Decreased physical function and increased pain sensitivity in mice deficient for type IX collagen.
OBJECTIVE
In mice with Col9a1 gene inactivation (Col9a1(-/-)), osteoarthritis (OA) and intervertebral disc degeneration develop prematurely. The aim of this study was to investigate Col9a1(-/-) mice for functional and symptomatic changes that may be associated with these pathologies.


METHODS
Col9a1(-/-) and wild-type mice were investigated for reflexes, functional impairment (beam walking, pole climbing, wire hang, grip strength), sensorimotor skills (rotarod), mechanical sensitivity (von Frey hair), and thermal sensitivity (hot plate/tail flick). Gait was also analyzed to determine velocity, stride frequency, symmetry, percentage stance time, stride length, and step width. Postmortem, sera obtained from the mice were analyzed for hyaluronan, and their knees and spines were graded histologically for degeneration.


RESULTS
Col9a1(-/-) mice had compensatory gait changes, increased mechanical sensitivity, and impaired physical ability. Col9a1(-/-) mice ambulated with gaits characterized by increased percentage stance times and shorter stride lengths. These mice also had heightened mechanical sensitivity and were deficient in contact righting, wire hang, rotarod, and pole climbing tasks. Male Col9a1(-/-) mice had the highest mean serum hyaluronan levels and strong histologic evidence of cartilage erosion. Intervertebral disc degeneration was also detected, with Col9a1(-/-) mice having an increased incidence of disc tears.


CONCLUSIONS
These data describe a Col9a1(-/-) behavioral phenotype characterized by altered gait, increased mechanical sensitivity, and impaired function. These gait and functional differences suggest that Col9a1(-/-) mice select locomotive behaviors that limit joint loads. The nature and magnitude of behavioral changes were largest in male mice, which also had the greatest evidence of knee degeneration. These findings suggest that Col9a1(-/-) mice present behavioral changes consistent with anatomic signs of OA and intervertebral disc degeneration.
Allen
Kyle D
KD
Duke University Medical Center and Duke University, Durham, NC 27710, USA.
Griffin
Timothy M
TM
Rodriguiz
Ramona M
RM
Wetsel
William C
WC
Kraus
Virginia B
VB
Huebner
Janet L
JL
Boyd
Lawrence M
LM
Setton
Lori A
LA
D000818:Animals; D018771:Arthralgia / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D024081:Collagen Type IX / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005684:Gait / Q000502:physiology; D006820:Hyaluronic Acid / Q000097:blood; D007403:Intervertebral Disc / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008957:Models, Genetic; D009043:Motor Activity / Q000502:physiology*; D010003:Osteoarthritis / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology*; D012720:Severity of Illness Index
D024081:Collagen Type IX; D006820:Hyaluronic Acid