Expression of laminins and their integrin receptors in different conditions of synovial membrane and synovial membrane-like interface tissue

Objective-To demonstrate the expression of laminins (Lns) and their integri n (Int) receptors in different synovial samples and synovial membrane-like interface tissues from well fixed and aseptically loosened total hip replac ement (THR), and the potential role of Ln-Int interaction in the production of collagenases and cytokines. Methods-Immunohistochemical staining was done to detect the distribution of EHS Ln, Ln alpha 2, alpha 3, alpha 5, beta 1, beta 2 chains and Int alpha 1, alpha 2, alpha 3, alpha 6, beta 1, beta 4 subunits in different samples. Double immunofluorescence labelling was used to find colocalisation of Int alpha 6 subunit and collagenase-1/collagenase-3/TNF alpha/IL6. Results-General Ln immunoreactivity was detected in all specimens. Ln alpha 5, beta 1 and beta 2, but not a2 and a3 chains were seen in the synovial l ining and the basement membrane of blood vessels with the intensity/extent of labelling in the following rank order: rheumatoid arthritis (RA) loosene d prostheses, osteoarthritis, well fixed prostheses, traumatic knees. Among Int subunits, staining for pr was usually the strongest, followed by stain ing for Int alpha 6, alpha 1, alpha 3, and alpha 2 subunits, with the same rank order for overall expression of Lns. Int beta 4 subunit was not detect able in most of the specimens. Double labelling focused on Int a6 subunit d isclosed its frequent colocalisation with collagenases 1 and 3 and with tum our necrosis factor a and interleukin 6 in synovial lining. Conclusion-Synovial lining contains Ln-10, Ln-11, and Int alpha 6 beta 1 an d alpha 1 beta 1 receptors. In aseptic loosening of THR, interface tissue h as a similar Ln subtype and Int receptor composition as RA synovium, which confirms its "lining-like" phenotype. Synovial lining does not contain Ln-5 (alpha 3 beta 3 gamma 2) or Int alpha 6 beta 4, which are components of ep ithelial hemidesmosomes. The expression of Lns and their Int receptors is u pregulated in inflammation. The close spatial relation between Ln and its I nt receptors in synovial lining cells containing proteinases and cytokines suggests a potential role in joint destruction and prosthetic loosening.