Osteocyte Signaling Biomarkers in Skeletal Remodeling

Abstract

Osteocytes, the most abundant cells in bone tissue, orchestrate skeletal remodeling through complex signaling networks. Recent advances have identified several osteocyte-derived biomarkers that reflect bone metabolism and remodeling activity, offering potential utility in the diagnosis, prognosis, and management of metabolic bone diseases. This review synthesizes current knowledge on the clinical relevance, mechanistic underpinnings, and emerging therapeutic implications of osteocyte signaling biomarkers, with a focus on sclerostin, fibroblast growth factor 23 (FGF23), and DMP1, among others. Practical insights for clinicians and future research directions are discussed.

Introduction

Osteocytes play a pivotal role in maintaining bone homeostasis by integrating mechanical, hormonal, and metabolic cues. They mediate the balance between bone formation and resorption via autocrine and paracrine signaling, influencing the activity of osteoblasts and osteoclasts. The identification of osteocyte-specific signaling molecules as circulating biomarkers has led to a paradigm shift in the assessment and management of skeletal disorders. Understanding the biological significance and clinical application of these biomarkers is essential for advancing bone health diagnostics and therapeutics.

Epidemiology / Disease Burden

Disorders of skeletal remodeling, such as osteoporosis and chronic kidney disease–mineral and bone disorder (CKD-MBD), affect millions globally, contributing to significant morbidity, mortality, and healthcare costs. The global prevalence of osteoporosis alone is estimated to exceed 200 million individuals, with associated fragility fractures posing a major public health challenge. Early and accurate evaluation of bone remodeling status is critical to prevent disease progression and complications, highlighting the need for sensitive and specific biomarkers derived from osteocyte signaling pathways.

Pathophysiology

Osteocytes, embedded within the mineralized bone matrix, communicate via dendritic processes, forming an extensive lacuno-canalicular network. Key signaling molecules secreted by osteocytes include sclerostin, an inhibitor of the Wnt/β-catenin pathway that suppresses bone formation; FGF23, which regulates phosphate homeostasis and vitamin D metabolism; and DMP1, which modulates mineralization and FGF23 expression. Mechanical loading, hormonal influences (e.g., parathyroid hormone), and pathological states (e.g., CKD, glucocorticoid exposure) alter osteocyte signaling, thereby impacting skeletal remodeling and systemic mineral metabolism.

Risk Factors

Alterations in osteocyte signaling are influenced by both intrinsic and extrinsic factors. Age-related changes, estrogen deficiency, vitamin D insufficiency, chronic inflammation, renal insufficiency, and prolonged immobilization disrupt normal osteocyte function. Secondary factors, such as glucocorticoid therapy and certain genetic mutations (e.g., in SOST or PHEX genes), further perturb osteocyte-mediated signaling, increasing the risk of abnormal skeletal remodeling and related pathologies.

Clinical Features

Dysregulation of osteocyte signaling manifests clinically as impaired bone quality, increased fracture risk, altered phosphate and calcium metabolism, and extraskeletal complications (notably in CKD-MBD). While many patients remain asymptomatic until advanced disease, early detection of abnormal osteocyte biomarker profiles may reveal subclinical bone turnover disturbances, guide risk stratification, and inform therapeutic decision-making in conditions such as osteoporosis, osteomalacia, and rare hereditary bone diseases.

Diagnosis

Traditional diagnostic approaches for bone remodeling rely on imaging and generic biochemical markers of bone turnover, which have limited specificity for underlying cellular mechanisms. The quantification of circulating osteocyte-derived biomarkers such as sclerostin, FGF23, and DMP1 fragments offers a more targeted assessment of bone metabolism. Immunoassays and mass spectrometry techniques enable sensitive measurement of these analytes, facilitating early detection, monitoring of treatment response, and differentiation between disease etiologies. Integration with clinical parameters and imaging enhances diagnostic precision.

Treatment & Management

Therapeutic strategies targeting osteocyte signaling focus on modifying bone formation and resorption rates. Sclerostin inhibitors (e.g., romosozumab) have demonstrated efficacy in increasing bone mineral density and reducing fracture risk in osteoporosis by promoting Wnt signaling and osteoblast activity. Management of CKD-MBD involves modulation of FGF23 and phosphate levels to mitigate skeletal and cardiovascular complications. Individualized treatment selection is informed by biomarker profiles, risk factor assessment, and comorbidity evaluation, with periodic monitoring of osteocyte-derived markers to guide ongoing care.

Recent Advances / Emerging Therapies

Recent years have witnessed significant progress in the understanding and therapeutic targeting of osteocyte signaling. The introduction of monoclonal antibodies against sclerostin and ongoing trials investigating FGF23 antagonists and DMP1 modulators reflect the translational impact of basic science discoveries. Novel biomarkers, including circulating extracellular vesicles enriched in osteocyte-derived proteins and microRNAs, are being explored for their diagnostic and prognostic utility. Advances in single-cell transcriptomics and imaging are further elucidating osteocyte heterogeneity and functional dynamics in health and disease.

Guideline Recommendations

Current clinical guidelines acknowledge the emerging role of osteocyte biomarkers in specific contexts, such as the use of sclerostin levels to guide osteoporosis therapy or FGF23 in the evaluation of phosphate metabolism in CKD. However, widespread adoption into routine practice awaits further standardization of assay methods, establishment of reference ranges, and validation in diverse populations. Ongoing research is anticipated to inform future guideline updates and broader clinical application of osteocyte signaling biomarkers in skeletal health management.

Conclusion

Osteocyte signaling biomarkers represent a promising frontier in the clinical assessment of skeletal remodeling. Their mechanistic specificity, prognostic value, and therapeutic relevance underscore the importance of incorporating these tools into multidisciplinary bone health strategies. Continued research and guideline development are essential to optimize their integration into personalized patient care and to address unmet needs in the early detection and management of metabolic bone diseases.