Figure 7. Pro-OCN is not efficiently decarboxylated by osteoclasts.

(A and B) In vitro resorption assay of devitalized calvaria from Furin^fl/fl mice (n = 3) and Furin^osb–/– mice (n = 3) in the presence of osteoclast-like RAW 246.7 cells, with or without 10 ng/ml RANKL. (A) Total OCN and ucOCN ELISA measurements in the cell culture supernatant. ND, not detected. (B) Representative image of TRAP staining of calvaria. Scale bar: 500 μm. (C) Percentage of area with TRAP-positive staining (n = 3). (D) Western blot analysis of bone extracts from Furin^fl/fl and Furin^osb–/– mice incubated in phosphate-buffered solution at pH 7.5 or pH 4.3 for 14 days at 37°C. Graph shows quantification of the Gla OCN/OCN ratio (representative result from 3 independent experiments). The ELISAs used in A quantify both pro-OCN and mature OCN. Results represent the mean ± SEM. **P < 0.01 and ***P < 0.001, by 1-way ANOVA followed by Bonferroni’s multiple comparisons test.