Tumor necrosis factor-related apoptosis-inducing ligand expression correlates to temporomandibular joint disk degeneration

This study investigated if tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) immunohistochemical expression in human temporomandibular joint (TMJ)-degenerated disks correlates to the degree of tissue damage to elucidate the possible involvement of this apoptotic pathway in TMJ disk degeneration. Twenty-one TMJ displaced disk from 12 patients were affected by anterior disk displacement with reduction and 9 by anterior disk displacement without reduction processed immunohistochemically with TRAIL antibody. Histopathologic grading of the disk degeneration was carried out in each specimen. The mean histopathologic score of the TMJ degenerated disks was 4.77±1.26 (minimum, 2; maximum, 7). Immunolabeling for TRAIL was detected in the cytoplasm of the TMJ disk cells in every sample, although with different patterns of reactivity. The degree of TRAIL immunostaining was correlated to the histopathologic degeneration score obtained from the sample (Spearman ρ=0.617). Therefore, cell loss due to the involvement of TRAIL apoptotic pathway seems, in part, responsible for TMJ disk degeneration.