Effects of reproduction on sexual dimorphisms in rat bone mechanics |
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| Affiliation: | 1. McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States;2. Key Laboratory of Biorheological Science and Technology, Ministry of Education and Bioengineering College, Chongqing University, Chongqing, China;3. Pennsylvania State University, Berks Campus, Reading, PA, United States;4. Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China;1. Department of Plastic Surgery, Helsinki University Central Hospital, Helsinki, Finland;2. Aalto University, School of Electrical Engineering, Department of Electrical Engineering and Automation, Espoo, Finland;1. Stanford University;2. The University of Edinburgh;1. Women''s Cancer Research Center, University of Pittsburgh Cancer Institute, Magee Womens Research Institute, Pittsburgh, PA, USA;2. Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA;3. Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA;4. Computational Biology Program, Memorial Sloan Kettering Cancer Center, New York, USA;5. Department of Dermatology, University of Florida, Gainesville, FL, USA;6. Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA;7. Department of Molecular & Cellular Biology, Baylor College of Medicine, Houston, TX, USA;8. Institute for Academic Medicine & Department of Cardiovascular Sciences, The Methodist Hospital Research Institute, Houston, TX 77030, USA;9. Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, TX, USA;10. Department of Biomedical Informatics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA;1. Department of Orthopedics, The Second Affiliated Hospital of Suzhou University, Suzhou, China;2. Department of Orthopedics, Taizhou Municipal Hospital, Taizhou, China;3. Orthopedic Department, Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, China |
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| Abstract: | Osteoporosis most commonly affects postmenopausal women. Although men are also affected, women over 65 are 6 times more likely to develop osteoporosis than men of the same age. This is largely due to accelerated bone remodeling after menopause; however, the peak bone mass attained during young adulthood also plays an important role in osteoporosis risk. Multiple studies have demonstrated sexual dimorphisms in peak bone mass, and additionally, the female skeleton is significantly altered during pregnancy/lactation. Although clinical studies suggest that a reproductive history does not increase the risk of developing postmenopausal osteoporosis, reproduction has been shown to induce long-lasting alterations in maternal bone structure and mechanics, and the effects of pregnancy and lactation on maternal peak bone quality are not well understood. This study compared the structural and mechanical properties of male, virgin female, and post-reproductive female rat bone at multiple skeletal sites and at three different ages. We found that virgin females had a larger quantity of trabecular bone with greater trabecular number and more plate-like morphology, and, relative to their body weight, had a greater cortical bone size and greater bone strength than males. Post-reproductive females had altered trabecular microarchitecture relative to virgins, which was highly similar to that of male rats, and showed similar cortical bone size and bone mechanics to virgin females. This suggests that, to compensate for future reproductive bone losses, females may start off with more trabecular bone than is mechanically necessary, which may explain the paradox that reproduction induces long-lasting changes in maternal bone without increasing postmenopausal fracture risk. |
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| Keywords: | Sexual dimorphism Reproduction Lactation Bone microarchitecture Bone mechanical properties Puberty |
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