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Fracture healing in mice lacking Pten in osteoblasts: a micro-computed tomography image-based analysis of the mechanical properties of the femur.
J Biomech. 2015 Jan 21; 48(2):310-7.JB

Abstract

In the United States, approximately eight million osseous fractures are reported annually, of which 5-10% fail to create a bony union. Osteoblast-specific deletion of the gene Pten in mice has been found to stimulate bone growth and accelerate fracture healing. Healing rates at four weeks increased in femurs from Pten osteoblast conditional knock-out mice (Pten-CKO) compared to wild-type mice (WT) of the same genetic strain as measured by an increase in mechanical stiffness and failure load in four-point bending tests. Preceding mechanical testing, each femur was imaged using a Skyscan 1172 micro-computed tomography (μCT) scanner (Skyscan, Kontich, Belgium). The present study used µCT image-based analysis to test the hypothesis that the increased femoral fracture force and stiffness in Pten-CKO were due to greater section properties with the same effective material properties as that of the WT. The second moment of area and section modulus were computed in ImageJ 1.46 (National Institutes of Health) and used to predict the effective flexural modulus and the stress at failure for fourteen pairs of intact and callus WT and twelve pairs of intact and callus Pten-CKO femurs. For callus and intact femurs, the failure stress and tissue mineral density of the Pten-CKO and WT were not different; however, the section properties of the Pten-CKO were more than twice as large 28 days post-fracture. It was therefore concluded, when the gene Pten was conditionally knocked-out in osteoblasts, the resulting increased bending stiffness and force to fracture were due to increased section properties.

Authors+Show Affiliations

University of Wisconsin-Madison, Department of Mechanical Engineering, Madison, WI, USA.University of Wisconsin-Madison, Department of Mechanical Engineering, Madison, WI, USA; Universidad Adolfo Ibáñez, Facultad de Ingeniería y Ciencias, Viña del Mar, Chile.University of Wisconsin-Madison, Department of Mechanical Engineering, Madison, WI, USA.Van Andel Research Institute, Grand Rapids, MI, USA.Van Andel Research Institute, Grand Rapids, MI, USA.University of Wisconsin-Madison, Department of Mechanical Engineering, Madison, WI, USA. Electronic address: ploeg@engr.wisc.edu.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

25498366

Citation

Collins, Caitlyn J., et al. "Fracture Healing in Mice Lacking Pten in Osteoblasts: a Micro-computed Tomography Image-based Analysis of the Mechanical Properties of the Femur." Journal of Biomechanics, vol. 48, no. 2, 2015, pp. 310-7.
Collins CJ, Vivanco JF, Sokn SA, et al. Fracture healing in mice lacking Pten in osteoblasts: a micro-computed tomography image-based analysis of the mechanical properties of the femur. J Biomech. 2015;48(2):310-7.
Collins, C. J., Vivanco, J. F., Sokn, S. A., Williams, B. O., Burgers, T. A., & Ploeg, H. L. (2015). Fracture healing in mice lacking Pten in osteoblasts: a micro-computed tomography image-based analysis of the mechanical properties of the femur. Journal of Biomechanics, 48(2), 310-7. https://doi.org/10.1016/j.jbiomech.2014.11.028
Collins CJ, et al. Fracture Healing in Mice Lacking Pten in Osteoblasts: a Micro-computed Tomography Image-based Analysis of the Mechanical Properties of the Femur. J Biomech. 2015 Jan 21;48(2):310-7. PubMed PMID: 25498366.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Fracture healing in mice lacking Pten in osteoblasts: a micro-computed tomography image-based analysis of the mechanical properties of the femur. AU - Collins,Caitlyn J, AU - Vivanco,Juan F, AU - Sokn,Scott A, AU - Williams,Bart O, AU - Burgers,Travis A, AU - Ploeg,Heidi-Lynn, Y1 - 2014/11/28/ PY - 2014/03/01/received PY - 2014/11/17/revised PY - 2014/11/20/accepted PY - 2014/12/16/entrez PY - 2014/12/17/pubmed PY - 2015/5/23/medline KW - Four-point bend testing KW - Fracture healing KW - Mechanical properties KW - Micro computed tomography image-based analysis KW - Mouse femur KW - Pten gene KW - Section properties SP - 310 EP - 7 JF - Journal of biomechanics JO - J Biomech VL - 48 IS - 2 N2 - In the United States, approximately eight million osseous fractures are reported annually, of which 5-10% fail to create a bony union. Osteoblast-specific deletion of the gene Pten in mice has been found to stimulate bone growth and accelerate fracture healing. Healing rates at four weeks increased in femurs from Pten osteoblast conditional knock-out mice (Pten-CKO) compared to wild-type mice (WT) of the same genetic strain as measured by an increase in mechanical stiffness and failure load in four-point bending tests. Preceding mechanical testing, each femur was imaged using a Skyscan 1172 micro-computed tomography (μCT) scanner (Skyscan, Kontich, Belgium). The present study used µCT image-based analysis to test the hypothesis that the increased femoral fracture force and stiffness in Pten-CKO were due to greater section properties with the same effective material properties as that of the WT. The second moment of area and section modulus were computed in ImageJ 1.46 (National Institutes of Health) and used to predict the effective flexural modulus and the stress at failure for fourteen pairs of intact and callus WT and twelve pairs of intact and callus Pten-CKO femurs. For callus and intact femurs, the failure stress and tissue mineral density of the Pten-CKO and WT were not different; however, the section properties of the Pten-CKO were more than twice as large 28 days post-fracture. It was therefore concluded, when the gene Pten was conditionally knocked-out in osteoblasts, the resulting increased bending stiffness and force to fracture were due to increased section properties. SN - 1873-2380 UR - https://www.unboundmedicine.com/medline/citation/25498366/Fracture_healing_in_mice_lacking_Pten_in_osteoblasts:_a_micro_computed_tomography_image_based_analysis_of_the_mechanical_properties_of_the_femur_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0021-9290(14)00616-2 DB - PRIME DP - Unbound Medicine ER -