Comparative bone anatomy of commonly used laboratory animals: implications for drug discovery.

To accommodate functional demands, the composition and organization of the skeleton differ among species. Microcomputed tomography has improved our ability markedly to assess structural parameters of cortical and cancellous bone. The current study describes differences in cortical and cancellous bone structure, bone mineral density, and morphology (geometry) at the proximal femur, proximal femoral diaphysis, lumbar vertebrae, and mandible in mice, rats, rabbits, dogs, and nonhuman primates. This work enhances our understanding of bone gross and microanatomy across lab animal species and likely will enable scientists to select the most appropriate species and relevant bone sites for research involving skeleton. We evaluated the gross and microanatomy of the femora head and neck, lumbar spine, and mandible and parameters of cancellous bone, including trabecular number, thickness, plate separation, and connectivity among species. The skeletal characteristics of rabbits, including a very short femoral neck and small amounts of cancellous bone at the femoral neck, vertebral body, and mandible, seem to make this species the least desirable for preclinical research of human bone physiology; in comparison, nonhuman primates seem the most applicable for extrapolation of data to humans. However, rodent (particularly rat) models are extremely useful for conducting basic research involving the skeleton and represent reliable and affordable alternatives to dogs and nonhuman primates. Radiology and microcomputed tomography allow for reliable evaluation of bone morphology, microarchitecture, and bone mineral density in preclinical and clinical environments.