Receptor activator of nuclear factor-kappa B ligand [RANKL] and osteoprotegrin [OPG] in rheumatoid arthritis

ABSTRACT

To evaluate serum and synovial fluid levels of receptor activator of nuclear factor Kappa B ligand [RANKL] and osteoprotegrin [OPG] in patients with rheumatoid arthritis [RA] and to determine the level of osteoclastic bone resorption by the ratio of RANKL to OPG as well as their correlation with the clinical activity, radiological grades and bone mineral density. 45 RA female patients and 15 age-matched healthy females with post traumatic knee effusion [as controls] were subjected to full history taking, complete clinical examination, assessment of disease activity using DAS score, radiological progression assessment using Larsen score, laboratory investigations including ESR, CRP and RF. Also, serum and synovial fluid levels of RANKL and OPG and bone mineral density [BMD] were done. RA patients had significantly higher levels of serum and synovial fluid RANKL, OPG and RANKL/OPG ratio than controls. Levels of RANKL, OPG and RANKL/OPG ratio were significantly higher in SF than in serum and in the active than in non active RA patients. The serum RANKL significantly correlated with disease duration, RF, ESR, DAS score and T- score, with no correlation with CRP or Larsen score. Synovial RANKL did not correlate with any of the previous parameters. As regards to serum OPG, it correlated with disease duration, RF, T-score and Larsen score, while synovial OPG showed correlation only with CRP. The serum RANKL/OPG ratio had significant positive correlation with CRP, DAS score and Larsen score. RANKL has a crucial role in the pathogenesis of bone loss in rheumatoid arthritis and can be used as a marker of bone erosion and disease activity. OPG plays a protective role against bone erosion and joint destruction in RA. RANKL/OPG ratio is more informative about bone resorption than each of RANKL or OPG alone