Influence of Internal Fixator Stiffness on Murine Fracture Healing: Two Types of Fracture Healing Lead to Two Distinct Cellular Events and FGF-2 Expressions

• Published in: Experimental Animals Vol. 60; no. 1; pp. 79 - 87
• Main Authors: UCHIDA, Kentaroo, UENO, Masaki, URABE, Ken, WULLSCHLEGER, Martin E., YAMAMOTO, Takeaki, SCHUETZ, Michael A., NARUSE, Kouji, GREGORY, Laura, STECK, Roland, MINEHARA, Hiroaki, ITOMAN, Moritoshi
• Format: Journal Article
• Language: English
• Published: Japan Japanese Association for Laboratory Animal Science 2011
• Subjects: Animals; Bony Callus - metabolism; Bony Callus - physiology; callus formation; Cell Proliferation; Disease Models, Animal; Femoral Fractures - metabolism; Femoral Fractures - pathology; Femoral Fractures - physiopathology; Fibroblast Growth Factor 2 - metabolism; Fibroblasts - cytology; fracture; Fracture Healing - physiology; growth factor; internal fixator; Internal Fixators; Mice; mouse; Proliferating Cell Nuclear Antigen - metabolism; Stress, Mechanical
• ISSN: 1341-1357; 1881-7122
• DOI: 10.1538/expanim.60.79

This study aimed to clarify the relationship between the mechanical environment at the fracture site and endogenous fibroblast growth factor-2 (FGF-2). We compared two types of fracture healing with different callus formations and cellular events using MouseFixTM plate fixation systems for murine fracture models. Left femoral fractures were induced in 72 ten-week-old mice and then fixed with a flexible (Group F) or rigid (Group R) Mouse FixTM plate. Mice were sacrificed on days 3, 5, 7, 10, 14, and 21. The callus volumes were measured by 3D micro-CT and tissues were histologically stained with hematoxylin & eosin or safranin-O. Sections from days 3, 5, and 7 were immunostained for FGF-2 and Proliferating Cell Nuclear Antigen (PCNA). The callus in Group F was significantly larger than that in Group R. The rigid plate allowed bone union without a marked external callus or chondrogenesis. The flexible plate formed a large external callus as a result of endochondral ossification. Fibroblastic cells in the granulation tissue on days 5 and 7 in Group F showed marked FGF-2 expression compared with Group R. Fibroblastic cells showed ongoing proliferation in granulation tissue in group F, as indicated by PCNA expression, which explained the relative granulation tissue increase in group F. There were major differences in early phase endogenous FGF-2 expression between these two fracture healing processes, due to different mechanical environments.