The Evaluation of New-Generation Biomarker sCD14ST Provides New Insight into COVID-19's Effect on Bone Remodeling

Background/Objectives: The COVID-19 pandemic has increased interest in osteoimmunology because of the impact of SARS-CoV-2 on both the immune system and the bone microenvironment. Soluble CD14ST could influence the production of the osteoimmunological regulators of osteoclast differentiation. The aim of this study is to evaluate the role of sCD14ST in COVID-19's effects on bone remodeling-evaluating, in particular, the correlation with new-generation osteoimmunological biomarkers-and to acquire comprehensive knowledge of the effects of the disease on the immune and skeletal system. Methods: The serum level of sCD14ST was measured in COVID-19-positive and COVID-19-negative patients undergoing orthopedic surgery and correlated with the inflammatory and osteoimmunological biomarkers RANKL/OPG, FGF23, IL-6, C-reactive protein (CRP), procalcitonin (PCT), sRAGE, and SuPAR. Results: In our patients, sCD14ST showed a strong increase in COVID-19-positive patients, and a significant decrease in tandem with the infection resolution, confirming its diagnostic and prognostic value. sCD14ST was more clinically relevant than the two canonically inflammatory makers used in the clinical protocols, CRP and PCT, and displayed a good positive correlation with FGF23, RANKL/OPG, IL-6, and SuPAR and a negative correlation with sRAGE. Conclusions: Monitoring sCD14ST along with SuPAR may offer valuable insights into immune system dysregulation and bone-related complications in conditions characterized by inflammation. These soluble receptors represent important links between immune activation and bone metabolism, especially in the context of diseases like COVID-19, where the inflammatory response may impact bone fragility.