Osteoclast Function, Bone Turnover and Inflammatory Cytokines During Infective Exacerbations of Cystic Fibrosis

Background: Raised levels of pro-inflammatory, pro-resorptive cytokines during pulmonary infection may contribute to osteoporosis in cystic fibrosis (CF). We assessed osteoclast number and activity during infective exacerbations and examined their relationship to serum inflammatory cytokines and bone turnover markers.

Methods: Serum samples from 24 adults with CF were obtained before, during and after treatment of infection. Osteoclastic cells were generated from peripheral blood mononuclear cells and their number and activity assessed. Serum osteocalcin, type 1 collagen cross-linked N-telopeptide (NTx), interleukin-6 (IL-6), tumour necrosis factor alpha (TNFalpha), receptor activator of NFkB ligand (RANKL) and osteoprotegerin (OPG) were measured.

Results: Osteoclast number and activity were increased at the start of exacerbation and decreased with antibiotic therapy. Significant correlations were demonstrated between osteoclast formation and serum TNFalpha, OPG, osteocalcin and NTx and between osteoclast activity and serum IL-6 and NTx.

Conclusions: The systemic response to infection is associated with increased bone resorptive activity in patients with CF.