[Bone mass change and its possible mechanisms in murine knockout apolipoprotein E(ApoE-/-)].
OBJECTIVE
To study bone mass changes and its mechanisms in murine knockout apolipoprotein E (ApoE-/-).


METHODS
Both 28-week-old male ApoE-/- mice (n = 6) and wild-type (WT) mice (n = 10) were euthanized. The trabecular and cortical bone microarchitecture were assessed by micro-CT (microCT) in right distal femur. The total body BMD (bone mineral density) of left femur was determined by dual-energy X-ray absorptiometry (DXA). The serum concentrations of osteoprotegerin (OPG) and receptor activator of nuclear factor kappaB ligand (RANKL) were analyzed using enzyme-linked immunosorbent assay (ELISA). The left tibias were dissected and fixed in 4% paraformaldehyde after decalcified in 0.15M EDTA buffer for 30 days. And the expressions of OPG and RANKL were detected by immunohistochemical staining.


RESULTS
Compared with WT mice, the ApoE-/- mice showed an increased volumetric BMD (294 +/- 38) mg/mm(3), tissue BMD (627 +/- 23) mg/mm(3), BMC (bone mineral content) (0.57 +/- 0.08) mg, bone volume fraction (20.38 +/- 4.74)%, trabecular number (6.67 +/- 0.78) mm(-1), trabecular thickness (0.03 +/- 0.01) mm with an decreased bone surface fraction (69 +/- 18) mm(-1), trabecular separation (0.12 +/- 0.01) and structure mode index (1.73 +/- 0.24). The total body BMD was higher in ApoE-/- mice than WT mice [(0.063 +/- 0.004) g/cm(2) vs (0.056 +/- 0.004) g/cm(2)]. The serum level of OPG was significantly higher in ApoE-/- mice than WT mice [(4.98 +/- 0.97) ng/ml vs (3.54 +/- 0.65) ng/ml]. The results of immunohistochemical staining showed that the OPG expression was at a higher level in bone cell of ApoE-/- mice and RANKL showed no obvious change in either sera or bone cells.


CONCLUSIONS
A decreased bone resorption causes an increased bone mass in ApoE-/- mice and leads to an imbalanced ratio of OPG/ RANKL.
Department of Clinical Laboratory, Second Xiangya Hospital of Central South University, Changsha, China.
Min
M
Wang
Xian-ping
XP
Li
Li-ling
LL
Zhao
Er-yuan
EY
Liao
Xiang-hang
XH
Luo
D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics*; D015519:Bone Density; D001862:Bone Resorption; D005269:Femur / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053244:Osteoprotegerin / Q000097:blood / Q000378:metabolism; D053245:RANK Ligand / Q000097:blood / Q000378:metabolism
D001057:Apolipoproteins E; D053244:Osteoprotegerin; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse