Effects of PTH treatment on tibial bone of ovariectomized rats assessed by in vivo micro-CT

Abstract

Summary Using in vivo microcomputed tomography (micro-CT), we found in parathyroid hormone (PTH)-treated osteopenic rats linear increases in cortical and trabecular, due to increased trabecular thickness and number, bone mass. Bone was formed in cavities, leading to restoral of nearly cleaved trabeculae. For the first time, effects in PTH-treated rats were analyzed longitudinally. Introduction Our aims were to over time (1) determine changes in trabecular thickness and number after PTH, (2) compare responses to PTH between the meta-and epiphysis, (3) determine effects of PTH on mineralization and mechanical properties, (4) determine locations of new bone formation due to PTH on a microlevel, and (5) determine the predictive value of bone structural properties for gain in bone mass after PTH. Methods Adult rats were divided into ovariectomy (OVX; n=8), SHAM-OVX (n=8), and OVX and PTH treatment (n=9). Between weeks 8 and 14, PTH rats received daily subcutaneous PTH injections (60 μg/kg/day).At weeks 0, 8, 10, 12, and 14, in vivo micro-CT scans were made of the proximal and diaphyseal tibia. After sacrifice, all tibiae were tested in three-point bending.Results PTH increased bone volume fraction linearly over time in meta-and epiphysis, accompanied by increased trabecular thickness in both and increased trabecular number only in the latter one. CT-estimated mineralization increased in trabecular and remained constant in cortical bone. Ultimate load and energy were increased and ultimate displacement and stiffness unaltered compared to SHAM rats. For those trabeculae analyzed, bone was formed initially on places where it was most beneficial for increasing their strength and later on to all surfaces.

Challenges in longitudinal measurements with HR-pQCT: Evaluation of a 3D registration method to improve bone microarchitecture and strength measurement reproducibility

“…The accuracy of this 3D registration approach has not been previously reported on HR-pQCT images, but the algorithm has been previously used on ex vivo samples scanned at different resolutions [31] and on in vivo μCT images of rats with an isotropic resolution of 15 μm and gave satisfying results [32]. Our first validation step was to carefully visually check the registration result by overlying segmented baseline and transformed follow-up images into one image and color-code the result [34] for all patients.…”

“…The 3D rigid registration method used (Image Processing Language, V5.16, Scanco Medical AG, Brüttisellen, Switzerland) [31,32] was applied to the gray level images (110 slices), where the second and the third images were registered separately to the first one (reference image). The registration was applied only to the volume within the periosteal contours as determined using the standard workflow by an edge detection algorithm.…”

Scaling VOI size in 3D μCT studies of trabecular bone: A test of the over‐sampling hypothesis

“…Am J Phys Anthropol 144:196-203, 2011. V V C 2010 Wiley-Liss, Inc.Three-dimensional microcomputed tomography (3D lCT) has developed into a powerful tool for the noninvasive study of trabecular architecture that is employed across a variety of disciplines, including clinical medicine (Brouwers et al, 2009;Recker et al, 2009), bioengineering (Bevill et al, 2006Pontzer et al, 2006;Arlot et al, 2008), comparative functional adaptation (Ryan and Ketcham, 2005;Ryan and Rietbergen, 2005;Maga et al, 2006;Fajardo et al, 2007a;Spoor et al, 2007;Lazenby et al, 2008b), growth and development (Tanck et al, 2001;Ryan and Krovitz, 2006), and paleoanthropology (Thompson and Illerhaus, 1998;Griffin, 2008;Scherf, 2008). The perspectives and objectives of each of these realms differs considerably, from understanding the impacts of therapeutic interventions (Hopper et al, 2007), to finite element analysis of micromechanical properties (Liu et al, 2009), and trabecular bone adaptation to locomotion (Fajardo et al, 2007b) or dietary behaviors (Ryan et al, 2010).…”

Quantitative analysis of bone and soft tissue by micro-computed tomography: applications to ex vivo and in vivo studies

“…If the epiphyseal region is to be analysed, the entire proximal or distal region can be scanned. 5 In rats, the scan typically starts 1 mm away from the growth plate to capture the remodelling, rather than modelling, characteristics. [6][7][8][9] In mice, scans often start at the growth plate, as there is a smaller volume of bone available for analysis.…”

“…This ensures that the same region is analysed at each time point, and it has been Quantitative analysis of bone and soft tissue by micro-CT GM Campbell and A Sophocleous shown to improve the precision of repeated micro-CT measurements. 5,[40][41][42] In addition, image registration can be used to track changes in the structure of individual trabecular elements 43 and quantify local changes in bone resorption and formation in vivo.…”