Interaction between human lung fibroblasts and T-lymphocytes prevents activation of CD4+ cells

Interrelation Between Fibroblasts and T Cells in Fibrosing Interstitial Lung Diseases

Interstitial lung diseases (ILDs) are a heterogeneous group of diseases characterized by varying degrees of inflammation and fibrosis of the pulmonary interstitium. The interrelations between multiple immune cells and stromal cells participate in the pathogenesis of ILDs. While fibroblasts contribute to the development of ILDs through secreting extracellular matrix and proinflammatory cytokines upon activation, T cells are major mediators of adaptive immunity, as well as inflammation and autoimmune tissue destruction in the lung of ILDs patients. Fibroblasts play important roles in modulating T cell recruitment, differentiation and function and conversely, T cells can balance fibrotic sequelae with protective immunity in the lung. A more precise understanding of the interrelation between fibroblasts and T cells will enable a better future therapeutic design by targeting this interrelationship. Here we highlight recent work on the interactions between fibroblasts and T cells in ILDs, and consider the implications of these interactions in the future development of therapies for ILDs.

Adult stem cell niches for tissue homeostasis

Adult stem cells are fundamental to maintain tissue homeostasis, growth, and regeneration. They reside in specialized environments called niches. Following activating signals, they proliferate and differentiate into functional cells that are able to preserve tissue physiology, either to guarantee normal turnover or to counteract tissue damage caused by injury or disease. Multiple interactions occur within the niche between stem cell‐intrinsic factors, supporting cells, the extracellular matrix, and signaling pathways. Altogether, these interactions govern cell fate, preserving the stem cell pool, and regulating stem cell proliferation and differentiation. Based on their response to body needs, tissues can be largely classified into three main categories: tissues that even in normal conditions are characterized by an impressive turnover to replace rapidly exhausting cells (blood, epidermis, or intestinal epithelium); tissues that normally require only a basal cell replacement, though able to efficiently respond to increased tissue needs, injury, or disease (skeletal muscle); tissues that are equipped with less powerful stem cell niches, whose repairing ability is not able to overcome severe damage (heart or nervous tissue). The purpose of this review is to describe the main characteristics of stem cell niches in these different tissues, highlighting the various components influencing stem cell activity. Although much has been done, more work is needed to further increase our knowledge of niche interactions. This would be important not only to shed light on this fundamental chapter of human physiology but also to help the development of cell‐based strategies for clinical therapeutic applications, especially when other approaches fail.

Connexin 43 and Sonic Hedgehog Pathway Interplay in Glioblastoma Cell Proliferation and Migration

Simple Summary

Glioblastoma is the product of accumulated genetic and epigenetic alteration where tumor cells support each other through cellular communication mechanisms and deregulated signalling processes. The autocrine and paracrine pathways between the intracellular and extracellular milieu is mediated by connexin 43, the main gap junction-forming protein driving glioblastoma progression. In this scenario, sonic hedgehog pathway, a key deregulated pathway involved in cell network signalling may affect connexin 43 expression, promoting glioblastoma pathobiology. In this study, we sought to explore how the modulation of the sonic hedgehog affects connexin 43 inducing glioblastoma hallmarks. To do this we evaluated biological effects of sonic hedgehog pathway modulation by purmorphamine and cyclopamine, a smoothened agonist and antagonist, respectively. We revealed that cell migration and proliferation are associated with connexin 43 expression upon sonic hedgehog modulation. Our study suggests that sonic hedgehog and connexin 43 axis may represent a potential therapeutic strategy for glioblastoma.

Abstract

Glioblastoma (GBM) represents the most common primary brain tumor within the adult population. Current therapeutic options are still limited by high rate of recurrences and signalling axes that promote GBM aggressiveness. The contribution of gap junctions (GJs) to tumor growth and progression has been proven by experimental evidence. Concomitantly, tumor microenvironment has received increasing interest as a critical process in dysregulation and homeostatic escape, finding a close link between molecular mechanisms involved in connexin 43 (CX43)-based intercellular communication and tumorigenesis. Moreover, evidence has come to suggest a crucial role of sonic hedgehog (SHH) signalling pathway in GBM proliferation, cell fate and differentiation. Herein, we used two human GBM cell lines, modulating SHH signalling and CX43-based intercellular communication in in vitro models using proliferation and migration assays. Our evidence suggests that modulation of the SHH effector smoothened (SMO), by using a known agonist (i.e., purmorphamine) and a known antagonist (i.e., cyclopamine), affects the CX43 expression levels and therefore the related functions. Moreover, SMO activation also increased cell proliferation and migration. Importantly, inhibition of CX43 channels was able to prevent SMO-induced effects. SHH pathway and CX43 interplay acts inducing tumorigenic program and supporting cell migration, likely representing druggable targets to develop new therapeutic strategies for GBM.

Potential therapeutic applications of mesenchymal stem cells for the treatment of eye diseases

Stem cell-based treatments have been extensively explored in the last few decades to develop therapeutic strategies aimed at providing effective alternatives for those human pathologies in which surgical or pharmacological therapies produce limited effects. Among stem cells of different sources, mesenchymal stem cells (MSCs) offer several advantages, such as the absence of ethical concerns, easy harvesting, low immunogenicity and reduced tumorigenesis risks. Other than a multipotent differentiation ability, MSCs can release extracellular vesicles conveying proteins, mRNA and microRNA. Thanks to these properties, new therapeutic approaches have been designed for the treatment of various pathologies, including ocular diseases. In this review, the use of different MSCs and different administration strategies are described for the treatment of diabetic retinopathy, glaucoma, and retinitis pigmentosa. In a large number of investigations, positive results have been obtained by in vitro experiments and by MSC administration in animal models. Most authors agree that beneficial effects are likely related to MSC paracrine activity. Based on these considerations, many clinical trials have already been carried out. Overall, although some adverse effects have been described, promising outcomes are reported. It can be assumed that in the near future, safer and more effective protocols will be developed for more numerous clinical applications to improve the quality of life of patients affected by eye diseases.

Effects of High Glucose Concentration on Pericyte-Like Differentiated Human Adipose-Derived Mesenchymal Stem Cells

A pericyte-like differentiation of human adipose-derived mesenchymal stem cells (ASCs) was tested in in vitro experiments for possible therapeutic applications in cases of diabetic retinopathy (DR) to replace irreversibly lost pericytes. For this purpose, pericyte-like ASCs were obtained after their growth in a specific pericyte medium. They were then cultured in high glucose conditions to mimic the altered microenvironment of a diabetic eye. Several parameters were monitored, especially those particularly affected by disease progression: cell proliferation, viability and migration ability; reactive oxygen species (ROS) production; inflammation-related cytokines and angiogenic factors. Overall, encouraging results were obtained. In fact, even after glucose addition, ASCs pre-cultured in the pericyte medium (pmASCs) showed high proliferation rate, viability and migration ability. A considerable increase in mRNA expression levels of the anti-inflammatory cytokines transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10) was observed, associated with reduction in ROS production, and mRNA expression of pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and angiogenic factors. Finally, a pmASC-induced better organization of tube-like formation by retinal endothelial cells was observed in three-dimensional co-culture. The pericyte-like ASCs obtained in these experiments represent a valuable tool for the treatment of retinal damages occurring in diabetic patients.

Trained immunity modulates inflammation-induced fibrosis

Chronic inflammation and fibrosis can result from inappropriately activated immune responses that are mediated by macrophages. Macrophages can acquire memory-like characteristics in response to antigen exposure. Here, we show the effect of BCG or low-dose LPS stimulation on macrophage phenotype, cytokine production, chromatin and metabolic modifications. Low-dose LPS training alleviates fibrosis and inflammation in a mouse model of systemic sclerosis (SSc), whereas BCG-training exacerbates disease in this model. Adoptive transfer of low-dose LPS-trained or BCG-trained macrophages also has beneficial or harmful effects, respectively. Furthermore, coculture with low-dose LPS trained macrophages reduces the fibro-inflammatory profile of fibroblasts from mice and patients with SSc, indicating that trained immunity might be a phenomenon that can be targeted to treat SSc and other autoimmune and inflammatory fibrotic disorders.

Innate immune cells can be trained by some stimuli or pathogen exposures to be metabolically and epigenetically altered such that they have different responses to subsequent exposures. Here the authors show that low-dose LPS trained macrophages and BCG-trained macrophages have opposing effects on fibrosis and inflammation in the context of systemic sclerosis.

The Dark Side of Fibroblasts: Cancer-Associated Fibroblasts as Mediators of Immunosuppression in the Tumor Microenvironment

Cancer-associated fibroblasts (CAFs) are prominent components of the microenvironment in most types of solid tumors, and were shown to facilitate cancer progression by supporting tumor cell growth, extracellular matrix remodeling, promoting angiogenesis, and by mediating tumor-promoting inflammation. In addition to an inflammatory microenvironment, tumors are characterized by immune evasion and an immunosuppressive milieu. In recent years, CAFs are emerging as central players in immune regulation that shapes the tumor microenvironment. CAFs contribute to immune escape of tumors via multiple mechanisms, including secretion of multiple cytokines and chemokines and reciprocal interactions that mediate the recruitment and functional differentiation of innate and adaptive immune cells. Moreover, CAFs directly abrogate the function of cytotoxic lymphocytes, thus inhibiting killing of tumor cells. In this review, we focus on recent advancements in our understanding of how CAFs drive the recruitment and functional fate of tumor-infiltrating immune cells toward an immunosuppressive microenvironment, and provide outlook on future therapeutic implications that may lead to integration of preclinical findings into the design of novel combination strategies, aimed at impairing the tumor-supportive function of CAFs.

A short field guide to fibroblast function in immunity

Fibroblasts in secondary lymphoid organs, or fibroblastic reticular cells (FRC), are gate-keepers of immune responses. Here, we frame how these cells regulate immune responses via a three-part scheme in which FRC can setup, support or suppress immune responses. We also review how fibroblasts from non-lymphoid tissues influence immunity and highlight how they resemble and differ from FRC. Overall, we aim to focus attention on the emerging roles of lymphoid tissue and non-lymphoid tissue fibroblasts in control of innate and adaptive immunity.

An overlooked tumor promoting immunoregulation by non-hematopoietic stromal cells

Multidirectional complex communication between tumor-residing hematopoietic and non-hematopoietic stromal cells (NHSCs) decisively regulates cancer development, progression and therapeutic responses. HSCs predominantly participate in the immune regulations, while, NHSCs, provide parenchymal support or serve as a conduit for other cells or support angiogenesis. However, recent reports suggest NHSCs can additionally participate in ongoing tumor promoting immune reactions within tumor-microenvironment (TME). In this review, based on the state-of-art knowledge and accumulated evidence by us, we discuss the role of quite a few NHSCs in tumor from immunological perspectives. Understanding such consequence of NHSCs will surely pave the way in crafting effective cancer management.

Comparisons of phenotype and immunomodulatory capacity among rhesus bone-marrow-derived mesenchymal stem/stromal cells, multipotent adult progenitor cells, and dermal fibroblasts

BACKGROUND

Potent immunomodulatory effects have been reported for mesenchymal stem/stromal cells (MSCs), multipotent adult progenitor cells (MAPCs), and fibroblasts. However, side-by-side comparisons of these cells specifically regarding immunophenotype, gene expression, and suppression of proliferation of CD4(+) and CD8(+) lymphocyte populations have not been reported.

METHODS

We developed MAPC and MSC lines from rhesus macaque bone marrow and fibroblast cell lines from rhesus dermis and assessed phenotypes based upon differentiation potential, flow cytometric analysis of immunophenotype, and quantitative RT-PCR analysis of gene expression. Using allogeneic lymphocyte proliferation assays, we compared the in vitro immunomodulatory potency of each cell type.

RESULTS AND CONCLUSIONS

Extensive phenotypic similarities exist among each cell type, although immunosuppressive potencies are distinct. MAPCs are most potent, and fibroblasts are the least potent cell type. All three cell types demonstrated immunomodulatory capacity such that each may have potential therapeutic applications such as in organ transplantation, where reduced local immune response is desirable.

Thymosin β4 reduces IL-17-producing cells and IL-17 expression, and protects lungs from damage in bleomycin-treated mice

Thymosin β4 (Tβ4) is a highly conserved peptide with immunomodulatory properties. In this research we investigated the effects of Tβ4 on the bleomycin-induced lung damage in CD-1 mice and the changes in the number of IL-17-producing cells as well as the IL-17 expression in the lung. Male CD-1 mice were treated with bleomycin (1mg/kg) in the absence or the presence of Tβ4 (6mg/kg delivered intra-peritoneally on the day of bleomycin treatment and for 2 additional doses). After sacrifice one week later, lung histology, measurement of collagen content of the lung, Broncho Alveolar Lavage Fluid (BALF) analysis, evaluation of IL17-producing cells in the blood as well as RT-PCR and IHC in the lung tissue were performed. As expected, bleomycin-induced inflammation and lung damage were substantially reduced by Tβ4 treatment in CD-1 mice, as shown by the significant reduction of (i) leukocytes in BALF, (ii) histological evidence of the lung damage, and (iii) total collagen content in the lung. Importantly, the bleomycin-induced increase in the number of IL17-producing cells in the blood was significantly blocked by Tβ4. Accordingly, IHC and RT-PCR results demonstrated that Tβ4 substantially inhibited bleomycin-induced IL-17 over-expression in the lung tissue. This is the first report showing that a decreased amount of IL17-producing cells and inhibited IL-17 expression in the lung with Tβ4 treatment correlate with its anti-inflammatory and anti-fibrotic effects.

Human lung fibroblasts increase CD4(+)CD25(+)Foxp3(+) T cells in co-cultured CD4(+) lymphocytes

Aim of this study was to evaluate functional modifications induced by human lung fibroblasts in co-cultured CD4(+) T lymphocytes. CD4(+) T cells, resting or stimulated with ionomycin/PMA for 6h, were co-cultured with fibroblasts isolated from pulmonary biopsies, in contact or separated by a semi-permeable membrane. The expression of CD25, CTLA-4, TGF-β, IFNγ, IL-2, IL-4, IL-10 and Foxp3 was evaluated by flow cytometric analysis. Fibroblasts induced a significant increment in CD25(+) cells in co-cultured activated CD4(+) T lymphocytes separated by a membrane. Moreover, fibroblasts treatment with a COX2 inhibitor abrogated the increment in CD25(+) cells whereas exogenous PGE2 restored it. The CD25(+) subpopulation was characterized by increased presence of Fox-P3, CTLA-4, IL-10 and TGF-β positive cells while IFN-γ and IL-2 positive cells were diminished. Proliferative response of CD4(+) to the anti CD3/CD28-Abs was abrogated in CD4(+) co-cultured with fibroblasts thus demonstrating a suppressive feature of the expanded CD25(+) subpopulation.

Airway immune homeostasis and implications for influenza-induced inflammation

The lung is exposed to a myriad of innocuous antigens on a daily basis and must maintain a state of immune ignorance or tolerance to these harmless stimuli to retain pulmonary homeostasis and to prevent potentially fatal immunopathology. Here, we examine how, in the lower airways, resident cell populations contribute to the immune regulatory strategies that restrain inflammation. During influenza infection, these suppressive signals must be overcome to elicit a protective immune response that eliminates the virus. We also discuss how, after resolution of infection, the lung does not return to the original homeostatic state, and how the induced altered state can persist for long periods, which leaves the lung more susceptible to other infectious insults.

A method for isolation of rat lymphocyte-rich mononuclear cells from lung tissue useful for determination of nucleoside triphosphate diphosphohydrolase activity

Methods for the isolation of peripheral blood mononuclear cells (PBMCs) and human lung mononuclear cells (LMCs) have been proposed previously. This study describes a method that allows the separation of lymphocyte-rich LMCs from rats. Trypan blue was applied to determine cell viability. White blood cell and differential cell counts were also performed. Relationships between nucleoside triphosphate diphosphohydrolase (NTPDase, EC 3.6.1.5) activities expressed in milligrams of protein, millions of cells, and millions of viable cells were examined as linear correlations. The lung tissue yielded 82.46% lymphocytes, 8.6% macrophages, 2.20% monocytes, and 1.27% polymorphonuclear cells (PMNs). In LMCs, a very strong correlation was observed as follows: between NTPDase activity, as determined using ATP or ADP as a substrate, expressed in milligrams of protein and that expressed in millions of cells (r ≥ 0.91), between that expressed in milligrams of protein and that expressed in millions of viable cells (r ≥ 0.91), and between that expressed in millions of cells and that expressed in millions of viable cells (r ≥ 0.98). Based on our results, we affirm that NTPDase activity could be expressed in millions of viable cells, millions of cells, or milligrams of protein.

Crosstalk between T cells and bronchial fibroblasts obtained from asthmatic subjects involves CD40L/alpha 5 beta 1 interaction

BACKGROUND

Allergic asthma is characterized by infiltration of inflammatory cells into the airways. T cell-derived cytokines regulate both airway inflammation and remodelling. In the human airways, T cell-fibroblast interactions may have a role in regulating inflammation and remodelling.

OBJECTIVES

To evaluate the effect of bronchial fibroblast-T cell interaction on profibrogenic cytokine release and determine the nature of the molecules involved in this interaction.

METHODS

Human bronchial fibroblasts obtained from healthy and asthmatic donors were co-cultured with purified T cells derived from peripheral blood of the same subjects. IL-6 mRNA and protein levels were measured by real time PCR and ELISA. CD40, CD40L and alpha 5 beta 1 were evaluated by flow cytometry. Bronchial fibroblasts were stimulated with rsCD40L. Neutralisation was performed using neutralizing antibodies anti-CD40L and anti-alpha 5.

RESULTS

Contact of T cells with bronchial fibroblasts up-regulated IL-6 at both gene and protein levels. This effect was significantly higher in fibroblasts from asthmatics than those from controls. Blocking CD40L and alpha 5 beta 1 integrin showed a significant inhibition of IL-6 expression in asthmatics but not in healthy controls. Stimulation of fibroblasts with recombinant soluble CD40L up-regulated IL-6 production in asthmatics but not in controls. Adhesion to fibronectin, a alpha 5 beta 1 integrin ligand, is increased in fibroblasts from asthmatics compared to fibroblasts from controls.

CONCLUSION

These results showed that interaction of bronchial fibroblasts with T cells increases the production of profibrogenic cytokine IL-6. In asthmatic condition this interaction involves CD40L/alpha 5 beta 1. These results suggest that T cells and structural cells crosstalk in asthma may maintain local mucosal inflammation.

The alpha/beta interferon receptor provides protection against influenza virus replication but is dispensable for inflammatory response signaling

The innate immune response provides the first line of defense against foreign pathogens by responding to molecules that are a signature of a pathogenic infection. Certain RNA viruses, such as influenza virus, produce double-stranded RNA as an intermediate during the replication life cycle, which activates pathogen recognition receptors capable of inducing interferon production. By engaging interferon receptors, interferon activates the JAK-STAT pathway and results in the positive feedback of interferon production, amplifying the response to viral infection. To examine how deficiencies in interferon signaling affect the cellular response to infection, we performed influenza virus infections of mouse embryonic fibroblasts lacking the alpha/beta interferon receptor, the gamma interferon receptor, or both. In the absence of the alpha/beta interferon receptor, we observed increased viral replication but decreased activation of PKR, Stat1, and NF-kappaB; the presence or absence of the gamma interferon receptor did not exhibit discernible differences in these readouts. Analysis of gene expression profiles showed that while cells lacking the alpha/beta interferon receptor exhibited decreased levels of transcription of antiviral genes, genes related to inflammatory and apoptotic responses were transcribed to levels similar to those of cells containing the receptor. These results indicate that while the alpha/beta interferon receptor is needed to curb viral replication, it is dispensable for the induction of certain inflammatory and apoptotic genes. We have identified potential pathways, via interferon regulatory factor 3 (IRF3) activation or Hoxa13, Polr2a, Nr4a1, or Ing1 induction, that contribute to this redundancy. This study illustrates another way in which the host has evolved to establish several overlapping mechanisms to respond to viral infections.

Proteome analysis of bronchoalveolar lavage in lung diseases

The proteomic approach is complementary to genomics and enables protein composition to be investigated under various clinical conditions. Its application to the study of bronchoalveolar lavage (BAL) is extremely promising. BAL proteomic studies were initially based on two-dimensional electrophoretic separation of complex protein samples and subsequent identification of proteins by different methods. With the techniques available today it is possible to attain many different research objectives. BAL proteomics can contribute to the identification of proteins in alveolar spaces with possible insights into pathogenesis and clinical application for diagnosis, prognosis and therapy. Many proteins with different functions have already been identified in BAL. Some could be biomarkers that need to be individually confirmed by correlation with clinical parameters and validation by other methods on larger cohorts of patients. The standardization of BAL sample preparation and processing for proteomic studies is an important goal that would promote and facilitate clinical applications. Here, we review the principal literature on BAL proteomic analysis applied to the study of lung diseases.

Tissue remodelling in upper airways: where is the link with lower airway remodelling?

Tissue remodelling reported in upper airways include epithelial hyperplasia, increased matrix deposition in the nasal or paranasal lining, matrix degradation and accumulation of plasma proteins. Genetic influences, foetal exposures and early life events may contribute to structural changes such as subepithelial fibrosis from an early age. Other structural alterations are related to duration of the disease and long-term uncontrolled inflammation. Structural changes may increase alteration of the protective functions of the upper airways namely by affecting mucociliary clearance and conditioning of inspired air. The sequences of tissue changes during wound repair of upper airway mucosa after surgery are illustrative of the complexicity of tissue modelling and remodelling and could be considered as an important source of information for a better understanding of the complex relationship between inflammatory reaction, of the subsequent tissue damages and fibroblast metabolism of upper airways.