Article

Calcified Tissue International

, Volume 74, Issue 4, pp 351-356

First online:

Treatment with Parathyroid Hormone hPTH(1-34), hPTH(1-31), and Monocyclic hPTH(1-31) Enhances Fracture Strength and Callus Amount After Withdrawal Fracture Strength and Callus Mechanical Quality Continue to Increase

  • T. T. AndreassenAffiliated withDepartment of Connective Tissue Biology, Institute of Anatomy, University of Aarhus, Aarhus Email author 
  • , G. E. WillickAffiliated withInstitute for Biological Science, National Research Council of Canada, Ottawa, Ontario
  • , P. MorleyAffiliated withInstitute for Biological Science, National Research Council of Canada, Ottawa, Ontario
  • , J. F. WhitfieldAffiliated withInstitute for Biological Science, National Research Council of Canada, Ottawa, Ontario

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Abstract

The influence of intermittent hPTH(l-34)NH2, hPTH(1-31)NH2, and monocyclic [Leu27]cyclo(Glu22-Lys26)hPTH(1-31)NH2 treatment on callus formation, mechanical strength, and callus tissue mechanical quality of tibial fractures in rats was investigated after 8 and 16 weeks of healing. In the 8 weeks of healing animals, the PTH-peptides were injected subcutaneously during the entire observation period (15 nmol/kg/day [hPTH(1-34)NH2: 15 nmol = 60 µg]), and control animals with fractures were given vehicle. In the 16 weeks of healing animals, the PTH-peptides were injected only during the first 8 weeks of healing (15 nmol/kg/day), after which the animals were left untreated during the rest of the healing period. After the first 8 weeks of healing, increased fracture strength and callus volume were seen in the PTH-treated rats (ultimate load 66%, ultimate stiffness 58%, callus volume 28%), and the three peptides were equally effective. No difference in callus tissue mechanical quality was found between PTH and vehicle animals. After 16 weeks of healing, no differences in fracture strength, callus volume, or callus tissue mechanical quality were seen between PTH and vehicle. When comparing PTH-treated animals at 8 and 16 weeks, fracture strength and callus tissue mechanical quality continued to increase after the withdrawal of PTH (ultimate load 23%, ultimate stress 88%, elastic modulus 87%) and external callus volume declined during this period (27%).

Keywords

Fracture healing PTH peptides Withdrawal Mechanical strength