Endothelial nitric oxide synthase gene-deficient mice demonstrate marked retardation in postnatal bone formation, reduced bone volume, and defects in osteoblast maturation and activity.
Nitric oxide (NO) has been implicated in the local regulation of bone metabolism. However, the contribution made by specific NO synthase (NOS) enzymes is unclear. Here we show that endothelial NOS gene knockout mice (eNOS-/-) have marked abnormalities in bone formation. Histomorphometric analysis of eNOS-/- femurs showed bone volume and bone formation rate was reduced by up to 45% (P: < 0.01) and 52% (P: < 0.01), respectively. These abnormalities were prevalent in young (6 to 9 weeks old) adults but by 12 to 18 weeks bone phenotype was restored toward wild-type. Dual energy X-ray absorptiometry analysis confirmed the age-related bone abnormalities revealing significant reductions in femoral (P: < 0.05) and spinal bone mineral densities (P: < 0.01) at 8 weeks that were normalized at 12 weeks. Reduction in bone formation and volume was not related to increased osteoclast numbers or activity but rather to dysfunctional osteoblasts. Osteoblast numbers and mineralizing activity were reduced in eNOS-/- mice. In vitro, osteoblasts from calvarial explants showed retarded proliferation and differentiation (alkaline phosphatase activity and mineral deposition) that could be restored by exogenous administration of a NO donor. These cells were also unresponsive to 17ss-estradiol and had an attenuated chemotactic response to transforming growth factor-beta. In conclusion, eNOS is involved in the postnatal regulation of bone mass and lack of eNOS gene results in reduced bone formation and volume and this is related to impaired osteoblast function.
Aguirre
J
J
Department of Histochemistry, Imperial College School of Medicine, Hammersmith Campus, London, United Kingdom.
Buttery
L
L
O'Shaughnessy
M
M
Afzal
F
F
Fernandez de Marticorena
I
I
Hukkanen
M
M
Huang
P
P
MacIntyre
I
I
Polak
J
J
D015502:Absorptiometry, Photon; D000818:Animals; D015519:Bone Density; D001846:Bone Development / Q000235:genetics*; D001842:Bone and Bones / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D002633:Chemotaxis / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005838:Genotype; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D019001:Nitric Oxide Synthase / Q000172:deficiency* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1
C110881:S-nitro-N-acetylpenicillamine; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D004958:Estradiol; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D010396:Penicillamine