Rotator cuff diseases combined with cuff tear are the most common causes of pain and disability of the upper extremity. Most rotator cuff tears are of partial thickness and respond well to conservative treatment. Many authors have addressed the capacity of cuff tendon healing, but little is known of the precise healing process. The MMPs (matrix metalloproteinases) are synthesized and secreted from connective tissue cells and are known to participate in the degradation and remodeling of organs in both normal and pathologic states. Using a rat model, we studied the healing process of rotator cuff tendon tear with reference to the expression of MMP-2.

Forty Mature Sprague-Dawley rats were used in this anima study. Twenty rats were assigned to the experimental group, the other twenty to the control group. In the experimental group, a partial thickness tear of the rotator cufft tendon was made and rats were examined 4 weeks after surgery.

On gross inspection, the defects were covered with granulation tissue, and on microscopic evaluation, proliferation of fibrob-lasts and vessels at the defect demonstrated the healing capacity of rotator cuff tendon. The expression of MMP-2 was determined by immunohistochemistry and RT-PCR. Immunohistochemistry demonstrated MMP-2 positively stained cells at the defect site. Also, RT-PCR demonstrated MMP-2 expression.

These results suggest that the remodeling and healing processes of injured rotator cuff tendon are associated with the expression of MMP-2.