Decreased bone strength in HLA-B27 transgenic rat model of spondyloarthropathy.
OBJECTIVE
To investigate the nature of osteopenia/osteoporosis in spondyloarthropathy, an inflammatory disorder, using the HLA-B27 transgenic rat model.


METHODS
HLA-B27 transgenic rats were housed individually and sacrificed at the peak of their disease (8-month-old). The spine and femurs were removed and stored in saline at -20 degrees C until analysis. The bone structure and strength were determined using a micro-computed tomography (micro-CT) device (Scanco Medical) and mechanical testing (Instron 5543). Vertebral bodies and femurs were scanned to determine trabecular structural properties in terms of bone volume (BV/TV), trabecular thickness, and spacing. After scanning, the mid-shaft femurs were subjected to a 3-point bending test (along anterior-posterior direction), the femoral necks were tested in bending, and the vertebral bodies (L4) were tested in compression. Structural (ultimate/yield load, stiffness) and apparent material (ultimate/yield stress, modulus) strength parameters were then determined.


RESULTS
The majority of the bone structural and strength parameters were significantly lower (P < 0.05) in the HLA-B27 transgenic rats as compared with control littermates. Micro-CT data suggested that the transgenic animals had lower BV/TV and trabecular thickness in their vertebral bodies. The poor trabecular structure observed in HLA-B27 rats is also indicative of the poor biomechanical strength properties in the vertebral bodies as well.


CONCLUSIONS
The HLA-B27 transgenic rats develop bone fragility similar to that seen in spondyloarthropathy and may be an important model for the study of osteoporosis in spondyloarthropathy.
Akhter
M P
MP
Medicine, Creighton University, Suite 4820, 610N, 30th Street, Omaha, NE 68131, USA. akhtermp@creighton.edu
Jung
L K L
LK
D000818:Animals; D030801:Animals, Genetically Modified; D019245:Compressive Strength; D004195:Disease Models, Animal; D004548:Elasticity; D005269:Femur / Q000503:physiopathology; D015796:HLA-B27 Antigen / Q000235:genetics*; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D010024:Osteoporosis / Q000209:etiology* / Q000235:genetics / Q000503:physiopathology; D051381:Rats; D025242:Spondylarthropathies / Q000150:complications* / Q000235:genetics / Q000503:physiopathology; D013314:Stress, Mechanical
D015796:HLA-B27 Antigen