Release of soluble IL-6R by osteocytes in vitro. Shown are sclerostin (Sost; A and D) and IL-6 receptor (Il6ra; B and E) mRNA levels and sIL-6R protein levels (C and F) in cell lysates and conditioned media from differentiating Ocy454 cells (A–C) and Kusa4b10 cells (D–F). Data are the mean ± S.E. (error bars) from three independent preparations. *, p < 0.05, **, p < 0.01, ***, p < 0.001 versus undifferentiated cells by one-way ANOVA with Tukey post hoc test; C and F do not contain statistics because levels were undetectable at day 0.