Alterations in skeletal muscle health and biomechanical properties in patients with early rheumatoid arthritis: an exploratory cross-sectional study

Brian J Andonian^1,2*Hailee Patel^3,4Mingzhi Xu³Alyssa M Sudnick²Johanna L. Johnson²William E Kraus^1,2George A Truskey³Kim M Huffman^1,2

• ¹School of Medicine, Duke University, Durham, United States
• ²Duke Molecular Physiology Institute, School of Medicine, Duke University, Durham, North Carolina, United States
• ³Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina, United States
• ⁴Department of Biomedical Engineering, College of Engineering, Texas A&M University College Station, College Station, Texas, United States

Background: Skeletal muscle disease in patients with early-stage rheumatoid arthritis (RA) is understudied. The objective of this study was to identify if patients with early RA (symptoms < 6 months) have impaired skeletal muscle health.Methods: Participants with early RA (n=10) and age-, sex-, and BMI-matched healthy controls (n=10) underwent cross-sectional clinical, physiological, and muscle biomechanical property assessments. Upper and lower extremity muscles underwent in vivo passive biomechanical property -tone, stiffness, and elasticity -assessments via myotonometry (MyotonPro®). In vitro muscle force production and stiffness were assessed using 3D bioengineered myobundles derived from myoblasts obtained from vastus lateralis muscle biopsies.Results: Despite similar muscle mass and self-reported physical activity behaviors for early RA patients and healthy controls, early RA patients had poorer self-reported physical function, selfreported physical health, and right-handed grip strength (p < 0.05 for all). Early RA muscle tone and stiffness was less than controls (p < 0.05) and with an inverse association with prednisone use (rho=-0.72, p=0.02). While 3D bioengineered myobundle force production and passive stiffness were similar to controls, early RA myobundle stiffness correlated with swollen joint counts (rho=-0.67, p=0.04).In this exploratory study, as compared to controls with similar muscle mass and physical activity, patients with early RA exhibited multiple skeletal muscle deficits across clinical, physiologic, and biomechanical domains. Use of skeletal muscle biomechanical assessments -both in vivo and in vitro -may be useful to identify these deficits to better understand and improve RA muscle health.