Article
Modified endothelial cells and rheumatoid arthritis synovial fibroblasts interactions via activin A andfollistatin
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Authors
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Iris Aykara
- Kerckhoff-Klinik GmbH, Abteilung für Rheumatologie und Klinische Immunologie, Department of Rheumatology and Clinical Immunology, University of Giessen and Kerckhoff Clinic, Bad Nauheim
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Magnus Diller
- Kerckhoff-Klinik GmBH, Abteilung für Rheumatologie und Klinische Immunologie, Department of Rheumatology and Clinical Immunology, University of Giessen and Kerckhoff Clinic, Bad Nauheim
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Stefan Rehart
- Agaplesion Markus Hospital, Department of Orthopaedics and Trauma Surgery, Frankfurt am Main
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Ulf Müller-Ladner
- Kerckhoff-Klinik GmbH, Abteilung für Rheumatologie und Klinische Immunologie, Department of Rheumatology and Clinical Immunology, University of Giessen and Kerckhoff Clinic, Bad Nauheim
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Elena Neumann
- Department of Rheumatology and Clinical Immunology, University of Giessen and Kerckhoff Clinic, Kerckhoff-Klinik GmbH, Bad Nauheim
| Published: | September 9, 2020 |
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Outline
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Introduction: The autoregulatory antiinflammatory activin/follistatin-cycle is known from the hypothalamic-pituitary-gonadal axis. Rheumatoid arthritis (RA) patients have elevated activin A levels in synovial fluid and tissue. Activin A is released during inflammation then inducing its antagonist follistatin. However, this negative feedback is not active in RA synovial fibroblasts (RASF). In RA, chronic inflammation and increased neoangiogenesis affect interaction of RASF with endothelial cells (EC). Therefore, we evaluated RASF/EC interactions under treatment with IL-1β, activin A and follistatin.
Methods: RASF were isolated from RA synovial tissue and EC (HUVEC) were commercially obtained. RASF and HUVEC were stimulated in monoculture (n=5 each), direct (n=5) or indirect coculture (n=6, HUVEC in culture inserts separated from RASF). Cultures were stimulated with activin A (15ng/ml), follistatin (500ng/ml) and/or IL-1β (1ng/ml). Activin A, follistatin, VEGF and IL-6 were measured by ELISA. Cell proliferation rates were determined by BrDU incorporation.
Results: IL-1β-induced activin A release was observed in RASF/HUVEC monoculture and direct/indirect coculture (mono: RASF 8-fold, p<0.01; HUVEC 4-fold, p<0.05; coculture direct: 5-fold, p<0.05; indirect: 4-fold, p<0.05). IL-1β-induced activin A was reduced by follistatin in HUVECs and cocultures (mono HUVEC: 12-fold, p<0.01; n=5, coculture direct: 10-fold, p<0.01, n=5; indirect: 5-fold, p<0.01) but not in RASF monoculture. IL-1β-induced IL-6 release was reduced by activin A in HUVEC and indirect coculture (mono HUVEC: 43%, p<0.05; coculture indirect: 32%, p<0.05) but not RASF and direct coculture. The IL-6-response was not altered by follistatin. IL-1β-induced VEGF was observed in RASF (89%) but not in HUVEC. VEGF-induction in RASF was increased by activin A combined with IL-1β (148%) and follistatin with IL-1β (84%). However, the induction was less prominent in coculture with HUVEC (IL-1β: 75%; activin A/IL-1β: 101%; follistatin/IL-1β: 67%). Neither Activin A nor follistatin affected proliferation of RASF, HUVEC or cocultures with/without IL-1β activation.
Conclusion: Follistatin decreased IL-1β-induced activin A release in HUVEC but not in RASF monoculture. Interestingly, the effect observed for HUVEC is dominant in direct and indirect coculture of RASF/HUVEC leading to a reduced activin A release. Activin A was able to reduce the IL-6 release of IL-1β-stimulated in HUVEC monoculture and indirect coculture but not in RASF and direct coculture. Therefore, the direct interaction of RASF with HUVEC seems to prevent the attenuating activin A effect on IL-6 release mediated in EC under inflammatory conditions and were not mediated by altered proliferation.
Disclosures: None declared
