TNF-α/TNF-R System May Represent a Crucial Mediator of Proliferative Synovitis in Hemophilia A

• Main Authors: Mirko Manetti, Silvia Linari, Eloisa Romano, Irene Rosa, Christian Carulli, Massimo Innocenti, Marco Matucci-Cerinic, Lidia Ibba-Manneschi, Giancarlo Castaman, Daniela Melchiorre
• Format: Article
• Language: English
• Published: MDPI AG 2019-06-01
• Series: Journal of Clinical Medicine
• Subjects: hemophilic arthropathy; TNF-α; TNF receptors; fibroblast-like synoviocytes; proliferative synovitis
• Online Access: https://www.mdpi.com/2077-0383/8/7/939

Hemophilic arthropathy (HA) typically begins with proliferative synovitis that shares some similarities with inflammatory arthritides, in which the proinflammatory cytokine tumor necrosis factor (TNF)-&#945; has a crucial pathogenetic role. Inappropriate release of TNF-&#945; was shown to contribute to arthropathy development following intra-articular bleeding in hemophilic mice. Here, we were interested in determining whether systemic levels of TNF-&#945; and synovial tissue expression of the TNF-&#945;/TNF receptor (TNF-R) system could be increased and related to joint damage in hemophilia A patients with severe HA. Serum levels of TNF-&#945; measured by quantitative enzyme-linked immunosorbent assay (ELISA) were significantly increased in HA patients (<i>n</i> = 67) compared to healthy controls (<i>n</i> = 20). In HA patients, elevated TNF-&#945; levels were significantly associated with the number of hemarthroses, the grade of synovial hypertrophy, and both the clinical World Federation of Hemophilia score and ultrasound score. The expression of TNF-&#945;, TNF-R1, and TNF-R2 was strongly increased in HA synovium (<i>n</i> = 10) compared to the non-inflamed osteoarthritis control synovium (<i>n</i> = 8), as assessed by both immunohistochemistry and Western blotting. Increased protein levels of TNF-&#945;, TNF-R1, and TNF-R2 were retained in vitro by HA fibroblast-like synoviocytes (<i>n</i> = 6) with respect to osteoarthritis control fibroblast-like synoviocytes (<i>n</i> = 6). Stimulation with TNF-&#945; resulted in a significant increase in HA fibroblast-like synoviocyte proliferation quantified by the water-soluble tetrazolium (WST)-1 assay, while it had no relevant effect on osteoarthritis fibroblast-like synoviocytes. Quantification of active/cleaved caspase-3 by ELISA demonstrated that TNF-&#945; did not induce apoptosis either in HA or in osteoarthritis fibroblast-like synoviocytes. The TNF-&#945;/TNF-R system may represent a crucial mediator of proliferative synovitis and, therefore, a new attractive target for the prevention and treatment of joint damage in HA patients. Our findings provide the groundwork for further clinical investigation of anti-TNF-&#945; therapeutic feasibility in hemophiliacs.