Innate Type-2 Cytokines: From Immune Regulation to Therapeutic Targets.

The intricate role of innate type-2 cytokines in immune responses is increasingly acknowledged for its dual nature, encompassing both protective and pathogenic dimensions. Ranging from defense against parasitic infections to contributing to inflammatory diseases like asthma, fibrosis, and obesity, these cytokines intricately engage with various innate immune cells. This review meticulously explores the cellular origins of innate type-2 cytokines and their intricate interactions, shedding light on factors that amplify the innate type-2 response, including TSLP, IL-25, and IL-33. Recent advancements in therapeutic strategies, specifically the utilization of biologics targeting pivotal cytokines (IL-4, IL-5, and IL-13), are discussed, offering insights into both challenges and opportunities. Acknowledging the pivotal role of innate type-2 cytokines in orchestrating immune responses positions them as promising therapeutic targets. The evolving landscape of research and development in this field not only propels immunological knowledge forward but also holds the promise of more effective treatments in the future.

CRIF1 deficiency induces FOXP3LOW inflammatory non-suppressive regulatory T cells, thereby promoting antitumor immunity.

Recently identified human FOXP3lowCD45RA- inflammatory non-suppressive (INS) cells produce proinflammatory cytokines, exhibit reduced suppressiveness, and promote antitumor immunity unlike conventional regulatory T cells (Tregs). In spite of their implication in tumors, the mechanism for generation of FOXP3lowCD45RA- INS cells in vivo is unclear. We showed that the FOXP3lowCD45RA- cells in human tumors demonstrate attenuated expression of CRIF1, a vital mitochondrial regulator. Mice with CRIF1 deficiency in Tregs bore Foxp3lowINS-Tregs with mitochondrial dysfunction and metabolic reprograming. The enhanced glutaminolysis activated α-ketoglutarate-mTORC1 axis, which promoted proinflammatory cytokine expression by inducing EOMES and SATB1 expression. Moreover, chromatin openness of the regulatory regions of the Ifng and Il4 genes was increased, which facilitated EOMES/SATB1 binding. The increased α-ketoglutarate-derived 2-hydroxyglutarate down-regulated Foxp3 expression by methylating the Foxp3 gene regulatory regions. Furthermore, CRIF1 deficiency-induced Foxp3lowINS-Tregs suppressed tumor growth in an IFN-γ-dependent manner. Thus, CRIF1 deficiency-mediated mitochondrial dysfunction results in the induction of Foxp3lowINS-Tregs including FOXP3lowCD45RA- cells that promote antitumor immunity.

Comprehensive Transcriptomic Analysis for Thymic Epithelial Cells of Aged Mice and Humans.

Thymic epithelial cells (TECs) play a critical role in thymic development and thymopoiesis. As individuals age, TECs undergo various changes that impact their functions, leading to a reduction in cell numbers and impaired thymic selection. These age-related alterations have been observed in both mice and humans. However, the precise mechanisms underlying age-related TEC dysfunction remain unclear. Furthermore, there is a lack of a comprehensive study that connects mouse and human biological processes in this area. To address this gap, we conducted an extensive transcriptome analysis of young and old TECs in mice, complemented by further analysis of publicly available human TEC single-cell RNA sequencing data. Our analysis revealed alterations in both known and unknown pathways that potentially contribute to age-related TEC dysfunction. Specifically, we observed downregulation of pathways related to cell proliferation, T cell development, metabolism, and cytokine signaling in old age TECs. Conversely, TGF-ß, BMP, and Wnt signaling pathways were upregulated, which have been known to be associated with age-related TEC dysfunctions or newly discovered in this study. Importantly, we found that these age-related changes in mouse TECs were consistently present in human TECs as well. This cross-species validation further strengthens the significance of our findings. In conclusion, our comprehensive analysis provides valuable insight into the biological and immunological characteristics of aged TECs in both mice and humans. These findings contribute to a better understanding of thymic involution and age-induced immune dysfunction.

De novo fatty-acid synthesis protects invariant NKT cells from cell death, thereby promoting their homeostasis and pathogenic roles in airway hyperresponsiveness.

Invariant natural-killer T (iNKT) cells play pathogenic roles in allergic asthma in murine models and possibly also humans. While many studies show that the development and functions of innate and adaptive immune cells depend on their metabolic state, the evidence for this in iNKT cells is very limited. It is also not clear whether such metabolic regulation of iNKT cells could participate in their pathogenic activities in asthma. Here, we showed that acetyl-coA-carboxylase 1 (ACC1)-mediated de novo fatty-acid synthesis is required for the survival of iNKT cells and their deleterious functions in allergic asthma. ACC1, which is a key fatty-acid synthesis enzyme, was highly expressed by lung iNKT cells from WT mice that were developing asthma. Cd4-Cre::Acc1fl/fl mice failed to develop OVA-induced and HDM-induced asthma. Moreover, iNKT cell-deficient mice that were reconstituted with ACC1-deficient iNKT cells failed to develop asthma, unlike when WT iNKT cells were transferred. ACC1 deficiency in iNKT cells associated with reduced expression of fatty acid-binding proteins (FABPs) and peroxisome proliferator-activated receptor (PPAR)γ, but increased glycolytic capacity that promoted iNKT-cell death. Furthermore, circulating iNKT cells from allergic-asthma patients expressed higher ACC1 and PPARG levels than the corresponding cells from non-allergic-asthma patients and healthy individuals. Thus, de novo fatty-acid synthesis prevents iNKT-cell death via an ACC1-FABP-PPARγ axis, which contributes to their homeostasis and their pathogenic roles in allergic asthma.

Comparison of Two Variant Analysis Programs for Next-Generation Sequencing Data of Whole Mitochondrial Genome.

BACKGROUND: With advance of next-generation sequencing (NGS) techniques, the need for mitochondrial DNA analysis is increasing not only in the forensic area, but also in medical fields. METHODS: Two commercial programs, Converge Software (CS) and Torrent Variant Caller for variant calling of NGS data, were compared with a considerable amount of sequence data of 50 samples with a homogeneous ethnicity. RESULTS: About 2,300 variants were identified and the two programs showed about 90% of consistency. CS, a dedicated analysis program for mitochondrial DNA, showed some advantages for forensic use. By additional visual inspection, several causes of discrepancy in variant calling results were identified. Application of different notation rules for mitochondrial sequence and the minor allele frequency close to detection threshold were the two most significant reasons. CONCLUSION: With prospective improvement of each program, researchers and practitioners should be aware of characteristics of the analysis program they use and prepare their own strategies to determine variants.

Invariant natural killer T cells in lung diseases.

Invariant natural killer T (iNKT) cells are a subset of T cells that are characterized by a restricted T-cell receptor (TCR) repertoire and a unique ability to recognize glycolipid antigens. These cells are found in all tissues, and evidence to date suggests that they play many immunological roles in both homeostasis and inflammatory conditions. The latter include lung inflammatory diseases such as asthma and infections: the roles of lung-resident iNKT cells in these diseases have been extensively researched. Here, we provide insights into the biology of iNKT cells in health and disease, with a particular focus on the role of pulmonary iNKT cells in airway inflammation and other lung diseases.

Triple-Negative Breast Cancer-Derived Extracellular Vesicles Promote a Hepatic Premetastatic Niche via a Cascade of Microenvironment Remodeling.

Patients with triple-negative breast cancer (TNBC) often develop metastases in visceral organs including the liver, but the detailed molecular mechanisms of TNBC liver metastasis is not clearly understood. In this study, we tried to dissect the process of premetastatic niche formation in the liver by using patient-derived xenograft (PDX) models of TNBC with different metastatic propensity. RNA sequencing of TNBC PDX models that successfully metastasized to liver showed upregulation of the Cx3cr1 gene in the liver microenvironment. In syngeneic breast cancer models, the Cx3cr1 upregulation in liver preceded the development of cancer cell metastasis and was the result of recruitment of CX3CR1-expressing macrophages. The recruitment was induced by the CX3CL1 production from the liver endothelial cells and this CX3CL1-CX3CR1 signaling in the premetastatic niche resulted in upregulation of MMP9 that promoted macrophage migration and cancer cell invasion. In addition, our data suggest that the extracellular vesicles derived from the breast cancer cells induced the TNFα expression in liver, which leads to the CX3CL1 upregulation. Lastly, the plasma CX3CL1 levels in 155 patients with breast cancer were significantly associated with development of liver metastasis. IMPLICATIONS: Our data provides previously unknown cascades regarding the molecular education of premetastatic niche in liver for TNBC.

Computed Tomography-based Prognostication in Lung Adenocarcinomas through Histopathological Feature Learning: A Retrospective Multicenter Study.

Rationale: Modeling imaging surrogates for well-validated histopathological risk factors would enable prognostication in early-stage lung adenocarcinomas. Objectives: We aimed to develop and validate computed tomography (CT)-based deep learning (DL) models for the prognostication of early-stage lung adenocarcinomas through learning histopathological features and to investigate the models' reproducibility using retrospective, multicenter datasets. Methods: Two DL models were trained to predict visceral pleural invasion and lymphovascular invasion, respectively, using preoperative chest CT scans from 1,426 patients with stage I-IV lung adenocarcinomas. The averaged model output was defined as the composite score and evaluated for the prognostic discrimination and its added value to clinicopathological factors in temporal (n = 610) and external test sets (n = 681) of stage I lung adenocarcinomas. The study outcomes were freedom from recurrence (FFR) and overall survival (OS). Interscan and interreader reproducibility were analyzed in 31 patients with lung cancer who underwent same-day repeated CT scans. Results: For the temporal test set, the time-dependent area under the receiver operating characteristic curve was 0.76 (95% confidence interval [CI], 0.71-0.81) for 5-year FFR and 0.67 (95% CI, 0.59-0.75) for 5-year OS. For the external test set, the area under the curve was 0.69 (95% CI, 0.63-0.75) for 5-year OS. The discrimination performance remained stable in 10-year follow-up for both outcomes. The prognostic value of the composite score was independent of and complementary to the clinical factors (adjusted per-percent hazard ratio for FFR [temporal test], 1.04 [95% CI, 1.03-1.05; P < 0.001]; OS [temporal test], 1.03 [95% CI, 1.02-1.04; P < 0.001]; OS [external test], 1.03 [95% CI, 1.02-1.04; P < 0.001]). The likelihood ratio tests indicated added value of the composite score (all P < 0.05). The interscan and interreader reproducibility were excellent (Pearson's correlation coefficient, 0.98 for both). Conclusions: The CT-based composite score obtained from DL of histopathological features predicted survival in early-stage lung adenocarcinomas with high reproducibility.

Whole Mitochondrial Genome Analysis in Non-Small Cell Lung Carcinoma Reveals Unique Tumor-Specific Somatic Mutations.

CONTEXT.­: Mitochondria and mitochondrial DNA have been suggested to play a role in cancer initiation and progression. Knowledge of mitochondrial DNA could provide a breakthrough to advance cancer management. OBJECTIVE.­: To identify the mitochondrial DNA landscape in non-small cell lung carcinoma. DESIGN.­: The adenocarcinoma set consisted of 365 pairs of adenocarcinomas and normal lung tissues, whereas the metastasis set included 12 primary non-small cell carcinomas, 15 metastatic tumors, and their normal counterparts. Tumor-specific somatic variants were identified, and if a variant showed heteroplasmy, the proportion of minor alleles was evaluated. Variants with greater than 10% change in allele frequency between tumor and normal pairs were identified as "heteroplasmic shifts." RESULTS.­: Tumor-specific variants appeared throughout the whole mitochondrial genome, without a common hot spot. Distinct variant profiles were seen in 289 (79.18%) of all individual adenocarcinomas. The presence of a unique profile and the number and loading of heteroplasmic shifts in tumors increased with higher stage or lymph node metastasis, and were related to shorter survival. In the metastasis set, the primary tumor variants were generally found in metastatic tumors. CONCLUSIONS.­: This study shows that somatic mitochondrial DNA mutations present with diverse locations and unique profiles in each individual tumor, implying their clinicopathologic utility.

High tumor hexokinase-2 expression promotes a pro-tumorigenic immune microenvironment by modulating CD8+/regulatory T-cell infiltration.

BACKGROUND: Relationship between cancer cell glycolysis and the landscape of tumor immune microenvironment in human cancers was investigated. METHODS: Forty-one fresh lung adenocarcinoma (ADC) tissues were analyzed using flow cytometry for comprehensive immunoprofiling. Formalin-fixed tissues were immunostained for hexokinase-2 (HK2) to assess cancer cell glycolysis. For validation, formalin-fixed tissues from 375 lung ADC, 118 lung squamous cell carcinoma (SqCC), 338 colon ADC, and 78 lung cancer patients treated with anti-PD-1/PD-L1 immunotherapy were immunostained for HK2, CD8, and FOXP3. RESULTS: Based on immunoprofiling of lung ADC, HK2 tumor expression was associated with the composition of lymphoid cells rather than myeloid cells. High HK2 tumor expression was associated with immunosuppressive/pro-tumorigenic features, especially decreased ratio of CD8 + T-cells to Tregs (rho = -0.415, P = 0.012). This correlation was also confirmed in four different cohorts including lung ADC and SqCC, colon ADC, and the immunotherapy cohort (rho = -0.175~-0.335, all P < 0.05). A low CD8 + T-cell to Treg ratio was associated with poor progression-free survival and overall survival in lung SqCC patients, and a shorter overall survival in the immunotherapy cohort (all, P < 0.05). CONCLUSION: An increase in HK2 expression may contribute to shaping the immunosuppressive/pro-tumorigenic tumor microenvironment by modulating the CD8 + T-cell to Treg ratio. Targeting tumor HK2 expression might be a potential strategy for enhancing anti-tumor immunity.

Design and Optimization of an α-Helical Bundle Dimer Cell-Penetrating Peptide for In Vivo Drug Delivery.

To deliver membrane-impermeable drugs into eukaryotic cells, a lot of cell-penetrating peptides (CPPs) were discovered. Previously we designed an amphipathic α-helical peptide which dimerizes itself via its two C-residues. This bis-disulfide-linked dimeric bundle, LK-3, has remarkable cell-penetrating ability at nanomolar concentration, which is an essential prerequisite for CPP. In an effort to optimize the sequence of LK-3, we adjusted its length and evaluated changes in the dimerization rate. We found that a 10-amino-acid monomer has the fastest dimerization rate and subsequently modified its hydrophobic and hydrophilic residues to construct a small peptide library. The evaluation of cell permeability of these derivatives showed that their cell-penetrating ability is comparable to that of the LK-3, except V- or H-containing ones. In this library, diLR10 was found to display fast nanomolar cell membrane penetration, low toxicity, and ease of production. The methotrexate (MTX) conjugate of diLR10, MTX-diLR10, has a 19-fold increased efficacy over MTX in MDA-MB-231 cells and efficiently deflates lesions in a rheumatoid arthritis (RA) in vivo mouse model.

TCF1+PD-1+ tumour-infiltrating lymphocytes predict a favorable response and prolonged survival after immune checkpoint inhibitor therapy for non-small-cell lung cancer.

BACKGROUND: T-cell factor 1 (TCF1)+Programmed cell death-1 (PD-1)+ tumour-infiltrating lymphocytes (TILs) are a recently defined subset of exhausted T-cells (Texh-cells) that exhibit a progenitor phenotype. They have been associated with a response to immune checkpoint inhibitor (ICI) therapy in murine tumour models and in patients with malignant melanoma. We investigated the significance of TCF1+PD-1+ TILs as a predictive biomarker for ICI therapy response in non-small-cell lung cancer (NSCLC). METHODS: Two different cohorts of NSCLC patients treated with ICI targeting the PD-1/PD-L1 pathway were included. RNA-seq was performed using NSCLC tissues obtained from 234 patients prior to immunotherapy (RNA-seq cohort). Double immunostaining of TCF1 and PD-1 and single immunostaining of other immunologic markers were performed in resected tumour tissues from another 116 patients (immunohistochemistry cohort). RESULTS: In the RNA-seq cohort, both Texh-cell and progenitor Texh-cell gene sets were enriched in responders compared with non-responders. Larger Texh-cell fractions and increased progenitor Texh-cell gene sets were significantly associated with better progression-free survival (PFS). In the immunohistochemistry cohort, the TCF1+PD-1+ TIL number and PD-L1 tumour proportion score were significantly higher in responders than in non-responders. A high number of TCF1+PD-1+ TILs was significantly associated with both PFS and overall survival (OS) after ICI therapy, and it independently predicted a better PFS and OS according to multivariate analysis. CONCLUSION: TCF1+PD-1+ TILs, representing progenitor Texh-cells, predict both better response and survival in NSCLC patients after ICI therapy. Thus, they may be a useful predictive biomarker for ICI therapy in NSCLC.

Cigarette smoke aggravates asthma by inducing memory-like type 3 innate lymphoid cells.

Although cigarette smoking is known to exacerbate asthma, only a few clinical asthma studies have been conducted involving smokers. Here we show, by comparing paired sputum and blood samples from smoking and non-smoking patients with asthma, that smoking associates with significantly higher frequencies of pro-inflammatory, natural-cytotoxicity-receptor-non-expressing type 3 innate lymphoid cells (ILC3) in the sputum and memory-like, CD45RO-expressing ILC3s in the blood. These ILC3 frequencies positively correlate with circulating neutrophil counts and M1 alveolar macrophage frequencies, which are known to increase in uncontrolled severe asthma, yet do not correlate with circulating eosinophil frequencies that characterize allergic asthma. In vitro exposure of ILCs to cigarette smoke extract induces expression of the memory marker CD45RO in ILC3s. Cigarette smoke extract also impairs the barrier function of airway epithelial cells and increases their production of IL-1ß, which is a known activating factor for ILC3s. Thus, our study suggests that cigarette smoking increases local and circulating frequencies of activated ILC3 cells, plays a role in their activation, thereby aggravating non-allergic inflammation and the severity of asthma.

Histopathologic Basis for a Chest CT Deep Learning Survival Prediction Model in Patients with Lung Adenocarcinoma.

Background A preoperative CT-based deep learning (DL) prediction model was proposed to estimate disease-free survival in patients with resected lung adenocarcinoma. However, the black-box nature of DL hinders interpretation of its results. Purpose To provide histopathologic evidence underpinning the DL survival prediction model and to demonstrate the feasibility of the model in identifying patients with histopathologic risk factors through unsupervised clustering and a series of regression analyses. Materials and Methods For this retrospective study, data from patients who underwent curative resection for lung adenocarcinoma without neoadjuvant therapy from January 2016 to September 2020 were collected from a tertiary care center. Seven histopathologic risk factors for the resected adenocarcinoma were documented: the aggressive adenocarcinoma subtype (cribriform, morular, solid, or micropapillary-predominant subtype); mediastinal nodal metastasis (pN2); presence of lymphatic, venous, and perineural invasion; visceral pleural invasion (VPI); and EGFR mutation status. Unsupervised clustering using 80 DL model-driven CT features was performed, and associations between the patient clusters and the histopathologic features were analyzed. Multivariable regression analyses were performed to investigate the added value of the DL model output to the semantic CT features (clinical T category and radiologic nodule type [ie, solid or subsolid]) for histopathologic associations. Results A total of 1667 patients (median age, 64 years [IQR, 57-71 years]; 975 women) were evaluated. Unsupervised patient clusters 3 and 4 were associated with all histopathologic risk factors (P < .01) except for EGFR mutation status (P = .30 for cluster 3). After multivariable adjustment, model output was associated with the aggressive adenocarcinoma subtype (odds ratio [OR], 1.03; 95% CI: 1.002, 1.05; P = .03), venous invasion (OR, 1.03; 95% CI: 1.004, 1.06; P = .02), and VPI (OR, 1.08; 95% CI: 1.06, 1.10; P < .001), independently of the semantic CT features. Conclusion The deep learning model extracted CT imaging surrogates for the histopathologic profiles of lung adenocarcinoma. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Yanagawa in this issue.

OASL1-Mediated Inhibition of Type I IFN Reduces Influenza A Infection-Induced Airway Inflammation by Regulating ILC2s.

PURPOSE: Three observations drove this study. First, 2'-5'-oligoadenylate synthetase-like protein (OASL) is a negative regulator of type I interferon (IFN). Second, type I IFN plays a central role during virus infections and the pathogenesis of various diseases, including asthma. Third, influenza A virus (IAV) causes non-eosinophilic asthma. To evaluate the potential relationships between OASL, type I IFN, and pulmonary innate immune cells in IAV-induced acute airway inflammation by using Oasl1-/- mice. METHODS: Asthma was induced in wild-type (WT) and Oasl1-/- mice with IAV or ovalbumin (OVA). Airway hyperreactivity (AHR) and immune cell infiltration in the bronchoalveolar lavage (BAL) fluids were measured. The immune cells in the lungs were analyzed by flow cytometry. To investigate the ability of type I IFN to shape the response of lung type 2 innate lymphoid cells (ILC2s), IFN-α was treated intratracheally. Plasmacytoid dendritic cells (pDCs) sorted from bone marrow and ILC2s sorted from lungs of naive mice were co-cultured with/without interferon-alpha receptor subunit 1 (IFNAR-1)-blocking antibodies. RESULTS: In the IAV-induced asthma model, Oasl1-/- mice developed greater AHR and immune cell infiltration in the BAL fluids than WT mice. This was not observed in OVA-induced asthma, a standard model of allergen-induced asthma. The lungs of infected Oasl1-/- mice also had elevated DC numbers and Ifna expression and depressed IAV-induced ILC2 responses, namely, proliferation and type 2 cytokine and amphiregulin production. Intratracheal administration of type I IFN in naïve mice suppressed lung ILC2 production of type 2 cytokines and amphiregulin. Co-culture of ILC2s with pDCs showed that pDCs inhibit the function of ILC2s by secreting type I IFN. CONCLUSIONS: OASL1 may impede the IAV-induced acute airway inflammation that drives AHR by inhibiting IAV-induced type I IFN production from lung DCs, thereby preserving the functions of lung ILC2s, including their amphiregulin production.

A unique population of neutrophils generated by air pollutant-induced lung damage exacerbates airway inflammation.

BACKGROUND: Diesel exhaust particles (DEPs) are the main component of traffic-related air pollution and have been implicated in the pathogenesis and exacerbation of asthma. However, the mechanism by which DEP exposure aggravates asthma symptoms remains unclear. OBJECTIVE: This study aimed to identify a key cellular player of air pollutant-induced asthma exacerbation and development. METHODS: We examined the distribution of innate immune cells in the murine models of asthma induced by house dust mite and DEP. Changes in immune cell profiles caused by DEP exposure were confirmed by flow cytometry and RNA-Seq analysis. The roles of sialic acid-binding, Ig-like lectin F (SiglecF)-positive neutrophils were further evaluated by adoptive transfer experiment and in vitro functional studies. RESULTS: DEP exposure induced a unique population of lung granulocytes that coexpressed Ly6G and SiglecF. These cells differed phenotypically, morphologically, functionally, and transcriptionally from other SiglecF-expressing cells in the lungs. Our findings with murine models suggest that intratracheal challenge with DEPs induces the local release of adenosine triphosphate, which is a damage-associated molecular pattern signal. Adenosine triphosphate promotes the expression of SiglecF on neutrophils, and these SiglecF+ neutrophils worsen type 2 and 3 airway inflammation by producing high levels of cysteinyl leukotrienes and neutrophil extracellular traps. We also found Siglec8- (which corresponds to murine SiglecF) expressing neutrophils, and we found it in patients with asthma-chronic obstructive pulmonary disease overlap. CONCLUSION: The SiglecF+ neutrophil is a novel and critical player in airway inflammation and targeting this population could reverse or ameliorate asthma.

Interactions between NCR+ILC3s and the Microbiome in the Airways Shape Asthma Severity.

Asthma is a heterogeneous disease whose development is shaped by a variety of environmental and genetic factors. While several recent studies suggest that microbial dysbiosis in the gut may promote asthma, little is known about the relationship between the recently discovered lung microbiome and asthma. Innate lymphoid cells (ILCs) have also been shown recently to participate in asthma. To investigate the relationship between the lung microbiome, ILCs, and asthma, we recruited 23 healthy controls (HC), 42 patients with non-severe asthma, and 32 patients with severe asthma. Flow cytometry analysis showed severe asthma associated with fewer natural cytotoxicity receptor (NCR)+ILC3s in the lung. Similar changes in other ILC subsets, macrophages, and monocytes were not observed. The asthma patients did not differ from the HC in terms of the alpha and beta-diversity of the lung and gut microbiomes. However, lung function correlated positively with both NCR+ILC3 frequencies and microbial diversity in the lung. Sputum NCR+ILC3 frequencies correlated positively with lung microbiome diversity in the HC, but this relationship was inversed in severe asthma. Together, these data suggest that airway NCR+ILC3s may contribute to a healthy commensal diversity and normal lung function.

Mesenchymal Stem Cells Suppress Severe Asthma by Directly Regulating Th2 Cells and Type 2 Innate Lymphoid Cells.

Patients with severe asthma have unmet clinical needs for effective and safe therapies. One possibility may be mesenchymal stem cell (MSC) therapy, which can improve asthma in murine models. However, it remains unclear how MSCs exert their beneficial effects in asthma. Here, we examined the effect of human umbilical cord blood-derived MSCs (hUC-MSC) on two mouse models of severe asthma, namely, Alternaria alternata-induced and house dust mite (HDM)/diesel exhaust particle (DEP)-induced asthma. hUC-MSC treatment attenuated lung type 2 (Th2 and type 2 innate lymphoid cell) inflammation in both models. However, these effects were only observed with particular treatment routes and timings. In vitro co-culture showed that hUC-MSC directly downregulated the interleukin (IL)-5 and IL-13 production of differentiated mouse Th2 cells and peripheral blood mononuclear cells from asthma patients. Thus, these results showed that hUC-MSC treatment can ameliorate asthma by suppressing the asthmogenic cytokine production of effector cells. However, the successful clinical application of MSCs in the future is likely to require careful optimization of the route, dosage, and timing.