Longitudinal in vivo analysis of the region-specific efficacy of parathyroid hormone in a rat cortical defect model.
PTH has been shown to enhance fracture repair; however, exactly when and where PTH acts in this process remains to be elucidated. Therefore, we conducted a longitudinal, region-specific analysis of bone regeneration in mature, osteopenic rats using a cortical defect model. Six-month-old rats were ovariectomized, and allowed to lose bone for 2 months, before being subjected to bilateral 2-mm circular defects in their femoral diaphyses. They were then treated for 5 wk with hPTH1-38 at doses of 0, 3, 10, or 30 microg/kg . d and scanned weekly by in vivo quantitative computed tomography. Quantitative computed tomography analyses showed temporal, dose-dependent increases in mineralization in the defects, intramedullary (IM) spaces, and whole diaphyses at the defect sites. Histomorphometry confirmed PTH stimulation of primarily woven bone in the defects and IM spaces, but not the periosteum. After necropsy, biomechanical testing identified an increase in strength at the highest PTH dose. Serum procollagen type I N-terminal propeptide concentration showed a transient increase due to drilling, but procollagen type I N-terminal propeptide also increased with PTH treatment, whereas tartrate-resistant acid phosphatase unexpectedly decreased. Analyses of lumber vertebra confirmed systemic efficacy of PTH at a nonfracture site. In summary, PTH dose dependently induced new bone formation within defects, at endocortical surfaces, and in IM spaces, resulting in faster and greater bone healing, as well as efficacy at other skeletal sites. The effects of PTH were kinetic, region specific, and most apparent at high doses that may not be entirely clinically relevant; therefore, clinical studies are necessary to clarify the therapeutic utility of PTH in bone healing.
Komatsu
David E
DE
InMotion Musculoskeletal Institute, Memphis, Tennessee 38103, USA. dkomatsu@gmail.com
Brune
Kellie A
KA
Liu
Hong
H
Schmidt
Allen L
AL
Han
Bomie
B
Zeng
Qing Q
QQ
Yang
Xuhao
X
Nunes
Jairo S
JS
Lu
Yuefeng
Y
Geiser
Andrew G
AG
Ma
Yanfei L
YL
Wolos
Jeffrey A
JA
Westmore
Michael S
MS
Sato
Masahiko
M
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000187:drug effects; D001861:Bone Regeneration / Q000187:drug effects*; D024042:Collagen Type I / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005260:Female; D005269:Femur / Q000187:drug effects / Q000473:pathology; D007527:Isoenzymes / Q000378:metabolism; D010052:Ovariectomy; D010281:Parathyroid Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071681:Tartrate-Resistant Acid Phosphatase; D015898:Tomography Scanners, X-Ray Computed
D024042:Collagen Type I; D007527:Isoenzymes; D010281:Parathyroid Hormone; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase