Short-term effects of parathyroid hormone on rat lumbar vertebrae.
METHODS
This study is an experimental study in the rat osteopenia model.


OBJECTIVE
The aim of this study was to evaluate the short-term effects of daily application of parathyroid hormone (PTH) on bone quality and quantity using a new biomechanical compression test for intact rat lumbar vertebrae.


BACKGROUND
Because of their high clinical relevance, trabecular content and thick cortical shell vertebrae are of high interest for osteoporosis research. Biomechanical stability depends on both trabecular and cortical bone. Anabolic effects on bone after long-term application of PTH have already been proven.


METHODS
After an intraindividual comparison (n = 20), the capability of a new test to identify biomechanical properties of the mature rat model was assessed. In the following, 33 three-month-old rats were ovariectomized. After 10 weeks, the animals were divided into 3 groups. The control group (C) received no additional food supplementation. The other groups received hormone treatment with either estradiol (E) or PTH for another 5 weeks. The effects on bone biomechanical properties and bone microstructure were analyzed.


RESULTS
After establishing the new biomechanical test for intact rat lumbar vertebrae, PTH-treated (yield stress: 2.95 N/mm, elastic limit: 2.39 N/mm) and then E-treated (yield stress: 2.13 N/mm, elastic limit: 1.68 N/mm) animals showed superior biomechanical results. Compression strength was significantly improved in these rats in comparison to the control group rats (yield stress: 1.86 N/mm, elastic limit: 1.38 N/mm). In the microradiographic evaluation, PTH significantly improved the morphologic results to produce thicker trabeculae. E led to a more densely branched trabecular network, which was not as important as trabecular thickness for bone stability.


CONCLUSIONS
After a short-term application, PTH is superior to E in recreating bone biomechanical propertiesand lumbar vertebral microstructure in advanced osteoporosis. The cortical shell and trabecular thickness are primarily responsible for the biomechanical strength of vertebrae.
Sehmisch
Stephan
S
Department of Trauma and Reconstructive Surgery, University of Goettingen, Germany. stephan.sehmisch@med.uni-goettingen.de
Erren
Matthias
M
Rack
Thomas
T
Tezval
Mohammed
M
Seidlova-Wuttke
Dana
D
Richter
Julia
J
Wuttke
Wolfgang
W
Stuermer
Klaus M
KM
Stuermer
Ewa K
EK
D000284:Administration, Oral; D000818:Animals; D015415:Biomarkers / Q000097:blood; D001696:Biomechanical Phenomena; D050071:Bone Density Conservation Agents / Q000008:administration & dosage*; D016723:Bone Remodeling / Q000187:drug effects; D019245:Compressive Strength; D004195:Disease Models, Animal; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives; D015914:Estrogen Replacement Therapy; D005260:Female; D007279:Injections, Subcutaneous; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000503:physiopathology; D008852:Microradiography; D015675:Osteocalcin / Q000097:blood; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000503:physiopathology; D010052:Ovariectomy; D010281:Parathyroid Hormone / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D015415:Biomarkers; D050071:Bone Density Conservation Agents; D010281:Parathyroid Hormone; D015675:Osteocalcin; C074283:estradiol 3-benzoate; D004958:Estradiol