Fibrocyte Phenotype of ENTPD1+CD55+ Cells and Its Association with Pain in Osteoarthritic Synovium

Osteoarthritis (OA) is a prevalent degenerative joint disorder characterized by cartilage erosion, structural changes, and inflammation. Synovial fibroblasts play a crucial role in OA pathophysiology, with abnormal fibroblastic cells contributing significantly to joint pathology. Fibrocytes, expressing markers of both hematopoietic and stromal cells, are implicated in inflammation and fibrosis, yet their marker and role in OA remain unclear. ENTPD1, an ectonucleotidase involved in purinergic signaling and expressed in specific fibroblasts in fibrotic conditions, led us to speculate that ENTPD1 plays a role in OA pathology by being expressed in fibrocytes. This study aimed to investigate the phenotype of ENTPD1+CD55+ and ENTPD1-CD55+ synovial fibroblasts in OA patients. Proteomic analysis revealed a distinct molecular profile in ENTPD1+CD55+ cells, including the upregulation of fibrocyte markers and extracellular matrix-related proteins. Pathway analysis suggested shared mechanisms between OA and rheumatoid arthritis. Correlation analysis revealed an association between ENTPD1+CD55+ fibrocytes and resting pain in OA. These findings highlight the potential involvement of ENTPD1 in OA pain and suggest avenues for targeted therapeutic strategies. Further research is needed to elucidate the underlying molecular mechanisms and validate potential therapeutic targets.

The implication of mesenteric functions and the biological effects of nanomaterials on the mesentery

A growing number of nanomaterials are being broadly used in food-related fields as well as therapeutics. Oral exposure to these widespread nanomaterials is inevitable, with the intestine being a major target organ. Upon encountering the intestine, these nanoparticles can cross the intestinal barrier, either bypassing cells or via endocytosis pathways to enter the adjacent mesentery. The intricate structure of the mesentery and its entanglement with the abdominal digestive organs determine the final fate of nanomaterials in the human body. Importantly, mesentery-governed dynamic processes determine the distribution and subsequent biological effects of nanomaterials that cross the intestine, thus there is a need to understand how nanomaterials interact with the mesentery. This review presents the recent progress in understanding the mesenteric structure and function and highlights the importance of the mesentery in health and disease, with a focus on providing new insights and research directions around the biological effects of nanomaterials on the mesentery. A thorough comprehension of the interactions between nanomaterials and the mesentery will facilitate the design of safer nanomaterial-containing products and the development of more effective nanomedicines to combat intestinal disorders.

Fibrocytes boost tumor-supportive phenotypic switches in the lung cancer niche via the endothelin system

Fibrocytes are bone marrow-derived monocytic cells implicated in wound healing. Here, we identify their role in lung cancer progression/ metastasis. Selective manipulation of fibrocytes in mouse lung tumor models documents the central role of fibrocytes in boosting niche features and enhancing metastasis. Importantly, lung cancer patients show increased number of circulating fibrocytes and marked fibrocyte accumulation in the cancer niche. Using double and triple co-culture systems with human lung cancer cells, fibrocytes, macrophages and endothelial cells, we substantiate the central features of cancer-supporting niche: enhanced cancer cell proliferation and migration, macrophage activation, augmented endothelial cell sprouting and fibrocyte maturation. Upregulation of endothelin and its receptors are noted, and dual endothelin receptor blockade suppresses all cancer-supportive phenotypic alterations via acting on fibrocyte interaction with the cancer niche. We thus provide evidence for a crucial role of fibrocytes in lung cancer progression and metastasis, suggesting targets for treatment strategies.

The synovial fluid fibroblast-like synoviocyte: A long-neglected piece in the puzzle of rheumatoid arthritis pathogenesis

Rheumatoid arthritis (RA) is a systemic autoimmune disease during which fibroblast-like synoviocytes (FLS) contribute to both joint inflammation and destruction. FLS represent the core component of the synovial membrane. Following inflammation of this membrane, an effusion of cell-rich synovial fluid (SF) fills the joint cavity. Unlikely, SF has been shown to contain fibroblasts with some shared phenotypic traits with the synovial membrane FLS. These cells are called SF-FLS and their origin is still unclear. They are either brought into the synovium via migration through blood vessels, or they could originate within the synovium and exist in projections of the synovial membrane. SF-FLS function and phenotype are poorly documented compared to recently well-characterized synovial membrane FLS subsets. Furthermore, no study has yet reported a SF-FLS single-cell profiling analysis. This review will discuss the origin and cellular characteristics of SF-FLS in patients with RA. In addition, recent advances on the involvement of SF-FLS in the pathogenesis of RA will be summarized. Current knowledge on possible relationships between SF-FLS and other types of fibroblasts, including synovial membrane FLS, circulating fibrocytes, and pre- inflammatory mesenchymal (PRIME) cells will also be addressed. Finally, recent therapeutic strategies employed to specifically target SF-FLS in RA will be discussed.

Intriguing Role of the Mesentery in Ileocolic Crohn's Disease

Crohn's disease (CD) is a chronic relapsing inflammatory bowel disease with unknown etiology. Up to 80% of patients will eventually require surgery throughout their lifetime, and often repeated resections are required for disease recurrence. Observations of “creeping fat” surrounding the diseased intestine renewed interest in the mesentery, recently defined as an organ with endocrine and immune functions. According to the inside-out model, the mesentery may be primarily affected in CD and subsequent cause alterations in the mucosa. Recently, lower surgical recurrence rates have been reported with en-bloc excision of the mesentery adjoining the diseased intestine. Results of ongoing randomized controlled trials may clarify the role of the mesentery in CD and possibly lead to its adoption as standard during surgery for Crohn's disease.

Peripheral blood mononuclear cells - Can they provide a clue to the pathogenesis of Graves' Orbitopathy?

PURPOSE

Graves' disease (GD) is an autoimmune disorder affecting primarily the thyroid gland. The most common extrathyroidal manifestation of GD is known as Graves' orbitopathy (GO). Bone marrow-derived fibrocytes represent a subset of monocytes in peripheral blood mononuclear cells (PBMCs), infiltrate the orbital tissues, and contribute to the pathogenesis of GO. Hence objectives of the study included whether the concentration of fibrocytes in peripheral blood was higher in GO, whether TSHR m RNA expression and TSHR surface expression in peripheral blood were higher in GO in comparison to Graves' Disease (GD) and Control subjects.

METHODS

The percentage of circulating fibrocytes (FC) along with TSHR on its cell surface (CD 34⁺, CD 45⁺, CXCR4⁺, Collagen 1⁺, TSHR⁺) were assessed by flow cytometry of 50 patients with GD and GO and 15 healthy donors (Control). TSHR mRNA expression was measured by q RT PCR.

RESULT

The concentration of circulating fibrocytes was significantly higher in GO compared to GD and control [GO 17% vs GD 3% vs control 0.7% (p < 0.05)]. Moreover, these fibrocytes express a significantly higher level of TSHR in GO. This was corroborated by the measure of TSH mRNA; in GD it was 2.3-fold higher and in GO it was 3.9 fold higher than in control, in GO this transcript level was 1.7fold higher than GD (p < 0.05). TSHR⁺ fibrocytes were significantly positively correlated with CAS (p = 0.004) and negatively correlated with age (p = 0.01) and duration of disease (p = 0.01) in GO.

CONCLUSION

This study sheds further light on the pathogenesis of GO.

Review: Serum Biomarkers of Lung Fibrosis in Interstitial Pneumonia with Autoimmune Features-What Do We Already Know?

Interstitial pneumonia with autoimmune features (IPAF) belongs to a group of diseases called interstitial lung diseases (ILDs), which are disorders of a varied prognosis and course. Finding sufficiently specific and sensitive biomarkers would enable the progression to be predicted, the natural history to be monitored and patients to be stratified according to their treatment. To assess the significance of pulmonary fibrosis biomarkers studied thus far, we searched the PubMed, Medline and Cochrane Library databases for papers published between January 2015 and June 2021. We focused on circulating biomarkers. A primary review of the databases identified 38 articles of potential interest. Overall, seven articles fulfilled the inclusion criteria. This review aims to assess the diagnostic and prognostic value of molecules such as KL-6, SP-A, SP-D, circulating fibrocytes, CCL2, CXCL13, CXCL9, CXCL10 and CXCL11. All of these biomarkers have previously been studied in idiopathic pulmonary fibrosis (IPF) and connective tissue disease-associated interstitial lung disease (CTD-ILD). IPAF is a disorder of a heterogeneous nature. It explains the lack of coherent observations in terms of correlations with functional parameters. There is still no meta-analysis of pulmonary fibrosis biomarkers in IPAF. This is mainly due to the heterogeneity of the methodology and groups analysed in the research. More research in this area is needed.

The Role of the Stromal Extracellular Matrix in the Development of Pterygium Pathology: An Update

Pterygium is a benign fibrovascular lesion of the bulbar conjunctiva with frequent involvement of the corneal limbus. Its pathogenesis has been mainly attributed to sun exposure to ultraviolet-B radiation. Obtained evidence has shown that it is a complex and multifactorial process which involves multiple mechanisms such as oxidative stress, dysregulation of cell cycle checkpoints, induction of inflammatory mediators and growth factors, angiogenic stimulation, extracellular matrix (ECM) disorders, and, most likely, viruses and hereditary changes. In this review, we aim to collect all authors’ experiences and our own, with respect to the study of fibroelastic ECM of pterygium. Collagen and elastin are intrinsic indicators of physiological and pathological states. Here, we focus on an in-depth analysis of collagen (types I and III), as well as the main constituents of elastic fibers (tropoelastin (TE), fibrillins (FBNs), and fibulins (FBLNs)) and the enzymes (lysyl oxidases (LOXs)) that carry out their assembly or crosslinking. All the studies established that changes in the fibroelastic ECM occur in pterygium, based on the following facts: An increase in the synthesis and deposition of an immature form of collagen type III, which showed the process of tissue remodeling. An increase in protein levels in most of the constituents necessary for the development of elastic fibers, except FBLN4, whose biological roles are critical in the binding of the enzyme LOX, as well as FBN1 for the development of stable elastin. There was gene overexpression of TE, FBN1, FBLN5, and LOXL1, while the expression of LOX and FBLN2 and -4 remained stable. In conclusion, collagen and elastin, as well as several constituents involved in elastic fiber assembly are overexpressed in human pterygium, thus, supporting the hypothesis that there is dysregulation in the synthesis and crosslinking of the fibroelastic component, constituting an important pathogenetic mechanism for the development of the disease.

Expression of extracellular matrix components and cytokine receptors in human fibrocytes during rheumatoid arthritis

Purpose: Fibroblast-like synoviocytes (FLS) represent one of the principal effectors of joint damage in rheumatoid arthritis (RA). Recent discovery of the circulating fibrocyte, a potential precursor of FLS, has raised issues regarding the characterization of fibrocytes with respect to their morphology and their biological role. In this study, we evaluated the morphology of fibrocytes in vitro and their ability to produce different extracellular matrix (ECM) components in comparison with two populations of RA FLS: synovial fluid FLS (fd-FLS) and intimal lining FLS (td-FLS). We also studied the expression of ECM regulators and a set of cytokine receptors involved in the pathogenesis of RA. Materials and Methods: Fibrocytes were cultured from peripheral blood of patients with RA. FLS were cultured from synovial fluids and tissues. ECM proteins (collagen I (col I) and fibronectin), Matrix metalloproteinases (MMP) (MMP3, and MMP9), ECM regulators (β catenin, TCF4, and c-fos), and cytokine receptors (CXCR1, CXCR2, CXCR3, IL1RI, IL1RII, and IL6Rα) were analyzed using qRT-PCR and/or western blot. Results: Our results demonstrated that fibronectin and MMP3 levels were higher in FLS compared to fibrocytes. Although MMP9 was expressed in the three cell types, its level was greater in fibrocytes than in td/fd FLS. The three cell types expressed CXCR3, IL1RI, IL1RII, and IL6Rα, while the expression of CXCR1 and CXCR2 was restricted to fibrocytes. Conclusion: Our results demonstrated that fibrocytes express ECM molecules and cytokines receptors. The observed differences between fibrocytes and FLS may be due to their distinct functions or differentiation state during RA.Abbreviations: RA: Rheumatoid ArthritisFLS: fibroblast-like synoviocytestd: tissue derivedfd: fluid derivedSF: Synovial FluidWnt: WinglessMMP: Matrix MetalloproteinaseCIA: murine collagen induced arthritisECM: Extracellular matrixcol I: Collagen ITCF/LEF: T-cell factor/lymphoid enhancer-binding factorAP1: Activator Protein 1.

Monocyte M1/M2 profile is altered in paediatric burn patients with hypertrophic scarring

Hypertrophic scars (HTS) remain a common outcome of burn injury, particularly in children. They can arise from variations in the wound healing stages, such as an excessive inflammatory response or inefficient remodelling. Of the cells contributing to these healing stages, macrophages and fibrocytes are crucial. Specifically, the inflammatory phase is dominated by M1 macrophages, the proliferation/remodelling stages by M2 macrophages, and scar tissue contains numerous fibrocytes. As the progenitors to these cells, monocytes, can also exhibit M1- and M2-skewing, we proposed that their profile, or circulating fibrocyte counts, could be used to predict poor healing outcomes. To investigate this, we obtained blood samples from paediatric controls and burns patients, which were then divided into HTS and NoHTS groups upon scar assessment at 12 months. The samples were assessed by whole blood flow cytometry to quantify fibrocytes and monocyte subset proportions and to determine monocyte levels of M1 (CD86, CD120b, CD319) and M2 (CD93, CD163, CD200R) markers. Both burns groups had higher proportions of classical monocytes compared to controls, indicating increased cell turnover and/or entry of other subsets into the wound. In burns patients who took more than 21 days to heal, the HTS group had lower M2 (CD200R) expression with the ratio of M1/M2 (CD86/CD200R) being significantly higher. These results suggest an elevated early inflammatory monocyte response contributes to development of HTS. Correlations of marker expression with remaining healing time revealed a significant positive correlation with M1 (CD120b) and M1/M2 (CD120b/CD200R), suggesting a potential role for CD120b as an indicator of healing delay. Fibrocytes did not significantly differ between the groups. In conclusion, increased monocyte inflammation likely contributes to slower healing and development of scarring, but further studies are needed to determine the predictive power of monocyte inflammatory profile.

Mass Cytometry Reveals Global Immune Remodeling with Multi-lineage Hypersensitivity to Type I Interferon in Down Syndrome

People with Down syndrome (DS; trisomy 21) display a different disease spectrum relative to the general population, including lower rates of solid malignancies and higher incidence of neurological and autoimmune conditions. However, the mechanisms driving this unique clinical profile await elucidation. We completed a deep mapping of the immune system in adults with DS using mass cytometry to evaluate 100 immune cell types, which revealed global immune dysregulation consistent with chronic inflammation, including key changes in the myeloid and lymphoid cell compartments. Furthermore, measurement of interferon-inducible phosphorylation events revealed widespread hypersensitivity to interferon-α in DS, with cell-type-specific variations in downstream intracellular signaling. Mechanistically, this could be explained by overexpression of the interferon receptors encoded on chromosome 21, as demonstrated by increased IFNAR1 surface expression in all immune lineages tested. These results point to interferon-driven immune dysregulation as a likely contributor to the developmental and clinical hallmarks of DS.

Corneal wound healing

The corneal wound healing response is typically initiated by injuries to the epithelium and/or endothelium that may also involve the stroma. However, it can also be triggered by immune or infectious processes that enter the stroma via the limbal blood vessels. For mild injuries or infections, such as epithelial abrasions or mild controlled microbial infections, limited keratocyte apoptosis occurs and the epithelium or endothelium regenerates, the epithelial basement membrane (EBM) and/or Descemet's basement membrane (DBM) is repaired, and keratocyte- or fibrocyte-derived myofibroblast precursors either undergo apoptosis or revert to the parent cell types. For more severe injuries with extensive damage to EBM and/or DBM, delayed regeneration of the basement membranes leads to ongoing penetration of the pro-fibrotic cytokines transforming growth factor (TGF) β1, TGFβ2 and platelet-derived growth factor (PDGF) that drive the development of mature alpha-smooth muscle actin (SMA)+ myofibroblasts that secrete large amounts of disordered extracellular matrix (ECM) components to produce scarring stromal fibrosis. Fibrosis is dynamic with ongoing mitosis and development of SMA + myofibroblasts and continued autocrine-or paracrine interleukin (IL)-1-mediated apoptosis of myofibroblasts and their precursors. Eventual repair of the EBM and/or DBM can lead to at least partial resolution of scarring fibrosis.

TGF-β in fibrosis by acting as a conductor for contractile properties of myofibroblasts

Myofibroblasts are non-muscle contractile cells that play a key physiologically role in organs such as the stem villi of the human placenta during physiological pregnancy. They are able to contract and relax in response to changes in the volume of the intervillous chamber. Myofibroblasts have also been observed in several diseases and are involved in wound healing and the fibrotic processes affecting several organs, such as the liver, lungs, kidneys and heart. During the fibrotic process, tissue retraction rather than contraction is correlated with collagen synthesis in the extracellular matrix, leading to irreversible fibrosis and, finally, apoptosis of myofibroblasts. The molecular motor of myofibroblasts is the non-muscle type IIA and B myosin (NMMIIA and NMMIIB). Fibroblast differentiation into myofibroblasts is largely governed by the transforming growth factor-β1 (TGF-β1). This system controls the canonical WNT/β-catenin pathway in a positive manner, and PPARγ in a negative manner. The WNT/β-catenin pathway promotes fibrosis, while PPARγ prevents it. This review focuses on the contractile properties of myofibroblasts and the conductor, TGF-β1, which together control the opposing interplay between PPARγ and the canonical WNT/β-catenin pathway.

The myofibroblast, biological activities and roles in eye repair and fibrosis. A focus on healing mechanisms in avascular cornea

Tissue healing is one of the mysteries of modern medicine. Healing involves complex processes and many cellular types, amongst which the myofibroblast plays a major role. In the eye, when needed, myofibroblasts can be found from the cornea to the retina, derived from a wide variety of different cells, and aimed at effectively repairing tissue damage. Myofibroblast differentiation requires transforming growth factor (TGF)-β1, the presence of specific extracellular matrix components such as the ED-A domain of fibronectin, and mechanical tension. Control of this process may, in some cases, be abnormal leading to development of fibrotic tissue, which alters and compromises the integrity of the original tissue. The eye is no exception to this rule with normal visual function, a highly demanding process, only possible in a fully integrated organ. The cornea, a transparent protective tissue and first dioptre of the eye, has the particularity of being entirely avascular and very richly innervated under normal physiological conditions. However, these anatomical features do not prevent it from developing myofibroblasts in the event of a deep corneal lesion. Activated by growth factors such as TGF-β1 and platelet-derived growth factor from the aqueous humour, tears or corneal epithelial cells, myofibroblasts can cause corneal scarring, sometimes with devastating consequences. Understanding the factors involved in healing and its signalling pathways, will potentially enable us to control corneal healing in the future, and thus avoid fibrotic ocular surface disease and the blindness that this may induce. Currently, this issue is the subject of very active research and development with the aim of discovering new antifibrotic therapies.

Fibroblasts and Their Pathological Functions in the Fibrosis of Aortic Valve Sclerosis and Atherosclerosis

Cardiovascular diseases, such as atherosclerosis and aortic valve sclerosis (AVS) are driven by inflammation induced by a variety of stimuli, including low-density lipoproteins (LDL), reactive oxygen species (ROS), infections, mechanical stress, and chemical insults. Fibrosis is the process of compensating for tissue injury caused by chronic inflammation. Fibrosis is initially beneficial and maintains extracellular homeostasis. However, in the case of AVS and atherosclerosis, persistently active resident fibroblasts, myofibroblasts, and smooth muscle cells (SMCs) perpetually remodel the extracellular matrix under the control of autocrine and paracrine signaling from the immune cells. Myofibroblasts also produce pro-fibrotic factors, such as transforming growth factor-β1 (TGF-β1), angiotensin II (Ang II), and interleukin-1 (IL-1), which allow them to assist in the activation and migration of resident immune cells. Post wound repair, these cells undergo apoptosis or become senescent; however, in the presence of unresolved inflammation and persistence signaling for myofibroblast activation, the tissue homeostasis is disturbed, leading to excessive extracellular matrix (ECM) secretion, disorganized ECM, and thickening of the affected tissue. Accumulating evidence suggests that diverse mechanisms drive fibrosis in cardiovascular pathologies, and it is crucial to understand the impact and contribution of the various mechanisms for the control of fibrosis before the onset of a severe pathological consequence.

Infiltrating CCR2+ monocytes and their progenies, fibrocytes, contribute to colon fibrosis by inhibiting collagen degradation through the production of TIMP-1

Intestinal fibrosis is a serious complication in inflammatory bowel disease (IBD). Despite the remarkable success of recent anti-inflammatory therapies for IBD, incidence of intestinal fibrosis and need for bowel resection have not significantly changed. To clarify the contribution of haematopoietic-derived cells in intestinal fibrosis, we prepared bone marrow (BM) chimeric mice (chimeras), which were reconstituted with BM cells derived from enhanced green fluorescent protein (EGFP)-transgenic mice or CC chemokine receptor 2 (CCR2)-deficient mice. After 2 months of transplantation, BM chimeras were treated with azoxymethane/dextran sodium sulphate. During chronic inflammation, CCR2⁺ BM-derived monocyte and fibrocyte infiltration into the colon and CC chemokine ligand 2 production increased, leading to colon fibrosis in EGFP BM chimeras. In CCR2-deficient BM chimeras, monocyte and fibrocyte numbers in the colonic lamina propria significantly decreased, and colon fibrosis was attenuated. In colon tissue, mRNA expression of tissue inhibitor of metalloproteinase (TIMP)-1 but not of collagen I, transforming growth factor-β1 or matrix metalloproteinases was significantly different between the two chimeras. CCR2⁺ monocytes and fibrocytes showed high Timp1 mRNA expression. Our results suggest that infiltrating CCR2⁺ monocytes and their progenies, fibrocytes, promote colon fibrosis by inhibiting collagen degradation through TIMP-1 production.

Correlation between circulating fibrocytes and dermal thickness in limited cutaneous systemic sclerosis patients: a pilot study

The objective is to detect any possible correlation between the modified Rodnan skin score (mRSS) and dermal thickness (DT) measured by skin high-frequency ultrasound (US) and the percentage of circulating fibrocytes in patients with limited cutaneous systemic sclerosis (lcSSc). Eight lcSSc patients and five healthy subjects (control group, CNT) were enrolled. The skin involvement was evaluated by mRSS and US (18 and 22 MHz probes) in all 13 subjects in the 17 standard skin areas evaluated by mRss. Circulating fibrocytes were isolated from the peripheral blood mononuclear cells (PBMCs) of all lcSSc patients and the CNT group to analyze their percentage at baseline time (T0) when the experiments started with PBMCs' isolation and collection and after 8 days of culture (T8). Non-parametric tests were used for the statistical analysis. A positive correlation between the percentage of circulating fibrocytes at T0, mRSS (p = 0.04 r = 0.96), and DT-US, evaluated by the 22 MHz and the 18 MHz probes (p = 0.03, r = 0.66 and p = 0.05, r = 0.52, respectively), was observed in lcSSc patients. Conversely, at T8, there was no correlation (p > 0.05) between these parameters in lcSSc group. In the CNT group, no correlations between mRSS or DT-US and the percentage of circulating fibrocytes were observed both at T0 and T8. The study shows the presence of a significant relationship between the percentage of circulating fibrocytes and DT, as evidenced by both mRSS and US, in limited cutaneus SSc. This observation may well suggest the reasonable hypothesis of a crucial contribution of circulating fibrocytes to skin fibrosis progression, which might be considered as further biomarkers.

Interaction Between CCR6+ Th17 Cells and CD34+ Fibrocytes Promotes Inflammation: Implications in Graves' Orbitopathy in Chinese Population

Purpose

Recent reports suggest that Th17 immunity and bone marrow-derived CD34+ fibrocytes contribute to the pathogenesis of Graves' orbitopathy (GO). This study investigated interactions between Th17 cells and fibrocytes in GO inflammation in Chinese subjects.

Methods

Th17 cells and fibrocytes were derived from blood samples from Chinese GO patients and healthy controls. Proportions and phenotypes of Th17 cells, regulatory T cells (Tregs), and fibrocytes were examined by flow cytometry. Exogenous IL-17A was used to study inflammatory activity of fibrocytes from GO patients and control subjects. Coculture, quantitative RT-PCR, Luminex, and transwell assays were performed to investigate the relationship between Th17 cells and fibrocytes.

Results

CC-chemokine receptor 6 (CCR6+) Th17 cells were increased in both active (P < 0.001) and inactive (P < 0.05) GO patients, compared with healthy controls. There was a positive correlation between number of CCR6+ Th17 cells and GO clinical activity score (P < 0.0001, r = 0.8176). Further, CD34+ fibrocytes were increased in GO patients, with increased expression of IL-17RA (P < 0.05), CD80 (P < 0.05), and CD86 (P < 0.05). A decreased population of effector Treg cells (P < 0.01) and increased CTLA-4 expression on naïve Treg cells (P < 0.05) were observed in GO patients. IL-17A stimulated cytokine production in fibrocytes; GO fibrocytes exhibited more robust production than normal fibrocytes. Autologous Th17 cells promoted inflammatory and antigen-presenting functions of GO fibrocytes; conversely, fibrocytes enhanced Th17 cell-function and recruited Th17 cells in a macrophage inflammatory protein 3 (MIP-3)/CCR6-dependent manner.

Conclusions

The crosstalk between CCR6+ Th17 cells and fibrocytes plays a role in the pathogenesis of GO. Suppressing these interactions may be a candidate molecular target for therapeutic approaches of GO.

The Mesentery, Systemic Inflammation, and Crohn's Disease

Initially thought to be a structure that only provided support to the abdominal contents, the mesentery has now gained special attention in the scientific community. The new approach of studying the mesentery as an individual organ has highlighted its importance in the development of local and systemic inflammatory diseases and its potential role in Crohn's disease. Its topographical relationship with the intestine in the setting of active inflammation and "creeping fat" is possibly one of the most important arguments for including the mesentery as an important factor in the pathogenesis of Crohn's disease. In this review, we discuss the importance of the mesentery from the anatomical and embryological standpoints. We also will summarize data on mesenteric inflammation in patients with Crohn's disease. The significance of the mesentery in systemic inflammatory syndromes will be discussed, and we provide an overview of primary inflammatory disorders of the mesentery. Finally, we discuss surgical approaches for patients requiring resection for Crohn's disease that incorporate mesenteric factors, pointing out recent data suggesting that these have the potential for improving outcomes and reducing disease recurrence. 10.1093/ibd/izy201_video1izy201.video15794169491001.

Wound Healing: A Cellular Perspective

Wound healing is one of the most complex processes in the human body. It involves the spatial and temporal synchronization of a variety of cell types with distinct roles in the phases of hemostasis, inflammation, growth, re-epithelialization, and remodeling. With the evolution of single cell technologies, it has been possible to uncover phenotypic and functional heterogeneity within several of these cell types. There have also been discoveries of rare, stem cell subsets within the skin, which are unipotent in the uninjured state, but become multipotent following skin injury. Unraveling the roles of each of these cell types and their interactions with each other is important in understanding the mechanisms of normal wound closure. Changes in the microenvironment including alterations in mechanical forces, oxygen levels, chemokines, extracellular matrix and growth factor synthesis directly impact cellular recruitment and activation, leading to impaired states of wound healing. Single cell technologies can be used to decipher these cellular alterations in diseased states such as in chronic wounds and hypertrophic scarring so that effective therapeutic solutions for healing wounds can be developed.

Inhibitory effect of circulating fibrocytes on injury repair in acute lung injury/acute respiratory distress syndrome mice model

The study was aimed to explore the functions of circulating fibrocytes (CFs) on injury repair in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) mice model and its clinical value as a biomarker for ALI/ARDS. ALI/ARDS mice model was established by intratracheal instillation of lipopolysaccharide (LPS). Mononuclear cells were isolated from peripheral blood of ALI/ARDS model and flow cytometry was used to measure CFs defined as cells positive for CD45 and collagen-1. Histological changes of lung tissues were evaluated by H&E staining and Masson's trichrome staining. The correlations of CFs counts with damnification of lung tissue and the severity of pulmonary fibrosis were evaluated by Pearson correlation analyses. Western blot was used to detect the protein expression of collagen-1. ELISA was applied to determine cytokine CXCL12 concentration. Clinical relevance between CFs and ALI/ARDS was investigated. The greater number of CFs in the ALI/ARDS group implied higher degree of lung injury and more severe pulmonary fibrosis. The protein expression of collagen-1 and concentration of cytokine CXCL12 in ALI/ARDS group were higher than that in control group. Clinical and prognostic analysis revealed the higher injury degree and death rates in ALI/ARDS group than those in control group, and identified a greater severity and mortality for patients with ARDS than those with ALI. ROC curve analysis indicated the counts of CFs greater than 5.85% can predict death rates with AUC = 0.928. CFs had an inhibitory effect on injury repair in ALI/ARDS mice model. This might be unfavorable as a clinical marker for progression of ALI/ARDS.

Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Inflammation and Fibrosis of Skeletal Muscles

In skeletal muscles, levels and activity of Matrix MetalloProteinases (MMPs) and Tissue Inhibitors of MetalloProteinases (TIMPs) have been involved in myoblast migration, fusion and various physiological and pathological remodeling situations including neuromuscular diseases. This has opened perspectives for the use of MMPs' overexpression to improve the efficiency of cell therapy in muscular dystrophies and resolve fibrosis. Alternatively, inhibition of individual MMPs in animal models of muscular dystrophies has provided evidence of beneficial, dual or adverse effects on muscle morphology or function. We review here the role played by MMPs/TIMPs in skeletal muscle inflammation and fibrosis, two major hurdles that limit the success of cell and gene therapy. We report and analyze the consequences of genetic or pharmacological modulation of MMP levels on the inflammation of skeletal muscles and their repair in light of experimental findings. We further discuss how the interplay between MMPs/TIMPs levels, cytokines/chemokines, growth factors and permanent low-grade inflammation favor cellular and molecular modifications resulting in fibrosis.

Interleukin-10 Attenuates Hypochlorous Acid-Mediated Cytotoxicity to HEI-OC1 Cochlear Cells

Inflammatory reaction plays a crucial role in the pathophysiology of acquired hearing loss such as ototoxicity and labyrinthitis. In our earlier work, we showed the pivotal role of otic fibrocytes in cochlear inflammation and the critical involvement of proinflammatory cytokines in cisplatin ototoxicity. We also demonstrated that otic fibrocytes inhibit monocyte chemoattractant protein 1 (CCL2) upregulation in response to interleukin-10 (IL-10) via heme oxygenase 1 (HMOX1) signaling, resulting in suppression of cochlear inflammation. However, it is still unclear how IL-10 affects inflammation-mediated cochlear injury. Here we aim to determine how hypochlorous acid, a model inflammation mediator affects cochlear cell viability and how IL-10 affects hypochlorous acid-mediated cochlear cell injury. NaOCl, a sodium salt of hypochlorous acid (HOCl) was found to induce cytotoxicity of HEI-OC1 cells in a dose-dependent manner. Combination of hydrogen peroxide and myeloperoxidase augmented cisplatin cytotoxicity, and this synergism was inhibited by N-Acetyl-L-cysteine and ML-171. The rat spiral ligament cell line (RSL) appeared to upregulate the antioxidant response element (ARE) activities upon exposure to IL-10. RSL cells upregulated the expression of NRF2 (an ARE ligand) and NR0B2 in response to CoPP (a HMOX1 inducer), but not to ZnPP (a HMOX1 inhibitor). Adenovirus-mediated overexpression of NR0B2 was found to suppress CCL2 upregulation. IL-10-positive cells appeared in the mouse stria vascularis 1 day after intraperitoneal injection of lipopolysaccharide (LPS). Five days after injection, IL-10-positive cells were observed in the spiral ligament, spiral limbus, spiral ganglia, and suprastrial area, but not in the stria vascularis. IL-10R1 appeared to be expressed in the mouse organ of Corti as well as HEI-OC1 cells. HEI-OC1 cells upregulated Bcl-xL expression in response to IL-10, and IL-10 was shown to attenuate NaOCl-induced cytotoxicity. In addition, HEI-OC1 cells upregulated IL-22RA upon exposure to cisplatin, and NaOCl cytotoxicity was inhibited by IL-22. Taken together, our findings suggest that hypochlorous acid is involved in cochlear injury and that IL-10 potentially reduces cochlear injury through not only inhibition of inflammation but also enhancement of cochlear cell viability. Further studies are needed to determine immunological characteristics of intracochlear IL-10-positive cells and elucidate molecular mechanisms involved in the otoprotective activity of IL-10.

Interleukin-34 Promotes Fibrocyte Proliferation

Rheumatoid arthritis (RA) is a systemic autoimmune disease affecting multiple joints. It remains unclear which factors in the circulation are associated with the systemic spread of the disease. Fibrocytes are pluripotent mesenchymal stem cells present in the circulation of RA patients. Our earlier findings implicated activated fibrocytes in the etiology of onset and pathogenesis of RA. Elevated levels of interleukin-34 (IL-34) in the serum and synovial fluid of RA patients are associated with rheumatoid factor and anticyclic citrullinated peptide antibodies, indicators of RA. Moreover, IL-34 levels are independent predictors of radiographic progression in RA patients. We provide evidence of simultaneous elevated levels of IL-34 and increased numbers of activated fibrocytes in the circulation of mice induced to develop arthritis. In vitro, IL-34 treatment induced the proliferation of fibrocytes, mediated by activation of cognate CSF-R1s on fibrocytes. Taken together, we infer that IL-34 has a role in stimulating fibrocyte proliferation and activation during arthritis, thereby contributing to both onset of RA and systemic spread of disease.

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

Radiation therapy induces DNA damage and inflammation leading to fibrosis. Fibrosis can occur 4 to 12 months after radiation therapy. This process worsens with time and years. Radiation-induced fibrosis is characterized by fibroblasts proliferation, myofibroblast differentiation, and synthesis of collagen, proteoglycans and extracellular matrix. Myofibroblasts are non-muscle cells that can contract and relax. Myofibroblasts evolve towards irreversible retraction during fibrosis process. In this review, we discussed the interplays between transforming growth factor-β1 (TGF-β1), canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR γ) in regulating the molecular mechanisms underlying the radiation-induced fibrosis, and the potential role of PPAR γ agonists. Overexpression of TGF-β and canonical WNT/β-catenin pathway stimulate fibroblasts accumulation and myofibroblast differentiation whereas PPAR γ expression decreases due to the opposite interplay of canonical WNT/β-catenin pathway. Both TGF-β1 and canonical WNT/β-catenin pathway stimulate each other through the Smad pathway and non-Smad pathways such as phosphatidylinositol 3-kinase/serine/threonine kinase (PI3K/Akt) signaling. WNT/β-catenin pathway and PPAR γ interact in an opposite manner. PPAR γ agonists decrease β-catenin levels through activation of inhibitors of the WNT pathway such as Smad7, glycogen synthase kinase-3 (GSK-3 β) and dickkopf-related protein 1 (DKK1). PPAR γ agonists also stimulate phosphatase and tensin homolog (PTEN) expression, which decreases both TGF-β1 and PI3K/Akt pathways. PPAR γ agonists by activating Smad7 decrease Smads pathway and then TGF-β signaling leading to decrease radiation-induced fibrosis. TGF-β1 and canonical WNT/β-catenin pathway promote radiation-induced fibrosis whereas PPAR γ agonists can prevent radiation-induced fibrosis.

Deficiency of KLF4 compromises the lung function in an acute mouse model of allergic asthma

Asthma is a chronic inflammatory disease of the airways and the mechanisms are not fully understood. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of monocytes, granulocyte and myeloid cells at early stage of differentiation. They possess phenotypic plasticity and regulate airway inflammation. We recently reported that Kruppel-like factor 4 (KLF4) regulates MDSC differentiation into fibrocytes, emerging effectors in chronic inflammation. However, the role of KLF4 in asthma is not known. Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine and a key initiator of allergic airway inflammation. Given the fact that TSLP promotes Th2 cytokine production that increases MDSC differentiation into fibrocytes, we postulate that KLF4 regulates asthma in a TSLP-dependent manner. In this study, we utilized a model of allergic asthma with ovalbumin challenge (OVA). We found that upon OVA treatment the wild type mice had increased MDSC infiltration into the lung, up-regulation of KLF4 and TSLP gene expression, and higher levels of Th2 cytokines including IL4 and IL13. Consistently, lack of KLF4 expression in monocytes and lung epithelial cells resulted in decreased TSLP expression and lower levels of Th2 cytokines in mice, and fibrocyte generation was compromised. KLF4 deficiency in these cells also led to decreased airway hyperresponsiveness (AHR), a cardinal feature of asthma, as assessed by whole body plethysmography. Moreover, lung fibrosis as measured by trichome staining was attenuated and the population of CD45 + COL1A1+ fibrocytes was diminished in this setting. Together, our results suggest that KLF4 regulates asthma development in a TSLP- and fibrocyte-dependent manner.

Fibrocyte measurement in peripheral blood correlates with number of cultured mature fibrocytes in vitro and is a potential biomarker for interstitial lung disease in Rheumatoid Arthritis

Background

Interstitial lung disease (ILD) can be a severe extra-articular disease manifestation in Rheumatoid Arthritis (RA). A potential role of fibrocytes in RA associated ILD (RA-ILD) has not previously been described. We present a modified faster method for measuring circulating fibrocytes, without intracellular staining. The results are compared to the traditional culture method, where the number of monocytes that differentiate into mature fibrocytes in vitro are counted. The results are following compared to disease activity in patients with severe asthma, ILD, RA (without diagnosed ILD) and RA with verified ILD (RA-ILD).

Method

CD45⁺ CD34⁺ CD11b⁺ (7-AAD⁻ CD3⁻ CD19⁻ CD294⁻) cells were isolated by cell sorting and stained for pro-collagen type 1. Thirty-nine patients (10 RA, 9 ILD and 10 with severe asthma, 10 with RA-ILD) and 10 healthy controls (HC) were included. Current medication, disease activity, pulmonary function test and radiographic data were collected. Circulating fibrocytes were quantified by flow cytometry. Peripheral blood mononuclear cells were isolated and cultured for 5 days and the numbers of mature fibrocytes were counted.

Results

90.2% (mean, SD = 1.5%) of the sorted cells were pro-collagen type 1 positive and thereby fulfilled the criteria for being circulating fibrocytes. The ILD and RA-ILD groups had increased levels of circulating fibrocytes compared to HC (p < 0.05). Levels of circulating fibrocytes correlated overall to number of monocytes that subsequently in vitro differentiated to mature fibrocytes (r = 0.81, p < 0.001). RA patients with pathologically reduced diffusion capacity for carbon monoxide adjusted for hemoglobin (DLCO_c) in both the RA and in the combined RA + RA-ILD group, had significantly higher levels of both circulating and number of cultured mature fibrocytes (both p < 0.05). In both groups, the level of circulating fibrocytes and number of mature fibrocytes in culture also correlated to a reduction in DLCO_c (r = −0.61 an r = −0.58 both p < 0.05).

Conclusions

We presented a fast and valid method for measuring circulating fibrocytes using flow cytometry on lysed peripheral blood. Further, we showed for the first time, that the level of circulating fibrocytes correlated with the number of peripheral blood mononuclear cells, that differentiated into mature fibrocytes in vitro. Reduced DLCO_c was correlated with high levels of circulating and mature fibrocytes in RA, which have not been reported previously. In such, this study suggests that fibrocytes may exhibit an important role in the pathogenesis of RA-ILD, which requires further clarification in future studies.

Trial registration

ClinicalTrials.gov:NCT02711657, registered 13/3–2016, retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0623-9) contains supplementary material, which is available to authorized users.

Netrin-1 Regulates Fibrocyte Accumulation in the Decellularized Fibrotic Sclerodermatous Lung Microenvironment and in Bleomycin-Induced Pulmonary Fibrosis

OBJECTIVE

Fibrocytes are collagen-producing leukocytes that accumulate in patients with systemic sclerosis (SSc; scleroderma)-related interstitial lung disease (ILD) via unknown mechanisms that have been associated with altered expression of neuroimmune proteins. The extracellular matrix (ECM) influences cellular phenotypes. However, a relationship between the lung ECM and fibrocytes in SSc has not been explored. The aim of this study was to use a novel translational platform based on decellularized human lungs to determine whether the lung ECM of patients with scleroderma controls the development of fibrocytes from peripheral blood mononuclear cells.

METHODS

We performed biomechanical evaluation of decellularized scaffolds prepared from lung explants from healthy control subjects and patients with scleroderma, using tensile testing and biochemical and proteomic analysis. Cells obtained from healthy controls and patients with SSc-related ILD were cultured on these scaffolds, and CD45+pro-ColIα1+ cells meeting the criteria for fibrocytes were quantified. The contribution of the neuromolecule netrin-1 to fibrosis was assessed using neutralizing antibodies in this system and by administering bleomycin via inhalation to netrin-1(+/-) mice.

RESULTS

Compared with control lung scaffolds, lung scaffolds from patients with SSc-related ILD showed aberrant anatomy, enhanced stiffness, and abnormal ECM composition. Culture of control cells in lung scaffolds from patients with SSc-related ILD increased production of pro-ColIα1+ cells, which was stimulated by enhanced stiffness and abnormal ECM composition. Cells from patients with SSc-related ILD demonstrated increased pro-ColIα1 responsiveness to lung scaffolds from scleroderma patients but not enhanced stiffness. Enhanced detection of netrin-1-expressing CD14(low) cells in patients with SSc-related ILD was observed, and antibody-mediated netrin-1 neutralization attenuated detection of CD45+pro-ColIα1+ cells in all settings. Netrin-1(+/-) mice were protected against bleomycin-induced lung fibrosis and fibrocyte accumulation.

CONCLUSION

Factors present in the lung matrices of patients with scleroderma regulate fibrocyte accumulation via a netrin-1-dependent pathway. Netrin-1 regulates bleomycin-induced pulmonary fibrosis in mice. Netrin-1 might be a novel therapeutic target in SSc-related ILD.

Inflammation and its resolution and the musculoskeletal system

Inflammation, an essential tissue response to extrinsic/intrinsic damage, is a very dynamic process in terms of complexity and extension of cellular and metabolic involvement. The aim of the inflammatory response is to eliminate the pathogenic initiator with limited collateral damage of the inflamed tissue, followed by a complex tissue repair to the preinflammation phenotype. Persistent inflammation is a major contributor to the pathogenesis of many musculoskeletal diseases including ageing-related pathologies such as osteoporosis, osteoarthritis, and sarcopaenia. Understanding the mechanisms of inflammation and its resolution is therefore critical for the development of effective regenerative, and therapeutic strategies in orthopaedics.

Circulating fibrocytes are involved in inflammation and leukocyte trafficking in neonates with necrotizing enterocolitis

Fibrocytes, ahematopoietic stem cell source of fibroblasts/myofibroblasts, were previously implicated to infiltrate into the intestinal and enhance inflammation.The aims of the present study were to elucidate the role of fibrocytes in necrotizing enterocolitis (NEC) pathogenesis and to explore the mechanisms by which fibrocytes contributed to the inflammatory responses.We investigated circulating and intestinal local fibrocytes from 32 patients with NEC, 8 patients with noninflammatory conditions of the gastrointestinal tract and 12 normal subjects.Significantly higher numbers of circulating fibrocytes were found in the peripheral blood from NEC patients than the controls (P < .01). Numerous fibrocytes were found infiltrating the NEC intestinal mucous membranes. The percentage of fibrocytes to total leukocytes in the NEC inflammatory lesions was significantly increased compared with the percentage in the noninflammatory gastrointestinal tract. The fibrocyte attractant chemokine C-X-C motif chemokine ligand 12 (CXCL12) was significantly increased in the plasma and was detectable in 80% of the peritoneal lavage fluid from NEC patients but not the controls. Furthermore, chemokine expression was increased in fibrocytes infiltrating and trafficking to leukocyte sites. In culture, lipopolysaccharide (LPS) induced a significant increase in the expression of the Toll-like receptor (TLR4) signal, with the upregulation of p38 in both the isolated fibrocytes and macrophages. Similarly, interleukin (IL)-1β induced increased the upregulation of the IL-6, tumor necrosis factor (TNF)-α, and intercellular cell adhesion molecule-1 mRNAs but downregulated ColI in fibrocytes isolated from NEC patients compared with the controls.These findings indicate that circulating fibrocytes are increased in NEC patients and may be recruited to the inflammatory intestinal track, most likely through the CXCR4/CXCL12 axis. These cells may contribute to intestinal inflammation through TLR4 signaling by producing the TNF-α and IL-6 cytokines.

TGFβ signaling and the control of myofibroblast differentiation: Implications for chronic inflammatory disorders

The myofibroblast is a highly specialized cell type that plays a critical role during normal tissue wound healing, but also contributes pathologically to chronic inflammatory conditions such as fibrosis and cancer. As fibrotic conditions continue to be a major burden to the public health system, novel therapies that target the function of myofibroblasts may show promise in the clinic. The cytokine transforming growth factor β (TGFβ) is the most potent known inducer of myofibroblast differentiation and thus represents a powerful target to modify myofibroblast function during disease. This review focuses on our current understanding of the key signaling pathways activated by TGFβ during myofibroblast differentiation.

Involvement of fibrocytes in asthma and clinical implications

Bloodborne fibrocytes are bone marrow-derived cells that participate in immune responses and exhibit pro-inflammatory and matrix remodelling properties. In patients with asthma receiving an adequate treatment, the blood fibrocyte count is very low and comparable to that obtained in healthy individuals. In these patients, a transient increase in fibrocyte numbers in the peripheral blood and in the airways occurs in concomitance with increased bronchial inflammation and reflects disease worsening and the need for more intensive treatment. Persistently elevated numbers of fibrocytes in the peripheral blood and in the bronchial mucosa are observed in chronically undertreated or corticosteroid-resistant asthma and are associated with persistent airway inflammation and ongoing remodelling of the bronchial wall. The asthmatic bronchial epithelium is the main source of fibrocyte chemoattractants in asthma and contributes with T helper type 2 lymphocytes and eosinophils to promote the proliferation and pro-remodelling function of recruited fibrocytes. The presence of elevated numbers of fibrocytes in the bronchial mucosa of allergic patients with undertreated or treatment-resistant asthma may also increase the risk of acute exacerbations because these cells can amplify T helper type 2 lymphocyte-driven inflammation on every exposure to the clinically relevant allergen and can promote further inflammation on rhinovirus infections by allowing viral replication and releasing additional pro-inflammatory factors. Improved methods for the isolation and functional analysis of pure populations of viable circulating fibrocytes have allowed a better understanding of the effector role of these cells. A reliable and clinically applicable assay has been developed to measure blood fibrocyte counts as outcome measure in future clinical trials. New therapeutic agents are needed to block both persistent inflammation and fibrocytosis in corticosteroid-resistant asthma.

The myofibroblast in wound healing and fibrosis: answered and unanswered questions

The discovery of the myofibroblast has allowed definition of the cell responsible for wound contraction and for the development of fibrotic changes. This review summarizes the main features of the myofibroblast and the mechanisms of myofibroblast generation. Myofibroblasts originate from a variety of cells according to the organ and the type of lesion. The mechanisms of myofibroblast contraction, which appear clearly different to those of smooth muscle cell contraction, are described. Finally, we summarize the possible strategies in order to reduce myofibroblast activities and thus influence several pathologies, such as hypertrophic scars and organ fibrosis.

Vascular Remodelling and Mesenchymal Transition in Systemic Sclerosis

Fibrosis of the skin and of internal organs, autoimmunity, and vascular inflammation are hallmarks of Systemic Sclerosis (SSc). The injury and activation of endothelial cells, with hyperplasia of the intima and eventual obliteration of the vascular lumen, are early features of SSc. Reduced capillary blood flow coupled with deficient angiogenesis leads to chronic hypoxia and tissue ischemia, enforcing a positive feed-forward loop sustaining vascular remodelling, further exacerbated by extracellular matrix accumulation due to fibrosis. Despite numerous developments and a growing number of controlled clinical trials no treatment has been shown so far to alter SSc natural history, outlining the need of further investigation in the molecular pathways involved in the pathogenesis of the disease. We review some processes potentially involved in SSc vasculopathy, with attention to the possible effect of sustained vascular inflammation on the plasticity of vascular cells. Specifically we focus on mesenchymal transition, a key phenomenon in the cardiac and vascular development as well as in the remodelling of injured vessels. Recent work supports the role of transforming growth factor-beta, Wnt, and Notch signaling in these processes. Importantly, endothelial-mesenchymal transition may be reversible, possibly offering novel cues for treatment.

Heme Oxygenase-1 Induction Prevents Autoimmune Diabetes in Association With Pancreatic Recruitment of M2-Like Macrophages, Mesenchymal Cells, and Fibrocytes

Immunoregulatory and regenerative processes are activated in the pancreas during the development of type 1 diabetes (T1D) but are insufficient to prevent the disease. We hypothesized that the induction of cytoprotective heme oxygenase-1 (HO-1) by cobalt protophoryrin (CoPP) would prevent T1D by promoting anti-inflammatory and pro-repair processes. Diabetes-prone BioBreeding rats received ip CoPP or saline twice per week for 3 weeks, starting at 30 days and were monitored for T1D. Immunohistochemistry, confocal microscopy, quantitative RT-PCR, and microarrays were used to evaluate postinjection pancreatic changes at 51 days, when islet inflammation is first visible. T1D was prevented in CoPP-treated rats (29% vs 73%). Pancreatic Hmox1 was up-regulated along with islet-associated CD68(+)HO-1(+) cells, which were also observed in a striking peri-lobular interstitial infiltrate. Most interstitial cells expressed the mesenchymal marker vimentin and the hematopoietic marker CD34. Spindle-shaped, CD34(+)vimentin(+) cells coexpressed collagen V, characteristic of fibrocytes. M2 macrophage factors Krüppel-like factor 4, CD163, and CD206 were expressed by interstitial cells, consistent with pancreatic upregulation of several M2-associated genes. CoPP upregulated islet-regenerating REG genes and increased neogenic REG3β(+) and insulin(+) clusters. Thus, short-term induction of HO-1 promoted a protective M2-like milieu in the pancreas and recruited mesenchymal cells, M2 macrophages, and fibrocytes that imparted immunoregulatory and pro-repair effects, preventing T1D.

Fibrocytes Differ from Macrophages but Can Be Infected with HIV-1

Fibrocytes (fibroblastic leukocytes) are recently identified as unique hematopoietic cells with features of both macrophages and fibroblasts. Fibrocytes are known to contribute to the remodeling or fibrosis of various injured tissues. However, their role in viral infection is not fully understood. In this study, we show that differentiated fibrocytes are phenotypically distinguishable from macrophages but can be infected with HIV-1. Importantly, fibrocytes exhibited persistently infected cell-like phenotypes, the degree of which was more apparent than macrophages. The infected fibrocytes produced replication-competent HIV-1, but expressed HIV-1 mRNA at low levels and strongly resisted HIV-1-induced cell death, which enabled them to support an extremely long-term HIV-1 production at low but steady levels. More importantly, our results suggested that fibrocytes were susceptible to HIV-1 regardless of their differentiation state, in contrast to the fact that monocytes become susceptible to HIV-1 after the differentiation into macrophages. Our findings indicate that fibrocytes are the previously unreported HIV-1 host cells, and they suggest the importance of considering fibrocytes as one of the long-lived persistently infected cells for curing HIV-1.

Bone Regeneration of Blood-derived Stem Cells within Dental Implants

Peripheral blood (PB) is known as a source of mesenchymal stem cells (MSCs), as is bone marrow (BM), and is acquired easily. However, it is difficult to have enough MSCs, and their osteogenic capacity with dental implantations is scarce. Therefore, we characterized peripheral blood mesenchymal stem cells (PBMSCs) cultured on a bone marrow–derived mesenchymal stem cell (BMMSC) natural extracellular matrix (ECM) and demonstrated the osteogenic capability in an experimental chamber implant surgery model in rabbits. We isolated PBMSCs from rabbits by culturing on a natural ECM-coated plate during primary culture. We characterized the PBMSCs using a fluorescence-activated cell scanner, cell proliferation assay, and multiple differentiation assay and compared them with BMMSCs. We also analyzed the osteogenic potential of PBMSCs mixed with hydroxyapatite/tricalcium phosphate (HA/TCP) by transplanting them into immunocompromised mice. Then, the mixture was applied to the canals. After 3 and 6 wk, we analyzed new bone (NB) formation inside the chambers using histological and histomorphometric analyses. The PBMSCs had a similar rate of BrdU-positive cells to BMMSCs, positively expressing CD90 but negative for CD14. The PBMSCs also showed osteogenic, adipogenic, and chondrogenic ability in vitro and osteogenic ability in vivo. Histological and histomorphometric results illustrated that the PBMSC and BMMSC groups showed higher NB than the HA/TCP and defect groups in the upper and lower chambers at 6 wk and in the upper canal at 3 wk; however, there was no difference in NB among all groups in the lower canal at 3 wk. The PBMSCs have characteristics and bone regeneration ability similar to BMMSCs both in vitro and in vivo. ECM was effective for obtaining PBMSCs. Therefore, PBMSCs are a promising source for bone regeneration for clinical use.

CCR1-mediated accumulation of myeloid cells in the liver microenvironment promoting mouse colon cancer metastasis

To understand colon cancer metastasis, we earlier analyzed a mouse model that developed liver metastasis of cancer cells disseminated from the spleen. We suggested that CCR1(+) bone marrow (BM)-derived cells are recruited to the microenvironment of disseminated colon cancer cells, and produce metalloproteinases MMP9 and MMP2, helping metastatic colonization. In the present study, we have examined these myeloid cells expressing CCR1 and/or MMPs in detail. To this end, we have established bacterial artificial chromosome (BAC)-based transgenic mouse lines in which membrane-targeted Venus fluorescent protein (mVenus) was expressed under the control of Ccr1 gene promoter. Then, myeloid cells obtained from the BM and liver metastatic foci were analyzed by the combination of flow cytometry and cytology/immunohistochemistry, in situ RNA hybridization, or quantitative RT-PCR. We have found four distinct types of myeloid cells recruited to the metastatic foci; neutrophils, eosinophils, monocytes and fibrocytes. These cell types exhibited distinct expression patterns for CCR1, MMP2 and MMP9. Namely, neutrophils found in the early phase of cancer cell dissemination expressed CCR1 exclusively and MMP9 preferentially, whereas fibrocytes accumulated in later phase expressed MMP2 exclusively. Either genetic inactivation of Ccr1 or antibody-mediated neutrophil depletion reduced subsequent recruitment of fibrocytes. The recruitment of CCR1(+) neutrophils in early phase of colon cancer dissemination appears to cause that of fibrocytes in late phase. These results implicate the key role of CCR1 in colon cancer metastasis in this mouse model, and explain why both MMP9 and MMP2 are essential as genetically demonstrated previously. The results also suggest relevant mechanisms in humans.

Human fibrocytic myeloid-derived suppressor cells express IDO and promote tolerance via Treg-cell expansion

By restraining T-cell activation and promoting Treg-cell expansion, myeloid-derived suppressor cells (MDSCs) and tolerogenic DCs can control self-reactive and antigraft effector T cells in autoimmunity and transplantation. Their therapeutic use and characterization, however, is limited by their scarce availability in the peripheral blood of tumor-free donors. In the present study, we describe and characterize a novel population of human myeloid suppressor cells, named fibrocytic MDSC, which are differentiated from umbilical cord blood precursors by 4-day culture with FDA-approved cytokines (recombinant human-GM-CSF and recombinant human-G-CSF). This MDSC subset, characterized by the expression of MDSC-, DC-, and fibrocyte-associated markers, promotes Treg-cell expansion and induces normoglycemia in a xenogeneic mouse model of Type 1 diabetes. In order to exert their protolerogenic function, fibrocytic MDSCs require direct contact with activated T cells, which leads to the production and secretion of IDO. This new myeloid subset may have an important role in the in vitro and in vivo production of Treg cells for the treatment of autoimmune diseases, and in either the prevention or control of allograft rejection.

Enumeration of circulating fibrocytes for clinical use in asthma by an optimized single-platform flow cytometry assay

Background

Elevated numbers of circulating fibrocytes are associated with inadequately controlled asthma, poor response to available therapies, and increased risk of adverse outcomes. The lack of reliable and clinically-applicable assays precludes a proper evaluation of blood fibrocyte count as a prognostic biomarker in asthma. This report concerns the use of a multiparameter flow cytometry assay for the enumeration of fibrocytes in the whole blood.

Methods

Consenting fibrocyte donors were 19 patients with asthma well controlled by current treatment, 16 patients with treatment-resistant asthma, 9 patients with transiently uncontrolled asthma and 14 age-matched normal individuals. Blood sampling was performed once in patients with transiently uncontrolled asthma and twice, at an interval of one week, in the other subjects. The assay was performed in 100 μl of whole blood and involved a sequential gating strategy and absolute fibrocyte counting with a single instrument (single-platform assay).

Results

The quantification of circulating fibrocytes by this assay was analytically and clinically valid. In individuals with stable clinical conditions, the repeatability of blood fibrocyte counts over one week was good. The intraclass correlation coefficient was 0.939 and 96.88% of the total variability reflected on-average differences among the tested subjects. Stabilized blood samples could be stored at 4 °C for up to 96 h before processing.

Conclusions

The novel assay for the enumeration of fibrocytes in the whole blood is reliable and clinically applicable.

General significance

This report demonstrates the validity and reliability of the first optimized assay for the enumeration of circulating fibrocytes in multicenter clinical trials.

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Elevated blood fibrocyte count is an emerging prognostic biomarker in asthma.

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The lack of reliable, clinically-applicable assays precludes further evaluation.

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An optimized whole-blood single-platform flow cytometry assay is described here.

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The assay is analytically and clinically valid and provides reproducible measures.

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Stabilized blood samples can be stored for 96 h at 4 °C before processing.

Mechanisms of tumor escape from immune system: role of mesenchymal stromal cells

Tumor microenvironment represents the site where the tumor tries to survive and escape from immune system-mediated recognition. Indeed, to proliferate tumor cells can divert the immune response inducing the generation of myeloid derived suppressor cells and regulatory T cells which can limit the efficiency of effector antitumor lymphocytes in eliminating neoplastic cells. Many components of the tumor microenvironment can serve as a double sword for the tumor and the host. Several types of fibroblast-like cells, which herein we define mesenchymal stromal cells (MSC), secrete extracellular matrix components and surrounding the tumor mass can limit the expansion of the tumor. On the other hand, MSC can interfere with the immune recognition of tumor cells producing immunoregulatory cytokines as transforming growth factor (TGF)ß, releasing soluble ligands of the activating receptors expressed on cytolytic effector cells as decoy molecules, affecting the correct interaction among lymphocytes and tumor cells. MSC can also serve as target for the same anti-tumor effector lymphocytes or simply impede the interaction between these lymphocytes and neoplastic cells. Thus, several evidences point out the role of MSC, both in epithelial solid tumors and hematological malignancies, in regulating tumor cell growth and immune response. Herein, we review these evidences and suggest that MSC can be a suitable target for a more efficient anti-tumor therapy.

Circulating fibrocytes stabilize blood vessels during angiogenesis in a paracrine manner

Accumulating evidence supports that circulating fibrocytes play important roles in angiogenesis. However, the specific role of fibrocytes in angiogenesis and the underlying mechanisms remain unclear. In this study, we found that fibrocytes stabilized newly formed blood vessels in a mouse wound-healing model by inhibiting angiogenesis during the proliferative phase and inhibiting blood vessel regression during the remodeling phase. Fibrocytes also inhibited angiogenesis in a Matrigel mouse model. In vitro study showed that fibrocytes inhibited both the apoptosis and proliferation of vascular endothelial cells (VECs) in a permeable support (Transwell) co-culture system. In a three-dimensional collagen gel, fibrocytes stabilized the VEC tubes by decreasing VEC tube density on stimulation with growth factors and preventing VEC tube regression on withdrawal of growth factors. Further mechanistic investigation revealed that fibrocytes expressed many prosurvival factors that are responsible for the prosurvival effect of fibrocytes on VECs and blood vessels. Fibrocytes also expressed angiogenesis inhibitors, including thrombospondin-1 (THBS1). THBS1 knockdown partially blocked the fibrocyte-induced inhibition of VEC proliferation in the Transwell co-culture system and recovered the fibrocyte-induced decrease of VEC tube density in collagen gel. Purified fibrocytes transfected with THBS1 siRNA partially recovered the fibrocyte-induced inhibition of angiogenesis in both the wound-healing and Matrigel models. In conclusion, our findings reveal that fibrocytes stabilize blood vessels via prosurvival factors and anti-angiogenic factors, including THBS1.