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


BACKGROUND
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 microg/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.
Brouwers
J E M
JE
Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands. j.e.m.brouwers@tue.nl
van Rietbergen
B
B
Huiskes
R
R
Ito
K
K
D000818:Animals; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D016723:Bone Remodeling / Q000187:drug effects; D018483:Diaphyses / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004838:Epiphyses / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D005260:Female; D010052:Ovariectomy; D010281:Parathyroid Hormone / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D013977:Tibia / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D055114:X-Ray Microtomography
D050071:Bone Density Conservation Agents; D010281:Parathyroid Hormone