Chronic arthritis directly induces quantitative and qualitative bone disturbances leading to compromised biomechanical properties.
OBJECTIVE
Rheumatoid arthritis (RA) is associated with an increased risk of fragility fractures. In RA patients, the direct effect of inflammation on bone is difficult to study because their skeleton is also affected by medication with corticosteroids and other drugs as well as aging and menopause, which contribute to bone fragility. This study used an animal model of chronic arthritis to evaluate the direct impact of chronic inflammation on biomechanical properties and structure of bone.


METHODS
In the SKG mouse chronic arthritis model three point bending tests were performed on femoral bones and compression tests on vertebral bodies. Collagen structure was analysed using second-harmonic generation (SHG) imaging with a two-photon microscope, ultramorphology by scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS) and bone density using water pycnometer.


RESULTS
Arthritic bones had poor biomechanical quality compared to control bones. SHG, SEM and pycnometry disclosed variable signs of impaired collagen organization, poor trabecular architecture and low bone density.


CONCLUSIONS
Present data demonstrate for the first time that chronic inflammation per se, without confounding influence of drugs and aging, leads to impairment of bone biomechanics in terms of stiffness, ductility and ultimate strength (fracture).
Caetano-Lopes
J
J
Rheumatology Research Unit, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisbon, Portugal.
Nery
A M
AM
Henriques
R
R
Canhão
H
H
Duarte
J
J
Amaral
P M
PM
Vale
M
M
Moura
R A
RA
Pereira
P A
PA
Weinmann
P
P
Abdulghani
S
S
Souto-Carneiro
M
M
Rego
P
P
Monteiro
J
J
Sakagushi
S
S
Queiroz
M V
MV
Konttinen
Y T
YT
Graça
L
L
Vaz
M F
MF
Fonseca
J E
JE
D000818:Animals; D001168:Arthritis / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D002908:Chronic Disease; D003094:Collagen / Q000378:metabolism / Q000648:ultrastructure; D004195:Disease Models, Animal; D005260:Female; D005269:Femur / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008817:Mice, Mutant Strains; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission
D003094:Collagen