title: Androgen receptor disruption increases the osteogenic response to mechanical loading in male mice.
abstract: In female mice, estrogen receptor-alpha (ERalpha) mediates the anabolic response of bone to mechanical loading. Whether ERalpha plays a similar role in the male skeleton and to what extent androgens and androgen receptor (AR) affect this response in males remain unaddressed. Therefore, we studied the adaptive response of in vivo ulna loading in AR-ERalpha knockout (KO) mice and corresponding male and female single KO and wild-type (WT) littermates using dynamic histomorphometry and immunohistochemistry. Additionally, cultured bone cells from WT and AR KO mice were subjected to mechanical loading by pulsating fluid flow in the presence or absence of testosterone. In contrast with female mice, ERalpha inactivation in male mice had no effect on the response to loading. Interestingly, loading induced significantly more periosteal bone formation in AR KO (+320%) and AR-ERalpha KO mice (+256%) compared with male WT mice (+114%) and had a stronger inhibitory effect on SOST/sclerostin expression in AR KO versus WT mice. In accordance, the fluid flow-induced nitric oxide production was higher in the absence of testosterone in bone cells from WT but not AR KO mice. In conclusion, AR but not ERalpha activation limits the osteogenic response to loading in male mice possibly via an effect on WNT signaling.
authors.affiliation: Center for Musculoskeletal Research, Department of Experimental Medicine, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: Callewaert
authors.forename: Astrid
authors.initials: A
authors.lastname: Bakker
authors.forename: Jan
authors.initials: J
authors.lastname: Schrooten
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
authors.forename: Guido
authors.initials: G
authors.lastname: Verhoeven
authors.forename: Steven
authors.initials: S
authors.lastname: Boonen
authors.forename: Dirk
authors.initials: D
authors.lastname: Vanderschueren
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D001842:Bone and Bones / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D005260:Female; D005819:Genetic Markers; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000096:biosynthesis; D010012:Osteogenesis / Q000187:drug effects; D010521:Periosteum / Q000187:drug effects / Q000378:metabolism; D011944:Receptors, Androgen / Q000172:deficiency / Q000378:metabolism*; D013314:Stress, Mechanical; D013739:Testosterone / Q000494:pharmacology; D016474:Weight-Bearing
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D011944:Receptors, Androgen; C486030:Sost protein, mouse; D009569:Nitric Oxide; D013739:Testosterone; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2