title: Grizzly bears (Ursus arctos horribilis) and black bears (Ursus americanus) prevent trabecular bone loss during disuse (hibernation).
abstract: Disuse typically causes an imbalance in bone formation and bone resorption, leading to losses of cortical and trabecular bone. In contrast, bears maintain balanced intracortical remodeling and prevent cortical bone loss during disuse (hibernation). Trabecular bone, however, is more detrimentally affected than cortical bone in other animal models of disuse. Here we investigated the effects of hibernation on bone remodeling, architectural properties, and mineral density of grizzly bear (Ursus arctos horribilis) and black bear (Ursus americanus) trabecular bone in several skeletal locations. There were no differences in bone volume fraction or tissue mineral density between hibernating and active bears or between pre- and post-hibernation bears in the ilium, distal femur, or calcaneus. Though indices of cellular activity level (mineral apposition rate, osteoid thickness) decreased, trabecular bone resorption and formation indices remained balanced in hibernating grizzly bears. These data suggest that bears prevent bone loss during disuse by maintaining a balance between bone formation and bone resorption, which consequently preserves bone structure and strength. Further investigation of bone metabolism in hibernating bears may lead to the translation of mechanisms preventing disuse-induced bone loss in bears into novel treatments for osteoporosis.
authors.affiliation: Department of Biomedical Engineering, Michigan Technological University, 309 Minerals and Materials Engineering Building, 1400 Townsend Drive, Houghton, MI 49931, USA.
authors.forename: Meghan E
authors.initials: ME
authors.lastname: McGee-Lawrence
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Wojda
authors.forename: Lindsay N
authors.initials: LN
authors.lastname: Barlow
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Drummer
authors.forename: Alesha B
authors.initials: AB
authors.lastname: Castillo
authors.forename: Oran
authors.initials: O
authors.lastname: Kennedy
authors.forename: Keith W
authors.initials: KW
authors.lastname: Condon
authors.forename: Janene
authors.initials: J
authors.lastname: Auger
authors.forename: Hal L
authors.initials: HL
authors.lastname: Black
authors.forename: O Lynne
authors.initials: OL
authors.lastname: Nelson
authors.forename: Charles T
authors.initials: CT
authors.lastname: Robbins
authors.forename: Seth W
authors.initials: SW
authors.lastname: Donahue
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology; D001862:Bone Resorption / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D006605:Hibernation / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009043:Motor Activity / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology; D012756:Sheep; D001503:Ursidae / Q000502:physiology*; D055114:X-Ray Microtomography
references.citation: Lancet. 2000 May 6;355(9215):1607-11
references.pmid: 10821365
references.citation: Virchows Arch. 1997 Dec;431(6):449-52
references.pmid: 9428933
references.citation: J Anat. 2007 Feb;210(2):160-9
references.pmid: 17261138
references.citation: Calcif Tissue Int. 1992 Sep;51(3):189-94
references.pmid: 1422963
references.citation: J Bone Miner Res. 2004 Jun;19(6):1006-12
references.pmid: 15125798
references.citation: Eur Spine J. 2007 Jun;16(6):771-6
references.pmid: 16830131
references.citation: J Bone Miner Res. 1998 Oct;13(10):1594-601
references.pmid: 9783548
references.citation: FASEB J. 1990 Jan;4(1):47-54
references.pmid: 2295378
references.citation: Osteoporos Int. 2004 Mar;15(3):180-9
references.pmid: 14722626
references.citation: J Bone Miner Res. 1987 Dec;2(6):595-610
references.pmid: 3455637
references.citation: Cell. 2008 Nov 28;135(5):825-37
references.pmid: 19041748
references.citation: Bone. 2005 Sep;37(3):287-95
references.pmid: 16006205
references.citation: J Med Invest. 2001 Aug;48(3-4):147-56
references.pmid: 11694954
references.citation: J Bone Joint Surg Am. 1996 Oct;78(10):1523-33
references.pmid: 8876580
references.citation: J Orthop Res. 2002 May;20(3):615-21
references.pmid: 12038639
references.citation: J Appl Physiol (1985). 1996 Jan;80(1):198-202
references.pmid: 8847302
references.citation: Bone. 1995 Oct;17(4 Suppl):225S-232S
references.pmid: 8579921
references.citation: J Bone Miner Res. 1990 Aug;5(8):843-50
references.pmid: 2239368
references.citation: J Appl Physiol (1985). 2004 Jul;97(1):119-29
references.pmid: 15220316
references.citation: Kidney Int Suppl. 1978 Jun;(8):S177-9
references.pmid: 278887
references.citation: J Biomech. 2005 Nov;38(11):2143-50
references.pmid: 16115638
references.citation: J Biomech. 2004 Oct;37(10):1513-20
references.pmid: 15336926
references.citation: Bone. 1989;10(3):187-94
references.pmid: 2803854
references.citation: Am J Phys Anthropol. 2000 Nov;113(3):389-410
references.pmid: 11042540
references.citation: Bone. 2008 Feb;42(2):396-404
references.pmid: 18037367
references.citation: J Exp Biol. 2006 May;209(Pt 9):1630-8
references.pmid: 16621944
references.citation: Am J Physiol. 1999 Jan;276(1 Pt 1):E62-9
references.pmid: 9886951
references.citation: Aviat Space Environ Med. 1995 Aug;66(8):770-4
references.pmid: 7487811
references.citation: Clin Chem. 1998 Mar;44(3):578-85
references.pmid: 9510865
references.citation: Bone. 2006 Dec;39(6):1196-202
references.pmid: 16920051
references.citation: J Bone Miner Res. 2004 Jan;19(1):48-55
references.pmid: 14753736
references.citation: Bone. 1997 Jun;20(6):547-51
references.pmid: 9177869
references.citation: BMC Vet Res. 2008 Jan 25;4:3
references.pmid: 18221526
references.citation: Am J Physiol. 1973 Feb;224(2):491-6
references.pmid: 4686505
references.citation: Bone. 1997 Nov;21(5):419-23
references.pmid: 9356735
references.citation: Clin Orthop Relat Res. 1990 Jun;(255):301-9
references.pmid: 2189632
references.citation: Mayo Clin Proc. 1973 Oct;48(10):733-7
references.pmid: 4745546
references.citation: Calcif Tissue Int. 1995 Sep;57(3):224-8
references.pmid: 8574941
references.citation: Aviat Space Environ Med. 2000 Jun;71(6):586-92
references.pmid: 10870817
references.citation: Calcif Tissue Int. 1994 Mar;54(3):231-6
references.pmid: 8055372