The Effects of Tocilizumab on Inflammatory and Differentiation Pathways in Primary Human Chondrocytes: A Bioinformatic and In Vitro Approaches

Introduction

This study investigates the effects of Tocilizumab, an interleukin-6 (IL-6) receptor inhibitor, on human primary chondrocyte cells, focusing on bone morphogenetic protein 2 (BMP-2), hypoxia-inducible factor 1-alpha (HIF-1α), interleukin-1 beta (IL-1β), SRY-box transcription factor 9 (SOX-9), and IL-6 genes.

Methods

Combining bioinformatic and experimental approaches, we assessed Tocilizumab's impact on inflammatory signaling pathways, cellular differentiation, and viability. Reactome and Gene Ontology (GO) enrichment analyses revealed the involvement of interleukin signaling, BMP, and mitogen-activated protein kinase (MAPK) pathways.

Results

Protein–protein interaction (PPI) network analysis indicated strong interactions among the studied genes, with BMP-2 and SOX-9 identified as central nodes. Western blot analysis demonstrated a 71% reduction in SOX-9, a 55% reduction in HIF-1α, and an 81% reduction in BMP-2 expression levels by day 15. Conversely, IL-1β levels decreased by 67% after prolonged treatment. MTT assays showed a 27.7% reduction in cell viability at day 15 compared to controls. Despite these changes, staining analyses confirmed preserved cell membrane integrity and nuclear morphology, indicating minimal cytotoxic effects.

Conclusion

These findings highlight Tocilizumab's role in modulating inflammation and differentiation pathways in human primary chondrocytes. Further studies should explore the long-term effects of IL-6 blockade on cartilage remodeling and regenerative capacity in chronic inflammatory settings.