title: Mouse genetic model for bone strength and size phenotypes: NZB/B1NJ and RF/J inbred strains.
abstract: The relationships of bone size, bone strength, and bone formation were investigated in two strains of mice, NZB/B1NJ and RF/J. Measurement of the femur midshaft size by peripheral quantitative computed tomography (pQCT) showed that the RF/J mice had a 32% greater cross-sectional area than NZB/B1NJ mice at 10 weeks of age, and a 38% greater cross-sectional area at 22 weeks of age. Body weight in the RF/J mice was 10% higher at 10 weeks but 9% lower at 22 weeks. Bone strength was determined by a three-point bending method. In agreement with the difference in bone cross-sectional area, the femurs of the RF/J mice were stronger (80% greater) and stiffer (80% greater) than the bones of the NZB/B1NJ mice. To determine whether periosteal bone formation played a role in the greater size of the RF/J mice, the mice were injected with tetracycline to label areas of new bone formation. Histomorphometrical analysis of the femur diaphysis demonstrated higher rates of periosteal bone formation (131% greater) and of periosteal forming surface (81% greater) in RF/J than in NZB/B1NJ mice. We conclude that a high rate of periosteal bone formation increases bone size and strength in RF/J mice when compared with NZB/B1NJ mice. The NZB/B1NJ and RF/J mice should be an excellent model to investigate the genes that regulate femur size and strength.
authors.affiliation: Musculoskeletal Disease Center and Department of Medicine and Biochemistry, Loma Linda University, Loma Linda, CA 92357, USA. jon.wergedal@med.va.gov
authors.forename: J E
authors.initials: JE
authors.lastname: Wergedal
authors.forename: M H-C
authors.initials: MH
authors.lastname: Sheng
authors.forename: C L
authors.initials: CL
authors.lastname: Ackert-Bicknell
authors.forename: W G
authors.initials: WG
authors.lastname: Beamer
authors.forename: D J
authors.initials: DJ
authors.lastname: Baylink
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000254:growth & development / Q000502:physiology*; D051379:Mice; D008814:Mice, Inbred NZB; D008815:Mice, Inbred Strains; D023421:Models, Animal; D010012:Osteogenesis / Q000235:genetics*; D010641:Phenotype; D013045:Species Specificity