Molecular Profiling of Axial Spondyloarthritis Patients Reveals an Association between Innate and Adaptive Cell Populations and Therapeutic Response to Tumor Necrosis Factor Inhibitors.

This study aims at identifying molecular biomarkers differentiating responders and non-responders to treatment with Tumor Necrosis Factor inhibitors (TNFi) among patients with axial spondyloarthritis (axSpA). Whole blood mRNA and plasma proteins were measured in a cohort of biologic-naïve axSpA patients (n = 35), pre and post (14 weeks) TNFi treatment with adalimumab. Differential expression analysis was used to identify the most enriched pathways and in predictive models to distinguish responses to TNFi. A treatment-associated signature suggests a reduction in inflammatory activity. We found transcripts and proteins robustly differentially expressed between baseline and week 14 in responders. C-reactive protein (CRP) and Haptoglobin (HP) proteins showed strong and early decrease in the plasma of axSpA patients, while a cluster of apolipoproteins (APOD, APOA2, APOA1) showed increased expression at week 14. Responders to TNFi treatment present higher levels of markers of innate immunity at baseline, and lower levels of adaptive immunity markers, particularly B-cells. A logistic regression model incorporating ASDAS-CRP, gender, and AFF3, the top differentially expressed gene at baseline, enabled an accurate prediction of response to adalimumab in our cohort (AUC = 0.97). In conclusion, innate and adaptive immune cell type composition at baseline may be a major contributor to response to adalimumab in axSpA patients. A model including clinical and gene expression variables should also be considered.

Sex and body mass index impact on digit circumference for Leeds Dactylitis Index calculation.

OBJECTIVES: To estimate digit circumference and the impact of sex and body mass index (BMI) for the calculation of the Leeds Dactylitis Index (LDI) in psoriatic arthritis (PsA) patients with bilateral dactylitis. METHODS: Digit circumference of the hands and the foot were measured with a dactylometer and were studied according to sex and BMI (divided in 4 weight categories) in healthy Portuguese subjects, using Student's t-test and One-way ANOVA, respectively. The effect size of sex and BMI were calculated using Cohen's d test and Eta squared, respectively. Multiple linear regression was used to calculate the effect of sex and BMI, as well as their interaction, to create a formula to predict digit circumference. RESULTS: Fifty-nine participants (33 women, 26 men) with a mean BMI of 24.8 were included. Men's mean digit circumferences were statistically higher than those of women (p<0.001), with a large sex effect size in most of the digits. Differences in the mean circumference between the four BMI categories were statistically significant (p<0.05) for all digits, with a large BMI effect size. Sex and BMI were independent variables to predict mean digit circumference (p<0.001). A new tool (based on regression analysis) allowing to estimate the circumference of digits for males and females of different BMIs is presented. CONCLUSIONS: Our data allows the calculation of digit circumference for males and females of different BMIs in the Portuguese population; and shows that BMI influences digital circumference supporting BMI inclusion in LDI references tables.

Muscle dysfunction in axial spondylarthritis: the MyoSpA study.

OBJECTIVES: We aimed to investigate muscle physical properties, strength, mass, physical performance, and the prevalence of sarcopenia in patients with axial spondylarthritis (axSpA) compared to the healthy controls (HC). METHODS: We performed a cross-sectional study on 54 participants: 27 patients with axSpA and 27 HC, matched by age, gender, and level of physical activity. Muscle physical properties (stiffness, tone and elasticity), muscle strength (five-times sit-to-stand [5STS] test), muscle mass, physical performance (measured through gait speed) and sarcopenia were compared between the groups. Linear regression models were conducted allowing adjustment for relevant variables. RESULTS: Patients with axSpA (mean age 36.5 (SD 7.5) years, 67% males, mean disease duration 6.5 (3.2) years) had no significant difference in segmental muscle stiffness, tone or elasticity, compared with the HC, despite showing a slight numerically higher lower lumbar (L3-L4) stiffness [median 246.5 (IQR 230.5-286.5) vs. 232.5 (211.0-293.5), p=0.38]. No participants presented sarcopenia. Patients with axSpA, compared to the HC, had lower total strength [B=1.88 (95% CI 0.43;3.33)], as well as lower strength in the upper (B=-17.02 (-27.33;-6.70)] and lower limbs [B=-11.14 (-18.25;-4.04)], independently of muscle physical properties. Patients had also significantly lower gait speed than the HC [B=-0.11 (-0.21;-0.01)], adjusted for muscle mass, strength and muscle physical properties. CONCLUSIONS: Young axSpA patients with a relatively short disease duration presented similar segmental muscle physical properties as the HC and had no sarcopenia. Patients with axSpA had reduced physical performance and lower strength compared to the HC, despite normal muscle mass, suggesting a possible muscle dysfunction. Gait characteristics may be a potential biomarker of interest in axSpA.

The role of muscle in the susceptibility and progression of axial Spondyloarthritis: The MyoSpA Study Protocol.

BACKGROUND: Axial Spondyloarthritis (axSpA) is a chronic, inflammatory rheumatic disease that affects the axial skeleton, causing pain, stiffness, and fatigue. Genetics and environmental factors such as microbiota and microtrauma are known causes of disease susceptibility and progression. Murine models of axSpA found a decisive role for biomechanical stress as an inducer of enthesitis and new bone formation. Here, we hypothesize that muscle properties in axSpA patients are compromised and influenced by genetic background. OBJECTIVES: To improve our current knowledge of axSpA physiopathology, we aim to characterize axial and peripheral muscle properties and identify genetic and protein biomarker that might explain such properties. METHODS: A cross-sectional study will be conducted on 48 participants aged 18-50 years old, involving patients with axSpA (according to ASAS classification criteria, symptoms duration < 10 years) and healthy controls matched by gender, age, and levels of physical activity. We will collect epidemiological and clinical data and perform a detailed, whole body and segmental, myofascial characterization (focusing on multifidus, brachioradialis and the gastrocnemius lateralis) concerning: a) Physical Properties (stiffness, tone and elasticity), assessed by MyotonPRO®; b) Strength, by a dynamometer; c) Mass, by bioimpedance; d) Performance through gait speed and 60-second sit-to-stand test; e) Histological and cellular/ molecular characterization through ultrasound-guided biopsies of multifidus muscle; f) Magnetic Resonance Imaging (MRI) characterization of paravertebral muscles. Furthermore, we will perform an integrated transcriptomics and proteomics analysis of peripheral blood samples. DISCUSSION: The innovative and multidisciplinary approaches of this project rely on the elucidation of myofascial physical properties in axSpA and also on the establishment of a biological signature that relates to specific muscle properties. This hitherto unstudied link between gene/protein signatures and muscle properties may enhance our understanding of axSpA physiopathology and reveal new and useful diagnostic and therapeutic targets.

Lumbar myofascial physical properties in healthy adults: myotonometry vs. shear wave elastography measurements.

OBJECTIVE: The human resting myofascial tone maintains the body tone in a neutral posture, the assessment of this and other muscle physical properties (MPP) is relevant, since, it is altered in many pathological states. PATIENTS AND METHODS: Seventeen healthy subjects (8 males), between 18-50 years old, were assessed. The MPP of lower lumbar muscles was evaluated on right and left sides during prone resting position using two devices; myotonometry (stiffness, elasticity and tone) and ultrasound-based shear-wave elastography (SWE) (shear modulus). MTM measurements were performed at two anatomic points (ANp), selected by an experienced reader and at an adjacent ultra-sound determined point (USp). Myotonometry measurements of the erector spinae and SWE measurements of multifidus muscles at the L3-4 level were compared between genders and sides. The intra-reader reliability (IRR) for each device and correlations between techniques were analysed. MTM measurements performed at ANp and USp were compared. The intraclass correlation coefficient (ICC) was assessed for both devices. Correlations between stiffness (myotonometry) and shear modulus (SWE) at the respective muscle depths were assessed with Spearman correlation. RESULTS: Males had greater stiffness and tone than females, particularly on the dominant side. MPP assessed by myotonometry were not different between ANp and USp. Good/Excellent IRR was documented for measurements by MTM (ICC≥0.90) and SWE (ICC≥0.85). No correlation in myotonometry stiffness and SWE shear modulus was found. For myotonometry assessments, the addition of ultrasonography was not different from anatomic localizations. No correlation of measurements was found between devices assessing respective L3-4 level muscles. CONCLUSIONS: Gender and side differences must be considered when assessing MPP in axial muscles. For MTM assessments, the addition of ultrasonography was not different to anatomic references. No correlation was found between devices.

​ Cultural adaptation of the Rheumatoid Arthritis Quality of Life (RAQoL) for Portugal.

BACKGROUND: Rheumatoid Arthritis (RA) is a chronic inflammatory disease that has a major impact on patients´ quality of life. The Rheumatoid Arthritis Quality of Life (RAQoL) questionnaire is a patient-reported outcome measure, specific to RA. The aim of this study was to translate and perform the cross-cultural adaptation of the RAQoL into Portuguese. MATERIAL AND METHODS: The dual panel methodology was used to translate the UK RAQoL into Portuguese. This involved conducting a bilingual panel (providing the initial translation into Portuguese) followed by a lay panel (where items are assessed for comprehension and acceptability). Cognitive debriefing interviews were conducted with Portuguese RA patients to determine the face and content validity of the translated scale. RESULTS: The translation panels produced a Portuguese version of the RAQoL that was easily understood and considered natural by native speakers. Twelve RA patients participated in the cognitive debriefing interviews. Patients considered the translated questionnaire to be clear, relevant and appropriate. CONCLUSION: The Portuguese version of the RAQoL was found to be comprehensible and demonstrated excellent face and content validity. Research examining the psychometric properties of this Portuguese version of the RAQoL is underway.