Fibrin generated in the synovial fluid activates intimal cells from their apical surface: a sequential morphological study in antigen-induced arthritis.
OBJECTIVE
Fibrin deposits adhered to the synovial surface are typical of rheumatoid joints. Since fibrin appears to have a role in arthritis perpetuation our aim was to investigate how these deposits are formed and the consequences of their adhesion to the tissue.


METHODS
The appearance of fibrin aggregates either free in the synovial fluid or attached to the membrane was studied in rabbits with antigen-induced arthritis by histological techniques at different time points from challenge. In the fixed synovial membranes areas of fibrin-bound synovium were evaluated by qualitative variables to obtain a sequential profile of morphological changes.


RESULTS
Fibrin aggregates appeared from the initial stages of the disease in the synovial effusion. Later on, they were localized on the synovial surface and progressive changes were noted at the fibrin-tissue interface, ending with the invasion of the aggregates by synovial cells and their incorporation into the tissue.


CONCLUSIONS
Fibrin aggregates generated inside the joint cavity may constitute a source of activation and acquisition of invasiveness of the synovial fibroblasts, a process to explore within the perpetuating mechanisms of rheumatoid arthritis.
Sánchez-Pernaute
O
O
Inflammation Research Unit, Division of Rheumatology, Fundación Jiménez Díaz, Universidad Autónoma, Av. Reyes Católicos 2, 28040 Madrid, Spain. Osanchez@fjd.es
López-Armada
M J
MJ
Calvo
E
E
Díez-Ortego
I
I
Largo
R
R
Egido
J
J
Herrero-Beaumont
G
G
D000818:Animals; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D005337:Fibrin / Q000032:analysis*; D005340:Fibrinogen / Q000032:analysis; D005347:Fibroblasts / Q000473:pathology; D005353:Fibronectins / Q000032:analysis; D006614:Hindlimb; D007150:Immunohistochemistry; D023421:Models, Animal; D010047:Ovalbumin; D011817:Rabbits; D013582:Synovial Fluid / Q000378:metabolism*; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology; D013585:Synovitis / Q000378:metabolism*; D013997:Time Factors; D000267:Tissue Adhesions
D005353:Fibronectins; D005337:Fibrin; D005340:Fibrinogen; D010047:Ovalbumin