Decreased numbers of endothelial progenitor cells in patients in the early stages of systemic sclerosis

What have we learned on pre, very early, and early systemic sclerosis microcirculatory pathophysiology? A scoping review

OBJECTIVE

Microvascular dysfunction is an early event in the pathogenesis of systemic sclerosis (SSc). The objective of this scoping review is to update the current information and the level of knowledge about the mechanisms of microvascular dysfunction in pre-SSc, very early diagnosis of SSc (VEDOSS) and early SSc.

METHODS

A PubMed® database search allowed us to include original data from full-length articles in English in which the main topic was microvascular dysfunction in pre-SSC, VEDOSS or early SSc. Data was extracted using a customized form.

RESULTS

In the present review 437 articles were identified, and 42 studies included, reporting data from a total of 1069 patients with pre-SSc, VEDOSS or early-SSc. Distinct mechanisms of microvascular injury were identified comprising, angiogenesis and vasculogenesis, cell surface proteins and adhesion, molecules expression, cytokines profile, inflammatory and oxidation pathways, and skin perfusion determinants. Most of the studies were conducted in early SSc, with a reduced number in pre-disease stages, in which the prompt recognition of specific mechanisms and biomarkers may allow targeted treatment to prevent disease progression.

CONCLUSIONS

Although different molecular expression patterns and signaling pathways related to microvascular dysfunction in pre-SSc, VEDOSS, and early SSc were identified, additional prospective longitudinal studies and combined work with functional evaluation of peripheral skin perfusion are needed.

Neurological, cardiac, musculoskeletal, and renal manifestations of scleroderma along with insights into its genetics, pathophysiology, diagnostic, and therapeutic updates

Background

Scleroderma, also referred to as systemic sclerosis, is a multifaceted autoimmune condition characterized by abnormal fibrosis and impaired vascular function. Pathologically, it encompasses the persistent presence of inflammation, abnormal collagen buildup, and restructuring of blood vessels in various organs, resulting in a wide range of clinical symptoms. This review incorporates the most recent scientific literature on scleroderma, with a particular emphasis on its pathophysiology, clinical manifestations, diagnostic approaches, and treatment options.

Methodology

A comprehensive investigation was carried out on numerous databases, such as PubMed, MEDLINE, Scopus, Web of Science, and Google Scholar, to collect pertinent studies covering diverse facets of scleroderma research.

Results

Scleroderma presents with a range of systemic manifestations, such as interstitial lung disease, gastrointestinal dysmotility, Raynaud's phenomenon, pulmonary arterial hypertension, renal complications, neurological symptoms, and cardiac abnormalities. Serological markers, such as antinuclear antibodies, anti-centromere antibodies, and anti-topoisomerase antibodies, are important for classifying diseases and predicting their outcomes.

Discussion

The precise identification of scleroderma is crucial for promptly and correctly implementing effective treatment plans. Treatment approaches aim to improve symptoms, reduce complications, and slow down the progression of the disease. An integrated approach that combines pharmacological agents, including immunosuppressants, endothelin receptor antagonists, and prostanoids, with nonpharmacological interventions such as physical and occupational therapy is essential for maximizing patient care.

Conclusion

Through the clarification of existing gaps in knowledge and identification of emerging trends, our goal is to improve the accuracy of diagnosis, enhance the effectiveness of therapeutic interventions, and ultimately enhance the overall quality of life for individuals suffering from scleroderma. Ongoing cooperation and creative research are necessary to advance the field and achieve improved patient outcomes and new therapeutic discoveries.

Endothelial Progenitor Cells in Autoimmune Disorders

Circulating endothelial progenitor cells (EPCs) were first described in 1997 by Asahara et al. as "putative endothelial cells" from human peripheral blood. The study of endothelial progenitors is also intensifying in several pathologies associated with endothelial damage, including diabetes, myocardial infarction, sepsis, pulmonary arterial hypertension, obstructive bronchopneumopathy and transplantation. EPCs have been studied in several autoimmune diseases with endothelial involvement such as systemic lupus erythematosus, thrombotic thrombocytopenic purpura, antineutrophil cytoplasmic antibodies, vasculitis, rheumatoid arthritis, Goujerot-Sjögren and antiphospholipid syndrome. Factors involved in endothelial damage are due to overexpression of pro-inflammatory cytokines and/or autoantibodies. Management of these pathologies, particularly the long-term use of glucocorticoids and methotrexate, promote atherosclerosis. A lack of standardized assessment of the number and function of EPCs represents a serious challenge for the use of EPCs as prognostic markers of cardiovascular diseases (CVD). The objective of this review was to describe EPCs, their properties and their involvement in several autoimmune diseases.

Endothelial Dysfunction in Systemic Sclerosis

Systemic sclerosis, commonly known as scleroderma, is an autoimmune disorder characterized by vascular abnormalities, autoimmunity, and multiorgan fibrosis. The exact etiology is not known but believed to be triggered by environmental agents in a genetically susceptible host. Vascular symptoms such as the Raynaud phenomenon often precede other fibrotic manifestations such as skin thickening indicating that vascular dysfunction is the primary event. Endothelial damage and activation occur early, possibly triggered by various infectious agents and autoantibodies. Endothelial dysfunction, along with defects in endothelial progenitor cells, leads to defective angiogenesis and vasculogenesis. Endothelial to mesenchymal cell transformation is another seminal event during pathogenesis that progresses to tissue fibrosis. The goal of the review is to discuss the molecular aspect of the endothelial dysfunction that leads to the development of systemic sclerosis.

CD34+CD133+CD309+ circulating angiogenic cell level is reduced but positively related to hydroxychloroquine use in SLE patients-a case-control study and meta-regression analysis

OBJECTIVES

To identify and quantify the level of CD34+CD133+CD309+ circulating angiogenic cells (CAC) and explore factors associated with the level of CAC in patients with SLE.

METHODS

The peripheral blood mononuclear cells of consecutive SLE patients and demographically matched healthy controls (HC) were extracted and identified, enumerated and compared for CAC levels by multi-colour flow cytometry based on the EULAR Scleroderma Trials and Research (EUSTAR) recommendation. Meta-analyses were performed by combining the current and previous case-control studies, aiming to increase the statistical power to discern the difference in CAC level between SLE patients and HC. Mixed-model meta-regression was conducted to explore potential demographic and clinical factors that were associated with CAC level.

RESULTS

A lower level of CAC was found in 29 SLE patients compared with 24 HC [mean (s.d.) 10.76 (13.9) vs 24.58 (25.4) cells/ml, P = 0.015]. Random-effects meta-analyses of the current and six previously published case-control studies involving 401 SLE patients and 228 HC revealed a lower CAC level compared with HC (standardized mean difference = -2.439, P = 0.001). Meta-regression analysis demonstrated that HCQ use was associated with a more discrepant CAC level between both groups (P = 0.01115).

CONCLUSION

SLE patients had a significantly lower CD34+CD133+CD309+ CAC level than HC, and HCQ use was associated with a more discrepant CAC level between SLE patients and HC. This study triggers further observational, interventional and mechanistic studies to address the beneficial impact of HCQ on the functionality of CAC in SLE patients.

Endothelial Progenitor Cells: Relevant Players in the Vasculopathy and Lung Fibrosis Associated with the Presence of Interstitial Lung Disease in Systemic Sclerosis Patients

Endothelial progenitor cells (EPC), which are key effectors in the physiologic vascular network, have been described as relevant players in autoimmune diseases. We previously showed that EPC frequency may help to identify the presence of interstitial lung disease (ILD) in rheumatoid arthritis patients. Given that ILD constitutes the main cause of mortality in systemic sclerosis (SSc) patients, we aimed to determine the EPC contribution to the pathogenic processes of vasculopathy and lung fibrosis in SSc-ILD⁺. EPC quantification was performed by flow cytometry on blood from 83 individuals: 21 SSc-ILD⁺ patients and subjects from comparative groups (20 SSc-ILD⁻ and 21 idiopathic pulmonary fibrosis (IPF) patients and 21 healthy controls (HC)). EPC were considered as CD34⁺, CD45^low, CD309⁺, and CD133⁺. A significant increase in EPC frequency was found in SSc-ILD⁺ patients when compared to HC (p < 0.001). SSc-ILD⁺ patients exhibited a higher EPC frequency than SSc-ILD⁻ patients (p = 0.012), whereas it was markedly reduced compared to IPF patients (p < 0.001). EPC frequency was higher in males (p = 0.04) and negatively correlated to SSc duration (p = 0.04) in SSc-ILD⁺ patients. Our results indicate a role of EPC in the processes of vasculopathy and lung fibrosis in SSc-ILD⁺. EPC frequency may be considered as a biomarker of ILD in SSc patients.

Endocan and Circulating Progenitor Cells in Women with Systemic Sclerosis: Association with Inflammation and Pulmonary Hypertension

Background: Systemic sclerosis (SSc) is characterized by early vasculopathy and fibrosis in the skin, lungs, and other tissues. Vascular manifestations of SSc include Raynaud’s phenomenon, digital ulcers, and pulmonary artery hypertension (PAH). PAH is the second most common cause of mortality in SSc. Circulating CD34+ cells associated with cardiovascular health status in several conditions, including chronic immune-inflammatory disease. CD34+ cell numbers have been found inconstantly reduced in SSc. Endocan, a proteoglycan expressed by endothelial cells, was recently suggested as a marker of vascular stress. We tested the relationships among CD34+ cells, endocan, inflammatory markers, vitamin D levels, and clinical parameters in SSc patients with PAH. METHODS: Standard echocardiography was performed. Vitamin D levels, CD34+ cells, inflammatory markers, endocan plasma levels were determined in 36 female SSc patients (24 diffuse/12 limited) and 36 matched controls (HC). RESULTS: We found no difference in CD34+ and vitamin D levels in SSc as compared to controls; ESR, CRP, fibrinogen, endocan, sPAP were higher in SSc with respect to controls. We found a correlation between endocan and: CD34+ cells (r: −0.540, p = 0.002), pulmonary arterial pressure (sPAP) (r: 0.565, p < 0.001), tricuspid annular plane excursion (TAPSE) (r: −0.311, p < 0.01), and E/A ratio (r: −0.487, p < 0.001), but not with ejection fraction (r: −0.057, p = 0.785) in SSc. CD34+ cells correlate with fibrinogen (r: −0.619, p < 0.001), sPAP (r: −0.404, p = 0.011), E/A (r: 0.470, p < 0.005 in SSc. CONCLUSION: CD34+ cell number was significantly correlated with endocan levels and with sPAP in SSc; endocan and CD34+ progenitor cells might be suggested as a potential marker of disease status.

Endothelial cells and endothelial progenitor cells in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease characterized by excessive fibrosis, microvasculopathy, and autoimmunity. Endothelial cell (EC) injury and subsequent endothelial cell dysfunction is believed to be an initial event that eventually leads to a vicious pathogenic cycle. This process is further enhanced by defective angiogenesis and vasculogenesis, as the vascular repair machinery does not work properly. Endothelial progenitor cells (EPCs) are functionally and quantitatively insufficient to recover the endothelium in SSc patients. The dysfunctional ECs and EPCs not only trigger the formation of typical vascular lesions, such as progressive intimal fibrosis in small arteries and the loss of capillaries, but also promote a series of inflammatory and profibrotic processes, such as endothelial-mesenchymal transition and recruitment and accumulation of monocytic EPCs with profibrotic properties. These processes together contribute to the accumulation of extracellular matrix in the affected tissue. This review features current insights into the roles of ECs and EPCs in the pathogenesis of SSc.

[Updates in systemic sclerosis pathogenesis: Toward new therapeutic opportunities]

Systemic sclerosis is a rare connective tissue disease characterized by skin and several internal organ fibrosis, systemic vasculopathy and immune abnormalities. Even if fibroblasts and endothelial cells dysfunction, as well as lymphocytes and other immune cells implication are now well described, the exact origin and chronology of the disease pathogenesis remain unclear. Oxidative stress, influenced by genetic and environmental factors, seems to play a key role. Indeed, it seems to be implicated in the early phases of fibrosis development, vasculopathy and in immune tolerance abnormalities shared by all patients, although disease expression is heterogeneous. To date, no curative treatment is available. Even if immunosuppressive treatment or drugs acting on vascular system are proposed for some patients, overall, treatment efficiency remains modest. Only autologous hematopoietic stem cells transplantation, reserved for patients with severe or rapidly progressive fibrosis, has recently demonstrated efficiency, with lasting regression of fibrosis. Nevertheless, this treatment can expose to important, life-threatening toxicity. In the last decade, new mechanisms implicated in the pathogenesis of systemic sclerosis have been unraveled, bringing new therapeutic opportunities. In this review, we offer to focus on recent insights in the knowledge of systemic sclerosis pathogenesis and its implication in current and future medical care.

The Role of Endothelial Progenitors in the Repair of Vascular Damage in Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease characterized by a complex pathological process where the main scenario is represented by progressive loss of microvascular bed, with the consequent progressive fibrotic changes in involved organ and tissues. Although most aspects of vascular injury in scleroderma are poorly understood, recent data suggest that the scleroderma impairment of neovascularization could be related to both angiogenesis and vasculogenesis failure. Particularly, compensatory angiogenesis does not occur normally in spite of an important increase in many angiogenic factors either in SSc skin or serum. Besides insufficient angiogenesis, the contribution of defective vasculogenesis to SSc vasculopathy has been extensively studied. Over the last decades, our understanding of the processes responsible for the formation of new vessels after tissue ischemia has increased. In the past, adult neovascularization was thought to depend mainly on angiogenesis (a process by which new vessels are formed by the proliferation and migration of mature endothelial cells). More recently, increased evidence suggests that stem cells mobilize from the bone marrow into the peripheral blood (PB), differentiate in circulating endothelial progenitors (EPCs), and home to site of ischemia to contribute to de novo vessel formation. Significant advances have been made in understanding the biology of EPCs, and molecular mechanisms regulating EPC function. Autologous EPCs now are becoming a novel treatment option for therapeutic vascularization and vascular repair, mainly in ischemic diseases. However, different diseases, such as cardiovascular diseases, diabetes, and peripheral artery ischemia are related to EPC dysfunction. Several studies have shown that EPCs can be detected in the PB of patients with SSc and are impaired in their function. Based on an online literature search (PubMed, EMBASE, and Web of Science, last updated December 2017) using keywords related to “endothelial progenitor cells” and “Systemic Sclerosis,” “scleroderma vasculopathy,” “angiogenesis,” “vasculogenesis,” this review gives an overview on the large body of data of current research in this issue, including controversies over the identity and functions of EPCs, their meaning as biomarker of SSc microangiopathy and their clinical potency.

Angiogenic T cell expansion correlates with severity of peripheral vascular damage in systemic sclerosis

The mechanisms underlying endothelial cell injury and defective vascular repair in systemic sclerosis (SSc) remain unclear. Since the recently discovered angiogenic T cells (Tang) may have an important role in the repair of damaged endothelium, this study aimed to analyze the Tang population in relation to disease-related peripheral vascular features in SSc patients. Tang (CD3⁺CD31⁺CXCR4⁺) were quantified by flow cytometry in peripheral blood samples from 39 SSc patients and 18 healthy controls (HC). Circulating levels of the CXCR4 ligand stromal cell-derived factor (SDF)-1α and proangiogenic factors were assessed in paired serum samples by immunoassay. Serial skin sections from SSc patients and HC were subjected to CD3/CD31 and CD3/CXCR4 double immunofluorescence. Circulating Tang were significantly increased in SSc patients with digital ulcers (DU) compared either with SSc patients without DU or with HC. Tang levels were significantly higher in SSc patients with late nailfold videocapillaroscopy (NVC) pattern than in those with early/active NVC patterns and in HC. No difference in circulating Tang was found when comparing either SSc patients without DU or patients with early/active NVC patterns and HC. In SSc peripheral blood, Tang percentage was inversely correlated to levels of SDF-1α and CD34⁺CD133⁺VEGFR-2⁺ endothelial progenitor cells (EPC), and positively correlated to levels of vascular endothelial growth factor and matrix metalloproteinase-9. Tang were frequently detected in SSc dermal perivascular inflammatory infiltrates. In summary, our findings demonstrate for the first time that Tang cells are selectively expanded in the circulation of SSc patients displaying severe peripheral vascular complications like DU. In SSc, Tang may represent a potentially useful biomarker reflecting peripheral vascular damage severity. Tang expansion may be an ineffective attempt to compensate the need for increased angiogenesis and EPC function. Further studies are required to clarify the function of Tang cells and investigate the mechanisms responsible for their change in SSc.

The impact of transcription factor Fli1 deficiency on the regulation of angiogenesis

The insufficiency of Friend leukaemia virus integration 1 (Fli1), a member of the Ets family transcription factors, is implicated in the pathogenesis of vasculopathy associated with systemic sclerosis (SSc). Fli1 deficiency accelerates early steps of angiogenesis, including detachment of pre-existing pericytes and extracellular matrix degradation by endothelial proteinases, but the impact of Fli1 deficiency on the other steps of angiogenesis has not been investigated. Therefore, we evaluated the effect of Fli1 deficiency on migration, proliferation, cell survival and tube formation of human dermal microvascular endothelial cells (HDMECs). HDMECs transfected with FLI1 siRNA exhibited a greater migratory property in scratch assay and transwell migration assay and a higher proliferation rate in BrdU assay than HDMECs transfected with non-silencing scrambled RNA. In flow cytometry-based apoptosis assay, FLI1 siRNA-transduced HDMECs revealed the decreased number of annexin and propidium iodide-double-positive apoptotic cells compared with control cells, reflecting the promotion of cell survival. On the other hand, tubulogenic activity on Matrigel was remarkably suppressed in Fli1-deficient HDMECs relative to control cells. These results indicate that Fli1 deficiency promotes migration, proliferation and cell survival, while abating tube formation of endothelial cells, suggesting that Fli1 deficiency is potentially attributable to the development of both proliferative obliterative vasculopathy (occlusion of arterioles and small arteries) and destructive vasculopathy (loss of small vessels) characteristic of SSc vasculopathy.

The role of endothelial cells in the vasculopathy of systemic sclerosis: A systematic review

INTRODUCTION

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by fibroproliferative vasculopathy, immunological abnormalities and progressive fibrosis of multiple organs including the skin. In this study, all English speaking articles concerning the role of endothelial cells (ECs) in SSc vasculopathy and representing biomarkers are systematically reviewed and categorized according to endothelial cell (EC) (dys)function in SSc.

METHODS

A sensitive search on behalf of the EULAR study group on microcirculation in Rheumatic Diseases was developed in Pubmed, The Cochrane Library and Web of Science to identify articles on SSc vasculopathy and the role of ECs using the following Mesh terms: (systemic sclerosis OR scleroderma) AND pathogenesis AND (endothelial cells OR marker). All selected papers were read and discussed by two independent reviewers. The selection process was based on title, abstract and full text level. Additionally, both reviewers further searched the reference lists of the articles selected for reading on full text level for supplementary papers. These additional articles went through the same selection process.

RESULTS

In total 193 resulting articles were selected and the identified biomarkers were categorized according to description of EC (dys)function in SSc. The most representing and reliable biomarkers described by the selected articles were adhesion molecules for EC activation, anti-endothelial cell antibodies for EC apoptosis, vascular endothelial growth factor (VEGF), its receptor VEGFR-2 and endostatin for disturbed angiogenesis, endothelial progenitors cells for defective vasculogenesis, endothelin-1 for disturbed vascular tone control, Von Willebrand factor for coagulopathy and interleukin (IL)-33 for EC-immune system communication. Emerging, relatively new discovered biomarkers described in the selected articles, are VEGF₁₆₅b, IL-17A and the adipocytokines. Finally, myofibroblasts involved in tissue fibrosis in SSc can derive from ECs or epithelial cells through a process known as endothelial-to-mesenchymal transition.

CONCLUSION

This systematic review emphasizes the growing evidence that SSc is primarily a vascular disease where EC dysfunction is present and prominent in different aspects of cell survival (activation and apoptosis), angiogenesis and vasculogenesis and where disturbed interactions between ECs and various other cells contribute to SSc vasculopathy.

Recent updates in experimental protocols for endothelial cells

Scleroderma (systemic sclerosis, SSc) is a multisystem autoimmune disease of unknown etiology. The disease is characterized by vascular disorder, activation of the immune system, and excessive deposition of matrix proteins in the skin and involved organs. The vascular disorder is believed to play a crucial role in disease pathogenesis. Endothelial injury and dysfunction, subsequent capillary loss and arteriolar wall thickness, are well documented in all involved organs. The resulting tissue hypoxia and ischemia fail to initiate new vessel formation leading to progressive loss of vasculature with no apparent replenishment. Issues related to endothelial injury/activation, dysfunction and failure of angio/vasculogenesis are central to the understanding of SSc vasculopathy. Isolation of endothelial cells and cells involved in the genesis of new vessels is enormously important in the investigation of mechanisms involved in SSc vasculopathy. Nevertheless, this goal has been difficult to achieve in view of the charac­teristic slow growth of endothelial cells, the high demand for growth factors and rapid growth of contaminating cells and the scarcity of circulating cells involved in angio/vasculogenesis hampered this line of investigation. Nonetheless, recent technologic progress in the last decade provided us with the tools to isolate vascular cells with an acceptable purity based on unique cell surface markers using immunoselection methods. The purpose of this review is to update the readers on current technical state-of-the-art methods of isolation and propagation of vascular cells. We wish that this review will spark interest in more investigations of this crucial phase of SSc pathogenesis.

Endothelial progenitor cells: Are they displaying a function in autoimmune disorders?

Endothelial Progenitor Cells (EPCs) are bone marrow derived cells able to differentiate in mature endothelial cells (EC) contributing to the generation of new vessels, connecting to fibronectin, and forming colonies and/or colony forming units. Since circulating EPCs can be actively considered part of endothelial damage in several cardiovascular diseases and autoimmune disorders the possibility to have a measure for endothelium damage should be considered of interest to predict the patient out-come. At the same time the EPCs proliferative and regenerative role could be considered for therapeutic applications. Studies have been performed to elucidate the role of EPCs in Systemic Sclerosis and many review and articles published on this topic. In the present paper we aimed to review the role of EPCs in other autoimmune disorders.

Nailfold Capillary Abnormalities in Primary Open-Angle Glaucoma: A Multisite Study

PURPOSE

There is considerable evidence for systemic vascular dysfunction in primary open-angle glaucoma (POAG). We performed nailfold capillary video microscopy to observe directly the nature of nonocular microvasculature abnormalities in POAG.

METHODS

We enrolled 199 POAG patients and 124 control subjects from four sites. We used JH-1004 capillaroscopes to perform nailfold capillary video microscopy on the fourth and fifth digits of each subject's nondominant hand. Videos were evaluated for hemorrhages, dilated capillary loops > 50 μm, and avascular zones > 100 μm by graders masked to case status. Multivariable odds ratios (ORs) and 95% confidence intervals (CIs) for POAG were obtained by means of logistic regression analyses that were applied to data from all cases and controls. Corresponding estimates of moderate or severe POAG versus mild POAG (based on the Hodapp-Anderson-Parrish scale) were obtained among cases only.

RESULTS

After controlling for demographic factors, family history of glaucoma, systemic diseases, and use of anticoagulation and antiplatelet therapy, for each 100 nailfold capillaries assessed, all types of microvascular abnormalities were significantly associated with POAG. Specifically, the presence of any dilated capillaries (OR = 2.9; 95% CI, 1.6-5.6), avascular zones (OR = 4.4; 95% CI, 1.7-11.3) and hemorrhages (OR = 12.2; 95% CI, 5.9-25.1) were associated with POAG. Among cases, the frequency of microvascular abnormalities was not associated with glaucoma severity (P ≥ 0.43).

CONCLUSIONS

These data provided support for nonocular capillary bed abnormalities in POAG. Comparable vascular abnormalities in the optic nerve may render it susceptible to glaucomatous damage.