Biomarkers in the Management of Scleroderma: An Update

Biomarkers as an opportunity to stratify for outcome in systemic sclerosis

Systemic sclerosis (SSc) is a highly complex disease whose heterogeneity includes multiple aspects of the condition, such as clinical presentation, progression, extent and type of organ involvement, and clinical outcomes. Thus far, these features remain not easily predictable both at the patient group level and in a given patient with regard to age at onset and clinical course. The unpredictable clinical course represents an obstacle to focusing potentially effective treatment in patients that need it the most. At the time of organ involvement and clinical diagnosis, most of the clinical manifestations are irreversible; therefore, predicting outcomes becomes crucial. This can explain the multiple attempts to identify prognostic, predictive, and monitoring-both soluble and imaging-biomarkers over the past years. They range from the currently most used biomarkers, the autoantibodies associated with disease-specific clinical features and course, to the single recently proposed skin, lung, cardiac involvement biomarkers and to the composite scores capturing multiple aspects of the disease. This review will focus on soluble and imaging biomarkers that recently showed promising evidence for outcome stratification in patients with SSc.

Pathogenic Activation of Mesenchymal Stem Cells Is Induced by the Disease Microenvironment in Systemic Sclerosis

OBJECTIVE

In systemic sclerosis (SSc), a persistent tissue repair process leads to progressive fibrosis of the skin and internal organs. The role of mesenchymal stem cells (MSCs), which characteristically initiate and regulate tissue repair, has not been fully evaluated. We undertook this study to investigate whether dividing metakaryotic MSCs are present in SSc skin and to examine whether exposure to the disease microenvironment activates MSCs and leads to transdifferentiation.

METHODS

Skin biopsy material from patients with recent-onset diffuse SSc was examined by collagenase spread of 1-mm-thick surface-parallel sections, in order to identify dividing metakaryotic stem cells in each tissue plane. Adipose-derived MSCs from healthy controls were treated with dermal blister fluid (BF) from patients with diffuse SSc and profiled by next-generation sequencing, or they were evaluated for phenotypic changes relevant to SSc. Differential responses of dermal fibroblasts were studied in parallel.

RESULTS

MSC-like cells undergoing active metakaryotic division were identified in SSc sections (but not control sections) most prominently in the deep dermis and adjacent to damaged microvessels, in both clinically involved and uninvolved skin. Furthermore, exposure to SSc BF caused selective MSC activation, inducing a myofibroblast signature, while reducing signatures of vascular repair and adipogenesis and enhancing migration and contractility. Microenvironmental factors implicated in inducing transdifferentiation included the profibrotic transforming growth factor β, the presence of lactate, and mechanosensing, while the microenvironment Th2 cytokine, interleukin-31, enhanced osteogenic commitment (calcinosis).

CONCLUSION

Dividing MSC-like cells are present in the SSc disease microenvironment where multiple factors, likely acting in concert, promote transdifferentiation and lead to a complex and resistant disease state.

Ultrasound Vibroelastography for Evaluation of Secondary Extremity Lymphedema: A Clinical Pilot Study

BACKGROUND

Lymphedema treatment is an ongoing challenge. It impacts quality of life due to pain, loss of range of motion of the extremity, and repeated episodes of cellulitis. Different modalities have been used to evaluate lymphedema; some are more error-prone and some are more invasive. However, these measurements are poorly standardized, and intrarater and interrater reliabilities are difficult to achieve. This pilot study aims to assess the feasibility of ultrasound vibroelastography for assessing patients with extremity lymphedema via measuring shear wave speeds of subcutaneous tissues.

METHODS

Patients with clinical and lymphoscintigraphic diagnosis of secondary lymphedema in the extremities without prior surgical treatment were included. A 0.1-s harmonic vibration was generated at three frequencies (100, 150, and 200 Hz) by the indenter of a handheld shaker on the skin. An ultrasound probe was used for noninvasively capturing of wave propagation in the subcutaneous tissue. Wave speeds were measured in the subcutaneous tissues of both the control and affected extremities.

RESULTS

A total of 11 female patients with secondary lymphedema in the extremities were enrolled in this study. The magnitudes of the wave speeds of the region of interest in the subcutaneous tissue at lymphedema sites in the upper extremity (3.9 ± 0.17 m/s, 5.96 ± 0.67 m/s, and 7.41 ± 1.09 m/s) were statistically higher than those of the control sites (2.1 ± 0.27 m/s, 2.93 ± 0.57 m/s, and 3.56 ± 0.76 m/s) at 100, 150, and 200 Hz (P < 0.05), and at 100 and 200 Hz (P < 0.05) between lymphedema (4.33 ± 0.35 m/s, 4.17 ± 1.00 m/s, and 4.56 ± 0.37 m/s) and controls sites (2.48 ± 0.43 m/s, 2.77 ± 0.55 m/s, and 3.06 ± 0.29 m/s) in the lower extremity.

CONCLUSIONS

These preliminary data suggest that ultrasound vibroelastography may be useful in the evaluation of secondary lymphedema and can be a valuable tool to noninvasively track treatment progress.

European multicentre study validates enhanced liver fibrosis test as biomarker of fibrosis in systemic sclerosis

Objectives

To validate enhanced liver fibrosis (ELF) test and its components-amino-terminal propeptide of procollagen type III (PIIINP), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and HA-as biomarkers of fibrosis in SSc in an independent, international, multicentre cohort.

Methods

Two hundred and fifty-four SSc patients from six Rheumatology Centres were included. Sera were collected and stored according to EUSTAR biobanking recommendations and analysed through automated high throughput diagnostics. Statistical analysis was performed with SPSS software.

Results

Two hundred and forty-seven SSc patients (mean age 55.7 ± 13.9 years, 202 F) were analysed. ELF score, TIMP-1 and PIIINP levels were higher in males (P = 0.0197, P = 0.0107, P = 0.0108 respectively) and in dcSSc (P = 0.001, P = 0.0008, P < 0.0001 respectively). ELF score and the single markers significantly correlated with modified Rodnan skin score (r = 0.37, P < 0.0001), disease activity and severity (P < 0.0001 for all markers, except for HA P = 0.0001) and inversely with forced vital capacity, (FVC) % (TIMP-1, r = -0.21, P = 0.0012; PIIINP, r = -0.26, P = 0.0001), TLC% (ELF score, r = -0.20, P = 0.0036; TIMP-1, r = -0.32, P < 0.0001; PIIINP, r = -0.28, P < 0.0001), diffusion capacity of the lung for carbon monoxide (DLCO) % (P < 0.0001 for all markers, except for HA P = 0.0115). Multivariate analysis indicated that age (P < 0.001), modified Rodnan skin score (P < 0.001) and DLCO% (P = 0.005) were independently associated with ELF score.

Conclusion

Between the first and this validation studies, the value of the ELF score as independent marker of skin and lung involvement in SSc is confirmed in 457 patients. A longitudinal study is on-going to identify an SSc specific algorithm with predictive value for skin and lung progression.

Existing and novel biomarkers for precision medicine in systemic sclerosis

The discovery and validation of biomarkers resulting from technological advances in the analysis of genomic, transcriptomic, lipidomic and metabolomic pathways involved in the pathogenesis of complex human diseases have led to the development of personalized and rationally designed approaches for the clinical management of such disorders. Although some of these approaches have been applied to systemic sclerosis (SSc), an unmet need remains for validated, non-invasive biomarkers to aid in the diagnosis of SSc, as well as in the assessment of disease progression and response to therapeutic interventions. Advances in global transcriptomic technology over the past 15 years have enabled the assessment of microRNAs that circulate in the blood of patients and the analysis of the macromolecular content of a diverse group of lipid bilayer membrane-enclosed extracellular vesicles, such as exosomes and other microvesicles, which are released by all cells into the extracellular space and circulation. Such advances have provided new opportunities for the discovery of biomarkers in SSc that could potentially be used to improve the design and evaluation of clinical trials and that will undoubtedly enable the development of personalized and individualized medicine for patients with SSc.

An Ultrasound Surface Wave Technique for Assessing Skin and Lung Diseases

Systemic sclerosis (SSc) is a multi-organ connective tissue disease characterized by immune dysregulation and organ fibrosis. Severe organ involvement, especially of the skin and lung, is the cause of morbidity and mortality in SSc. Interstitial lung disease (ILD) includes multiple lung disorders in which the lung tissue is fibrotic and stiffened. The purpose of this study was to translate ultrasound surface wave elastography (USWE) for assessing patients with SSc and/or ILD via measuring surface wave speeds of both skin and superficial lung tissue. Forty-one patients with both SSc and ILD and 30 healthy patients were enrolled in this study. An external harmonic vibration was used to generate the wave propagation on the skin or lung. Three excitation frequencies of 100, 150 and 200 Hz were used. An ultrasound probe was used to measure the wave propagation in the tissue non-invasively. Surface wave speeds were measured on the forearm and upper arm of both left and right arm, as well as the upper and lower lungs, through six intercostal spaces of patients and healthy patients. Viscoelasticity of the skin was calculated by the wave speed dispersion with frequency using the Voigt model. The magnitudes of surface wave speed and viscoelasticity of patients' skin were significantly higher than those of healthy patients (p <0.0001) for each location and each frequency. The surface wave speeds of patients' lung were significantly higher than those of healthy patients (p <0.0001) for each location and each frequency. USWE is a non-invasive and non-ionizing technique for measuring both skin and lung surface wave speed and may be useful for quantitative assessment of SSc and/or ILD.

Systemic sclerosis: The need for structured care

Autoimmune connective tissue diseases (CTDs) have a propensity to affect multiple organ systems as well as physical function, quality of life, and survival. Their clinical heterogeneity, multisystem involvement, and low worldwide prevalence present challenges for researchers to establish a study design to help better understand the course and outcomes of CTDs. Systemic sclerosis (SSc) is a notable example of a CTD, wherein longitudinal cohort studies (LCS) have enabled us to elucidate disease manifestations, disease course, and risk and prognostic factors for clinically important outcomes, by embedding research in clinical practice. Nevertheless, further efforts are needed to better understand SSc especially with regard to recognizing organ involvement early, developing new therapies, optimizing the use of existing therapies, and defining treatment targets. The heterogeneous multi-organ nature of SSc would lend itself well to a structured model of care, wherein step-up treatment algorithms are used with the goal of attaining a prespecified treatment target. In this chapter, we discuss the rationale for a structured treatment approach in SSc and propose possible treatment algorithms for three of the more common disease manifestations, namely skin involvement, digital ulcers and gastrointestinal tract involvement. We discuss possible strategies for evaluating and implementing these algorithms in the setting of LCS. We conclude by presenting a research agenda for the development of structured models of care in SSc.

Update on biomarkers in systemic sclerosis: tools for diagnosis and treatment

Systemic sclerosis (SSc) is a complex autoimmune disease in which immune activation, vasculopathy, and extensive fibrosis of the skin and internal organs are among the principal features. SSc is a heterogeneous disease with varying manifestations and clinical outcomes. Currently, patients’ clinical evaluation often relies on subjective measures, non-quantitative methods, or requires invasive procedures as markers able to predict disease trajectory or response to therapy are lacking. Therefore, current research is focusing on the discovery of useful biomarkers reflecting ongoing inflammatory or fibrotic activity in the skin and internal organs, as well as being predictive of future disease course. Recently, remarkable progress has been made towards a better understanding of numerous mechanisms involved in the pathogenesis of SSc. This has opened new possibilities for the development of novel biomarkers and therapy. However, current proposed biomarkers that could reliably describe various aspects of SSc still require further investigation. This review will summarize studies describing the commonly used and validated biomarkers, the newly emerging and promising SSc biomarkers identified to date, and consideration of future directions in this field.

Quantitating skin fibrosis: innovative strategies and their clinical implications

Skin fibrosis is the final outcome of a variety of pathologic processes ranging from aberrant wound healing (keloids) to environmentally induced conditions (nephrogenic systemic fibrosis) to idiopathic or autoimmune conditions (morphea and systemic sclerosis). The quantitative assessment of skin fibrosis has been a major burden of clinical and biomarker research in the field for the past three decades. Here, we review the efforts that reached some sort of validation and the ones we envisage have the potential for further development focusing on systemic sclerosis as prototype of fibrotic disease.

Current status of systemic sclerosis biomarkers: applications for diagnosis, management and drug development

Systemic sclerosis (SSc) is a clinically heterogeneous orphan disease of unknown etiology and no effective therapy. It is characterized by protean manifestations, an unpredictable disease course and variable outcomes. Clinical manifestations reflect underlying autoimmunity, small vessel vasculopathy and progressive multi-organ fibrosis. Predicting disease progression, pattern and severity of complications and response to therapy in SSc remain major challenges both for the management of patients and for the development of effective disease-modifying therapies. This review summarizes contemporary understanding of novel and emerging biomarkers for SSc. We focus on the development of new classification criteria, the utility of SSc-specific autoantibodies as diagnostic and prognostic markers, and on biomarkers for skin and lung involvement. Finally, we review genome-wide expression analysis as a tool to predict therapeutic responses. We anticipate that the development, validation and application of these biomarkers, singly or more likely in combination, will have a transformative impact in SSc, informing early diagnosis, classification and management, as well as the design, execution and interpretation of clinical trials of novel therapeutic agents.

The enhanced liver fibrosis test: a clinical grade, validated serum test, biomarker of overall fibrosis in systemic sclerosis

OBJECTIVES

The absence of a serological surrogate outcome measure of fibrosis in systemic sclerosis (SSc) is a major deficiency for intervention studies and clinical management. An algorithm including the serum concentration of procollagen-III aminoterminal-propeptide, tissue inhibitor of matrix metalloproteinase-1 and hyaluronic acid, has recently been validated as predictive of severity and clinical outcome in chronic liver diseases (enhanced liver fibrosis (ELF) test) and implemented as a clinical grade test available for physicians. We evaluated the ELF test as a surrogate outcome measure in SSc.

METHODS

The ELF score was determined blindly in 210 patients with SSc. Results were correlated with clinical, functional and instrumental variables including disease severity, activity and disability.

RESULTS

The ELF test was above normal range in 83% of SSc patients (175/210). The ELF score showed a significant correlation (p<0.0001) with extent of skin involvement (r=0.28), diffusing lung capacity of carbon monoxide (DLCO) (r=-0.32), health assessment questionnaire-disability index (HAQ-DI) (r=0.32), disease severity score (r=0.3) and age (r=0.41). In addition, ELF correlated with disease activity (r=0.23; p=0.02). Using regression analysis, the extent of skin involvement, age, DLCO and gender were independently associated with the ELF score. The ELF score did not correlate with the presence of pulmonary artery hypertension, digital ulcers or any other measure of vasculopathy.

CONCLUSIONS

The ELF test is a clinical-grade serum test that significantly correlates with several measures of fibrosis in SSc and with overall disease activity, severity and HAQ-DI. The specific correlation with fibrosis and its face validity, together with the feasibility of the test, warrant its further development as a surrogate outcome measure of fibrosis in SSc.

Chitinase 1 is a biomarker for and therapeutic target in scleroderma-associated interstitial lung disease that augments TGF-β1 signaling

Interstitial lung disease (ILD) with pulmonary fibrosis is an important manifestation in systemic sclerosis (SSc, scleroderma) where it portends a poor prognosis. However, biomarkers that predict the development and or severity of SSc-ILD have not been validated, and the pathogenetic mechanisms that engender this pulmonary response are poorly understood. In this study, we demonstrate in two different patient cohorts that the levels of chitotriosidase (Chit1) bioactivity and protein are significantly increased in the circulation and lungs of SSc patients compared with demographically matched controls. We also demonstrate that, compared with patients without lung involvement, patients with ILD show high levels of circulating Chit1 activity that correlate with disease severity. Murine modeling shows that in comparison with wild-type mice, bleomycin-induced pulmonary fibrosis was significantly reduced in Chit1⁻/⁻ mice and significantly enhanced in lungs from Chit1 overexpressing transgenic animals. In vitro studies also demonstrated that Chit1 interacts with TGF-β1 to augment fibroblast TGF-β receptors 1 and 2 expression and TGF-β-induced Smad and MAPK/ERK activation. These studies indicate that Chit1 is potential biomarker for ILD in SSc and a therapeutic target in SSc-associated lung fibrosis and demonstrate that Chit1 augments TGF-β1 effects by increasing receptor expression and canonical and noncanonical TGF-β1 signaling.

Proteomics approaches to fibrotic disorders

This review provides an introduction to mass spectrometry based proteomics and discusses several proteomics approaches that are relevant in understanding the pathophysiology of fibrotic disorders and the approaches that are frequently used in biomarker discovery.

Tyrosine Kinase Inhibitors in the Treatment of Systemic Sclerosis: The Difficulty in Interpreting Proof-of-Concept Studies

Tyrosine kinase inhibitors (TKIs) have emerged as a targeted therapy of interest for the treatment of systemic sclerosis (SSc). Recently, several groups have performed pilot or "proof-of-concept" studies to determine the feasibility of this approach for the treatment of the cutaneous and pulmonary manifestations of this multisystem disease. The conclusions drawn by these different studies have been conflicting, and some controversy has arisen as to whether tyrosine kinase inhibition is a treatment approach worthy of continued study. This paper summarizes this research to date with emphasis on the challenges in interpreting proof-of-concept studies in this patient group.