(A) Western blotting of Cre recombinase and Bcl-xL in
Bcl-x cKO mice and their normal
Bcl-xfl/fl littermates using β-actin as an
internal control. Bcl-xL expression was markedly reduced in osteoclasts, but not
in osteoblasts, of Bcl-x cKO mice. (B) Histological
sections of proximal tibia and lumbar spine of male Bcl-x cKO
mice and their normal Bcl-xfl/fl littermates at 8
weeks of age. Bcl-x cKO mice exhibited reduced bone mass. Scale
bars: 100 μm. (C) Histomorphometric analysis of male
Bcl-x cKO mice and their normal
Bcl-xfl/fl littermates at 8 weeks of age. Bone volume
per trabecular volume (BV/TV) significantly decreased in Bcl-x
cKO mice (P < 0.01). Trabecular bone thickness (Tb.th) and
trabecular bone number (Tb.N) was reduced, and the trabecular separation (Tb.S)
was increased, in Bcl-x cKO mice, with marginal statistical
difference (P < 0.1). As for osteoclast markers, whereas
the eroded surface/bone surface (ES/BS) significantly increased in
Bcl-x cKO mice (P < 0.05), neither
osteoclast number nor osteoclast surface increased. The parameters of bone
formation in Bcl-x cKO mice were equivalent to those of normal
littermates. Results are mean ± SD of 3 different samples.
*P < 0.01 versus normal
Bcl-xfl/fl littermates. Oc.N/B.Pm, number of mature
osteoclasts per 100-μm bone perimeter; Oc.S/BS, bone surface covered
by mature osteoclasts; Osteoid V/BV, osteoid volume per bone volume; Osteoid S/BS;
osteoid surface per bone surface; Ob.S/BS, bone surface covered by cuboidal
osteoblasts; MAR, mineral apposition rate; BFR, bone formation rate.