Induced regulatory T cells suppress Tc1 cells through TGF-β signaling to ameliorate STZ-induced type 1 diabetes mellitus

Artificial Tolerogenic Dendritic Cell-Derived Vesicles Prepared by High-Pressure Homogenization for Potent Immunotherapy of Type 1 Diabetes

Tolerogenic dendritic cells (tolDCs) have emerged as a promising immunotherapeutic approach for type 1 diabetes (T1D) by promoting immune tolerance and modulating autoimmune responses against pancreatic β cells. However, their clinical applications are challenged by various limitations including cell viability, scalability, and manufacturing complexities. As an alternative, tolDC-derived extracellular vesicles could address some limitations of cell-based therapies, though their application in T1D treatment remains unexplored. Here, we developed the artificial tolDC-derived vesicles (ACDVtolDC) by a high-pressure homogenization approach, which retained immunosuppressive properties with high yield production and stability that improved the scalability for potential clinical use. In both chemically induced (STZ) and spontaneous (NOD) T1D mouse models, ACDVtolDC exhibited abilities to reduce T cell infiltration by approximately 4-fold in the pancreas and re-establish the balance between regulatory and cytotoxic T cells to a healthy baseline, thereby preserving β cells and ameliorating T1D onset. Additionally, the therapeutic effect of ACDVtolDC was superior to that of the tolDC treatment. These findings highlighted ACDVtolDC as a potent vesicle-based immunotherapy for T1D, offering practical advantages over traditional tolDC therapies.

Exploiting regulatory T cells (Tregs): Cutting-edge therapy for autoimmune diseases

Regulatory T cells (Tregs) are a specialized subset of suppressive T cells that are essential for maintaining self-tolerance, regulating effector T cells, managing microbial infections, preventing tumors, allergies, and autoimmune disorders, and facilitating allograft transplantation. Disruptions in Treg function or abundance contribute to an imbalance between pathogenic and protective immune cells in autoimmune diseases. Recently, one promising treatment strategy to restore immune balance involves the selective expansion or manipulation of Tregs using low-dose IL-2 therapy, adoptive Treg cell transfer, and chimeric antigen receptor (CAR)-Treg approaches. Tregs have been shown in an increasing number of research studies to prevent or even treat a variety of disorders, such as tumors, autoimmune and allergic diseases, transplant rejection, and graft-versus-host disease. A thorough comprehension of Treg function is anticipated to provide clear prospects for effective Treg immunotherapy in the treatment of a wide range of diseases. This review provides an overview of Tregs biology, including their functions, suppressive mechanisms, phenotypic markers, as well as their involvement in disease settings. Furthermore, we discuss the therapeutic potential of different Treg subpopulations and their translational applications in the treatment of autoimmune diseases.

Improving regulatory T cell-based therapy: insights into post-translational modification regulation

Regulatory T (Treg) cells are pivotal for maintaining immune homeostasis and play essential roles in various diseases, such as autoimmune diseases, graft-versus-host disease (GVHD), tumors, and infectious diseases. Treg cells exert suppressive function via distinct mechanisms, including inhibitory cytokines, granzyme or perforin-mediated cytolysis, metabolic disruption, and suppression of dendritic cells. Forkhead Box P3 (FOXP3), the characteristic transcription factor, is essential for Treg cell function and plasticity. Cumulative evidence has demonstrated that FOXP3 activity and Treg cell function are modulated by a variety of post-translational modifications (PTMs), including ubiquitination, acetylation, phosphorylation, methylation, glycosylation, poly(ADP-ribosyl)ation, and uncharacterized modifications. This review describes Treg cell suppressive mechanisms and summarizes the current evidence on PTM regulation of FOXP3 and Treg cell function. Understanding the regulatory role of PTMs in Treg cell plasticity and function will be helpful in designing therapeutic strategies for autoimmune diseases, GVHD, tumors, and infectious diseases.

Beneficial Actions of 4-Methylumbelliferone in Type 1 Diabetes by Promoting β Cell Renewal and Inhibiting Dedifferentiation

Background/Objectives: This study aims to investigate the effects of 4-methylumbelliferone (4-MU) on islet morphology, cell phenotype and function, and to explore possible mechanisms of β cell regeneration. Methods: The Type 1 diabetes (T1D) model was induced by continuous dose injection of streptozotocin (STZ), and mice were treated with 4-MU for 3 weeks. Plasma insulin level, islet cell phenotype and immune infiltration were determined by IPGTT, ELISA, HE and immunofluorescence. The Ins2Cre/+/Rosa26-eGFP transgenic mice model was used to detect β identity change. Primary rodent islets were incubated with 4-MU or vehicle in the presence or absence of STZ, AO/PI staining, and a scanning electron microscope (SEM), PCR and ELISA were used to evaluated islet viability, islet morphology, the specific markers of islet β cells and insulin secretion. Results: Treatment with 4-MU significantly decreased blood glucose and increased plasma insulin levels in STZ-induced diabetes. The plasma insulin level in the STZ group was 7.211 ± 2.602 ng/mL, which was significantly lower than the control group level (26.94 ± 4.300 ng/mL, p < 0.001). In contrast, the plasma insulin level in the STZ + 4-MU group was 22.29 ± 7.791 ng/mL, which was significantly higher than the STZ group (p < 0.05). The 4-MU treatment increased islet and β cells numbers and decreased α cell numbers in STZ-induced diabetes. Conclusions: Islet inflammation as indicated by insulin and CD3 was caused by infiltrates, and the β cell proliferation as indicated by insulin and Ki67 was boosted by 4-MU. β cell dedifferentiation was inhibited by 4-MU as assessed by insulin and glucagon double-positive cells and confirmed by Ins2Cre/+/Rosa26-eGFP mice. In cultured primary rodent islets, 4-MU restored islet viability, protected islet morphology, inhibited β-cell dedifferentiation, and promoted insulin secretion. The benefits of 4-MU in T1D have been proved to be associated with β cells self-replication, dedifferentiation inhibition and immune progression suppression, which help to maintain β cell mass.

Role of Peptidyl Arginine Deiminase 4-Dependent Macrophage Extracellular Trap Formation in Type 1 Diabetes Pathogenesis

Excessive formation of macrophage extracellular trap (MET) has been implicated in several autoimmune disease pathogeneses; however, its impact on type 1 diabetes (T1D) and related mechanisms remains enigmatic. We demonstrated the pivotal role of peptidyl arginine deiminase 4 (PAD4) in driving profuse MET formation and macrophage M1 polarization in intestinal inflammation in NOD mice. Genetic knockout of PAD4 or adoptive transfer of METs altered the proportion of proinflammatory T cells in the intestine, subsequently influencing their migration to the pancreas. Combining RNA sequencing and CUT&Tag analysis, we found activated PAD4 transcriptionally regulated CXCL10 expression. This study comprehensively investigated how excessive PAD4-mediated MET formation in the colon increases the aggravation of intestinal inflammation and proinflammatory T-cell migration and finally is involved in T1D progression, suggesting that inhibition of MET formation may be a potential therapeutic target in T1D.

ARTICLE HIGHLIGHTS

Alleviated diabetic osteoporosis and peripheral neuropathic pain by Rehmannia glutinosa Libosch polysaccharide via increasing regulatory T cells

Diabetic peripheral neuropathy (DPN) and diabetic osteoporosis (DOP) are conditions that significantly impact the quality of life of patients worldwide. Rehmanniae Radix Preparata, a component of traditional Chinese medicine with a history spanning thousands of years, has been utilized in the treatment of osteoporosis and diabetes. Specifically, Rehmannia glutinosa Libosch polysaccharide (RGP), a key bioactive compound of Rehmanniae Radix Preparata, has demonstrated immune-modulating properties and beneficial effects on hyperglycemia, hyperlipidemia, and vascular inflammation in diabetic mice. Despite these known actions, the precise mechanisms of RGP in addressing DOP and DPN remain unclear. Our study aimed to explore the impact of RGP on osteoporosis and peripheral neuropathic pain in diabetic mice induced by streptozotocin (STZ). The findings revealed that RGP not only improved hyperglycemia and osteoporosis in STZ-induced diabetic mice but also enhanced osteogenesis, insulin production, and nerve health. Specifically, RGP alleviated distal pain, improved nerve conduction velocity, nerve fiber integrity, and immune cell balance in the spleen. Mechanistically, RGP was found to upregulate HDAC6 mRNA expression in regulatory T cells, potentially shedding light on novel pathways for preventing DOP and DPN. These results offer promising insights for the development of new therapeutic approaches for diabetic complications.

The potential therapeutic role of IL-35 in pathophysiological processes in type 1 diabetes mellitus

A chronic autoimmune condition known as type 1 diabetes mellitus (T1DM) has characteristics marked by a gradual immune-mediated deterioration of the β-cells that produce insulin and causes overt hyperglycemia. it affects more than 1.2 million kids and teenagers (0-19 years old). In both, the initiation and elimination phases of T1DM, cytokine-mediated immunity is crucial in controlling inflammation. T regulatory (Treg) cells, a crucial anti-inflammatory CD4+ T cell subset, secretes interleukin-35 (IL-35). The IL-35 has immunomodulatory properties by inhibiting pro-inflammatory cells and cytokines, increasing the secretion of interleukin-10 (IL-10) as well as transforming Growth Factor- β (TGF-β), along with stimulating the Treg and B regulatory (Breg) cells. IL-35, it is a possible target for cutting-edge therapies for cancers, inflammatory, infectious, and autoimmune diseases, including TIDM. Unanswered questions surround IL-35's function in T1DM. Increasing data suggests Treg cells play a crucial role in avoiding autoimmune T1DM. Throughout this review, we will explain the biological impacts of IL-35 and highlight the most recently progresses in the roles of IL-35 in treatment of T1DM; the knowledge gathered from these findings might lead to the development of new T1DM treatments. This review demonstrates the potential of IL-35 as an effective autoimmune diabetes inhibitor and points to its potential therapeutic value in T1DM clinical trials.

Adipocyte-specific FAK deletion promotes pancreatic β-cell apoptosis via adipose inflammatory response to exacerbate diabetes mellitus

BACKGROUND

White adipose tissue (WAT) has a key role in maintaining energy balance throughout the body, and their dysfunction take part in the regulation of diabetes mellitus. However, the internal regulatory mechanisms underlying are still unknown.

METHODS AND RESULTS

We generated adipocyte-specific FAK KO (FAK-AKO) mice and investigated their phenotype. The cascade of adipocyte, macrophage in adipocyte tissues, and pancreatic β-cells were proposed in FAK-AKO mice and validated by cell line studies using 3T3-L1, Raw264.7 and Min6. The FAK-AKO mice exhibited glucose intolerance, reduced adipose tissue mass and increased apoptosis, lipolysis and inflammatory response in adipose tissue. We further demonstrate that adipocyte FAK deletion increases β cell apoptosis and inflammatory infiltrates into islets, which is potentiated if mice were treated with STZ. In the STZ-induced diabetes model, FAK AKO mice exhibit less serum insulin content and pancreatic β cell area. Moreover, serum pro-inflammatory factors increased and insulin levels decreased after glucose stimulation in FAK AKO mice. In a parallel vitro experiment, knockdown or inhibition of FAK during differentiation also increased apoptosis, lipolysis and inflammatory in 3T3-L1 adipocytes, whereas the opposite was observed upon overexpression of FAK. Moreover, coculturing LPS-treated RAW264.7 macrophages with knockdown FAK of 3T3-L1 adipocytes increased macrophage pro-inflammatory response. Furthermore, conditioned medium from above stimulated Min6 cells apoptosis (with or without STZ), whereas the opposite was observed upon overexpression of FAK. Mechanistically, FAK protein interact with TRAF6 in adipocytes and knockdown or inhibition of FAK activated TRAF6/TAK1/NF-κB signaling, which exacerbates inflammation of adipocytes themselves.

CONCLUSION

Adipocyte FAK deletion promotes both adipocyte apoptosis and adipose tissue inflammation. Pro-inflammatory factors released by the FAK-null adipose tissue further trigger apoptosis in pancreatic islets induced by the administration of STZ, thereby exacerbating the diabetes mellitus. This study reveals a link between FAK-mediated adipose inflammation and diabetes mellitus, a mechanism that has not been previously recognized.

Unveiling cell subpopulations in T1D mouse islets using single-cell RNA sequencing

Type 1 diabetes (T1D) is an autoimmune disease characterized by the destruction of beta cells by immune cells. The interactions among cells within the islets may be closely linked to the pathogenesis of T1D. In this study, we used single-cell RNA sequencing (scRNA-Seq) to analyze the cellular heterogeneity within the islets of a T1D mouse model. We established a T1D mouse model induced by streptozotocin and identified cell subpopulations using scRNA-Seq technology. Our results revealed 11 major cell types in the pancreatic islets of T1D mice, with heterogeneity observed in the alpha and beta cell subgroups, which may play a crucial role in the progression of T1D. Flow cytometry further confirmed a mature alpha and beta cell reduction in T1D mice. Overall, our scRNA-Seq analysis provided insights into the cellular heterogeneity of T1D islet tissue and highlighted the potential importance of alpha and beta cells in developing T1D.NEW & NOTEWORTHY In this study, we created a comprehensive single-cell atlas of pancreatic islets in a T1D mouse model using scRNA-Seq and identified 11 major cell types in the islets, highlighting the role of alpha and beta cells in T1D. This study revealed a significant reduction in the maturity alpha and beta cells in T1D mice through flow cytometry. It also demonstrated the heterogeneity of alpha and beta cells, potentially crucial for T1D progression. Overall, our scRNA-Seq analysis provided new insights for understanding and treating T1D by studying cell subtype changes and functions.

Effect of pegagan (Centella asiatica) nanoparticle coated with chitosan on the cytokine profile of chronic diabetic mice

Diabetes is closely related to immune response problems when it occurs chronically. Pegagan (Centella asiatica) is a medicinal plant with active compounds. Madecassoside is beneficial in treating diabetes, and nanoparticle technology is expected to enhance the medicinal potential and availability of pegagan compounds. The aim of this study was to determine the effect of chitosan-coated pegagan nanoparticles on the cytokine profile of chronic diabetic mice, which included CD4+TNF-α+, CD8+TNF-α+, CD4+IFN-γ+, CD8+IFN-γ+ and IL-6+. An experimental study with a randomized complete block design (CRD) consisting of six treatments with seven replicates was conducted. The groups were: healthy mice as negative control; diabetic mice treated with distilled water as positive control and diabetic mice treated with nanoparticle coated with chitosan (NPC) 20 mg/kg, 30 mg/kg, 40 mg/kg, and metformin 130 mg/kgBW. The data were tested using one-way analysis of variance (ANOVA) with a significance level of 5% and continued with the Duncan's multiple range test. The results showed that pegagan NPC could significantly reduce the relative number of CD4+TNF-α+, CD8+TNF-α+, CD4+IFN-γ+ and CD8+IFN-γ+ and IL-6 in the dose of 20 mg/kg, 30 mg/kg and 40 mg/kg (p<0.05). The treatment dose of 20 mg/kg reduced CD4+TNF-α+, CD8+TNF-α+, CD4+IFN-γ+, CD8+IFN-γ+ to the levels of healthy mice and a dose of 30 mg/kg could reduce IL-6 as in healthy mice. These findings suggest that chitosan-coated pegagan nanoparticles are a promising therapy for diabetes, as they have the potential to modulate the immune response associated with chronic diabetes.

Modulation of CXCL10 activity as a therapeutic target of ocular toxoplasmosis in diabetic mice

Ocular toxoplasmosis is likely the most common cause of infectious posterior uveitis worldwide. CXCL10 chemokine has an important role in the maintenance of the T-cell response and the control of Toxoplasma gondii in the eye during chronic infection. Drugs that can modulate the chemokine activity could be effective against the parasite. In this work, CXCL10 local retinal expression was investigated in a diabetic mouse model with ocular toxoplasmosis for the first time. In addition, the efficacy of naphthoquinones and quinolones was compared to spiramycin (SP) in treating the infection and modulating the chemokine expression. Our results revealed that chloroquine (CQ) achieved the best results regarding the reduction of cerebral cyst burden (84.36%), improving the retinal histopathological changes, cellular infiltrates, and vasculitis significantly (P < 0.005), and balancing the strong CXCL10 expression caused by the infection. Buparvaquone-treated mice showed a significant percentage of reduction of brain cysts (76.25%), moderate improvement of histopathology, and mild to moderate CXCL10 expression. While SP showed the least efficacy against the parasite in the eye in the form of mild improvement of histopathological changes and downregulation of retinal chemokine expression with the least reduction rate of cerebral parasitic burden (57%). In conclusion, Optimal control of pathogens probably needs a balanced immune response with an optimum expression of chemokines. So, targeting the modulation of retinal CXCL10 may eventually be beneficial in the management of ocular toxoplasmosis plus its potential to act as a marker for predictive local immunological response during the infection.

Genetic lineage tracing identifies adaptive mechanisms of pancreatic islet β cells in various mouse models of diabetes with distinct age of initiation

During the pathogenesis of type 1 diabetes (T1D) and type 2 diabetes (T2D), pancreatic islets, especially the β cells, face significant challenges. These insulin-producing cells adopt a regeneration strategy to compensate for the shortage of insulin, but the exact mechanism needs to be defined. High-fat diet (HFD) and streptozotocin (STZ) treatment are well-established models to study islet damage in T2D and T1D respectively. Therefore, we applied these two diabetic mouse models, triggered at different ages, to pursue the cell fate transition of islet β cells. Cre-LoxP systems were used to generate islet cell type-specific (α, β, or δ) green fluorescent protein (GFP)-labeled mice for genetic lineage tracing, thereinto β-cell GFP-labeled mice were tamoxifen induced. Single-cell RNA sequencing (scRNA-seq) was used to investigate the evolutionary trajectories and molecular mechanisms of the GFP-labeled β cells in STZ-treated mice. STZ-induced diabetes caused extensive dedifferentiation of β cells and some of which transdifferentiated into a or δ cells in both youth- and adulthood-initiated mice while this phenomenon was barely observed in HFD models. β cells in HFD mice were expanded via self-replication rather than via transdifferentiation from α or δ cells, in contrast, α or δ cells were induced to transdifferentiate into β cells in STZ-treated mice (both youth- and adulthood-initiated). In addition to the re-dedifferentiation of β cells, it is also highly likely that these "α or δ" cells transdifferentiated from pre-existing β cells could also re-trans-differentiate into insulin-producing β cells and be beneficial to islet recovery. The analysis of ScRNA-seq revealed that several pathways including mitochondrial function, chromatin modification, and remodeling are crucial in the dynamic transition of β cells. Our findings shed light on how islet β cells overcome the deficit of insulin and the molecular mechanism of islet recovery in T1D and T2D pathogenesis.

Preclinical models for Type 1 Diabetes Mellitus - A practical approach for research

Numerous preclinical models have been developed to advance biomedical research in type 1 diabetes mellitus (T1DM). They are essential for improving our knowledge of T1DM development and progression, allowing researchers to identify potential therapeutic targets and evaluate the effectiveness of new medications. A deeper comprehension of these models themselves is critical not only to determine the optimal strategies for their utilization but also to fully unlock their potential applications in both basic and translational research. Here, we will comprehensively summarize and discuss the applications, advantages, and limitations of the commonly used animal models for human T1DM and also overview the up-to-date human tissue bioengineering models for the investigation of T1DM. By combining these models with a better understanding of the pathophysiology of T1DM, we can enhance our insights into disease initiation and development, ultimately leading to improved therapeutic responses and outcomes.

Engineered Cytokine-Primed Extracellular Vesicles with High PD-L1 Expression Ameliorate Type 1 Diabetes

Type 1 diabetes (T1D), which is a chronic autoimmune disease, results from the destruction of insulin-producing β cells targeted by autoreactive T cells. The recent discovery that mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) function as therapeutic tools for autoimmune conditions has attracted substantial attention. However, the in vivo distribution and therapeutic effects of MSC-EVs potentiated by pro-inflammatory cytokines in the context of T1D have yet to be established. Here, it is reported that hexyl 5-aminolevulinate hydrochloride (HAL)-loaded engineered cytokine-primed MSC-EVs (H@TI-EVs) with high expression of immune checkpoint molecule programmed death-legend 1 (PD-L1) exert excellent inflammatory targeting and immunosuppressive effects for T1D imaging and therapy. The accumulated H@TI-EVs in injured pancreas not only enabled the fluorescence imaging and tracking of TI-EVs through the intermediate product protoporphyrin (PpIX) generated by HAL, but also promoted the proliferative and anti-apoptotic effects of islet β cells. Further analysis revealed that H@TI-EVs exhibited an impressive ability to reduce CD4+ T cell density and activation through the PD-L1/PD-1 axis, and induced M1-to-M2 macrophage transition to reshape the immune microenvironment, exhibiting high therapeutic efficiency in mice with T1D. This work identifies a novel strategy for the imaging and treatment of T1D with great potential for clinical application.

Ginseng-derived panaxadiol ameliorates STZ-induced type 1 diabetes through inhibiting RORγ/IL-17A axis

Retinoic-acid-receptor-related orphan receptor γ (RORγ) is a major transcription factor for proinflammatory IL-17A production. Here, we revealed that the RORγ deficiency protects mice from STZ-induced Type 1 diabetes (T1D) through inhibiting IL-17A production, leading to improved pancreatic islet β cell function, thereby uncovering a potential novel therapeutic target for treating T1D. We further identified a novel RORγ inverse agonist, ginseng-derived panaxadiol, which selectively inhibits RORγ transcriptional activity with a distinct cofactor recruitment profile from known RORγ ligands. Structural and functional studies of receptor-ligand interactions reveal the molecular basis for a unique binding mode for panaxadiol in the RORγ ligand-binding pocket. Despite its inverse agonist activity, panaxadiol induced the C-terminal AF-2 helix of RORγ to adopt a canonical active conformation. Interestingly, panaxadiol ameliorates mice from STZ-induced T1D through inhibiting IL-17A production in a RORγ-dependent manner. This study demonstrates a novel regulatory function of RORγ with linkage of the IL-17A pathway in pancreatic β cells, and provides a valuable molecule for further investigating RORγ functions in treating T1D.

AhR activation promotes Treg cell generation by enhancing Lkb1-mediated fatty acid oxidation via the Skp2/K63-ubiquitination pathway

Several aryl hydrocarbon receptor (AhR) agonists have been reported to promote the generation of regulatory T cells (Treg cells), and the action mechanisms need to be identified. In this study, we addressed the underlying mechanism of AhR activation to induce the generation of Treg cells in the view of cellular metabolism. Naïve CD4+ T cells were purified with mouse CD4+ CD62L+ T Cells Isolation Kits. The proportions of Treg cells were detected by flow cytometry. The value of oxygen consumption rate (OCR) of CD4+ T cells was detected by the Seahorse XFe 96 analyzer. The activation of fatty acid oxidation (FAO)-related metabolic pathways was detected by Western blotting. Intracellular localization of Lkb1 was detected by immunofluorescence. The Strad-Mo25-Lkb1 complex formation and K63 chain ubiquitination modification of Lkb1 were detected by co-immunoprecipitation. The binding of AhR to the Skp2 promoter was detected by constructing luciferase reporter gene. AhR or carnitine palmitoyltransferases 1 was knockdown in dextran sulphate sodium (DSS)-induced colitis or collagen-induced arthritis (CIA) mice by infecting mice with adeno-associated virus via the tail vein injection. Compared to the control group, exogenous and endogenous AhR agonists 3,3'-diindolylmethane (DIM) and 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) were shown to preferentially upregulate the mRNA expression of FAO-related enzymes and the value of OCR. Consistently, pharmacological or genetic inhibition of FAO markedly diminished the induction of DIM and ITE on the differentiation of Treg cells. DIM and ITE functioned mainly through activating the liver kinase B1 (Lkb1)-AMPK pathway via promotion of Lkb1-Strad-Mo25 complex formation and Lkb1 K63 ubiquitination. DIM and ITE were also shown to upregulate the mRNA expression of Skp2, a ubiquitination-related enzyme, and facilitate the binding of AhR to the xenobiotic responsive element of Skp2 promoter region by luciferase reporter gene assay. Furthermore, the contribution of Skp2/K63 ubiquitination/Lkb1/FAO axis was verified in (DSS)-induced colitis or CIA mice. In summary, these findings indicate that AhR activation promotes Treg cell generation by enhancing Lkb1-mediated FAO via the Skp2/K63-ubiquitination pathway, and AhR agonists may be used as inducers of Treg cells to prevent and treat autoimmune diseases.

Strategies for optimizing CITE-seq for human islets and other tissues

Defining the immunological landscape of human tissue is an important area of research, but challenges include the impact of tissue disaggregation on cell phenotypes and the low abundance of immune cells in many tissues. Here, we describe methods to troubleshoot and standardize Cellular Indexing of Transcriptomes and Epitopes by sequencing (CITE-seq) for studies involving enzymatic digestion of human tissue. We tested epitope susceptibility of 92 antibodies commonly used to differentiate immune lineages and cell states on human peripheral blood mononuclear cells following treatment with an enzymatic digestion cocktail used to isolate islets. We observed CD4, CD8a, CD25, CD27, CD120b, CCR4, CCR6, and PD1 display significant sensitivity to enzymatic treatment, effects that often could not be overcome with alternate antibodies. Comparison of flow cytometry-based CITE-seq antibody titrations and sequencing data supports that for the majority of antibodies, flow cytometry accurately predicts optimal antibody concentrations for CITE-seq. Comparison by CITE-seq of immune cells in enzymatically digested islet tissue and donor-matched spleen not treated with enzymes revealed little digestion-induced epitope cleavage, suggesting increased sensitivity of CITE-seq and/or that the islet structure may protect resident immune cells from enzymes. Within islets, CITE-seq identified immune cells difficult to identify by transcriptional signatures alone, such as distinct tissue-resident T cell subsets, mast cells, and innate lymphoid cells (ILCs). Collectively this study identifies strategies for the rational design and testing of CITE-seq antibodies for single-cell studies of immune cells within islets and other tissues.

The Inhibitory Effect of Regulatory T Cells on the Intimal Hyperplasia of Tissue-Engineered Blood Vessels in Diabetic Pigs

Severe inflammatory response and functional impairment of endothelial progenitor cells (EPCs) often lead to the implantation failure of EPC-captured tissue-engineered blood vessels (TEBVs) in diabetes. Regulatory T cells (Treg cells) are the most important inhibitory immune cells, but their effects in angiogenesis remain undefined, and the differences in the microenvironment may be an important reason. Here, we constructed a TEBV coated with an anti-CD34 antibody-functionalized heparin-collagen multilayer (anti-CD34 antibody-modified TEBV) using layer-by-layer self-assembly. Then, TEBVs were implanted into diabetic pigs. All TEBVs remained unobstructed 60 days after implantation, although varying degrees of intimal hyperplasia were detectable. Severe intimal hyperplasia was observed in the control group and peripheral injection of Treg cells group. Intravenous injection of Treg cells significantly inhibited intimal hyperplasia, inflammation, and cell apoptosis. Moreover, intravenous injection increased the proportion of circulating EPCs, while peripheral injection did not have these effects and reduced microvessel density around the TEBV. Interestingly, many Nestin+ cells could be detected in TEBVs, most of which were fusiform, showing the characteristics of smooth-muscle cells. Treg cell intravenous transplantation markedly reduced the number of Nestin+ cells in the TEBV. In conclusion, Treg cells inhibited the intimal hyperplasia of TEBVs in diabetic pigs by promoting EPC mobilization, anti-inflammatory action, and cellular protection.

Norisoboldine induces the development of Treg cells by promoting fatty acid oxidation-mediated H3K27 acetylation of Foxp3

Norisoboldine (NOR), an alkaloid isolated from Radix Lindera, was previously reported to promote the differentiation of regulatory T cells (Treg cells), an important subtype of lymphocytes capable of controlling autoimmune diseases. The present study was performed to explore the mechanism of NOR in the view of cellular metabolism. A global metabolomic analysis indicated that NOR preferentially altered the fatty acid oxidation (FAO) pathway and elevated the content of related metabolites during Treg cell differentiation. The detection of oxygen consumption rate (OCR) and mRNA expression of FAO-related enzymes demonstrated that NOR promoted FAO in the early stage of Treg cell differentiation. Consistently, pharmacological or genetic inhibition of FAO markedly diminished the induction of NOR on Treg cell differentiation. Furthermore, NOR was shown to elevate the level of acetyl-CoA derived from FAO and acetylation of lysine 27 on histone 3 (H3K27) at the Foxp3 promoter and CNS2 regions. A knockdown of CPT1, the rate-limiting enzyme of FAO, weakened the promotion of NOR on the development, acetyl-CoA level, and acetylation of H3K27 of Treg cells in vitro and in the mice with collagen-induced arthritis, and attenuated the anti-arthritic effect of NOR. These findings demonstrate that NOR induces the development of Treg cells through promoting FAO, therefore, facilitating gene transcription of Foxp3 via acetyl-CoA-mediated H3K27 acetylation modification, and FAO might serve as a novel target to induce Treg cell development.

Mechanisms and therapeutic strategies of immune checkpoint molecules and regulators in type 1 diabetes

BACKGROUND

Considered a significant risk to health and survival, type 1 diabetes (T1D) is a heterogeneous autoimmune disease characterized by hyperglycemia caused by an absolute deficiency of insulin, which is mainly due to the immune-mediated destruction of pancreatic beta cells.

SCOPE OF REVIEW

In recent years, the role of immune checkpoints in the treatment of cancer has been increasingly recognized, but unfortunately, little attention has been paid to the significant role they play both in the development of secondary diabetes with immune checkpoint inhibitors and the treatment of T1D, such as cytotoxic T-lymphocyte antigen 4(CTLA-4), programmed cell death protein-1(PD-1), lymphocyte activation gene-3(LAG-3), programmed death ligand-1(PD-L1), and T-cell immunoglobulin mucin protein-3(TIM-3). Here, this review summarizes recent research on the role and mechanisms of diverse immune checkpoint molecules in mediating the development of T1D and their potential and theoretical basis for the prevention and treatment of diabetes.

MAJOR CONCLUSIONS

Immune checkpoint inhibitors related diabetes, similar to T1D, are severe endocrine toxicity induced with immune checkpoint inhibitors. Interestingly, numerous treatment measures show excellent efficacy for T1D via regulating diverse immune checkpoint molecules, including co-inhibitory and co-stimulatory molecules. Thus, targeting immune checkpoint molecules may exhibit potential for T1D treatment and improve clinical outcomes.

Potential Therapeutic Application of Regulatory T Cells in Diabetes Mellitus Type 1

The autoimmune reaction against the beta cells of the pancreatic islets in type 1 diabetes mellitus (T1DM) patients is active in prediabetes and during the development of the clinical manifestation of T1DM, but it decreases within a few years of the clinical manifestation of this disease. A key role in the pathogenesis of T1DM is played by regulatory T cell (Treg) deficiency or dysfunction. Immune interventions, such as potential therapeutic applications or the induction of the Treg-cell population in T1DM, will be important in the development of new types of treatment. The aim of this study was to evaluate innovative immune interventions as treatments for T1DM. After an evaluation of full-length papers from the PubMed database from 2010 to 2021, 20 trials were included for the final analysis. The analysis led to the following conclusions: Treg cells play an important role in the limitation of the development of T1DM, the activation or application of Tregs may be more effective in the early stages of T1DM development, and the therapeutic use of Treg cells in T1DM is promising but requires long-term observation in a large group of patients.

Interactions between islets and regulatory immune cells in health and type 1 diabetes

Type 1 diabetes results from defects in immune self-tolerance that lead to inflammatory infiltrate in pancreatic islets, beta cell dysfunction and T cell-mediated killing of beta cells. Although therapies that broadly inhibit immunity show promise to mitigate autoinflammatory damage caused by effector T cells, these are unlikely to permanently reset tolerance or promote regeneration of the already diminished pool of beta cells. An emerging concept is that certain populations of immune cells may have the capacity to both promote tolerance and support the restoration of beta cells by supporting proliferation, differentiation and/or regeneration. Here we will highlight three immune cell types-macrophages, regulatory T cells and innate lymphoid cells-for which there is evidence of dual roles of immune regulation and tissue regeneration. We explore how findings in this area from other fields might be extrapolated to type 1 diabetes and highlight recent discoveries in the context of type 1 diabetes. We also discuss technological advances that are supporting this area of research and contextualise new therapeutic avenues to consider for type 1 diabetes.