Bone Matrix Levels of Dickkopf and Sclerostin are Positively Correlated with Bone Mass and Strength in Postmenopausal Osteoporosis

Wnt signaling plays a pivotal role in maintaining bone mass. Secreted pathway modulators such as sclerostin (SOST) and Dickkopfs (DKKs) may influence bone mass inhibiting the canonical Wnt pathway. We evaluated whether bone protein content of secreted Wnt antagonists is related to age, bone mass, and strength in postmenopausal osteoporosis. We measured cortical and trabecular bone contents of SOST and Dickkopf-1 (DKK1) in combined extracts obtained after ethylenediaminetetraacetic acid and guanidine hydrochloride extraction in 56 postmenopausal women aged 47–74 (mean, 63) yr with a previous distal forearm fracture and a hip or spine Z-score less than 0. Our findings were (i) SOST and DKK1 protein levels were higher in trabecular bone, (ii) cortical and trabecular DKK1 and trabecular SOST correlated positively with bone matrix levels of osteocalcin (r between 0.28 and 0.45, p < 0.05), (iii) cortical DKK1 correlated with lumbar spine bone mineral density (BMD) (r = 0.32, p < 0.05) and femoral neck BMD (r = 0.41, p < 0.01), and (iv) cortical DKK1 and SOST correlated with apparent bone volumetric density and compressive strength (r between 0.34 and 0.51, p < 0.01). In conclusion, cortical bone matrix levels of DKK1 and SOST were positively correlated with bone mass and bone strength in postmenopausal osteoporotic women.

Effect of sodium selenite on bone repair in tibiae of irradiated rats

This study evaluated the radioprotective effect of sodium selenite on the bone repair process in tibiae of female rats. For such purpose, 100 female Wistar rats (Rattus norvegicus, albinus) were randomly assigned to 4 groups (n=25), according to the treatment received: administration of distilled water (control); administration of sodium selenite; gamma radiation; and administration of sodium selenite plus gamma radiation. A bone defect was prepared on both tibiae of all animals. Three days after surgery, the gamma radiation and selenium/gamma radiation groups received 8 Gy gamma rays on the lower limbs. Five animals per group were sacrificed 7, 14, 21, 28 days after surgery for evaluation of the repair process by bone volumetric density analysis. The 5 animals remaining in each group were sacrificed 45 days postoperatively for examination of the mature bone by scanning electron microscopy. Based on all analyzed parameters, the results of the present study suggest that sodium selenite exerted a radioprotective effect in the bone repair of tibia of irradiated rats.

Estimation of Central Osteopenia in Children With Chronic Polyarthritis Treated With Glucocorticoids

Study objective. To investigate the degree and determinants of osteopenia in juvenile chronic polyarthritis. Design. Retrospective case-control study of central bone mineral density. Setting. Rheumatism Foundation Hospital and Kuopio University Hospital, Finland. Subjects. A sample of 43 girls aged 7 to 19 with juvenile chronic polyarthritis treated with systemic glucocorticoids and a control sample of 44 healthy girls matched for age. Main outcome measures. Bone mineral density and bone size (width) measured by dual-energy x-ray absorptiometry and bone volumetric density calculated as an approximation of true bone density at both the lumbar spine and femoral neck. Results. The girls with juvenile chronic arthritis had reduced bone mineral density, bone size, and bone volumetric density at both the lumbar spine and femoral neck (statistically significant findings, P = .022 for the bone size of the femoral neck and P &lt; .001 for the other parameters). At the spine, the mean bone mineral density was 80%, the mean bone size 89%, and the mean bone volumetric density 89% of the values in the control group. At the femoral neck, the values were 78%, 93%, and 83%, respectively. The groups were matched for age, but the girls with arthritis were smaller and lighter. In the juvenile arthritis group, the femoral bone mineral density and bone volumetric density and the spinal bone width correlated negatively with the mean glucocorticoid dose. Conclusion. Axial bone mineral density is clearly reduced in severe juvenile polyarthritis and is mediated by both decreased bone volumetric density and diminished growth.