title: [Nanomechanical properties of vertebral trabeculae in ovariectomized rats].
abstract: OBJECTIVE
  To study the nanomechanical properties of the vertebral trabeculae of ovariectomized rat using nanoindentation.
  
  
  METHODS
  Twenty 10-month-old SD rats were randomly divided into 2 equal groups: ovariectomized (OVX) group and Sham operation (SHAM) group. Fifteen weeks post-operationally dual energy X-ray absorptiometry was used to measure the bone mineral density (BMD) of the total body and of the sixth lumbar vertebra. Then the rats were killed. The BMD values of the sixth lumbar vertebrae were measured by DXA. Bone histomorphometry was performed on the proximal metaphysis of the right tibia. Three of the sixth lumbar vertebrae were randomly selected from each group and embedded in methyl methacrylate. Each vertebra was cut into two parts along the transverse direction in the middle point of longitudinal axis so as to expose the trabeculae on the cross section. The lower part was polished, trabeculae were randomly selected from 4 places, and 5 points from each place were randomly selected to undergo nanoindentation so as to measure the nanomechanical properties.
  
  
  RESULTS
  Compared with the SHAM rats, the BMD of the sixth lumbar vertebra of the OVX rats was reduced significantly (P < 0.05). The histomorphometry of the tibia showed an increase in trabecular separation and a decrease in trabecular bone area fraction (both P < 0.05); the trabecular number and thickness decreased in these 2 groups, however, without significant difference between them. Nanoindentation tests showed that the values of hardness and elastic modulus of the trabeculae of the OVX rats were 0.91 GPa +/- 0.13 GPa and 21.01 GPa +/- 2.48 GPa respectively, not significantly different from those of the SHAM rats, 0.90 GPa +/- 0.09 GPa and 22.03 GPa +/- 2.44 GPa respectively.
  
  
  CONCLUSIONS
  A novel technique, nanoindentation is able to directly measure the nanomechanical properties of trabeculae. Estrogen deficiency after ovariectomy induces significant osteoporotic change, but has no significant influence on the trabecular nanomechanical properties.
authors: Institute of Metabolism and Endocrinology, Second Xiangya Hospital, Central South University, Changsha 410011, China.
authors: Zhi-feng
authors: ZF
authors: Sheng
authors: Ru-chun
authors: RC
authors: Dai
authors: Peng
authors: P
authors: Wang
authors: Xue-feng
authors: XF
authors: Yao
authors: Xi-qiao
authors: XQ
authors: Feng
authors: Ling-Na
authors: LN
authors: Fang
authors: Hui-jie
authors: HJ
authors: Fan
authors: Xian-ping
authors: XP
authors: Wu
authors: Er-yuan
authors: EY
authors: Liao