Bone Abstracts

Sclerostin is a major negative regulator of osteoblastic activity. Serum sclerostin has a weak positive association with BMD but contradictory results have been described concerning associations with fractures. These contradictions could be explained by the fact that serum sclerostin does not reflect its action in bone. In this study we question whether serum sclerostin is associated with its expression in bone. In addition we aimed to detect associations between sclerostin in serum or in bone and bone density.

Twenty six patients with Crohn’s disease and osteopenia were included. These patients were a subgroup from a large randomized clinical trial, investigating treatment with risedronate (Crohn and Bone study registered as NTR 163 Dutch Trial Register). Serum sclerostin was measured with two different ELISA’s, Mesoscale diagnostics (MD) and Biomedica Gruppe (BG). Sclerostin expression in bone was detected on iliac crest bone biopsies, using immunohistochemistry (mouse-human antibody by R&D systems) and measured as sclerostin positive cortical area (Scl postive area) (NIS elements, Nikon). DEXA, using WHO standardized values, was used to obtain total hip (THP-BMD) and lower lumbal spine bone mineral density (LS-BMD).

Scl positive area and serum sclerostin correlated poorly. Scl positive area and Scl_MD, r=-0.135 (95% CI −0.535 to 0.315). Scl positive area and Scl_BG, r=0.118 (95% CI −0.300–0.498). Interassay correlation between Scl_MD and Scl_BG was weak, r=0.062 (95% CI −0.326–0.432).

Scl positive area had a positive correlation with bone mineral density. Respectively for LS-BMD and THP-BMD, r=0.38(95% CI 0.000–0.664) and r=0.55 (95% CI 0.265–0.746). Scl_MD had a positive correlation only with LS-BMD, r=0.55 (95% CI 0.25–0.75),

Serum sclerostin does not reflect sclerostin status in bone tissue in this study, indicating care should be taken when interpreting serum sclerostin values. A positive correlation was detected between sclerostin expression in bone and bone mineral density. This correlation was reported in serum previously, but this was confirmed in only one of the two assays used in this study.