Adipose Tissue Immunometabolism: Unveiling the Intersection of Metabolic and Immune Regulation.

UNASSIGNED: Excess body weight has become a global epidemic and a significant risk factor for developing chronic diseases, which are the leading causes of worldwide morbidities. Adipose tissue (AT), primarily composed of adipocytes, stores substantial amounts of energy and plays a crucial role in maintaining whole-body glucose and lipid metabolism. This helps prevent excessive body fat accumulation and lipotoxicity in peripheral tissues. In addition, AT contains endothelial cells and a substantial population of immune cells (constituting 60-70% of non-adipocyte cells), including macrophages, T and B lymphocytes, and natural killer cells. These resident immune cells engage in crosstalk with adipocytes, contributing to the maintenance of metabolic and immune homeostasis in AT. An exacerbated inflammatory response or inadequate immune resolution can lead to chronic systemic low-grade inflammation, triggering the development of metabolic alterations and the onset of chronic diseases. This review aims to elucidate the regulatory mechanisms through which immune cells influence AT function and energy homeostasis. We also focus on the interactions and functional dynamics of immune cell populations, highlighting their role in maintaining the delicate balance between metabolic health and obesity-related inflammation. Finally, understanding immunometabolism is crucial for unraveling the pathogenesis of metabolic diseases and developing targeted immunotherapeutic strategies. These strategies may offer innovative avenues in the rapidly evolving field of immunometabolism. (Rev Invest Clin. 2024;76(2):65-79).

Exploring exercise-driven exerkines: unraveling the regulation of metabolism and inflammation.

Exercise has many beneficial effects that provide health and metabolic benefits. Signaling molecules are released from organs and tissues in response to exercise stimuli and are widely termed exerkines, which exert influence on a multitude of intricate multi-tissue processes, such as muscle, adipose tissue, pancreas, liver, cardiovascular tissue, kidney, and bone. For the metabolic effect, exerkines regulate the metabolic homeostasis of organisms by increasing glucose uptake and improving fat synthesis. For the anti-inflammatory effect, exerkines positively influence various chronic inflammation-related diseases, such as type 2 diabetes and atherosclerosis. This review highlights the prospective contribution of exerkines in regulating metabolism, augmenting the anti-inflammatory effects, and providing additional advantages associated with exercise. Moreover, a comprehensive overview and analysis of recent advancements are provided in this review, in addition to predicting future applications used as a potential biomarker or therapeutic target to benefit patients with chronic diseases.

Notch signaling in adipose tissue macrophages prevents diet-induced inflammation and metabolic dysregulation.

The importance of macrophages in adipose tissue (AT) homeostasis and inflammation is well established. However, the potential cues that regulate their function remain incompletely understood. To bridge this important gap, we sought to characterize novel pathways involved using a mouse model of diet-induced obesity. By performing transcriptomics analysis of AT macrophages (ATMs), we found that late-stage ATMs from high-fat diet mice presented with perturbed Notch signaling accompanied by robust proinflammatory and metabolic changes. To explore the hypothesis that the deregulated Notch pathway contributes to the development of AT inflammation and diet-induced obesity, we employed a genetic approach to abrogate myeloid Notch1 and Notch2 receptors. Our results revealed that the combined loss of Notch1 and Notch2 worsened obesity-related metabolic dysregulation. Body and AT weight gain was higher, blood glucose levels increased and metabolic parameters were substantially worsened in deficient mice fed high-fat diet. Moreover, serum insulin and leptin were elevated as were triglycerides. Molecular analysis of ATMs showed that deletion of Notch receptors escalated inflammation through the induction of an M1-like pro-inflammatory phenotype. Our findings thus support a protective role of myeloid Notch signaling in adipose tissue inflammation and metabolic dysregulation.

Adipose failure through adipocyte overload and autoimmunity.

Metabolic syndrome poses a great worldwide threat to the health of the patients. Increased visceral adiposity is recognized as the main determinant of the detrimental clinical effects of insulin resistance. Inflammation and immune system activation in the adipose tissue (AT) have a central role in the pathophysiology of metabolic syndrome, but the mechanisms linking increased adiposity to immunity in the AT remain in part elusive. In this review, we support the central role of adipocyte overload and relative adipose failure as key determinants in triggering immune aggression to AT. This provides a mechanistic explanation of the relative metabolic wellness of metabolically normal obese people and the disruption in insulin signaling in metabolically obese lean people.

Adipose tissue macrophages as potential targets for obesity and metabolic diseases.

Macrophage infiltration into adipose tissue is a key pathological factor inducing adipose tissue dysfunction and contributing to obesity-induced inflammation and metabolic disorders. In this review, we aim to present the most recent research on macrophage heterogeneity in adipose tissue, with a focus on the molecular targets applied to macrophages as potential therapeutics for metabolic diseases. We begin by discussing the recruitment of macrophages and their roles in adipose tissue. While resident adipose tissue macrophages display an anti-inflammatory phenotype and promote the development of metabolically favorable beige adipose tissue, an increase in pro-inflammatory macrophages in adipose tissue has negative effects on adipose tissue function, including inhibition of adipogenesis, promotion of inflammation, insulin resistance, and fibrosis. Then, we presented the identities of the newly discovered adipose tissue macrophage subtypes (e.g. metabolically activated macrophages, CD9+ macrophages, lipid-associated macrophages, DARC+ macrophages, and MFehi macrophages), the majority of which are located in crown-like structures within adipose tissue during obesity. Finally, we discussed macrophage-targeting strategies to ameliorate obesity-related inflammation and metabolic abnormalities, with a focus on transcriptional factors such as PPARγ, KLF4, NFATc3, and HoxA5, which promote macrophage anti-inflammatory M2 polarization, as well as TLR4/NF-κB-mediated inflammatory pathways that activate pro-inflammatory M1 macrophages. In addition, a number of intracellular metabolic pathways closely associated with glucose metabolism, oxidative stress, nutrient sensing, and circadian clock regulation were examined. Understanding the complexities of macrophage plasticity and functionality may open up new avenues for the development of macrophage-based treatments for obesity and other metabolic diseases.

Metabolism in type 2 immune responses.

The immune response is tailored to the environment in which it takes place. Immune cells sense and adapt to changes in their surroundings, and it is now appreciated that in addition to cytokines made by stromal and epithelial cells, metabolic cues provide key adaptation signals. Changes in immune cell activation states are linked to changes in cellular metabolism that support function. Furthermore, metabolites themselves can signal between as well as within cells. Here, we discuss recent progress in our understanding of how metabolic regulation relates to type 2 immunity firstly by considering specifics of metabolism within type 2 immune cells and secondly by stressing how type 2 immune cells are integrated more broadly into the metabolism of the organism as a whole.

Distinct T cell subsets in adipose tissue are associated with obesity.

Adipose tissue inflammation is a driving factor for the development of obesity-associated metabolic disturbances, and a role of adipose tissue T cells in initiating the pro-inflammatory signaling is emerging. However, data on human adipose tissue T cells in obesity are limited, reflected by the lack of phenotypic markers to define tissue-resident T cell subsets. In this study, we performed a deep characterization of T cells in blood and adipose tissue depots using multicolor flow cytometry and RNA sequencing. We identified distinct subsets of T cells associated with obesity expressing the activation markers, CD26 and CCR5, and obesity-specific genes that are potentially engaged in activating pro-inflammatory pathway, including ceramide signaling, autophagy, and IL-6 signaling. These findings increase our knowledge on the heterogeneity of T cells in adipose tissue and on subsets that may play a role in obesity-related pathogenesis.

The brain-fat connection.

Type 2 innate lymphoid cells shape metabolism through a brain-body circuit.

Adipocyte-derived lactate is a signalling metabolite that potentiates adipose macrophage inflammation via targeting PHD2.

Adipose tissue macrophage (ATM) inflammation is involved with meta-inflammation and pathology of metabolic complications. Here we report that in adipocytes, elevated lactate production, previously regarded as the waste product of glycolysis, serves as a danger signal to promote ATM polarization to an inflammatory state in the context of obesity. Adipocyte-selective deletion of lactate dehydrogenase A (Ldha), the enzyme converting pyruvate to lactate, protects mice from obesity-associated glucose intolerance and insulin resistance, accompanied by a lower percentage of inflammatory ATM and reduced production of pro-inflammatory cytokines such as interleukin 1ß (IL-1ß). Mechanistically, lactate, at its physiological concentration, fosters the activation of inflammatory macrophages by directly binding to the catalytic domain of prolyl hydroxylase domain-containing 2 (PHD2) in a competitive manner with α-ketoglutarate and stabilizes hypoxia inducible factor (HIF-1α). Lactate-induced IL-1ß was abolished in PHD2-deficient macrophages. Human adipose lactate level is positively linked with local inflammatory features and insulin resistance index independent of the body mass index (BMI). Our study shows a critical function of adipocyte-derived lactate in promoting the pro-inflammatory microenvironment in adipose and identifies PHD2 as a direct sensor of lactate, which functions to connect chronic inflammation and energy metabolism.

Differential Immunometabolic Effects of High-Fat Diets Containing Coconut, Sunflower, and Extra Virgin Olive Oils in Female Mice.

SCOPE: To compare the effects of three high-fat diets (HFDs) based on coconut, sunflower, or extra virgin olive oils (EVOOs) on adipose tissue, metabolism, and inflammation. METHODS AND RESULTS: Mice are fed for 16 weeks on their respective HFD. HFD based on coconut oil produces significantly lower body weight than EVOO- or sunflower oil-based HFDs. Furthermore, the coconut oil HFD leads to metabolic disturbances such as reduction of circulating leptin and adiponectin concentrations, hypertriglyceridemia, hepatomegaly, and liver triglyceride accumulation. Likewise, this diet produces an increase in serum pro-inflammatory cytokines (interleukin 6 [IL-6] and tumor necrosis factor-α [TNF-α]). In white (WAT) and brown (BAT) adipose tissue, the HFD based on coconut oil does not cause significant changes in the expression of studied proteins related to thermogenesis (uncoupling protein 1 [UCP-1]), mitochondrial biogenesis, and browning (peroxisome proliferator-activated receptor-γ coactivator 1α [PGC-1α] and nuclear factor E2-related factor 2 [Nrf2]). However, the HFD based on EVOO induces upregulation of UCP-1, PGC-1α, and Nrf2 expression in BAT, increases the expression of UCP-1 and PGC-1α in inguinal WAT, and enhances the expression of PGC-1α in epididymal WAT. CONCLUSIONS: An HFD based on coconut oil could reduce circulating leptin and adiponectin concentrations, increase the liver fat content, raise serum triglycerides, and promote inflammation by increasing circulating pro-inflammatory cytokines, while an EVOO-based HFD could increase thermogenic activity.

Adipose­derived mesenchymal stem cell­derived HCAR1 regulates immune response in the attenuation of sepsis.

Sepsis serves as a leading cause of admission to and death of patients in the intensive care unit (ICU) and is described as a systemic inflammatory response syndrome caused by abnormal host response to infection. Adipose­derived mesenchymal stem cells (ADSCs) have exhibited reliable and promising clinical application potential in multiple disorders. However, the function and the mechanism of ADSCs in sepsis remain elusive. In the present study, the crucial inhibitory effect of ADSC­derived hydroxy­carboxylic acid receptor 1 (HCAR1) on sepsis was identified. Reverse transcription quantitative­PCR determined that the mRNA expression of HCAR1 was reduced while the mRNA expression of Toll­like receptor 4 (TLR4), major histocompatibility complex class II (MHC II), NOD­like receptor family pyrin domain containing 3 (NLRP3), and the levels of interleukin­1ß (IL­1ß), tumor necrosis factor­α (TNF­α), interleukin­10 (IL­10), and interleukin­18 (IL­18) were enhanced in the peripheral blood of patients with sepsis. The expression of HCAR1 was negatively correlated with TLR4 (r=­0.666), MHC II (r=­0.587), and NLRP3 (r=­0.621) expression and the expression of TLR4 was positively correlated with NLRP3 (r=0.641), IL­1ß (r=0.666), TNF­α (r=0.606), and IL­18 (r=0.624) levels in the samples. Receiver operating characteristic (ROC) curve analysis revealed that the area under the ROC curve (AUC) of HCAR1, TLR4, MHC II and NLRP3 mRNA expression was 0.830, 0.853, 0.735 and 0.945, respectively, in which NLRP3 exhibited the highest diagnostic value, and the AUC values of IL­1ß, IL­18, TNF­α, and IL­10 were 0.751, 0.841, 0.924 and 0.729, respectively, in which TNF­α exhibited the highest diagnostic value. A sepsis rat model was established by injecting lipopolysaccharide (LPS) and the rats were randomly divided into 5 groups, including a normal control group (NC group; n=6), a sepsis model group (LPS group; n=6), an ADSC transplantation group (L + M group; n=6), a combined HCAR1 receptor agonist group [L + HCAR1 inducer (Gi) + M group; n=6], and a combined HCAR1 receptor inhibitor group [L + HCAR1 blocker (Gk) + M group; n=6]. Hematoxylin and eosin staining determined that ADSCs attenuated the lung injury of septic rats and ADSC­derived HCAR1 enhanced the effect of ADSCs. The expression of HCAR1, TLR4, MHC II, NLRP3, IL­1ß, IL­18 and TNF­α levels were suppressed by ADSCs and the effect was further induced by ADSC­derived HCAR1. However, ADSC­derived HCAR1 induced the levels of anti­inflammatory factor IL­10. The negative correlation of HCAR1 expression with TLR4, MHC II, and NLRP3 expression in the peripheral blood and lung tissues of the rats was then identified. It is thus concluded that ADSC­derived HCAR1 regulates immune response in the attenuation of sepsis. ADSC­derived HCAR1 may be a promising therapeutic strategy for sepsis.

Integrative analyses of hub genes and their association with immune infiltration in adipose tissue, liver tissue and skeletal muscle of obese patients after bariatric surgery.

Bariatric surgery (BS) is an effective treatment for obesity. Adipose tissue, liver tissue and skeletal muscle are important metabolic tissues. This study investigated hub genes and their association with immune infiltration in these metabolic tissues of obese patients after BS by bioinformatic analysis with Gene Expression Omnibus datasets. Differentially expressed genes (DEGs) were identified, and a protein-protein interaction network was constructed to identify hub genes. As a result, 121 common DEGs were identified and mainly enriched in cytokine-cytokine receptor interactions, chemokine signaling pathway, neutrophil activation and immune responses. Immune cell infiltration analysis showed that the abundance of M1 macrophages was significantly lower in adipose and liver tissue after BS (p<0.05). Ten hub genes (TYROBP, TLR8, FGR, NCF2, HCK, CCL2, LAPTM5, MNDA and S100A9) that were all downregulated after BS were also associated with immune cells. Consistently, results in the validated dataset showed that the expression levels of these hub genes were increased in obese patients and mice, and decreased after BS. In conclusion, this study analysed the potential immune and inflammatory mechanisms of BS in three key metabolic tissues of obese patients, and revealed hub genes associated with immune cell infiltration, thus providing potential targets for obesity treatment.

Adipose tissue in COVID-19: detection of SARS-CoV-2 in adipocytes and activation of the interferon-alpha response.

OBJECTIVE: Obesity is a recognized risk factor for the progression to severe forms of COVID-19, yet the mechanisms of the association are unclear. METHODS: Subcutaneous abdominal adipose tissue specimens of subjects deceased from COVID-19 (n = 23) were compared to those of controls dying abruptly from causes other than infectious (accidental trauma, sudden cardiac death). Alterations of lung parenchyma consistent with moderate to severe disease were detected in all COVID-19 cases, not in controls. Investigations included: histopathologic features, detection of virus antigens and genome, characterization of infiltrating leukocytes, transcription levels of immune-related genes. RESULTS: By RT-PCR, the SARS-CoV-2 genome was detected in the adipose tissue of 13/23 (56%) cases of the COVID-19 cohort. The virus nucleocapsid antigen was detected in the cytoplasm of 1-5% adipocytes in 12/12 COVID-19 cases that were virus-positive by PCR in the adipose tissue (one case could not be assessed due insufficient tissue). The adipose tissue of COVID-19 cases showed leukocyte infiltrates and upregulation of the interferon-alpha pathway. After adjusting for age and sex, the activation score of IFN-alpha was directly related with transcription levels of the ACE2 gene, a key entry factor of SARS-CoV-2. CONCLUSIONS: In lethal COVID-19 cases, the SARS-CoV-2 nucleocapsid antigen has been detected in a sizeable proportion of adipocytes, showing that the virus may directly infect the parenchymal cells of subcutaneous fat. Infection appears to activate the IFN alpha pathway and to attract infiltrating leukocytes. Due to the huge numbers of adipocytes in adults, the adipose tissue represents a significant reservoir for SARS-CoV-2 and an important source of inflammatory mediators.

Kaempferol reduces obesity, prevents intestinal inflammation, and modulates gut microbiota in high-fat diet mice.

Kaempferol, a flavonoid identified in a wide variety of dietary sources, has been reported to possess anti-obesity properties; however, its underlying mechanism was poorly understood. Chronic, low-grade gut inflammation and dysbacteria are proposed as underlying factors as well as novel treatment approaches for obesity-associated pathologies. This present study aims to investigate the benefits of experimental treatment with kaempferol on intestinal inflammation and gut microbial balance in animal model of obesity. High fat diet (HFD) was applied to C57BL/6J mice for 16 weeks, during which the supplement of kaempferol served as a variable. Clearly, HFD induced obesity, fat accumulation, glucose intolerance and adipose inflammation, the metabolic syndrome of which was the main finding. All these metabolic disorders can be alleviated through kaempferol supplementation. In addition, increased intestinal permeability, infiltration of immunocytes (macrophage, dendritic cells and neutrophils) and overexpression of inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, monocyte chemoattractant protein-1) were also found in the HFD-induced mice. Kaempferol supplementation improved intestinal barrier integrity and inhibited gut inflammation, by reducing the activation of TLR4/NF-κB pathway. Furthermore, the characterization of the cecal microbiota by sequencing showed that kaempferol supplementation was able to counteract the dysbiosis associated to obesity. Our study delineated the multiple mechanism of action underlying the anti-obesity effect of kaempferol, and provide scientific evidence to support the development of kaempferol as a dietary supplement for obesity treatment.

Shades of white: new insights into tissue-resident leukocyte heterogeneity.

Populations of white blood cells (leukocytes) have been found in tissues and organs across the body, in states of both health and disease. The role leukocytes play within these tissues is often highly contested. For many leukocytes, there are studies outlining pro-inflammatory destructive functions, while other studies provide clear evidence of anti-inflammatory homeostatic activities of leukocytes within the same tissue. We discuss how this functional dissonance can be explained by leukocyte heterogeneity. Although cell morphology and surface receptor profiles are excellent methods to segregate cell types, the true degree of leukocyte heterogeneity that exists can only be appreciated by studying the variable and dynamic gene expression profile. Unbiased single-cell RNA sequencing profiling of tissue-resident leukocytes is transforming the way we understand leukocytes across health and disease. Recent investigations into adipose tissue-resident leukocytes have revealed unprecedented levels of heterogeneity among populations of macrophages. We use this example to pose emerging questions regarding tissue-resident leukocytes and review what is currently known (and unknown) about the diversity of tissue-resident leukocytes within different organs.

The immunomodulatory potential of murine adipose-derived mesenchymal stem cells is enhanced following culture on chitosan film.

INTRODUCTION: Recent studies show that the paracrine immunomodulatory effects of mesenchymal stem cells (MSCs) are mediated by the secretion of interleukin-10 (IL-10), transforming growth factor-beta (TGF ß), and nitric oxide (NO). The preconditioning of MSCs improves their immunomodulatory characteristics. Chitosan is a biopolymer with low toxicity and biodegradability, used as a membrane for MSCs three-dimensional culture. The present study aimed to evaluate the levels of immunomodulatory mediators of mesenchymal cells cultured on the chitosan film. MATERIALS & METHODS: MSCs were isolated from abdominal adipose tissue of BALB/c mice. Flow cytometry and differential culture medium were used to confirm the identity of isolated mesenchymal stem cells. The MSCs were divided into three groups; The first group was treated with 10 ng/mL LPS. The second group was seeded in the flasks coated with the chitosan film (3% w/v). The last group was cultured in the flasks without any preconditioning. After 72 h, IL-10, TGF-ß, and NO concentrations were measured in the conditioned media. In addition, the arginase activity in mesenchymal stem cells was measured using a colorimetric method. RESULTS: The proliferative spindle-shaped MSCs formed several three-dimensional spheroids on the chitosan film. It was shown that the level of TGF-ß and IL-10 were increased significantly after treatment with LPS (P = 0.02) and spheroid formation (P = 0.01). In addition, the arginase activity was enormously augmented in spheroids compared to controls (7.13-fold increase; 1.71 ± 0.08 and 0.24 ± 0.01 respectively; P = 0.021). On the other hand, the LPS treatment but not the culture on chitosan film increased the NO level significantly (P = 0.02 and P = 0.14, respectively). CONCLUSION: Using chitosan film as a three-dimensional culture strategy significantly affects the production of immunosuppressive factors by MSCs in vitro through increased secretion of TGF-ß and IL-10 and arginase activity.

Time-Restricted Feeding Restores Obesity-Induced Alteration in Adipose Tissue Immune Cell Phenotype.

Studies suggest that time-restricted feeding (TRF) may prevent obesity and its commodities. At present, little is known about how TRF impacts immune cells, and whether such an effect is linked to altered metabolic parameters under condition of a high-fat diet (HFD)-induced obesity. To address these issues, we conducted a study in which we determined whether TRF has therapeutic efficacy against weight gain, adiposity, as well as associated immune cell disturbance found in obese mice. Six-week-old male C57BL/6 mice were fed a low-fat diet (LFD) or HFD ad libitum for six weeks, after which time a subgroup of HFD mice was switched to the 10 h TRF paradigm (HFD-TRF) for additional eight weeks. We found that TRF intervention reduced HFD-induced weight gain. Even with comparable fat mass and mean adipocyte area, the HFD-TRF group had lower mRNA levels of proinflammatory cytokine Tnfα and chemokine Ccl8, along with reduced numbers of adipose tissue macrophages (ATM), CD11c+ ATM, and CD8+ T cell compared to the HFD group, while maintaining CD8+ to CD4+ ratio at levels similar to those in the LFD group. Furthermore, TRF intervention was effective in improving glucose tolerance and reducing HOMA-IR. Taken together, our findings suggest that TRF restores the obesity-induced alteration in immune cell composition, and this effect may in part contribute to health benefits (including insulin sensitivity) of practicing TRF.

Leptin Induces Apoptotic and Pyroptotic Cell Death via NLRP3 Inflammasome Activation in Rat Hepatocytes.

Leptin, a hormone that is predominantly produced by adipose tissue, is closely associated with various liver diseases. However, there is a lack of understanding as to whether leptin directly induces cytotoxic effects in hepatocytes as well as the mechanisms that are involved. Inflammasomes, which are critical components in the innate immune system, have been recently shown to modulate cell death. In this study, we examined the effect of leptin on the viability of rat hepatocytes and the underlying mechanisms, with a particular focus on the role of inflammasomes activation. Leptin treatment induced cytotoxicity in rat hepatocytes, as determined by decreased cell viability, increased caspase-3 activity, and the enhanced release of lactate dehydrogenase. NLRP3 inflammasomes were activated by leptin both in vitro and in vivo, as determined by the maturation of interleukin-1ß and caspase-1, and the increased expression of inflammasome components, including NLRP3 and ASC. Mechanistically, leptin-induced inflammasome activation is mediated via the axis of ROS production, ER stress, and autophagy. Notably, the inhibition of inflammasomes by treatment with the NLRP3 inhibitor or the IL-1 receptor antagonist protected the hepatocytes from leptin-induced cell death. Together, these results indicate that leptin exerts cytotoxic effects in hepatocytes, at least in part, via the activation of NLRP3 inflammasomes.

Thymus-Derived CD4+CD8+ Cells Reside in Mediastinal Adipose Tissue and the Aortic Arch.

Double-positive CD4+CD8αß+ (DP) cells are thought to reside as T cell progenitors exclusively within the thymus. We recently discovered an unexpected CD4+ and CD8αß+ immune cell population in healthy and atherosclerotic mice by single-cell RNA sequencing. Transcriptomically, these cells resembled thymic DPs. Flow cytometry and three-dimensional whole-mount imaging confirmed DPs in thymus, mediastinal adipose tissue, and aortic adventitia, but nowhere else. Deep transcriptional profiling revealed differences between DP cells isolated from the three locations. All DPs were dependent on RAG2 expression and the presence of the thymus. Mediastinal adipose tissue DPs resided in close vicinity to invariant NKT cells, which they could activate in vitro. Thymus transplantation failed to reconstitute extrathymic DPs, and frequencies of extrathymic DPs were unaltered by pharmacologic inhibition of S1P1, suggesting that their migration may be locally confined. Our results define two new, transcriptionally distinct subsets of extrathymic DPs that may play a role in aortic vascular homeostasis.