EDA-containing fibronectin is synthesized from rheumatoid synovial fibroblast-like cells.
OBJECTIVE
To identify the cells that synthesize EDA-containing fibronectin (FN) and examine the role of EDA+FN in the pathogenesis of rheumatoid joint lesions.


METHODS
Localization of EDA+FN and c-Fos protein in rheumatoid joints was studied immunohistochemically by utilizing antibodies for EDA+FN and c-Fos. Expression of EDA+FN was studied by immunoelectron microscopy and in situ hybridization. The amount of EDA+FN was measured by enzyme-linked immunosorbent assay.


RESULTS
EDA+FN was specifically localized in the synovial lining layer of synovium with active rheumatoid arthritis (RA) (n = 17), but not in that with osteoarthritis (n = 4) or with inactive fibrous RA (n = 2). EDA+FN messenger RNA was localized in the synovial lining layer. EDA+FN was immunoelectron microscopically localized in the synovial lining fibroblast-like (type B) cells. EDA+FN was also detected at the cartilage-pannus junction and on the surface of RA cartilage. Double staining showed that EDA+FN colocalized with c-Fos protein in the rheumatoid synovial lining layer. Quantification of EDA+FN showed that it was highly concentrated in rheumatoid synovial fluids.


CONCLUSIONS
EDA+FN is synthesized by the synovial lining fibroblast-like (type B) cells in situ in rheumatoid synovium, and appears to be expressed in association with activated or transformed states of synovium.
Hino
K
K
Kobe University, Japan.
Shiozawa
S
S
Kuroki
Y
Y
Ishikawa
H
H
Shiozawa
K
K
Sekiguchi
K
K
Hirano
H
H
Sakashita
E
E
Miyashita
K
K
Chihara
K
K
D000818:Animals; D000911:Antibodies, Monoclonal; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D005347:Fibroblasts / Q000378:metabolism*; D005353:Fibronectins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D051379:Mice; D016253:Microscopy, Immunoelectron; D011817:Rabbits; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology
D000911:Antibodies, Monoclonal; D005353:Fibronectins