Abstract
The laboratory rat is one of the most frequently-used animal models for studying bone biology and skeletal diseases. Here we show that a substantial portion of the cortical bone of mature rats is primary endochondral bone, consisting of a disorganized arrangement of mineralized collagen fibers. We characterize the structure and mechanical properties of the cortical bone of the rat. We show that the cortical bone consists of two architecturally distinct regions. One region, consisting of well-organized circumferential lamellae (CLB), is located in the endosteal and/or the periosteal regions while another, disorganized region, is located in the more central region of the cortex. Unexpectedly, we found that the disorganized region contains many islands of highly mineralized cartilage. Micro tomography showed different structural and compositional properties of the two primary structural elements; the CLB region has lower mineral density, lower porosity, larger but fewer blood vessels and fewer lacunae. However, no difference was found in the average lacunar volume. Additionally the mean indentation modulus of the CLB region was lower than that of the disorganized region. The islands of calcified cartilage were found to be extremely stiff, with an indentation modulus of 33.4 ± 3.5. GPa. We conclude that though the cortical bone of rats is in part lamellar, its architecture is markedly different from that of the cortical bone of humans, a fact that must be borne in mind when using the rat as a model animal for studies of human bone biology and disease.
| Original language | English |
|---|---|
| Pages (from-to) | 132-140 |
| Number of pages | 9 |
| Journal | Journal of Structural Biology |
| Volume | 183 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 2013 |
Bibliographical note
Funding Information:We wish to acknowledge support for this study from the Israel Science Foundation (Grant No 151/08). We acknowledge the Helmholtz-Zentrum Berlin for provision of synchrotron radiation beamtime at BAMline of BESSY II and would like to thank R. Britzke for assistance. P.Z. is grateful for partial funding by the BMBF through the Berlin-Brandenburg Center for Regenerative Therapies. We also wish to express our gratitude to the Max Planck Institute of colloids and interfaces, department of biomaterials, Potsdam, Germany for allowing us to use their facilities for parts of this study. The authors would like to express special thanks to Professor Peter Fratzl and Professor John Currey for most helpful discussions.
Keywords
- Cartilage islands
- Cortical bone
- Cortical bone structure
- Disorganized bone
- Endochondral bone
- Lamellar bone
- Mechanical properties
- Synchrotron based microtomography