Ultrastructural study of cells at the synovium-cartilage junction: response of synovial cells of the rat knee joint to intra-articularly injected latex particles.
To study phagocytosis in synovial cells at the synovium-cartilage junction, we used polystyrene latex spheres which induced no infiltration of inflammatory cells into the synovial tissues and observed them for a long term period. The latex bead suspension was injected into the knee joint cavities of 60 day-old male Wistar rats. The animals were then sacrificed at 1, 4, 7, 14, 28 and 56 days after the injections and their synovial tissues including the patellar cartilage were resected for subsequent examination with the transmission electron microscope. On day 1, particles were phagocytised intensively by both type A (macrophage-like) and type B (fibroblast-like) cells. Particles were more numerous in the cytoplasm of type A rather than type B cells. The number of synovial cells containing particles and the number of particles present in these cells decreased remarkably on day 4. By day 7, particles were also observed in the tendon. On day 14, particles were observed in the cytoplasm of chondrocyte. It was noted that particle density within cells began to increase again after day 28. On day 56, numerous particles were observed in type A and type B cells and moreover within the intercellular matrix. Even tendon cells actively engulfed the particles. The results of the present study suggest that both type A and B synovial cells, chondrocytes and tendon cells possess the ability to phagocytise foreign materials. Moreover, the possibility is proposed that the synovium-cartilage junction is the point where the synovial fluid exits and particles drain via the blood circulation.
Senda
H
H
Department of Orthopaedic Surgery, Nagoya City University, Japan.
Sakuma
E
E
Wada
I
I
Wang
H J
HJ
Maruyama
H
H
Matsui
N
N
D000818:Animals; D001775:Blood Circulation / Q000502:physiology; D002358:Cartilage, Articular / Q000098:blood supply; D007270:Injections, Intra-Articular; D007719:Knee Joint; D008297:Male; D008854:Microscopy, Electron; D008863:Microspheres; D010587:Phagocytosis; D051381:Rats; D017208:Rats, Wistar; D013583:Synovial Membrane / Q000502:physiology / Q000648:ultrastructure*