Endogenous glucocorticoids decrease skeletal angiogenesis, vascularity, hydration, and strength in aged mice.
Aging or glucocorticoid excess decrease bone strength more than bone mass in humans and mice, but an explanation for this mismatch remains elusive. We report that aging in C57BL/6 mice was associated with an increase in adrenal production of glucocorticoids as well as bone expression of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1, the enzyme that activates glucocorticoids. Aging also decreased the volume of the bone vasculature and solute transport from the peripheral circulation to the lacunar-canalicular system. The same changes were reproduced by pharmacologic hyperglucocorticoidism. Furthermore, mice in which osteoblasts and osteocytes were shielded from glucocorticoids via cell-specific transgenic expression of 11beta-HSD type 2, the enzyme that inactivates glucocorticoids, were protected from the adverse effects of aging on osteoblast and osteocyte apoptosis, bone formation rate and microarchitecture, crystallinity, vasculature volume, interstitial fluid, and strength. In addition, glucocorticoids suppressed angiogenesis in fetal metatarsals and hypoxia inducible factor-1alpha transcription and vascular endothelial growth factor production in osteoblasts and osteocytes. These results, together with the evidence that dehydration of bone decreases strength, reveal that endogenous glucocorticoids increase skeletal fragility in old age as a result of cell autonomous effects on osteoblasts and osteocytes leading to interconnected decrements in bone angiogenesis, vasculature volume, and osteocyte-lacunar-canalicular fluid.
Weinstein
Robert S
RS
Center for Osteoporosis and Metabolic Bone Diseases, Department of Internal Medicine, Central Arkansas Veterans Healthcare System, University of Arkansas for Medical Sciences, Little Rock, USA. weinsteinroberts@uams.edu
Wan
Chao
C
Liu
Qinglan
Q
Wang
Ying
Y
Almeida
Maria
M
O'Brien
Charles A
CA
Thostenson
Jeff
J
Roberson
Paula K
PK
Boskey
Adele L
AL
Clemens
Thomas L
TL
Manolagas
Stavros C
SC
D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2 / Q000378:metabolism; D000375:Aging; D000818:Animals; D015519:Bone Density / Q000187:drug effects; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018919:Neovascularization, Physiologic; D013314:Stress, Mechanical; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014867:Water / Q000378:metabolism*
D005938:Glucocorticoids; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; D014867:Water; D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2