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Site‐specific CGRP innervation coincides with bone formation during fracture healing and modeling: A study in rat angulated tibia
Author(s) -
Li Jian,
Kreicbergs Andris,
Bergström Jonas,
Stark Andreas,
Ahmed Mahmood
Publication year - 2007
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.20406
Subject(s) - bone healing , medicine , calcitonin gene related peptide , tibia , anatomy , reinnervation , reduction (mathematics) , fracture (geology) , neuropeptide , materials science , receptor , geometry , mathematics , composite material
Sensory neuropeptide involved in local bone turnover is known, but poorly understood. In the present study, we analyze the occurrence of neuronal CGRP during healing and modeling of straight and angular tibial fractures in 74 rats. Bone healing and modeling was assessed by radiography and reinnervation by semi‐quantitative immunohistochemistry method at fracture site between 1–12 weeks postfracture. The regenerating nerve fibers containing CGRP were observed in fracture callus as well as in close proximity to chondrocytes, with woven bone in both fractures already at week 1. Notably, it located predominantly on the concave side of angulated fracture in the manner of sprouting into bone from weeks 3 to 5 postfracture. In both fractures, fracture calluses peaked radiographically at week 3 postfracture. In angulated fracture, a reduction of 11% in callus thickness on convex side and an increase of 365% on concave side were noted from weeks 3 to 12. A 27‐fold increase in total neuronal CGRP in straight fracture and 38‐fold increases in angular fracture compared to intact bone was observed at week 3. In both types of fracture, neuronal CGRP was greater on the concave side than the convex; this difference was more pronounced in the angulated fracture. CGRP immunoreactivity clearly coincides with amount of new bone formation especially on the concave side of angulated fracture. The combined results suggest that fracture evokes an intense, localized in‐growth of new nerve fibers containing CGRP, which may prove to be a prerequisite of fracture healing and modeling. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1204–1212, 2007