Expression of proteoglycan mRNA in human temporomandibular joint disks in temporomandibualr disorders.

The purpose of this study was to investigate the expression of PG mRNA in human temporomandibular joint (TMJ ) disks from patients with temporomandibular disorders (TMD). Total RNA was isolated from the TMJ disks. All patients had undergone diskectomy under general anethesia. RT-PCR was performed using primers for the proteoglycans, aggrecan and decorin. On electrophoresis of a lysate of human TMJ disks, decorin was recognized in each sample. In the calcified part of the disk which we recognized visually, aggrecan was also recognized. These results suggest that TMJ disks contain decorin, and are fibrous tissue. If the disk was subjected to excessive compression in addition to tension, cells similar to chondrocytes and expression of aggrecan was induced. Calcification would be initiated in the part of the disk experiencing the increased compression.