Notch-1 Inhibition Promotes Immune Regulation in Transplantation Via Regulatory T Cell-Dependent Mechanisms

Human type 1 conventional dendritic cells contribute to skin transplant rejection

The skin is the most immunogenic tissue in transplantation and the most difficult tissue in which to induce immune modulation. Batf3-dependent type 1 conventional dendritic cells (cDC1s) are important in initiating rejection in murine skin transplantation. In humans, the CD141+ cDC1 subset is the functional counterpart of the murine Batf3-dependent cDC1s. However, their contribution to the rejection of human skin allografts remains unknown. Using samples from human face and upper extremity transplant recipients, we demonstrated that CD141+ cDC1s are increased and more activated in human skin grafts than native skin tissue from the same individual. Moreover, circulating and tissue CD141+ cDC1s were elevated at rejection time points. Local modulation of graft CD141+ cDC1s decreased HLA-DR expression and increased regulatory T cells, which correlated with a decreased presence of skin allogeneic T cells in a humanized transplantation model. Thus, CD141+ cDC1s play an important role in rejecting human skin allografts, and their local modulation is a promising therapeutic approach.

Tolerogenic Therapies in Cardiac Transplantation

Heart transplantation remains the gold-standard treatment for end-stage heart failure, yet long-term graft survival is hindered by chronic rejection and the morbidity and mortality caused by lifelong immunosuppression. While advances in medical and device-based therapies have reduced the overall need for transplantation, patients who ultimately require a transplant often present with more advanced disease and comorbidities. Recent advances in tolerance-inducing strategies offer promising avenues to improve allograft acceptance, while minimizing immunosuppressive toxicity. This review explores novel approaches aiming to achieve long-term immunological tolerance, including co-stimulation blockade, mixed chimerism, regulatory T-cell (Treg) therapies, thymic transplantation, and double-organ transplantation. These strategies seek to promote donor-specific unresponsiveness and mitigate chronic rejection. Additionally, expanding the donor pool remains a critical challenge in addressing organ shortages. Innovations such as ABO-incompatible heart transplantation are revolutionizing the field by increasing donor availability and accessibility. In this article, we discuss the mechanistic basis, clinical advancements, and challenges of these approaches, highlighting their potential to transform the future of heart transplantation with emphasis on clinical translation.

Conversion of T Effector Cells Into T Regulatory Cells in Type 1 Diabetes/Latent Autoimmune Diabetes of Adults by Inhibiting eIF5A and Notch Pathways

Background

The generation of functionally active, stable T regulatory cells (Tregs) is a crucial target of type 1 diabetes (T1D) immunotherapy. This study investigated therapeutic intervention for T1D/Latent autoimmune diabetes in adults (LADA), wherein the diabetogenic proinflammatory Treg (intermediate) cell subset was characterized and driven to a Treg phenotype (CD4+CD25+FOXP3+). This involved simultaneous inhibition of the eukaryotic initiation factor 5a (eIF5a) and Notch pathways using GC7 (N1-Guanyl-1,7-diaminoheptane) and Anti-DLL4 (Delta-like-ligand-4).

Methods

Peripheral blood from patients with T1D/LADA and healthy adults (n=7 each) was used to isolate the CD4+CD25- T cell population and CD4 deficient peripheral blood mononuclear cells (PBMCs). Cells were subjected to GAD65+GC7+anti-DLL4 treatment for seven days and compared with conventional anti-CD3/CD28/CD137 stimulation for conversion into the Tregs. Newly plasticized Tregs were assessed for their suppressive potential against freshly isolated autologous T responder cells. In addition, live, dead, and apoptotic cell counts were performed to evaluate the adverse effects of immunomodulatory treatment on immune cells. The data was analyzed with GraphPad Prism using 1- or 2-way ANOVA and a Student's t-test.

Results

A unique population of proinflammatory cytokines expressing intermediate Tregs (CD4+CD25-IFNg+IL17+FOXP3+) was characterized in T1D/LADA patients and found significantly increased compared to age-matched healthy adults. Simultaneous inhibition of eIF5a and Notch pathways could induce Treg phenotype in Treg-deficient CD4+ T cells and CD4 deficient PBMCs from T1D/LADA patients. GAD65+GC7+anti-DLL4 treatment plasticized Tregs withstanding a proinflammatory milieu mimicking T1D/LADA, and the plasticized Tregs exhibited a stable and suppressive functional phenotype. Furthermore, GAD65+GC7+anti-DLL4 treatment had no adverse effects on immune cells.The present approach is a multipronged approach involving the inhibition of eIF5a and Notch pathways that addresses the upregulation of immune tolerance, differentiation, and proliferation of cytotoxic T cells and alleviates β-cell dysfunction. Additionally, this treatment strategy could also be leveraged to boost Treg generation following islet transplantation or as a combinational therapy along with adoptive cell transfer.

A biodegradable capacitive-coupling neurostimulator for wireless electroceutical treatment of inflammatory bowel diseases

Electroceuticals based on peripheral nerve stimulation offer promising treatment for refractory inflammatory diseases such as inflammatory bowel diseases (IBDs). For pediatric IBD (PIBD) patients, wireless, biodegradable miniaturized bioelectronic devices are crucial to prevent neural damage and support neural development during and after therapy. Here we demonstrate a battery-free, miniaturized neurostimulator based on biodegradable materials and capacitive-coupling wireless power transfer. The biodegradable capacitive-coupling (BCC) neurostimulator consists of molybdenum (Mo) electronic components and self-healing biodegradable polyurethane elastomer (SBPUE) encapsulations. The self-healing property of SBPUE enables a stable neural interface. Capacitive coupling wirelessly transfers high-frequency electric fields through a single capacitor between wearable transmitters and implanted BCC neurostimulators. Programmed electrical stimulation of the vagus nerve alleviates PIBD symptoms by restoring CD4+ T cell balance, enhancing anti-inflammatory effects and suppressing pro-inflammatory effects in the intestines.

Recombinant humanized type I collagen remodels decidual immune microenvironment at maternal-fetal interface by modulating Th17/Treg imbalance

Disruption of the extracellular matrix and dysregulation of the balance between Th17 and regulatory T cells are recognized as risk factors for recurrent spontaneous abortion (RSA). However, the interaction between matrix components and the Th17/Treg axis remains poorly elucidated. The result of this study revealed that the absence of type I collagen in the decidua is linked to Th17/Treg imbalance in RSA. Furthermore, we discovered that biomaterial recombinant humanized type I collagen (rhCOLI) promoted T cell differentiation into Tregs by inhibition the Notch1/Hes1 signaling pathway and enhanced the immunosuppressive function of Tregs, as indicated by increased secretion level of IL-10 and TGF-β. Importantly, this study is the first to demonstrate that rhCOLI can modulate the Th17/Treg imbalance, reduce embryo resorption rates, reshape the immune microenvironment at the maternal-fetal interface, and improve fertility in an RSA mouse model. Collectively, these findings suggest that type I collagen deficiency may contribute to, rather than result from, RSA, and propose a potential intervention for RSA using rhCOLI.

The histone methyltransferase Mixed-lineage-leukemia-1 drives T cell phenotype via Notch signaling in diabetic tissue repair

Immune cell-mediated inflammation is important in normal tissue regeneration but can be pathologic in diabetic wounds. Limited literature exists on the role of CD4+ T cells in normal or diabetic wound repair; however, the imbalance of CD4+ Th17/Tregs has been found to promote inflammation in other diabetic tissues. Here, using human tissue and murine transgenic models, we identified that the histone methyltransferase Mixed-lineage-leukemia-1 (MLL1) directly regulates the Th17 transcription factor RORγ via an H3K4me3 mechanism and increases expression of Notch receptors and downstream Notch signaling. Furthermore, we found that Notch receptor signaling regulates CD4+ Th cell differentiation and is critical for normal wound repair, and loss of upstream Notch pathway mediators or receptors in CD4+ T cells resulted in the loss of CD4+ Th cell differentiation in wounds. In diabetes, MLL1 and Notch-receptor signaling was upregulated in wound CD4+ Th cells, driving CD4+ T cells toward the Th17 cell phenotype. Treatment of diabetic wound CD4+ T cells with a small molecule inhibitor of MLL1 (MI-2) yielded a significant reduction in CD4+ Th17 cells and IL-17A. This is the first study to our knowledge to identify the MLL1-mediated mechanisms responsible for regulating the Th17/Treg balance in normal and diabetic wounds and to define the complex role of Notch signaling in CD4+ T cells in wounds, where increased or decreased Notch signaling both result in pathologic wound repair. Therapeutic targeting of MLL1 in diabetic CD4+ Th cells may decrease pathologic inflammation through regulation of CD4+ T cell differentiation.

Many Faces of Regulatory T Cells: Heterogeneity or Plasticity?

Regulatory T cells (Tregs) are essential for maintaining the immune balance in normal and pathological conditions. In autoimmune diseases and transplantation, they restrain the loss of self-tolerance and promote engraftment, whereas in cancer, an increase in Treg numbers is mostly associated with tumor growth and poor prognosis. Numerous markers and their combinations have been used to identify Treg subsets, demonstrating the phenotypic diversity of Tregs. The complexity of Treg identification can be hampered by the unstable expression of some markers, the decrease in the expression of a specific marker over time or the emergence of a new marker. It remains unclear whether such phenotypic shifts are due to new conditions or whether the observed changes are due to initially different populations. In the first case, cellular plasticity is observed, whereas in the second, cellular heterogeneity is observed. The difference between these terms in relation to Tregs is rather blurred. Considering the promising perspectives of Tregs in regenerative cell-based therapy, the existing confusing data on Treg phenotypes require further investigation and analysis. In our review, we introduce criteria that allow us to distinguish between the heterogeneity and plasticity of Tregs normally and pathologically, taking a closer look at their diversity and drawing the line between two terms.

Regulatory T cells in dominant immunologic tolerance

Regulatory T cells expressing the transcription factor forkhead box protein 3 mediate peripheral immune tolerance both to self-antigens and to the commensal flora. Their defective function due to inborn errors of immunity or acquired insults is associated with a broad range of autoimmune and immune dysregulatory diseases. Although their function in suppressing autoimmunity and enforcing commensalism is established, a broader role for regulatory T cells in tissue repair and metabolic regulation has emerged, enabled by unique programs of tissue adaptability and specialization. In this review, we focus on the myriad roles played by regulatory T cells in immunologic tolerance and host homeostasis and the potential to harness these cells in novel therapeutic approaches to human diseases.

The role and mechanisms of mesenchymal stem cells regulating macrophage plasticity in spinal cord injury

Spinal Cord Injury (SCI) is a devastating neurological disorder comprising primary mechanical injury and secondary inflammatory response-mediated injury for which an effective treatment is still unavailable. It is well known that secondary inflammatory responses are a significant cause of difficulties in neurological recovery. An immune imbalance between M1/M2 macrophages at the sites of injury is involved in developing and progressing the secondary inflammatory response. Recently, Mesenchymal Stem Cells (MSCs) have shown significant therapeutic potential in tissue engineering and regenerative medicine due to their potential multidirectional differentiation and immunomodulatory properties. Accumulating evidence shows that MSCs can regulate the balance of M1/M2 macrophage polarization, suppress downstream inflammatory responses, facilitate tissue repair and regeneration, and improve the prognosis of SCI. This article briefly overviews the impact of macrophages and MSCs on SCI and repair. It discusses the mechanisms by which MSCs regulate macrophage plasticity, including paracrine action, release of exosomes and apoptotic bodies, and metabolic reprogramming. Additionally, the article summarizes the relevant signaling pathways of MSCs that regulate macrophage polarization.

The epigenetics orchestra of Notch signaling: a symphony for cancer therapy

The aberrant regulation of the Notch signaling pathway, which is a fundamental developmental pathway, has been implicated in a wide range of human cancers. The Notch pathway can be activated by both canonical and noncanonical Notch ligands, and its role can switch between acting as an oncogene or a tumor suppressor depending on the context. Epigenetic modifications have the potential to modulate Notch and its ligands, thereby influencing Notch signal transduction. Consequently, the utilization of epigenetic regulatory mechanisms may present novel therapeutic opportunities for both single and combined therapeutics targeted at the Notch signaling pathway. This review offers insights into the mechanisms governing the regulation of Notch signaling and explores their therapeutic potential.

MTHFD2 ablation in T cells protects against heart transplant rejection by perturbing IRF4/PD-1 pathway through the metabolic-epigenetic nexus

BACKGROUND

One-carbon metabolism supports the activation, proliferation, and function of multiple immune cells. However, researchers have not clearly determined whether and how one-carbon metabolic enzymes contribute to heart transplant rejection.

METHODS

We investigated the dynamic metabolic adaptation in grafts during heart transplant rejection by conducting transcriptomics, metabolomics and single-cell RNA sequencing studies of cardiac tissue from human and mouse heart transplant recipients. We also assessed the expression of the one-carbon metabolic enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) in cardiac grafts by immunofluorescence and flow cytometry assays. Then we constructed a murine heart transplant model with T cell-specific Mthfd2 knockout mice, analyzed T cells function by flow cytometry assays and enzyme-linked immunospot assays, and studied the mechanism by Cleavage Under Targets and Tagmentation assays. Finally, we studied the effect of a pharmacological inhibitor of MTHFD2 in humanized skin transplant model.

RESULTS

We revealed that the one-carbon metabolism enzyme MTHFD2 was a hallmark of alloreactive T cells and was linked to T cell proliferation and function after exposure to alloantigen. And, Mthfd2 ablation prevented murine heart transplant rejection. Mechanistically, we found Mthfd2 ablation affected the interferon regulatory factor 4/programmed death-1 pathway through a metabolic-epigenetic mechanism involving H3K4me3. Furthermore, we found that inhibiting MTHFD2 attenuated human allograft rejection in a humanized skin transplant model.

CONCLUSIONS

These data show that the one-carbon metabolic enzyme MTHFD2 serves as a metabolic checkpoint of alloreactive T cells and suggest that it may be a potential therapeutic target for heart transplant rejection.

Tregs in transplantation tolerance: role and therapeutic potential

CD4+ Foxp3+ regulatory T cells (Tregs) are indispensable for preventing autoimmunity, and they play a role in cancer and transplantation settings by restraining immune responses. In this review, we describe evidence for the importance of Tregs in the induction versus maintenance of transplantation tolerance, discussing insights into mechanisms of Treg control of the alloimmune response. Further, we address the therapeutic potential of Tregs as a clinical intervention after transplantation, highlighting engineered CAR-Tregs as well as expansion of donor and host Tregs.

Genome-wide DNA methylation profiling of CD4+ T lymphocytes identifies differentially methylated loci associated with adult primary refractory immune thrombocytopenia

BACKGROUND

DNA methylation played a crucial role in the pathogenesis of immune thrombocytopenia (ITP). However, genome-wide DNA methylation analysis has not been applied thus far. The present study aimed to provide the first DNA methylation profiling for ITP.

METHODS

Peripheral blood CD4+ T lymphocytes samples were collected from 4 primary refractory ITP cases and 4 age-matched healthy controls, and DNA methylome profiling was performed using Infinium MethylationEPIC BeadChip. Differentially methylated CpG sites were further validated in another independent cohort of 10 ITP patients and 10 healthy controls using qRT-PCR.

RESULTS

The DNA methylome profiling identified a total of 260 differentially methylated CpG sites mapping to 72 hypermethylated and 64 hypomethylated genes. These genes were mainly enriched in the actin nucleation of the Arp2/3 complex, vesicle transport, histone H3-K36 demethylation, Th1 and Th2 cell differentiation, and Notch signaling pathway according to the GO and KEGG databases. The mRNA expression of CASP9, C1orf109, and AMD1 were significantly different.

CONCLUSIONS

Given the altered DNA methylation profiling of ITP, our study provides new insights into its genetic mechanism and suggests candidate biomarkers for the diagnosis and treatment of ITP.

The Notch1/CD22 signaling axis disrupts Treg function in SARS-CoV-2-associated multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcomes were previously correlated with Notch4 expression on Tregs, here, we show that Tregs in MIS-C were destabilized through a Notch1-dependent mechanism. Genetic analysis revealed that patients with MIS-C had enrichment of rare deleterious variants affecting inflammation and autoimmunity pathways, including dominant-negative mutations in the Notch1 regulators NUMB and NUMBL leading to Notch1 upregulation. Notch1 signaling in Tregs induced CD22, leading to their destabilization in a mTORC1-dependent manner and to the promotion of systemic inflammation. These results identify a Notch1/CD22 signaling axis that disrupts Treg function in MIS-C and point to distinct immune checkpoints controlled by individual Treg Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

Ex vivo anchored PD-L1 functionally prevent in vivo renal allograft rejection

Organ transplantation is the optimal treatment for patients with end-stage diseases. T cell activation is a major contributing factor toward the trigger of rejection. Induction therapy with T cell depleting agent is a common option but increases the risk of severe systemic infections. The ideal therapy should precisely target the allograft. Here, we developed a membrane-anchored-protein PD-L1 (map-PD-L1), which effectively anchored onto the surface of rat glomerular endothelial cells (rgEC). The expression of PD-L1 increased directly with map-PD-L1 concentration and incubation time. Moreover, map-PD-L1 was even stably anchored to rgEC at low temperature. Map-PD-L1 could bind to PD-1 and significantly promote T cell apoptosis and inhibited T cell activation. Using kidney transplantation models, we found that ex vivo perfusion of donor kidneys with map-PD-L1 significantly protected grafts against acute injury without using any immunosuppressant. We found map-PD-L1 could reduce T cell graft infiltration and increase intragraft Treg infiltration, suggesting a long-term effect in allograft protection. More importantly, modifying donor organs in vitro was not only safe, but also significantly reduced the side effects of systemic application. Our results suggested that ex vivo perfusion of donor organ with map-PD-L1 might provide a viable clinical option for organ-targeted induction therapy in organ transplantation.

Different subpopulations of regulatory T cells in human autoimmune disease, transplantation, and tumor immunity

CD4⁺CD25⁺ regulatory T cells (Tregs), a subpopulation of naturally CD4⁺ T cells that characteristically express transcription factor Forkhead box P3 (FOXP3), play a pivotal role in the maintenance of immune homeostasis and the prevention of autoimmunity. With the development of biological technology, the understanding of plasticity and stability of Tregs has been further developed. Recent studies have suggested that human Tregs are functionally and phenotypically diverse. The functions and mechanisms of different phenotypes of Tregs in different disease settings, such as tumor microenvironment, autoimmune diseases, and transplantation, have gradually become hot spots of immunology research that arouse extensive attention. Among the complex functions, CD4⁺CD25⁺FOXP3⁺ Tregs possess a potent immunosuppressive capacity and can produce various cytokines, such as IL‐2, IL‐10, and TGF‐β, to regulate immune homeostasis. They can alleviate the progression of diseases by resisting inflammatory immune responses, whereas promoting the poor prognosis of diseases by helping cells evade immune surveillance or suppressing effector T cells activity. Therefore, methods for targeting Tregs to regulate their functions in the immune microenvironment, such as depleting them to strengthen tumor immunity or expanding them to treat immunological diseases, need to be developed. Here, we discuss that different subpopulations of Tregs are essential for the development of immunotherapeutic strategies involving Tregs in human diseases.

Notch signaling pathway: architecture, disease, and therapeutics

The NOTCH gene was identified approximately 110 years ago. Classical studies have revealed that NOTCH signaling is an evolutionarily conserved pathway. NOTCH receptors undergo three cleavages and translocate into the nucleus to regulate the transcription of target genes. NOTCH signaling deeply participates in the development and homeostasis of multiple tissues and organs, the aberration of which results in cancerous and noncancerous diseases. However, recent studies indicate that the outcomes of NOTCH signaling are changeable and highly dependent on context. In terms of cancers, NOTCH signaling can both promote and inhibit tumor development in various types of cancer. The overall performance of NOTCH-targeted therapies in clinical trials has failed to meet expectations. Additionally, NOTCH mutation has been proposed as a predictive biomarker for immune checkpoint blockade therapy in many cancers. Collectively, the NOTCH pathway needs to be integrally assessed with new perspectives to inspire discoveries and applications. In this review, we focus on both classical and the latest findings related to NOTCH signaling to illustrate the history, architecture, regulatory mechanisms, contributions to physiological development, related diseases, and therapeutic applications of the NOTCH pathway. The contributions of NOTCH signaling to the tumor immune microenvironment and cancer immunotherapy are also highlighted. We hope this review will help not only beginners but also experts to systematically and thoroughly understand the NOTCH signaling pathway.

Immune Cell Plasticity Allows for Resetting of Phenotype From Effector to Regulator With Combined Inhibition of Notch/eIF5A Pathways

Type 1 diabetes (T1D) results from the destruction of pancreatic β-cells caused by an altered immune balance in the pancreatic microenvironment. In humans as well as in mouse models, T cells are well recognized as key orchestrators of T1D, which is characterized by T helper (Th) 1 and Th17 cell bias and/or low/defective T-regulatory cells (Treg), and culminates in cytotoxic T-cell (CTL)-mediated destruction of β-cells. Refitting of immune cells toward the non-inflammatory phenotype in the pancreas may represent a way to prevent/treat T1D. Recently we developed a unique spontaneous humanized mouse model of type 1 diabetes, wherein mouse MHC-II molecules were replaced by human DQ8, and β-cells were made to express human glutamic acid decarboxylase (GAD) 65 auto-antigen. The mice spontaneously developed T1D resembling the human disease. Humanized T1D mice showed hyperglycemic (250-300 mg/dl) symptoms by the 4th week of life. The diabetogenic T cells (CD4, CD8) present in our model are GAD65 antigen-specific in nature. Intermolecular antigen spreading recorded during 3rd-6th week of age is like that observed in the human preclinical period of T1D. In this paper, we tested our hypothesis in our spontaneous humanized T1D mouse model. We targeted two cell-signaling pathways and their inhibitions: eIF5A pathway inhibition influences T helper cell dynamics toward the non-inflammatory phenotype and Notch signaling inhibition enrich Tregs and targets auto-reactive CTLs, rescues the pancreatic islet structure, and increases the functionality of β-cells in terms of insulin production. We report that inhibition of (eIF5A + Notch) signaling mediates suppression of diabetogenic T cells by inducing plasticity in CD4 + T cells co-expressing IL-17 and IFNγ (IL-17 + IFNγ +) toward the Treg cells phenotype.

MiR-363-5p modulates regulatory T cells through STAT4-HSPB1-Notch1 axis and is associated with the immunological abnormality in Graves' disease

MiRNAs are a class of small non-coding RNAs with ability to regulate function of Treg cells and are involved in many autoimmune diseases. Our previous study found that miR-363-5p expression was significantly upregulated in peripheral Treg cells of GD patients. Herein, we aimed to investigate its effect and mechanism on Treg cell dysfunction in GD patients. The results showed that miR-363-5p upregulation was significantly associated with the Treg cell dysfunction and inflammatory factors levels in GD patients. Transcriptome sequencing revealed that 883 genes were significantly regulated by miR-363-5p in Treg cells. These genes with significant differential expression were primarily involved in lymphocyte differentiation, immunity, as well as Notch1 and various interleukin signalling pathways. Moreover, miR-363-5p can regulate HSPB1 and Notch1 through the target gene STAT4, thereby regulating Notch1 signalling pathway and inhibiting Treg cells. The effects of miR-363-5p on Treg cell function and STAT4-HSPB1-Notch1 axis were also verified in GD patients. In conclusion, our results indicated that miR-363 could inhibit the proliferation, differentiation and function of Treg cells by regulating the STAT4-HSPB1-Notch1 axis through target gene STAT4. MiR-363-5p may play an important role in Treg cell dysfunction and immune tolerance abnormalities in GD patients.

Bioengineering Systems for Modulating Notch Signaling in Cardiovascular Development, Disease, and Regeneration

The Notch intercellular signaling pathways play significant roles in cardiovascular development, disease, and regeneration through modulating cardiovascular cell specification, proliferation, differentiation, and morphogenesis. The dysregulation of Notch signaling leads to malfunction and maldevelopment of the cardiovascular system. Currently, most findings on Notch signaling rely on animal models and a few clinical studies, which significantly bottleneck the understanding of Notch signaling-associated human cardiovascular development and disease. Recent advances in the bioengineering systems and human pluripotent stem cell-derived cardiovascular cells pave the way to decipher the role of Notch signaling in cardiovascular-related cells (endothelial cells, cardiomyocytes, smooth muscle cells, fibroblasts, and immune cells), and intercellular crosstalk in the physiological, pathological, and regenerative context of the complex human cardiovascular system. In this review, we first summarize the significant roles of Notch signaling in individual cardiac cell types. We then cover the bioengineering systems of microfluidics, hydrogel, spheroid, and 3D bioprinting, which are currently being used for modeling and studying Notch signaling in the cardiovascular system. At last, we provide insights into ancillary supports of bioengineering systems, varied types of cardiovascular cells, and advanced characterization approaches in further refining Notch signaling in cardiovascular development, disease, and regeneration.

Therapeutic Targeting of Notch Signaling: From Cancer to Inflammatory Disorders

Over the past two decades, the Notch signaling pathway has been investigated as a therapeutic target for the treatment of cancers, and more recently in the context of immune and inflammatory disorders. Notch is an evolutionary conserved pathway found in all metazoans that is critical for proper embryonic development and for the postnatal maintenance of selected tissues. Through cell-to-cell contacts, Notch orchestrates cell fate decisions and differentiation in non-hematopoietic and hematopoietic cell types, regulates immune cell development, and is integral to shaping the amplitude as well as the quality of different types of immune responses. Depriving some cancer types of Notch signals has been shown in preclinical studies to stunt tumor growth, consistent with an oncogenic function of Notch signaling. In addition, therapeutically antagonizing Notch signals showed preclinical potential to prevent or reverse inflammatory disorders, including autoimmune diseases, allergic inflammation and immune complications of life-saving procedures such allogeneic bone marrow and solid organ transplantation (graft-versus-host disease and graft rejection). In this review, we discuss some of these unique approaches, along with the successes and challenges encountered so far to target Notch signaling in preclinical and early clinical studies. Our goal is to emphasize lessons learned to provide guidance about emerging strategies of Notch-based therapeutics that could be deployed safely and efficiently in patients with immune and inflammatory disorders.

Mechanisms of melanocyte death in vitiligo

Vitiligo is an autoimmune depigment disease results from extensive melanocytes destruction. The destruction of melanocyte is thought to be of multifactorial causation. Genome-wide associated studies have identified single-nucleotide polymorphisms in a panel of susceptible loci as risk factors in melanocyte death. But vitiligo onset can't be solely attributed to a susceptive genetic background. Oxidative stress triggered by elevated levels of reactive oxygen species accounts for melanocytic molecular and organelle dysfunction, a minority of melanocyte demise, and melanocyte-specific antigens exposure. Of note, the self-responsive immune function directly contributes to the bulk of melanocyte deaths in vitiligo. The aberrantly heightened innate immunity, type-1-skewed T helper, and incompetent regulatory T cells tip the balance toward autoreaction and CD8+ cytotoxic T lymphocytes finally execute the killing of melanocytes, possibly alarmed by resident memory T cells. In addition to the well-established apoptosis and necrosis, we discuss several death modalities like oxeiptosis, ferroptosis, and necroptosis that are probably employed in melanocyte destruction. This review focuses on the various mechanisms of melanocytic death in vitiligo pathogenesis to demonstrate a panorama of that. We hope to provide new insights into vitiligo pathogenesis and treatment strategies by the review.

A regulatory T cell Notch4-GDF15 axis licenses tissue inflammation in asthma

Elucidating the mechanisms that sustain asthmatic inflammation is critical for precision therapies. We found that interleukin-6- and STAT3 transcription factor-dependent upregulation of Notch4 receptor on lung tissue regulatory T (T_reg) cells is necessary for allergens and particulate matter pollutants to promote airway inflammation. Notch4 subverted T_reg cells into the type 2 and type 17 helper (T_H2 and T_H17) effector T cells by Wnt and Hippo pathway-dependent mechanisms. Wnt activation induced growth and differentiation factor 15 expression in T_reg cells, which activated group 2 innate lymphoid cells to provide a feed-forward mechanism for aggravated inflammation. Notch4, Wnt and Hippo were upregulated in circulating T_reg cells of individuals with asthma as a function of disease severity, in association with reduced T_reg cell-mediated suppression. Our studies thus identify Notch4-mediated immune tolerance subversion as a fundamental mechanism that licenses tissue inflammation in asthma.

Triptolide Attenuates Transplant Vasculopathy Through Multiple Pathways

Transplant vasculopathy (TV), a hallmark of chronic allograft rejection, is the primary cause of allograft loss after organ transplantation. Because multiple mechanisms are involved in TV pathogenesis, effective therapy for it remains elusive. Here, we identify the role of triptolide, which has a wide spectrum of immuno-suppressive activities, in inhibiting TV development. Murine aortic transplants models were constructed and divided into triptolide-treated and untreated groups. We found that triptolide significantly alleviated intima thickening of allografts by inhibiting multiple pathways. Triptolide significantly reduced infiltration of T lymphocytes and macrophages and inhibited the levels of pro-inflammatory (TNF-α, IL-2, and IL-6) and pro-fibrotic factors (TGF-β, α-SMA, and MMP-9) in the graft. Additionally, triptolide significantly decreased the numbers of IFN-γ-producing T lymphocytes, as well as the expression of IFN-γ and IFN-γ-inducing factor (CXCL9 and CXCL10) in recipient. Moreover, triptolide decreased the numbers of B lymphocytes and plasma cells, as well as the levels of donor specific antibodies (DSAs) in recipient. Furthermore, triptolide not only inhibited vascular smooth muscle cell (VSMC) viability and promoted VSMC apoptosis but also significantly inhibited VSMC migration in vitro. These results emphasize the efficacy of triptolide in inhibiting TV development and provide a basis for developing new treatments to prevent TV-related complications and improve the long-term survival of transplant recipients.

GCNT1-Mediated O-Glycosylation of the Sialomucin CD43 Is a Sensitive Indicator of Notch Signaling in Activated T Cells

Notch signaling is emerging as a critical regulator of T cell activation and function. However, there is no reliable cell surface indicator of Notch signaling across activated T cell subsets. In this study, we show that Notch signals induce upregulated expression of the Gcnt1 glycosyltransferase gene in T cells mediating graft-versus-host disease after allogeneic bone marrow transplantation in mice. To determine if Gcnt1-mediated O-glycosylation could be used as a Notch signaling reporter, we quantified the core-2 O-glycoform of CD43 in multiple T cell subsets during graft-versus-host disease. Pharmacological blockade of Delta-like Notch ligands abrogated core-2 O-glycosylation in a dose-dependent manner after allogeneic bone marrow transplantation, both in donor-derived CD4⁺ and CD8⁺ effector T cells and in Foxp3⁺ regulatory T cells. CD43 core-2 O-glycosylation depended on cell-intrinsic canonical Notch signals and identified CD4⁺ and CD8⁺ T cells with high cytokine-producing ability. Gcnt1-deficient T cells still drove lethal alloreactivity, showing that core-2 O-glycosylation predicted, but did not cause, Notch-dependent T cell pathogenicity. Using core-2 O-glycosylation as a marker of Notch signaling, we identified Ccl19-Cre⁺ fibroblastic stromal cells as critical sources of Delta-like ligands in graft-versus-host responses irrespective of conditioning intensity. Core-2 O-glycosylation also reported Notch signaling in CD8⁺ T cell responses to dendritic cell immunization, Listeria infection, and viral infection. Thus, we uncovered a role for Notch in controlling core-2 O-glycosylation and identified a cell surface marker to quantify Notch signals in multiple immunological contexts. Our findings will help refine our understanding of the regulation, cellular source, and timing of Notch signals in T cell immunity.

Notch signalling in T cell homeostasis and differentiation

The evolutionarily conserved Notch signalling pathway regulates the differentiation and function of mature T lymphocytes with major context-dependent consequences in host defence, autoimmunity and alloimmunity. The emerging effects of Notch signalling in T cell responses build upon a more established role for Notch in T cell development. Here, we provide a critical review of this burgeoning literature to make sense of what has been learned so far and highlight the experimental strategies that have been most useful in gleaning physiologically relevant information. We outline the functional consequences of Notch signalling in mature T cells in addition to key specific Notch ligand–receptor interactions and downstream molecular signalling pathways. Our goal is to help clarify future directions for this expanding body of work and the best approaches to answer important open questions.