The Temporal Changes of Trabecular Architecture in Ovariectomized Rats Assessed by MicroCT

Abstract

To study the short- and long-term effects of estrogen deficiency on trabecular bone, three-dimensional measurements of proximal tibiae of ovariectomized rats were performed by micro-computed tomography (MicroCT). New three-dimensional (3D) techniques were employed to characterize the trabecular architecture from 0 to 110 days post-ovariectomy (OVX). These new methods no longer assume a plate or rod model of bone, but calculate trabecular thickness, separation, and number and their distribution by placing maximal spheres into the 3D representation of the structure. The model type of bone was quantified with the Structure Model Index (SMI). Utilizing these methods we found a rapid loss of trabecular bone in the first week after OVX. After the first week bone mass declined further, although the rate of loss was lower. In addition there was a complete change in model type from plate-like to rod-like within 7 days post-OVX, and then a very constant SMI after 12 days. After an initial thinning of trabecular structure, further bone loss seems to occur through removal of trabeculae, while the trabecular plate thickness remains constant. The heterogeneity of the network could be quantified by intra-individual standard deviation of local separations, which showed a stair-like progression, with a plateau between 12 and 60 days post-OVX. This study provides new insights into ovariectomy-related changes in cancellous bone structure evaluated by 3D MicroCT. In addition, these data suggest that the rapid change of model from plate-like to rod-like post-OVX may potentially introduce biases in the parameters that are determined using model-based algorithms, and these biases may modify the impact of age-related or therapeutic changes.

Orthodontic tooth movement and root resorption in ovariectomized rats treated by systemic administration of zoledronic acid

“…This time point has been remarked as the early time point when major degenerative bone changes were found. 28,42,43 Recently, a study has elucidated that after 4 weeks of OVX (only 2 weeks after the injection of ZOL was started), the OVX group has shown the loss of the bone volume fraction in 64 %, whereas the OVX+ZOL group has shown the bone volume fraction similarly to the baseline. 34 In our study, we started to apply orthodontic force 4 weeks after OVX and we found almost the same results of both orthodontic tooth movement and OIRR in OVX+ZOL and control groups.…”

Short-term continuous infusion of human parathyroid hormone 1–34 fragment is catabolic with decreased trabecular connectivity density accompanied by hypercalcemia in C57BL/J6 mice

“…The volume of interest with a length of 1·70 mm was placed in an axial direction in the secondary spongiosa of the distal femurs, just above the growth plate. Pixel dimensions were set at 2048 2048 170 longitudinally to expose the bone marrow (Laib et al 2000(Laib et al , 2001. Measured variables their abbreviations were as defined by Parfitt et al (1987).…”

Bone loss dynamics result in trabecular alignment in aging and ovariectomized rats

“…7 Again, the general picture is that bone loss preferentially occurs due to loss of entire trabeculae. [8][9][10] Immediately after ovariectomy (OVX), bone remodeling accelerates and entire trabeculae are lost. 8 This initial phase of rapid bone loss is followed by a gradual decrease of bone mass, which is also observed in normally aging rats.…”