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Single injection of PTH improves osteoclastic parameters of remodeling at a stress fracture site in rats
Author(s) -
Bakr Mahmoud M.,
Kelly Wendy L.,
Brunt Athena R.,
Paterson Bradley C.,
Massa Helen M.,
Morrison Nigel A.,
Forwood Mark R.
Publication year - 2019
Publication title -
journal of orthopaedic research®
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.24262
Subject(s) - medicine , bone remodeling , in vivo , saline , bisphosphonate , bone healing , endocrinology , osteoclast , osteoporosis , chemistry , surgery , receptor , microbiology and biotechnology , biology
Stress fractures (SFx) result from repetitive cyclical loading of bone. They are frequent athletic injuries and underlie atypical femoral fractures following long‐term bisphosphonate (BP) therapy. We investigated the effect of a single PTH injection on the healing of SFx in the rat ulna. SFx was induced in 120 female Wistar rats (300 ± 15 g) during a single loading session. A single PTH (8 µg.100g −1 ) or vehicle (VEH) saline injection was administered 24 h after loading. Rats were divided into four groups ( n = 15) and ulnae were examined 1, 2, 6, or 10 weeks following SFx. Two Toluidine Blue and TRAP‐stained sections of the SFx were examined for histomorphometric analysis using Osteomeasure™ software. An increase in osteoclast number (N.Oc) and perimeter (Oc.Pm) was observed two weeks following PTH treatment ( p < 0.01). At 6 weeks, bone formation was the main activity in BMUs. At 10 weeks, the proportion of healing along the SFx line remained 50% greater in PTH groups ( p = 0.839), leading to a 43% reduction in the porosity area of BMU ( p = 0.703). The main effect of time was a significant variable along the entire SFx remodeling cycle, with significant interactions between time and treatment type affecting (N.Oc) ( p = 0.047) and (Oc.Pm) ( p = 0.002). We conclude that a single PTH injection increases osteoclastogenesis by the second week of the remodeling cycle in a SFx in vivo. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res