Isolation and characterization of synovial cells from the human temporomandibular joint

Background:  The synovial tissues with temporomandibular disorders (TMDs) often show chronic inflammatory changes and the synovial cells participate in the pathogenic processes of TMDs. The synovial membrane is composed of a synovial lining layer and a connective sublining layer. The synovial lining layer is made up of two kinds of cells: macrophage‐like type A and fibroblastic type B cells. The aim of this study was to isolate and characterize synovial cells from the human temporomandibular joint (TMJ). Methods:  Synovial cells were isolated using an explant culture method. Then, we characterized the cultured synovial cells (SGA2 cells) using immunocytochemistry. Results:  SGA2 cells expressed the fibroblastic markers vimentin and prolyl 4‐hydroxylase; they also expressed laminin and heat shock protein 27, all of which are markers of type B cells. However, some cells expressed the macrophage marker CD68. These CD68‐positive cells simultaneously expressed laminin. Conclusions:  We isolated and cultured synovial type B cells from the human TMJ, and identified the presence of intermediate type synovial lining cells, having the phenotypic properties of both type A and type B cells, among the synovial lining cells.