A rat model of temporomandibular joint pain with histopathologic modifications.
OBJECTIVE
To develop a rat model of temporomandibular joint (TMJ) pain and to characterize in it the development and temporal response of behavioral hypersensitivity as well as to evaluate if and to what extent a loading protocol is associated with histological changes in the TMJ consistent with osteoarthritic pathology.


METHODS
A novel rat model of TMJ pain was developed using a noninvasive, mechanical loading protocol. Rats were exposed to steady mouth-opening for 7 days (2 N force, 1 hour/day), and mechanical hyperalgesia (increased pain response) was measured during the loading period and for 14 days thereafter. Histological modifications in the joint cartilage were also evaluated. Outcomes for the mouth-opening exposure were compared to age-matched controls. Thresholds for evoking responses were compared using a ranked ANOVA with repeated measures.


RESULTS
Increased mechanical hypersensitivity in the temporomandibular region developed during daily loading and persisted even after the termination of the loading protocol. Histologic characterization revealed thinning of the cartilaginous structures of the joint and irregular zonal cellular arrangements in the condylar cartilage of rats subjected to the daily loading protocol.


CONCLUSIONS
The injury model presented here is the first to demonstrate mechanically-induced behavioral hypersensitivity accompanied by osteoarthritic pathology in the TMJ.
Nicoll
Steven B
SB
Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Hee
Christopher K
CK
Davis
Martin B
MB
Winkelstein
Beth A
BA
D000818:Animals; D001522:Behavior, Animal; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000473:pathology; D004396:Coloring Agents; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000209:etiology / Q000503:physiopathology / Q000523:psychology; D008297:Male; D008335:Mandibular Condyle / Q000473:pathology; D010003:Osteoarthritis / Q000473:pathology* / Q000503:physiopathology; D010146:Pain / Q000503:physiopathology / Q000523:psychology; D017288:Pain Threshold / Q000502:physiology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013704:Temporomandibular Joint / Q000293:injuries; D019224:Temporomandibular Joint Disc / Q000473:pathology; D013705:Temporomandibular Joint Disorders / Q000473:pathology* / Q000503:physiopathology / Q000523:psychology; D013997:Time Factors; D014110:Touch
D004396:Coloring Agents