Biomechanically reduced expression of Derlin-3 is linked to the apoptosis of chondrocytes in the mandibular condylar cartilage via the endoplasmic reticulum stress pathway.

The present purpose was to investigate the involvement of Derlin-3 in the endoplasmic reticulum stress pathway-mediated apoptosis of chondrocytes in biomechanically stimulated mandibular condylar cartilage. First, fluid flow shear stress (FFSS) was applied to ATDC5 cells with or without overexpression of Derlin-3 by lentiviral transduction or silencing of Derlin-3 by siRNA transfection. Apoptosis was evaluated by TUNEL assay. Molecular markers related to the endoplasmic reticulum stress-apoptosis pathway, including GRP78, CHOP, ATF6, Caspase-12, and cleaved Caspase-3, were detected by real-time polymerase chain reaction and Western blotting. Second, the expression of proteins related to the endoplasmic reticulum stress-apoptosis pathway of the chondrocytes in mandibular condylar cartilage of mice treated with unilateral anterior crossbite (UAC) prostheses was evaluated by immunohistochemical staining and TUNEL assay. FFSS induced the endoplasmic reticulum stress-apoptosis pathway in ATDC5 cells. This apoptosis was suppressed by overexpressing Derlin-3 but was enhanced by silencing Derlin-3. UAC increased Derlin-3 expression in mandibular condylar cartilage at 1 and 3 weeks but decreased Derlin-3 expression at 7 and 11 weeks. The reduction of Derlin-3 expression by UAC was associated with the increase in the endoplasmic reticulum stress pathway-mediated apoptosis in degenerative mandibular condylar cartilage. UAC elicited changes in Derlin-3 expression and the endoplasmic reticulum stress pathway-mediated apoptosis was reversed after the removal of the prosthesis. Reduced Derlin-3 expression is associated with the biomechanically induced endoplasmic reticulum stress pathway-mediated apoptosis of chondrocytes in the mandibular condylar cartilage and could be a therapeutic target for the treatment of biomechanically stimulated cartilage degradation.