.0%), 40 to 49 years (71.9%), 50 to 59 years (52.6%), and 60 to 69 years (34.8%). Kappa comparisons for the entire sample were excellent (κ=0.86). Higher grades had higher region of interest values. CONCLUSIONS: Residual thymic tissue in adults on MDCT is both more prevalent and more prominent than that reported in earlier studies and can be visible into the seventh decade. We recommend that radiologists and clinicians familiarize themselves with the normal range appearances of the thymus on MDCT, in order to prevent misinterpretation of normal thymic tissue as pathology, which may result in unnecessary procedures.

Thymic tuft cells promote an IL-4-enriched medulla and shape thymocyte development.

The thymus is responsible for generating a diverse yet self-tolerant pool of T cells1. Although the thymic medulla consists mostly of developing and mature AIRE+ epithelial cells, recent evidence has suggested that there is far greater heterogeneity among medullary thymic epithelial cells than was previously thought2. Here we describe in detail an epithelial subset that is remarkably similar to peripheral tuft cells that are found at mucosal barriers3. Similar to the periphery, thymic tuft cells express the canonical taste transduction pathway and IL-25. However, they are unique in their spatial association with cornified aggregates, ability to present antigens and expression of a broad diversity of taste receptors. Some thymic tuft cells pass through an Aire-expressing stage and depend on a known AIRE-binding partner, HIPK2, for their development. Notably, the taste chemosensory protein TRPM5 is required for their thymic function through which they support the development and polarization of thymic invariant natural killer T cells and act to establish a medullary microenvironment that is enriched in the type 2 cytokine, IL-4. These findings indicate that there is a compartmentalized medullary environment in which differentiation of a minor and highly specialized epithelial subset has a non-redundant role in shaping thymic function.

The thymus gland in ancient Greek medicine.

The term thymus was used in ancient Greek medical literature to describe not only the thymus gland but also the warty excrescences found mainly in the genitals or the anus, but also over the entire body. Rufus of Ephesus (1st-2nd c. AD) gave the earliest anatomical description of this gland in humans, while Galen (1st-2nd c. AD) first described it in animals. However, the origins and meaning of this term have long mystified researchers. A careful investigation into its etymology together with the information derived from early anatomical descriptions has enabled us to propose a new interpretation of the origins of the name of the thymus gland.

Fast and reliable dissection of porcine parathyroid glands - A protocol for molecular and histological analyses.

As calcium and phosphorus are of vital importance for life, physiological activity of the parathyroid glands (PTGs) is crucial to maintain mineral homeostasis and bone mineralization. However, PTG-specific molecular routes in response to environmental factors and intrinsic hormonal responses are not yet fully understood. Since nutrient requirements, pathophysiology and functional genomics of pigs are similar to those of humans, pigs might be a suitable model to study the holistic gene expression and physiological aspects of the parathyroid gland, which could be used in both animal sciences and biomedical research. However, due to their small size and hidden location, the dissection of the PTGs, particularly in pigs, is difficult. Therefore, a protocol for untrained dissectors has been established that allows a fast and reliable identification of the PTGs in domestic pigs. Based on their localization within the cranial thymus near the carotid bifurcation, sampling was verified by histological staining and mRNA expression pattern. Analyses revealed the prominence of parathyroid hormone (PTH)-producing chief cells. Moreover, the copy numbers of PTH differed substantially between the PTGs and their surrounding thymus tissue, as PTH was expressed virtually exclusively in the PTGs. The developed protocol will substantially facilitate a fast and reliable dissection of porcine PTGs which is essential for studies characterizing the molecular mechanisms of parathyroid glands, e.g. when applying new feeding strategies in pigs.

Measurement of fat fraction in the human thymus by localized NMR and three-point Dixon MRI techniques.

PURPOSE: To develop a protocol to non-invasively measure and map fat fraction, fat/(fat+water), as a function of age in the adult thymus for future studies monitoring the effects of interventions aimed at promoting thymic rejuvenation and preservation of immunity in older adults. MATERIALS AND METHODS: Three-dimensional spoiled gradient echo 3T MRI with 3-point Dixon fat-water separation was performed at full inspiration for thymus conspicuity in 36 volunteers 19 to 56 years old. Reproducible breath-holding was facilitated by real-time pressure recording external to the console. The MRI method was validated against localized spectroscopy in vivo, with ECG triggering to compensate for stretching during the cardiac cycle. Fat fractions were corrected for T1 and T2 bias using relaxation times measured using inversion recovery-prepared PRESS with incremented echo time. RESULTS: In thymus at 3 T, T1water = 978 ±â€¯75 ms, T1fat = 323 ±â€¯37 ms, T2water = 43.4 ±â€¯9.7 ms and T2fat = 52.1 ±â€¯7.6 ms were measured. Mean T1-corrected MRI fat fractions varied from 0.2 to 0.8 and were positively correlated with age, weight and body mass index (BMI). In subjects with matching MRI and MRS fat fraction measurements, the difference between these measurements exhibited a mean of -0.008 with a 95% confidence interval of (0.123, -0.138). CONCLUSIONS: 3-point Dixon MRI of the thymus with T1 bias correction produces quantitative fat fraction maps that correlate with T2-corrected MRS measurements and show age trends consistent with thymic involution.

Anatomical variations of the thymus in relation to the left brachiocephalic vein, findings of necropsia.

Two cases of anatomical variations of the thymus are presented with respect to the anatomical relations with the left brachiocephalic vein and found during the necropsy process. Less than 2 days after birth with Noonan Syndrome, when the left brachiocephalic vein was scanning behind the upper thymus horns, there were other adjacent lesions consisting of three supernumerary spleens and three hepatic veins. The second case was an 8-year-old infant with child malpractice who died from urinary sepsis due to obstructive uropathy, in which case the upper lobes of the thymus were fused and formed a ring through which the left brachiocephalic vein passed.