Soluble thrombomodulin concentration is raised in scleroderma associated pulmonary hypertension

Biomarkers in the Pathogenesis, Diagnosis, and Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by vascular damage, vasoinstability, and decreased perfusion with ischemia, inflammation, and exuberant fibrosis of the skin and internal organs. Biomarkers are analytic indicators of the biological and disease processes within an individual that can be accurately and reproducibly measured. The field of biomarkers in SSc is complex as recent studies have implicated at least 240 pathways and dysregulated proteins in SSc pathogenesis. Anti-nuclear antibodies (ANA) are classical biomarkers with well-described clinical classifications and are present in more than 90% of SSc patients and include anti-centromere, anti-Th/To, anti-RNA polymerase III, and anti-topoisomerase I antibodies. Transforming growth factor-β (TGF-β) is central to the fibrotic process of SSc and is intimately intertwined with other biomarkers. Tyrosine kinases, interferon-1 signaling, IL-6 signaling, endogenous thrombin, peroxisome proliferator-activated receptors (PPARs), lysophosphatidic acid receptors, and amino acid metabolites are new biomarkers with the potential for developing new therapeutic agents. Other biomarkers implicated in SSc-ILD include signal transducer and activator of transcription 4 (STAT4), CD226 (DNAX accessory molecule 1), interferon regulatory factor 5 (IRF5), interleukin-1 receptor-associated kinase-1 (IRAK1), connective tissue growth factor (CTGF), pyrin domain containing 1 (NLRP1), T-cell surface glycoprotein zeta chain (CD3ζ) or CD247, the NLR family, SP-D (surfactant protein), KL-6, leucine-rich α2-glycoprotein-1 (LRG1), CCL19, genetic factors including DRB1 alleles, the interleukins (IL-1, IL-4, IL-6, IL-8, IL-10 IL-13, IL-16, IL-17, IL-18, IL-22, IL-32, and IL-35), the chemokines CCL (2,3,5,13,20,21,23), CXC (8,9,10,11,16), CX3CL1 (fractalkine), and GDF15. Adiponectin (an indicator of PPAR activation) and maresin 1 are reduced in SSc patients. A new trend has been the use of biomarker panels with combined complex multifactor analysis, machine learning, and artificial intelligence to determine disease activity and response to therapy. The present review is an update of the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

Serum Biomarkers in Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening complication of connective tissue diseases (CTDs) characterised by increased pulmonary arterial pressure and pulmonary vascular resistance. CTD-PAH is the result of a complex interplay among endothelial dysfunction and vascular remodelling, autoimmunity and inflammatory changes, ultimately leading to right heart dysfunction and failure. Due to the non-specific nature of the early symptoms and the lack of consensus on screening strategies-except for systemic sclerosis, with a yearly transthoracic echocardiography as recommended-CTD-PAH is often diagnosed at an advanced stage, when the pulmonary vessels are irreversibly damaged. According to the current guidelines, right heart catheterisation is the gold standard for the diagnosis of PAH; however, this technique is invasive, and may not be available in non-referral centres. Hence, there is a need for non-invasive tools to improve the early diagnosis and disease monitoring of CTD-PAH. Novel serum biomarkers may be an effective solution to this issue, as their detection is non-invasive, has a low cost and is reproducible. Our review aims to describe some of the most promising circulating biomarkers of CTD-PAH, classified according to their role in the pathophysiology of the disease.

Current Trends in Vascular Biomarkers for Systemic Sclerosis: A Narrative Review

Systemic sclerosis (SSc, scleroderma) is a multifaceted rare connective tissue disease whose pathogenesis is dominated by immune dysregulation, small vessel vasculopathy, impaired angiogenesis, and both cutaneous and visceral fibrosis. Microvascular impairment represents the initial event of the disease, preceding fibrosis by months or years and accounting for the main disabling and/or life-threatening clinical manifestations, including telangiectasias, pitting scars, periungual microvascular abnormalities (e.g., giant capillaries, hemorrhages, avascular areas, ramified/bushy capillaries) clinically detectable by nailfold videocapillaroscopy, ischemic digital ulcers, pulmonary arterial hypertension, and scleroderma renal crisis. Despite a variety of available treatment options, treatment of SSc-related vascular disease remains problematic, even considering SSc etherogenity and the quite narrow therapeutic window. In this context, plenty of studies have highlighted the great usefulness in clinical practice of vascular biomarkers allowing clinicians to assess the evolution of the pathological process affecting the vessels, as well as to predict the prognosis and the response to therapy. The current narrative review provides an up-to-date overview of the main candidate vascular biomarkers that have been proposed for SSc, focusing on their main reported associations with characteristic clinical vascular features of the disease.

Circulating Thrombomodulin: Release Mechanisms, Measurements, and Levels in Diseases and Medical Procedures

Thrombomodulin (TM) is a type-I transmembrane protein that is mainly expressed on endothelial cells and plays important roles in many biological processes. Circulating TM of different forms are also present in biofluids, such as blood and urine. Soluble TM (sTM), comprised of several domains of TM, is the major circulating TM which is generated by either enzymatic or chemical cleavage of the intact protein under different conditions. Under normal conditions, sTM is present in low concentrations (<10 ng/mL) in the blood but is elevated in several pathological conditions associated with endothelial dysfunction such as cardiovascular, inflammatory, infection, and metabolic diseases. Therefore, sTM level has been examined for monitoring disease development, such as disseminated intravascular coagulation (DIC), sepsis and multiple organ dysfunction syndrome in patients with novel coronavirus disease 2019 (COVID-19) recently. In addition, microvesicles (MVs) that contain membrane TM (MV-TM) have been found to be released from activated cells which also contribute to levels of circulating TM in certain diseases. Several release mechanisms of sTM and MV-TM have been reported, including enzymatic, chemical, and TM mutation mechanisms. Measurements of sTM and MV-TM have been developed and explored as biomarkers in many diseases. In this review, we summarize all these advances in three categories as follows: (1) release mechanisms of circulating TM, (2) methods for measuring circulating TM in biological samples, and (3) correlation of circulating TM with diseases. Altogether, it provides a whole picture of recent advances on circulating TM in health and disease.

Management of Endothelial Dysfunction in Systemic Sclerosis: Current and Developing Strategies

Systemic Sclerosis (SSc) is an autoimmune disease marked by dysregulation of the immune system, tissue fibrosis and dysfunction of the vasculature. Vascular damage, remodeling and inadequate endothelial repair are hallmarks of the disease. Since early stages of SSc, damage and apoptosis of endothelial cells (ECs) can lead to perivascular inflammation, oxidative stress and tissue hypoxia, resulting in multiple clinical manifestations. Raynaud's phenomenon, edematous puffy hands, digital ulcers, pulmonary artery hypertension, erectile dysfunction, scleroderma renal crisis and heart involvement severely affect quality of life and survival. Understanding pathogenic aspects and biomarkers that reflect endothelial damage in SSc is essential to guide therapeutic interventions. Treatment approaches described for SSc-associated vasculopathy include pharmacological options to improve blood flow and tissue perfusion and, more recently, cellular therapy to enhance endothelial repair, promote angiogenesis and heal injuries. This mini-review examines the current knowledge on cellular and molecular aspects of SSc vasculopathy, as well as established and developing therapeutic approaches for improving the vascular compartment.

C-type lectin family XIV members and angiogenesis

The growth and metastasis of tumors is dependent on angiogenesis. C-type lectins are carbohydrate-binding proteins with a diverse range of functions. The C-type lectin family XIV members are transmembrane glycoproteins, and all four members of this family have been reported to regulate angiogenesis, although the detailed mechanism of action has yet to be completely elucidated. They interact with extracellular matrix proteins and mediate cell-cell adhesion by their lectin-like domain. The aim of the present study was to summarize the available information on the function and mechanism of C-type lectin family XIV in angiogenesis and discuss their potential as targets for cancer therapy.

Circulating Protein Biomarkers in Systemic Sclerosis Related Pulmonary Arterial Hypertension: A Review of Published Data

Pulmonary arterial hypertension (PAH) develops in 7-12% of patients with systemic sclerosis (SSc) and is associated with a 3 year survival of 52%. Early detection by screening is therefore recommended for all patients with SSc. Historically, screening has been performed using echocardiography and measurement of gas transfer. More recently the DETECT protocol, using a combination of biomarkers (including N-terminal pro-brain natriuretic peptide) and clinical parameters, has been developed. The optimal method of screening for PAH with high sensitivity and specificity is, however, not clear. Protein expression differences between different SSc disease phenotypes have been reported, and include alterations in concentration of NT-proBNP, endoglin, soluble vascular endothelial growth factor receptor 1, placenta growth factor, growth differentiation factor-15, vascular endothelial growth factor alpha, resistin-like molecule beta, and soluble thrombomodulin. This review summarizes the current knowledge of these protein changes in patients with SSc and PAH.

Vascular disease in scleroderma: mechanisms of vascular injury

Vascular endothelial injury in systemic sclerosis (SSc) includes a spectrum of changes that involve predominantly the microcirculation and arterioles. The pathologic changes in the blood vessels adversely impact the physiology of many organ systems, with a reduction in the size of microvascular beds leading to decreased organ blood flow and ultimately to a state of chronic ischemia. Current hypotheses in SSc vascular disease suggest a possible chemical or infectious trigger.

Effects of oral cyclophosphamide and prednisolone therapy on the endothelial functions and clinical findings in patients with early diffuse systemic sclerosis

OBJECTIVE

The endothelial damage of microvascular structures in systemic sclerosis (SSc; scleroderma) is associated with increased levels of endothelial adhesion molecules and endothelium-associated cytokines, including E-selectin and thrombomodulin. Although there is still no ideal specific pharmacologic therapy for SSc, cyclophosphamide has resulted in clinical improvement in patients with SSc-related active alveolitis. This study was designed to assess the expression of E-selectin and thrombomodulin in patients with early diffuse SSc, and to investigate the effects of oral cyclophosphamide combined with prednisolone therapy on the levels of these endothelium-associated cytokines and on the patients' clinical outcomes.

METHODS

Thirteen patients with early diffuse SSc were treated with oral cyclophosphamide (2-2.5 mg/kg/day) and methylprednisolone (30 mg/every other day) for 1 year. The outcomes were determined as clinical (skin score) and laboratory parameters (including the erythrocyte sedimentation rate, complete blood cell count, levels of C-reactive protein, antinuclear antibody, anti-double-stranded DNA, rate of creatinine clearance, and findings on pulmonary function tests, esophageal manometry, and echocardiography). The concentrations of E-selectin and thrombomodulin were measured in the pretreatment and posttreatment serum samples from the SSc patients and from 12 healthy adults as controls.

RESULTS

In the patients with early diffuse SSc, pretreatment and posttreatment mean levels of E-selectin were 51 ng/ml (range 34.2-135.5) and 33.4 ng/ml (range 23-62.5), respectively (P = 0.01), and those of thrombomodulin were 82 ng/ml (range 35.8-120.5) and 74.6 ng/ml (range 23.3-91.3), respectively (P = 0.016). Clinical and laboratory parameters (the skin score and measures of pulmonary function [forced vital capacity and diffusing capacity for carbon monoxide]) were also improved (P < 0.05 for each) at the end of the followup period.

CONCLUSION

Combination therapy with cylophosphamide plus prednisolone is effective in the treatment of early diffuse SSc. Circulating levels of E-selectin and thrombomodulin not only demonstrate the extent of endothelial injury and/or activation, but also could be a useful marker to monitor the disease activity in SSc.

Natural history of systemic sclerosis and the assessment of disease activity, severity, functional status, and psychologic well-being

The natural history of systemic sclerosis (SSc) is best understood by dividing patients into those who have diffuse cutaneous involvement or limited cutaneous involvement; each of these subsets can be further divided into early and late disease. Each of these four stages has characteristic clinical and laboratory features. Findings that are typical of inflammation (eg, tendon friction rubs, carpal tunnel syndrome) appear in early disease, whereas those that represent vascular and other organ structural changes (eg, joint contractures, telangiectasias, calcinosis) occur predominantly in late disease. Preliminary methods to measure SSc activity and damage have been published but require external validation and refinement. Among patient-completed instruments that assess functional status, the disability index of the Health Assessment Questionnaire is the most widely used and has face and construct validity, reliability, and sensitivity to change and is an accurate predictor of survival.

Pulmonary hypertension in systemic sclerosis

Pulmonary arterial hypertension occurs in up to 15% of patients who have systemic sclerosis (SSc) and has a high mortality. It can develop as an isolated complication or secondary to pulmonary fibrosis. There have been significant advances in assessment and therapy for this complication. Patients should be screened regularly by Doppler-echocardiography and pulmonary function tests. Right heart catheterization provides important diagnostic and prognostic information. Drawing from experience with treating primary pulmonary hypertension, treatment in the context of SSc is now possible. Patients should receive oral anticoagulation and oxygen supplementation. Calcium channel blockers are rarely effective, but parenteral prostacyclin analogs improve functional capacity and pulmonary hemodynamics. The oral endothelin-receptor blocker, bosentan, was shown to be an effective therapy for established symptomatic pulmonary hypertension in SSc. The next major challenge is to improve diagnosis and treatment of early stage or presymptomatic pulmonary hypertension with the goal of preventing this important cause of premature SSc-related mortality.

Assessment of damage and activity in systemic sclerosis

The determination of damage and activity in the course of a disease are important matters. Monitoring damage activity is critical in the evaluation of individual patients and in evaluating treatment efficacy in clinical trials. A disease damage (severity) scale has been published for systemic sclerosis. A number of potential cytokine and other soluble protein markers of disease activity for this disease have been proposed in recent publications, reviewed here.