ERRγ regulates osteoblast number and differentiation, but does not affect osteoclast number or activity.

<p>(A) von Kossa/toluidine blue double stain was used to quantify osteoblast number and osteoblast surface per bone surface; both are significantly increased in 14 week <i>ERRγ +/−</i> compared to <i>ERRγ +/+</i> male femurs. Scale = 50 µm (N = <u>3</u><i>ERRγ +/+</i>; N = <u>3</u><i>ERRγ +/−</i>) (B) Adjacent femoral sections were immunostained for proliferating (Ki67) and apoptotic (TUNEL) osteoblasts; no significant differences were seen between genotypes. (N = 5 <i>ERRγ +/+</i>; N = 4 <i>ERRγ +/−</i>) (C) Double calcein labels were used to quantify bone formation rate (BFR), mineralizing surface per bone surface (MS/BS) and mineral apposition rate (MAR); both BFR and MS/BS were significantly increased, while MAR was not significantly increased in <i>ERRγ +/−</i> compared to <i>ERRγ +/+</i> mice. (N = 3 <i>ERRγ +/+</i>; N = 3 <i>ERRγ +/−</i>) (D) There was no significant difference observed between genotypes in either TRAP-positive osteoclast number (Oc.N/BS) or osteoclast surface per bone surface (Oc.S/BS) (N = 5 <i>ERRγ +/+</i>; N = 4 <i>ERRγ +/−</i>). All values are expressed as mean ± SD. * = p<0.05; ** = p<0.01.