kaolinite and Osteoarthritis--Knee

Joints are privileged compartments that enjoy increased protection against the inflammatory reactions affecting the extremities. We hypothesized that the functional characteristics of the microvasculature would contribute to the differential defensive potential of the synovial membrane.. We investigated the synovial microcirculatory reactions and compared them with those of the tibial periosteum in response to 60 min of total limb ischemia, followed by 180 min of ischemia-reperfusion (IR) in rats. Carrageenan/kaolin-induced knee monoarthritis, a neutrophil-driven synovial inflammation model, served as the positive control.. IR brought about a significant reduction in red blood cell velocity in the capillaries and increases in rolling and adherence of the neutrophil leukocytes in the postcapillary venules (intravital microscopy), in adhesion molecule expression (intercellular adhesion molecule-1 immunohistochemistry) and in xanthine oxidoreductase activity in the periosteum. These changes were also pronounced in carrageenan/kaolin-induced monoarthritis but were almost completely absent in the synovium after the IR challenge. Most importantly, even after IR and in carrageenan/kaolin monoarthritis, the synovial microcirculation was characterized by significantly greater red blood cell velocities than that in the periosteum under resting conditions.. The ischemic duration, which significantly affected the functional integrity of the periosteal microcirculation, did not bring about a marked deterioration in that of the synovial membrane, suggesting that the synovial microcirculation is less endangered to the consequences of short-term tourniquet exposure than the periosteum. The greater microcirculatory red blood cell velocities and lower IR-induced endothelial expression of intercellular adhesion molecule-1 in the synovial membrane might explain the greater resistance of this compartment to the inflammatory consequences of IR.

Topics: Animals; Carrageenan; Disease Models, Animal; Hindlimb; Intercellular Adhesion Molecule-1; Kaolin; Knee Joint; Male; Microcirculation; Neutrophils; Osteoarthritis, Knee; Periosteum; Rats; Rats, Wistar; Reperfusion Injury; Synovectomy; Synovial Membrane; Tibia; Xanthine Dehydrogenase

Nociceptive impulse activity was recorded extracellularly from single A delta and C primary afferents of the guinea pig's medial articular nerve after induction of an experimental osteoarthritis in the knee joint by partial medial menisectomy and transection of the anterior cruciate ligament (PMM+TACL). Also, the analgesic effects of intra-articular hyaluronan solutions were evaluated. Healthy, PMM+TACL operated, sham-operated (opening of the joint capsule without PMM and TACL surgery) and acutely inflamed (intra-articular kaolin-carrageenan, K-C) animals were used. The stimulus protocol consisted of torque meter-controlled, standardized innocuous and noxious inward and outward rotations of the joint. This stimulus protocol of 50 s duration was repeated every 5 min for 70 min. One day, one week and three weeks after PMM+TACL, the movement-evoked discharges of A delta articular afferents were increased significantly over values found in sham-operated animals. The discharges of C fibers were significantly augmented only one week after PMM+TACL surgery. Filling of the joint cavity with a high viscosity hyaluronan solution (hylan G-F 20, Synvisc) immediately and three days after surgery reduced significantly the enhanced nerve activity observed in joint afferent fibers one day and one week after surgery. Augmentation of movement-evoked discharges in K-C acutely inflamed knee joints was similar to that observed one week after PMM+TACL. Our results indicate that in the PMM+TACL model of osteoarthritis in guinea pigs, enhancement of nociceptive responses to joint movement was primarily associated to post-surgical inflammation. Intra-articular injection of an elastoviscous hyaluronan solution reduced the augmented nerve activity.

Topics: Adjuvants, Immunologic; Animals; Anterior Cruciate Ligament; Carrageenan; Disease Models, Animal; Evoked Potentials, Motor; Female; Guinea Pigs; Hyaluronic Acid; Injections, Intra-Articular; Joint Instability; Kaolin; Knee Joint; Male; Menisci, Tibial; Movement; Neural Conduction; Nociceptors; Osteoarthritis, Knee; Pain; Solutions