Perivascular Cells in Diffuse Cutaneous Systemic Sclerosis Overexpress Activated ADAM12 and Are Involved in Myofibroblast Transdifferentiation and Development of Fibrosis

Imaging mass cytometry-based characterisation of fibroblast subsets and their cellular niches in systemic sclerosis

OBJECTIVES

Transcriptomic data demonstrated that fibroblasts are heterogeneous with functionally diverse subpopulations. Although fibroblasts are key effector cells of fibrotic diseases such as systemic sclerosis (SSc), they have not yet been characterised spatially at the cellular level. Here, we aimed to investigate fibroblast subpopulations using imaging mass cytometry (IMC) as a proteomic-based, spatially resolved omics approach.

METHODS

We applied IMC to deconvolute the heterogeneity of 49 969 cells including 6501 fibroblasts at the single-cell level, to analyse their spatial distribution and to characterise their cellular niches in skin sections of patients with SSc and controls in situ.

RESULTS

We identified 13 different subpopulations of fibroblasts in SSc and control skin, the proportion increases in five fibroblast subpopulations (myofibroblasts, FAPhigh, S1PR+, Thy1+;ADAM12high;PU.1high and ADAM12+;GLI1+ fibroblasts) and decreases in three subpopulations (TFAMhigh, PI16+;FAP+ and Thy1+;ADAM12low fibroblasts). Several fibroblast subpopulations demonstrated spatial enrichment and altered cellular interactions in SSc. The proportion of S1PR+-fibroblast positively correlated with more extensive skin fibrosis, whereas high numbers of PI16+;FAP--fibroblasts were associated with milder skin fibrosis. The frequency of aberrant cellular interaction between S1PR+ and ADAM12+;GLI1+-fibroblasts also positively associated with the extent of skin fibrosis in SSc.

CONCLUSION

Using IMC, we demonstrated profound changes in composition and localisation of the majority of fibroblast subpopulations in SSc skin. These findings may provide a rationale for specific targeting of deregulated fibroblast subpopulations in SSc. Quantification of S1PR+-fibroblast and PI16+;FAP--fibroblasts may offer potential for patient stratification according to severity of skin fibrosis.

Identifying characteristics of dermal fibroblasts in skin homeostasis and disease

Heterogeneous dermal fibroblasts are the main components that constitute the dermis. Distinct fibroblast subgroups show specific characteristics and functional plasticity that determine dermal structure during skin development and wound healing. Although researchers have described the roles of fibroblast subsets, this is not completely understood. We review recent evidence supporting understanding about the heterogeneity of fibroblasts. We summarize the origins and the identified profiles of fibroblast subpopulations. The characteristics of fibroblast subpopulations in both healthy and diseased states are highlighted, and the potential of subpopulations to be involved in wound healing in different ways was discussed. Additionally, we review the plasticity of subpopulations and the underlying signalling mechanisms. This review may provide greater insights into potential novel therapeutic targets and tissue regeneration strategies for the future.

Fibroblast expression of CD248 may contribute to exacerbation of microvascular damage during systemic sclerosis

OBJECTIVES

CD248 is a glycoprotein, highly expressed on pericytes and fibroblasts (FBs), that is implicated in the fibrotic process. During angiogenesis, CD248 can promote vessel regression, binding multimerin-2 (MMRN-2). Thus, we investigated the expression of MMRN-2 in systemic sclerosis (SSc)-skin and of CD248 in isolated SSc-FBs. The anti-angiogenic property of CD248+ SSc-FBs was evaluated by co-culturing these cells with healthy control endothelial cells (HC-ECs). The apoptotic effect of CD248 on HC-ECs was evaluated. Finally, the ability of CD248 to prevent activation of VEGF receptor 2 (VEGFR2) was assessed.

METHODS

By IF, MMRN-2 was investigated in SSc-skin and CD248 in SSc FBs. The anti-angiogenic property of CD248+ SSc-FBs was evaluated by HC-ECs/SSc-FBs co-cultures. Lentiviral-induced CD248 short-hairpin RNA delivery was employed for loss-of-function studies in SSc-FBs. HC-ECs were cultured in the presence of CD248 to assess apoptosis by IF and VEGFR2 phosphorylation by western blot.

RESULTS

MMRN-2 expression was increased in skin SSc-ECs, whereas CD248 expression was increased in SSc-FBs. Functionally, CD248+-SSc-FBs suppressed angiogenesis in the organotypic model, as assessed by the reduction in total tube length of HC-ECs. This anti-angiogenetic behaviour was reversed by CD248 silencing. Furthermore, the presence of CD248 promoted the apoptosis of HC-ECs. Finally, CD248 prevented activation of VEGFR2 by reducing its phosphorylation after VEGF stimulation.

CONCLUSION

CD248 was anti-angiogenic in vitro due to a reduction in tube formation and to induction of apoptosis of ECs. Increased expression of CD248 in SSc could contribute to the microvascular rarefaction observed at the tissue level in SSc. Our results suggest a pathogenic role for CD248-MMRN-2 in SSc.

The Role of Mesenchymal Stromal Cells in Tissue Repair and Fibrosis

Significance: The present review covers an overview of the current understanding of biology of mesenchymal stromal cells (MSCs) and suggests an important role of their differential potential for clinical approaches associated with tissue repair and fibrosis. Recent Advances: Genetic lineage tracing technology has enabled the delineation of cellular hierarchies and examination of MSC cellular origins and myofibroblast sources. This technique has led to the characterization of perivascular MSC populations and suggests that pericytes might provide a local source of tissue-specific MSCs, which can differentiate into tissue-specific cells for tissue repair and fibrosis. Autologous adipose tissue MSCs led to the advance in tissue engineering for regeneration of damaged tissues. Critical Issues: Recent investigation has revealed that perivascular MSCs might be the origin of myofibroblasts during fibrosis development, and perivascular MSCs might be the major source of myofibroblasts in fibrogenic disease. Adipose tissue MSCs combined with cytokines and biomaterials are available in the treatment of soft tissue defect and skin wound healing. Future Directions: Further investigation of the roles of perivascular MSCs may enable new approaches in the treatment of fibrogenic disease; moreover, perivascular MSCs might have potential as an antifibrotic target for fibrogenic disease. Autologous adipose tissue MSCs combined with cytokines and biomaterials will be an alternative method for the treatment of soft tissue defect and skin wound healing.

Tofacitinib May Inhibit Myofibroblast Differentiation from Rheumatoid-Fibroblast-like Synoviocytes Induced by TGF-β and IL-6

During rheumatoid arthritis (RA), the pathogenic role of resident cells within the synovial membrane is suggested, especially for a population frequently referred to as fibroblast-like synoviocytes (FLSs). In this study, we assess the markers of myofibroblast differentiation of RA-FLSs by ex vivo observations and in vitro evaluations following the stimulation with both TGF-β and IL-6. Furthermore, we investigated the possible inhibiting role of tofacitinib, a JAK inhibitor, in this context. Myofibroblast differentiation markers were evaluated on RA synovial tissues by immune-fluorescence or immune-histochemistry. RA-FLSs, stimulated with transforming growth factor (TGF-β) and interleukin-6 (IL-6) with/without tofacitinib, were assessed for myofibroblast differentiation markers expression by qRT-PCR and Western blot. The same markers were evaluated following JAK-1 silencing by siRNA assay. The presence of myofibroblast differentiation markers in RA synovial tissue was significantly higher than healthy controls. Ex vivo, α-SMA was increased, whereas E-Cadherin decreased. In vitro, TGF-β and IL-6 stimulation of RA-FLSs promoted a significant increased mRNA expression of collagen I and α-SMA, whereas E-Cadherin mRNA expression was decreased. In the same conditions, the stimulation with tofacitinib significantly reduced the mRNA expression of collagen I and α-SMA, even if the Western blot did not confirm this finding. JAK-1 gene silencing did not fully prevent the effects of stimulation with TGF-β and IL-6 on these features. TGF-β and IL-6 stimulation may play a role in mediating myofibroblast differentiation from RA-FLSs, promoting collagen I and α-SMA while decreasing E-Cadherin. Following the same stimulation, tofacitinib reduced the increases of both collagen I and α-SMA on RA-FLSs, although further studies are needed to fully evaluate this issue and confirm our results.

Novel Concepts in Systemic Sclerosis Pathogenesis: Role for miRNAs

Systemic sclerosis (SSc) is a rare connective tissue disease with heterogeneous clinical phenotypes. It is characterized by the pathogenic triad: microangiopathy, immune dysfunction, and fibrosis. Epigenetic mechanisms modulate gene expression without interfering with the DNA sequence. Epigenetic marks may be reversible and their differential response to external stimuli could explain the protean clinical manifestations of SSc while offering the opportunity of targeted drug development. Small, non-coding RNA sequences (miRNAs) have demonstrated complex interactions between vasculature, immune activation, and extracellular matrices. Distinct miRNA profiles were identified in SSc skin specimens and blood samples containing a wide variety of dysregulated miRNAs. Their target genes are mainly involved in profibrotic pathways, but new lines of evidence also confirm their participation in impaired angiogenesis and aberrant immune responses. Research approaches focusing on earlier stages of the disease and on differential miRNA expression in various tissues could bring novel insights into SSc pathogenesis and validate the clinical utility of miRNAs as biomarkers and therapeutic targets.

Bone morphogenetic protein-7 inhibits endothelial-to-mesenchymal transition in primary human umbilical vein endothelial cells and mouse model of systemic sclerosis via Akt/mTOR/p70S6K pathway

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune inflammatory and vascular disorder that causes tissue fibrosis of the skin and internal organs. Endothelial-to-mesenchymal transition (EndoMT) has been considered an important mechanism in the pathogenesis of vascular remodeling in SSc. Recent studies suggested that bone morphogenic protein 7 (BMP-7) has anti-fibrotic effects in several fibrotic diseases.

OBJECTIVES

To investigate the mechanism of BMP-7 in inhibiting TGF-β-induced EndoMT in systemic sclerosis (SSc).

METHODS

Skin tissues of both healthy controls and SSc patients were detected the distribution of BMP-7. TGF-β was applied to induce the EndoMT model of human umbilical vein endothelial cells (HUVECs), and bleomycin was used to established the SSc mouse model. After treatment of BMP-7, the protein levels of endothelial specific markers, mesenchymal cell products, transcription factors and Akt signal pathway were examined by western blotting, immunofluorescence or immunohistochemistry both in vivo and in vitro.

RESULTS

The expression of BMP-7 was decreased in the basal layer of epidermis and dermis of SSc patients. EndoMT in TGF-β-treated HUVECs and skins of SSc mouse model were markedly attenuated after treatment with rh-BMP-7. Moreover, Akt/mTOR/p70S6K phosphorylation was involved in EndoMT and BMP-7 suppressed TGF-β- or bleomycin-induced theses phosphorylation in HUVECs or SSc mouse model.

CONCLUSION

BMP-7 reduced the production of TGF-β-induced EndoMT in HUVECs and SSc mouse model through Akt/mTOR/p70S6K signaling pathway. These findings suggested that BMP-7 could be employed as a promising antifibrotic therapy for SSc.

New Insights into Profibrotic Myofibroblast Formation in Systemic Sclerosis: When the Vascular Wall Becomes the Enemy

In systemic sclerosis (SSc), abnormalities in microvessel morphology occur early and evolve into a distinctive vasculopathy that relentlessly advances in parallel with the development of tissue fibrosis orchestrated by myofibroblasts in nearly all affected organs. Our knowledge of the cellular and molecular mechanisms underlying such a unique relationship between SSc-related vasculopathy and fibrosis has profoundly changed over the last few years. Indeed, increasing evidence has suggested that endothelial-to-mesenchymal transition (EndoMT), a process in which profibrotic myofibroblasts originate from endothelial cells, may take center stage in SSc pathogenesis. While in arterioles and small arteries EndoMT may lead to the accumulation of myofibroblasts within the vessel wall and development of fibroproliferative vascular lesions, in capillary vessels it may instead result in vascular destruction and formation of myofibroblasts that migrate into the perivascular space with consequent tissue fibrosis and microvessel rarefaction, which are hallmarks of SSc. Besides endothelial cells, other vascular wall-resident cells, such as pericytes and vascular smooth muscle cells, may acquire a myofibroblast-like synthetic phenotype contributing to both SSc-related vascular dysfunction and fibrosis. A deeper understanding of the mechanisms underlying the differentiation of myofibroblasts inside the vessel wall provides the rationale for novel targeted therapeutic strategies for the treatment of SSc.

Endothelial-to-mesenchymal transition in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by significant vascular alterations and multi-organ fibrosis. Microvascular alterations are the first event of SSc and injured endothelial cells (ECs) may transdifferentiate towards myofibroblasts, the cells responsible for fibrosis and collagen deposition. This process is identified as endothelial-to-mesenchymal transition (EndMT), and understanding of its development is pivotal to identify early pathogenetic events and new therapeutic targets for SSc. In this review, we have highlighted the molecular mechanisms of EndMT and summarize the evidence of the role played by EndMT during the development of progressive fibrosis in SSc, also exploring the possible therapeutic role of its inhibition.

The Role of Pro-fibrotic Myofibroblasts in Systemic Sclerosis: from Origin to Therapeutic Targeting

Systemic sclerosis (SSc, scleroderma) is a complex connective tissue disorder characterized by multisystem clinical manifestations resulting from immune dysregulation/autoimmunity, vasculopathy and, most notably, progressive fibrosis of the skin and internal organs. In recent years, it has emerged that the main drivers of SSc-related tissue fibrosis are myofibroblasts, a type of mesenchymal cells with both the extracellular matrix-synthesizing features of fibroblasts and the cytoskeletal characteristics of contractile smooth muscle cells. The accumulation and persistent activation of pro-fibrotic myofibroblasts during SSc development and progression result into elevated mechanical stress and reduced matrix plasticity within the affected tissues and may be ascribed to a reduced susceptibility of these cells to pro-apoptotic stimuli, as well as their increased formation from tissue-resident fibroblasts or transition from different cell types. Given the crucial role of myofibroblasts in SSc pathogenesis, finding the way to inhibit myofibroblast differentiation and accumulation by targeting their formation, function and survival may represent an effective approach to hamper the fibrotic process or even halt or reverse established fibrosis. In this review, we discuss the role of myofibroblasts in SSc-related fibrosis, with a special focus on their cellular origin and the signaling pathways implicated in their formation and persistent activation. Furthermore, we provide an overview of potential therapeutic strategies targeting myofibroblasts that may be able to counteract fibrosis in this pathological condition.

The contribution of mesenchymal transitions to the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a multifaceted connective tissue disease characterized by widespread vasculopathy and autoimmune reactions that evolve into progressive interstitial, perivascular, and vessel wall fibrosis that affects the skin and multiple internal organs. Such an uncontrolled fibrotic process gradually disrupts the physiologic architecture of the affected tissues and frequently leads to significant organ dysfunction, thus representing a major cause of death in SSc patients. The main fibrosis orchestrators in SSc are represented by chronically activated myofibroblasts, a peculiar population of mesenchymal cells combining the extracellular matrix-synthesizing features of fibroblasts with cytoskeletal characteristics of contractile smooth muscle cells. Multiple lines of evidence support the notion that profibrotic myofibroblasts may derive not only from the activation of tissue resident fibroblasts but also from a variety of additional cell types, including pericytes, epithelial cells, vascular endothelial cells and preadipocytes/adipocytes. Here we overview an emerging picture that espouses that several cell transitional processes may be novel essential contributors to the pool of profibrotic myofibroblasts in SSc, potentially representing new suitable targets for therapeutic purposes. An in-depth dissection of the multiple origins of myofibroblasts and the underlying molecular mechanisms may be crucial in the process of deciphering the cellular bases of fibrosis persistence and refractoriness to the treatment and, therefore, may help in developing more effective and personalized therapeutic opportunities for SSc patients.

Haematopoietic stem cell transplantation in systemic sclerosis: Challenges and perspectives

Systemic Sclerosis is chronic progressive autoimmune disease, characterised by microangiopathy and fibrosis. Due to disease heterogeneity, in terms of extent, severity, and rate of progression, optimal therapeutic interventions are still lacking. Haematopoietic stem cells may be a new therapeutic option in this disease and, although the results of the first trials are encouraging, several issues remain to be addressed. On these bases, the stem cells transplantation is an area of active investigation, and an overview of the current available literature may help to define the role of this therapeutic strategy. Although the promising results, some unmet needs remain, including the transplantation protocols and their effects on immune system, the selection of the ideal patient and the pre-transplant cardiopulmonary evaluations. An improvement in these fields will allow us to optimize the haematopoietic stem cell therapies in SSc.

Radiological diagnosis of Coronavirus Disease 2019 (COVID-19): a Practical Guide

Novel beta-coronavirus (2019-nCoV) is the cause of Coronavirus disease-19 (COVID-19), and on March 12th 2020, the World Health Organization defined COVID-19 as a controllable pandemic. Currently, the 2019 novel coronavirus (SARS-CoV-2) can be identified by virus isolation or viral nucleic acid detection; however, false negatives associated with the nucleic acid detection provide a clinical challenge. Imaging examination has become the indispensable means not only in the early detection and diagnosis but also in monitoring the clinical course, evaluating the disease severity, and may be presented as an important warning signal preceding the negative RT-PCR test results. Different radiological modalities can be used in different disease settings. Radiology Departments must be nimble in implementing operational changes to ensure continued radiology services and protect patients and staff health.

Extranodal Lymphomas: a pictorial review for CT and MRI classification

Extranodal lymphomas represent an extranodal location of both non-Hodgkin and Hodgkin lymphomas. This study aims to evaluate the role of CT and MRI in the assessment of relationships of extranodal lymphomas with surrounding tissues and in the characterization of the lesion. We selected and reviewed ten recent studies among the most recent ones present in literature exclusively about CT and MRI imaging of extranodal lymphomas. Contrast-enhanced computed tomography (CT) is usually the first-line imaging modality in the evaluation of extranodal lymphomas, according to Lugano classification. However, MRI has a crucial role thanks to the superior soft-tissue contrast resolution, particularly in the anatomical region as head and neck. (www.actabiomedica.it)

Diagnostic and interventional management of infective spine diseases

Spondylodiscitis (SD) is one of the main causes of back pain. Although the low mortality, high morbidity is related to spondilodiscitys, leading spine instability, chronic pain or neurological deficit. Diagnostic imaging plays a primary role in diagnosing spondylodiscitis. However different accuracy is highlighted by different diagnostic tool, depending also on timing of disease which represents a cardinal element for the phenotypic manifestation of the disease, beyond spatial resolution and tissue characterization proper of specific modality imaging. Conventional Radiology (CR), Computed Tomography (CT) and MRI (Magnetic Resonance Imaging) all have proven to be of primary importance in the approach to spondylodiscitis, although magnetic resonance imaging has demonstrated the greatest advantage in identifying the disease from its earliest stages, demonstrating high sensitivity and specificity (92% and 96%, respectively). This review focus on the role of different imaging modality in the approach to the spondylodiscitis, also addressing the role of interventional radiology that is pivotal not only for a diagnosis of certainty through biopsy, but also for a minimally-invasive treatment of paravertebral abscesses spondylodiscitis-related. (www.actabiomedica.it)

Clinical utility of Dual Energy Computed Tomography in gout: current concepts and applications

Gout is the most common inflammatory arthritis and is increasing in prevalence and incidence in many countries worldwide. Dual Energy Computed Tomography (DECT) has a high diagnostic accuracy in established gout, but its diagnostic sensitivity is low in subjects with recent-onset gout. A meta-analysis of 17 studies showed a pooled sensitivity and specificity of 0.85 and 0.88, respectively. DECT is a useful diagnostic tool for patients with contraindications for joint aspiration or for those who refuse joint aspiration. This article aims to give an up to date review and summary of existing literature on the role and accuracy of DECT in the imaging of gout. (www.actabiomedica.it)

Advanced diagnostic imaging and intervention in tendon diseases

Degenerative tendon pathology represents one of the most frequent and disabling musculoskeletal disorders. Diagnostic radiology plays a fundamental role in the clinical evaluation of tendon pathologies. Moreover, several minimally invasive treatments can be performed under imaging guidance to treat tendon disorders, maximizing the efficacy and reducing procedural complications. In this review article we describe the most relevant diagnostic features of conventional and advanced US and MRI imaging in tendon disorders, along with the main options for image-guided intervention. (www.actabiomedica.it)

Diagnostic and interventional radiology fundamentals of synovial pathology

The synovial membrane is a specialized mesenchymal tissue that lines the diarthrodial joints surfaces, bursae, and tendon sheaths of the body. This article aims to provide an overview of the fundamentals of synovial tissue, with particular regard to the imaging findings of the main pathologic processes that can affect the synovia and the role of image-guided interventions. (www.actabiomedica.it)

Adipose-Derived Stem Cells from Systemic Sclerosis Patients Maintain Pro-Angiogenic and Antifibrotic Paracrine Effects In Vitro

Innovative therapies based on autologous adipose-derived stem/stromal cells (ASC) are currently being evaluated for treatment of systemic sclerosis (SSc). Although paracrine angiogenic and antifibrotic effects are considered the predominant mechanisms of ASC therapeutic potential, the impact of SSc on ASC paracrine functions remains controversial. In this study, phenotype, senescence, differentiation potential, and molecular profile were determined in ASC from SSc patients (SSc-ASC) (n = 7) and healthy donors (HD-ASC) (n = 7). ASC were co-cultured in indirect models with dermal fibroblasts (DF) from SSc patients or endothelial cells to assess their pro-angiogenic and antifibrotic paracrine effects. The angiogenic activity of endothelial cells was measured in vitro using tube formation and spheroid assays. DF collagen and alpha smooth muscle actin (αSMA) content were quantified after five days of co-culture with ASC. Differentiation capacity, senescence, and mRNA profiles did not differ significantly between SSc-ASC and HD-ASC. SSc-ASC retained the ability to stimulate angiogenesis through paracrine mechanisms; however, functional assays revealed reduced potential compared to HD-ASC. DF fibrosis markers were significantly decreased after co-culture with SSc-ASC. Together, these results indicate that SSc effects do not significantly compromise the angiogenic and the antifibrotic paracrine properties of ASC, thereby supporting further development of ASC-based autologous therapies for SSc treatment.

Regulation of Fibrotic Processes in the Liver by ADAM Proteases

Fibrosis in the liver is mainly associated with the activation of hepatic stellate cells (HSCs). Both activation and clearance of HSCs can be mediated by ligand–receptor interactions. Members of the a disintegrin and metalloprotease (ADAM) family are involved in the proteolytic release of membrane-bound ligands and receptor ectodomains and the remodelling of the extracellular matrix. ADAM proteases are therefore major regulators of intercellular signalling pathways. In the present review we discuss how ADAM proteases modulate pro- and anti-fibrotic processes and how ADAM proteases might be harnessed therapeutically in the future.

A novel miRNA-4484 is up-regulated on microarray and associated with increased MMP-21 expression in serum of systemic sclerosis patients

Systemic sclerosis (SSc) is a complex, heterogeneous connective tissue disease, characterized by fibrosis and ECM deposition in skin and internal organs, autoimmunity, and changes in the microvasculature. Profiling of circulating miRNAs in serum has been found to be changed in pathological states, creating new possibilities for molecular diagnostics as blood-based biomarkers. This study was designed to identify miRNAs that are differentially expressed in SSc and might be potentially contributing to the disease etiopathogenesis or be used for diagnostic purposes. Thus, we compared the expression pattern of multiple miRNAs in serum of 10 SSc patients to 6 healthy controls using microarray analysis, and RT-qPCR to confirm the obtained results. In addition, bioinformatics analysis was performed to explore miRNAs target genes and the signaling pathways that may be potentially involved in SSc pathogenesis. Our study shows a different expression of 15 miRNAs in SSc patients. We identified that miR-4484, located on chromosome 10q26.2, was an 18-fold up-regulated in SSc patients compared to a control group. Bioinformatics analysis of the miR-4484 target genes and the signaling pathways showed that it might be potentially involved in the TGF-β signaling pathway, ECM-receptor interaction, and metalloproteinases expression. Based on the chromosomal location, the most interesting target gene of miR-4484 may be MMP-21. We found that the expression of MMP-21 significantly increased in SSc patients compared to healthy subjects (P < 0.05). Our results suggest that miR-4484, and MMP-21 might be novel serum biomarkers that may correspond to pathological fibrosis in SSc, but it needs to be validated in further studies.

Tissue-resident mesenchymal stromal cells: Implications for tissue-specific antifibrotic therapies

Recent scientific findings support the notion that fibrosis is driven by tissue-specific cellular and molecular mechanisms. Analysis of seemingly equivalent mesenchymal stromal cell (MSC) populations residing in different organs revealed unique properties and lineage capabilities that vary from one anatomical location to another. We review recently characterized tissue-resident MSC populations with a prominent role in fibrosis and highlight therapeutically relevant molecular pathways regulating their activity in chronic disease.

Role of microRNA in the pathogenesis of systemic sclerosis tissue fibrosis and vasculopathy

Systemic Sclerosis (SSc) pathogenesis involves multiple immunological, vascular and fibroproliferative abnormalities that contribute to a severe and complex clinical picture. Vasculopathy and fibroproliferative alterations are two hallmark pathological processes in SSc that are responsible for the most severe clinical manifestations of the disease and determine its clinical outcome and mortality. However, the pathogenesis of SSc vasculopathy and of the uncontrolled SSc fibrotic process remain incompletely understood. Recent investigations into the molecular pathways involved in these processes have identified an important role for epigenetic processes that contribute to overall disease progression and have emphasized microRNAs (miRNAs) as crucial epigenetic regulators. MiRNAs hold unique potential for elucidating SSc pathogenesis, improving diagnosis and developing effective targeted therapies for the disease. This review examines the important role that miRNAs play in the development and regulation of vascular and fibroproliferative alterations associated with SSc pathogenesis and their possible participation in the establishment of pathogenetic connections between these two processes. This review also emphasizes that further understanding of the involvement of miRNA in SSc fibrosis and vasculopathy will very likely provide novel future research directions and allow for the identification of groundbreaking therapeutic interventions within these processes. MiR-21, miR- 31, and miR-155 are of particular interest owing to their important involvement in both SSc vasculopathy and fibroproliferative alterations.

Macrophages with regulatory functions, a possible new therapeutic perspective in autoimmune diseases

Macrophages are pivotal cells involved in chronic inflammatory and autoimmune diseases. In fact, during these diseases, activated macrophages may play a critical role, promoting the inflammation as well as mediating the damage resolution. This dichotomy is referred to two end-stage phenotypes of macrophages, conventionally known as M1 and M2, playing a pro-inflammatory and anti-inflammatory role, respectively. The M1 macrophages are the mainly subset involved during inflammatory processes, producing pro-inflammatory mediators. Conversely, the M2 macrophages are proposed to contribute to the resolution phase of inflammation, when cells with pro-resolving property are recruited and activated. In fact, this subset of macrophages may activate regulatory T lymphocytes, which play a critical role in the maintenance of peripheral tolerance and preventing the occurrence of autoimmune diseases. On these bases, the polarization toward the M2 phenotype could play a therapeutic role for autoimmune diseases. In this Review we discussed the characteristic of M1 and M2 macrophages, focusing on the immunoregulatory role of M2 cells and their potential ability to control the inflammation and to promote the immunological tolerance.

Evolving insights into the cellular and molecular pathogenesis of fibrosis in systemic sclerosis

Systemic sclerosis (SSc, scleroderma) is a complex multisystem disease characterized by autoimmunity, vasculopathy, and most notably, fibrosis. Multiple lines of evidence demonstrate a variety of emerging cellular and molecular pathways which are relevant to fibrosis in SSc. The myofibroblast remains the key effector cell in SSc. Understanding the development, differentiation, and function of the myofibroblast is therefore crucial to understanding the fibrotic phenotype of SSc. Studies now show that (1) multiple cell types give rise to myofibroblasts, (2) fibroblasts and myofibroblasts are heterogeneous, and (3) that a large number of (primarily immune) cells have important influences on the transition of fibroblasts to an activated myofibroblasts. In SSc, this differentiation process involves multiple pathways, including well known signaling cascades such as TGF-β and Wnt/β-Catenin signaling, as well as epigenetic reprogramming and a number of more recently defined cellular pathways. After reviewing the major and emerging cellular and molecular mechanisms underlying SSc, this article looks to identify clinical applications where this new molecular knowledge may allow for targeted treatment and personalized medicine approaches.

Linking myofibroblast generation and microvascular alteration: The role of CD248 from pathogenesis to therapeutic target (Review)

Fibrosis is characterized by excessive extracellular matrix (ECM) deposition, and is the pathological outcome of tissue injury in a number of disorders. Accumulation of the ECM may disrupt the structure and function of native tissues and organs, including the lungs, heart, liver and skin, resulting in significant morbidity and mortality. On this basis, multiple lines of evidence have focused on the molecular pathways and cellular mechanisms involved in fibrosis, which has led to the development of novel antifibrotic therapies. CD248 is one of several proteins identified to be localized to the stromal compartment in cancers and fibroproliferative disease, and may serve a key role in myofibroblast generation and accumulation. Numerous studies have supported the contribution of CD248 to tumour growth and fibrosis, stimulating interest in this molecule as a therapeutic target. In addition, it has been revealed that CD248 may be involved in pathological angiogenesis. The present review describes the current understanding of the structure and function of CD248 during angiogenesis and fibrosis, supporting the hypothesis that blocking CD248 signalling may prevent both myofibroblast generation and microvascular alterations during tissue fibrosis.

Pathophysiology of systemic sclerosis: current understanding and new insights

Introduction: Systemic sclerosis (SSc) is a complex autoimmune connective tissue disease characterized by chronic and progressive tissue and organ fibrosis with broad patient-to-patient variability. Some risk factors are known and include combination of persistent Raynaud's phenomenon, steroid hormone imbalance, selected chemicals, thermal, or other injuries. Endogenous and/or exogenous environmental trigger/risk factors promote epigenetic mechanisms in genetically primed subjects. Disease pathogenesis presents early microvascular changes with endothelial cell dysfunction, followed by the activation of mechanisms promoting their transition into myofibroblasts. A complex autoimmune response, involving innate and adaptive immunity with specific/functional autoantibody production, characterizes the disease. Progressive fibrosis and ischemia involve skin and visceral organs resulting in their irreversible damage/failure. Progenitor circulating cells (monocytes, fibrocytes), together with growth factors and cytokines participate in disease diffusion and evolution. Epigenetic, vascular and immunologic mechanisms implicated in systemic fibrosis, represent major targets for incoming disease modifying therapeutic approaches. Areas covered: This review discusses current understanding and new insights of SSc pathogenesis, through an overview of the most relevant advancements to present aspects and mechanisms involved in disease pathogenesis. Expert opinion: Considering SSc intricacy/heterogeneity, early combination therapy with vasodilators, immunosuppressive and antifibrotic drugs should successfully downregulate the disease progression, especially if started from the beginning.

Mesenchymal stem cells of Systemic Sclerosis patients, derived from different sources, show a profibrotic microRNA profiling

Systemic Sclerosis (SSc) is a disease with limited therapeutic possibilities. Mesenchymal stem cells (MSCs)-therapy could be a promising therapeutic option, however the ideal MSCs source has not yet been found. To address this problem, we perform comparison between bone marrow (BM)-MSCs and adipose (A)-MSCs, by the miRs expression profile, to identify the gene modulation in these two MSCs source. MicroRNAs (miRs) are RNAs sequences, regulating gene expression and MSCs, derived from different tissues, may differently respond to the SSc microenvironment. The miRs array was used for the miRs profiling and by DIANA-mirPath tool we identified the biological functions of the dysregulated miRs. In SSc-BM-MSCs, 6 miRs were significantly down-regulated and 4 miRs up-regulated. In SSc-A-MSCs, 11 miRs were significantly down-regulated and 3 miRs up-regulated. Interestingly, in both the sources, the involved pathways included the senescence mechanisms and the pro-fibrotic behaviour. Furthermore, both the MSCs sources showed potential compensatory ability. A deeper knowledge of this miRs signature might give more information about some pathogenic steps of the disease and in the same time clarify the possible therapeutic role of autologous MSCs in the regenerative therapy in SSc.

Blocking CD248 molecules in perivascular stromal cells of patients with systemic sclerosis strongly inhibits their differentiation toward myofibroblasts and proliferation: a new potential target for antifibrotic therapy

BACKGROUND

Fibrosis may be considered the hallmark of systemic sclerosis (SSc), the end stage triggered by different pathological events. Transforming growth factor-β (TGF-β) and platelet-derived growth factor BB (PDGF-BB) are profibrotic molecules modulating myofibroblast differentiation and proliferation, respectively. There is evidence linking CD248 with these two molecules, both highly expressed in patients with SSc, and suggesting that CD248 may be a therapeutic target for several diseases. The aim of this work was to evaluate the expression of CD248 in SSc skin and its ability to modulate SSc fibrotic process.

METHODS

After ethical approval was obtained, skin biopsies were collected from 20 patients with SSc and 10 healthy control subjects (HC). CD248 expression was investigated in the skin, as well as in bone marrow mesenchymal stem cells (MSCs) treated with TGF-β or PDGF-BB, by immunofluorescence, qRT-PCR, and Western blotting. Finally, in SSc-MSCs, the CD248 gene was silenced by siRNA.

RESULTS

Increased expression of CD248 was found in endothelial cells and perivascular stromal cells of SSc skin. In SSc-MSCs, the levels of CD248 and α-smooth muscle actin expression were significantly higher than in HC-MSCs. In both SSc- and HC-MSCs, PDGF-BB induced increased expression of Ki-67 when compared with untreated cells but was unable to modulate CD248 levels. After CD248 silencing, both TGF-β and PDGF-BB signaling were inhibited in SSc-MSCs.

CONCLUSIONS

CD248 overexpression may play an important role in the fibrotic process by modulating the molecular target, leading to perivascular cells differentiation toward myofibroblasts and interfering with its expression, and thus might open a new therapeutic strategy to inhibit myofibroblast generation during SSc.

Mesenchymal Stromal Cells Based Therapy in Systemic Sclerosis: Rational and Challenges

Systemic Sclerosis (SSc) is a rare chronic disease, related to autoimmune connective tissue diseases such as Systemic Lupus Erythematosus and Sjögren's Syndrome. Although its clinical heterogeneity, main features of the disease are: extensive tissue fibrosis with increase matrix deposition in skin and internal organ, microvascular alterations and activation of the immune system with autoantibodies against various cellular antigens. In the diffuse cutaneous scleroderma subtype, the disease is rapidly progressive with a poor prognosis, leading to failure of almost any internal organ, especially lung which is the leading cause of death. Primary trigger is unknown but may involve an immune process against mesenchymal cells in a genetically receptive host. Pathophysiology reveals a pivotal role of fibrosis and inflammation alterations implicating different cell subtypes, cytokines and growth factors, autoantibodies and reactive oxygen species. Despite improvement, the overall survival of SSc patients is still lower than that of other inflammatory diseases. Recommended drugs are agents capable of modulating fibrotic and inflammatory pathways. Cellular therapy has recently emerged as a credible option. Besides autologous hematopoietic stem cell transplantation which demonstrated remarkable improvement, mesenchymal stromal cells (MSCs) represent promising therapeutic candidates. Indeed, these cells possess anti-inflammatory, antiproliferative, antifibrotic, and immunomodulary properties especially by secreting a large panel of bioactive molecules, addressing the most important key points of the SSc. In addition, these cells are very sensitive to their environment and are able to modulate their activity according to the pathophysiological context in which they are located. Autologous or allogeneic MSCs from various sources have been tested in many trials in different auto-immune diseases such as multiple sclerosis, Crohn's disease or systemic lupus erythematosus. They are characterized by a broad availability and no or low acute toxicity. However, few randomized prospective clinical trials were published and their production under ATMP regulatory procedures is complex and time-consuming. Many aspects have still to be addressed to ascertain their potential as well as the potential of their derived products in the management of SSc, probably in association with other therapies.

Mesenchymal Stem Cells in Fibrotic Disease

Fibrosis is associated with organ failure and high mortality and is commonly characterized by aberrant myofibroblast accumulation. Investigating the cellular origin of myofibroblasts in various diseases is thus a promising strategy for developing targeted anti-fibrotic treatments. Recent studies using genetic lineage tracing technology have implicated diverse organ-resident perivascular mesenchymal stem cell (MSC)-like cells and bone marrow-MSCs in myofibroblast generation during fibrosis development. In this Review, we give an overview of the emerging role of MSCs and MSC-like cells in myofibroblast-mediated fibrotic disease in the kidney, lung, heart, liver, skin, and bone marrow.

The perivascular origin of pathological fibroblasts

The ability to repair tissues is essential for the survival of organisms. In chronic settings, the failure of the repair process to terminate results in overproduction of collagen, a pathology known as fibrosis, which compromises organ recovery and impairs function. The origin of the collagen-overproducing cell has been debated for years. Here we review recent insights gained from the use of lineage tracing approaches in several organs. The resulting evidence points toward specific subsets of tissue-resident mesenchymal cells, mainly localized in a perivascular position, as the major source for collagen-producing cells after injury. We discuss these findings in view of the functional heterogeneity of mesenchymal cells of the perivascular niche, which have essential vascular, immune, and regenerative functions that need to be preserved for efficient repair.

Certainties and uncertainties concerning the contribution of pericytes to the pathogenesis of systemic sclerosis

The role of pericytes in systemic sclerosis (SSc) is unclear because of the difficulty in phenotyping them. They are mainly distributed in the pre-capillary, capillary and post-capillary abluminal side of non-muscular micro-vessels, express platelet-derived growth factor receptors (PDGFRs), and preside over vascular integrity and regeneration. By establishing close contact with many endothelial cells, a single pericyte can regulate ion influx, mechanical stress, leukocyte diapedesis, and platelet activation. Moreover, under pathological conditions such as SSc, pericytes may acquire a contractile phenotype and respond to various stimuli, including endothelin, angiotensin II and reactive oxygen species. The pericytes of SSc patients share some molecular patterns with myofibroblasts or fibroblasts, including A disintegrin and metalloproteinase domain 12 (ADAM-12), α-smooth muscle actin (α-SMA), the extra domain A (ED-A) variant of fibronectin, and Thy-1. Following stimulation with PDGF-β or transforming growth factor-β (TGF-β), pericytes may acquire a myofibroblast phenotype, and produce extracellular matrix or indirectly promote fibroblast activation. They may also contribute to fibrosis by means of epigenetic regulation. The pericyte plasmalemma is particularly rich in caveolae containing caveolin-1, a deficit of which has been associated with defective vessel tone control and lung fibrosis in mice. Consequently, dysfunctional pericytes may underlie the microangiopathy and fibrosis observed in SSc patients. However, given its variability in biological behaviour and the lack of a pan-pericyte marker, the exact role of these cells in SSc warrants further investigation.

Identification of a myofibroblast-specific expression signature in skin wounds

After skin injury fibroblasts migrate into the wound and transform into contractile, extracellular matrix-producing myofibroblasts to promote skin repair. Persistent activation of myofibroblasts can cause excessive fibrotic reactions, but the underlying mechanisms are not fully understood. We used SMA-GFP transgenic mice to study myofibroblast recruitment and activation in skin wounds. Myofibroblasts were initially recruited to wounds three days post injury, their number reached a maximum after seven days and subsequently declined. Expression profiling showed that 1749 genes were differentially expressed in sorted myofibroblasts from wounds seven days post injury. Most of these genes were linked with the extracellular region and cell periphery including genes encoding for extracellular matrix proteins. A unique panel of core matrisome and matrisome-associated genes was differentially expressed in myofibroblasts and several genes not yet known to be linked to myofibroblast-mediated wound healing were found (e.g. Col24a1, Podnl1, Bvcan, Tinagl1, Thbs3, Adamts16, Adamts19, Cxcl's, Ccl's). In addition, a complex network of G protein-coupled signaling events was regulated in myofibroblasts (e.g. Adcy1, Plbc4, Gnas). Hence, this first characterization of a myofibroblast-specific expression profile at the peak of in situ granulation tissue formation provides important insights into novel target genes that may control excessive ECM deposition during fibrotic reactions.

Soluble Factors on Stage to Direct Mesenchymal Stem Cells Fate

Mesenchymal stem cells (MSCs) are multipotent stromal cells that are identified by in vitro plastic adherence, colony-forming capacity, expression of a panel of surface molecules, and ability to differentiate at least toward osteogenic, adipogenic, and chondrogenic lineages. They also produce trophic factors with immunomodulatory, proangiogenic, and antiapoptotic functions influencing the behavior of neighboring cells. On the other hand, a reciprocal regulation takes place; in fact, MSCs can be isolated from several tissues, and depending on the original microenvironment and the range of stimuli received from there, they can display differences in their essential characteristics. Here, we focus mainly on the bone tissue and how soluble factors, such as growth factors, cytokines, and hormones, present in this microenvironment can orchestrate bone marrow-derived MSCs fate. We also briefly describe the alteration of MSCs behavior in pathological settings such as hematological cancer, bone metastasis, and bone marrow failure syndromes. Overall, the possibility to modulate MSCs plasticity makes them an attractive tool for diverse applications of tissue regeneration in cell therapy. Therefore, the comprehensive understanding of the microenvironment characteristics and components better suited to obtain a specific MSCs response can be extremely useful for clinical use.

Role of MicroRNA-103a Targeting ADAM10 in Abdominal Aortic Aneurysm

MicroRNAs (miRNAs) are deregulated in various vascular ailments including abdominal aortic aneurysm (AAA). MiR-103 is involved in vascular, metabolic, and malignant diseases, but whether it participates in the pathogenesis of AAA remains elusive. ADAM10 plays a vital role in the formation of aneurysm, but whether miRs modulate its activity during AAA formation is totally unknown. In this study, we detected the significantly increased protein expression of ADAM10 in angiotensin II induced murine AAA specimens, while the mRNA expression of ADAM10 was similar between AAA and control, suggesting the posttranscriptional regulation. The ADAM10 specific inhibitor GI254023X dramatically reduced the macrophage infiltration of murine abdominal aorta. Bioinformatic predictions suggest that ADAM10 is the target of miR-103a/107 but the binding site is exclusive. At the cellular level, miR-103a-1 suppressed the protein expression of ADAM10, while antisense miR-103a-1 increased its expression. Particularly, with the progression of murine AAA, the mRNA expression of miR-103a/107 substantially decreased and the protein expression of ADAM10 greatly increased. Together, our data afford the new insight that miR-103a inhibited AAA growth via targeting ADAM10, which might be a promising therapeutic strategy to alleviate AAA.