Treatment With Glycogen Synthase Kinase 3β Inhibitor Decreases Apoptotic and Autophagic Reactions in Rat Rotator Cuff Tears.

Abstract

Background:Apoptosis and autophagy are known to be correlated with the extent of damage in torn rotator cuffs, and there is no biological evidence for self-recovery or healing of the rotator cuff tear.Purpose:To establish in a rat model of partial- and full-thickness rotator cuff tears how a glycogen synthase kinase 3β (GSK-3β) inhibitor affects the expression of apoptotic and autophagic markers.Study Design:Controlled laboratory study.Methods:Twelve-week-old Sprague Dawley rats were divided into 3 groups (n = 16 per group). Group 1 acted as the control, with no treatment; group 2 received partial-thickness (right side) and full-thickness (left side) rotator cuff tears only; and group 3 received the same rotator cuff injuries, with GSK-3β inhibitor injected afterward. The tendons from each group were harvested 42 days after surgery. Evaluation of gene expression, immunohistochemistry, and TUNEL staining (terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling) were performed for the following markers: caspases 3, 8, and 9 as well as Bcl-2 (B-cell lymphoma 2); BAX (Bcl-2-associated X protein); beclin 1; p53; and GSK-3β; which represented apoptotic and autophagic reactions. Statistical analysis was performed using 1-way analysis of variance.Results:In the group 2 rats with partial- and full-thickness tears, there were significant increases in the mRNA levels (fold changes) of all 8 markers as compared with group 1 (control). All these increased markers showed significant downregulation by the GSK-3β inhibitor in partial-thickness tears. However, the response to the GSK-3β inhibitor in full-thickness tears was not as prominent as in partial-thickness tears. The number of TUNEL-positive cells in group 2 (partial, 35.08% ± 1.625% [mean ± SE]; full, 46.92% ± 1.319%) was significantly higher than in group 1 (18.02% ± 1.036%; P < .01) and group 3 (partial, 28.04% ± 2.607% [P < .01]; full, 38.97% ± 2.772% [P < .01]), and immunohistochemistry revealed increased expression of all the markers in group 2 as compared with control.Conclusion:The apoptotic and autophagic activity induced in a rat model of an acute rotator cuff tear was downregulated after treatment with a GSK-3β inhibitor, particularly with partial-thickness rotator cuff tears.Clinical Relevance:A GSK-3β inhibitor may be able to modulate deterioration in a torn rotator cuff.