JOINT STRUCTURE MOLECULAR EXPRESSION ALTERATION IN A MODEL OF POST-TRAUMATIC CONTRACTURES

Abstract

Ligaments, menisci and joint capsules were obtained from experimental knees with post-traumatic joint contractures and their unoperated contralateral controls in 6 rabbits. Relative mRNA expression was altered for six of seven matrix molecules, growth factors and _-SMA (myofibroblast marker) in the joint capsule, four of seven molecules in the ACL, and two of seven molecules in the MCL and medial meniscus. The joint capsule had the most molecules with altered expression corresponding to it’s acknowledged key role in joint contracture development. Changes in molecular expression of several joint structures in post-traumatic contractures is similar to changes seen following ligament injury.

To evaluate alteration of mRNA expression in ligaments, meniscus and joint capsules in post-traumatic contractures. mRNA expression was altered most frequently in the joint capsule.

The mRNA expression alterations in the joint capsule reflect it’s significant contribution to contractures.

The right knee had a stable intraarticular fracture coupled with Kirschner wire immobilization while the left knee was not surgically manipulated. The rabbits (n=6) were sacrificed two weeks later, and the ACL, MCL, posterior joint capsule and medial meniscus were obtained from both knees. Semiquantitative RT-PCR was used to evaluate relative mRNA expression of selected matrix molecules, growth factors and _-smooth muscle actin (_-SMA), a myofibroblast marker. Glyc-eraldehyde-3-phosphate dehydrogenase, a housekeeping gene, served as a normalization. Optical density measures of the gels were used for analysis. Statistical comparisons were made with a paired t-test. Statistical significance was p< 0.05.

Relative mRNA expression was altered for six of seven molecules in the joint capsule, four of seven molecules in the ACL, and two of seven molecules for the MCL and meniscus. For the joint capsule, relative mRNA expression in the contracture capsule was 2-4x greater than the expression in the control capsules, except for TIMP one where the expression in the contracture capsule was 1/3 of the control capsules. As has been noted with other joint injuries (ligament instability), several structures in the joint display altered molecular expression as was found in this model of joint injury, post-traumatic joint contractures.

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