Endothelial protein C receptor associated invasiveness of rheumatoid synovial fibroblasts is driven by group V secretory phospholipase A<sub>2</sub> — The Association Specialists
  1. Schedule
  2. Posters - Monday
  3. Endothelial protein C receptor associated invasiveness of rheumatoid synovial fibroblasts is driven by group V secretory phospholipase A2

Endothelial protein C receptor associated invasiveness of rheumatoid synovial fibroblasts is driven by group V secretory phospholipase A2 (391)

Kelly McKelvey 1 , Chris Jackson 1 , Kaitlin Shen 1 , Juan Li 1 , Yee-Ka Agnes Chan 1 , Vicky Hatzis 1 , Lyn March 2 , Christopher Little 3 , Michael Tonkin 4 , Meilang Xue 1
  1. Sutton Arthritis Research Laboratory, Kolling Institute of Medical Research, University of Sydney at Royal North Shore Hospital, St Leonards, NSW, Australia
  2. Department of Rheumatology, Royal North Shore Hospital, St Leonards, NSW, Australia
  3. Raymond Purves Research Laboratory, Kolling Institue of Medical Research, University of Sydney at Royal North Shore Hospital, St Leonards, NSW, Australia
  4. Department of Hand Surgery & Peripheral Nerve Surgery, Royal North Shore Hospital, St Leonards, NSW, Australia

Introduction: Rheumatoid synovial fibroblasts (RASF) mediate the joint inflammation and destruction of rheumatoid arthritis (RA). Endothelial protein C receptor (EPCR) is a specific receptor for the natural anticoagulant activated protein C (APC). It mediates the cytoprotective properties of APC and is expressed in rheumatoid synovial tissue. The aim of this study was to investigate the expression and function of EPCR on RASF.

Methods: Human SF were isolated from RA or osteoarthritis (OA) synovial tissues and treated with EPCR and group V secretory phospholipase A2 (sPLA2V) siRNAs, recombinant APC, tumour necrosis factor (TNF)-α, sPLA2V with or without co-incubation with human articular cartilage. Cell viability and migration/invasion of RASF were measured by MTT and collagen gel migration/invasion assays, respectively, and cartilage degradation by 1, 9-dimethylmethylene blue (DMMB) assay. Expression of cytokines, EPCR, MAP kinase, nuclear factor (NF)-κB and cadherin-11 were detected by enzyme-linked immunosorbent assay, western blot or immunostaining.

Results: EPCR was expressed by OASF and RASF but markedly increased in RASF. Inhibition of EPCR by siRNA or blocking antibody reduced cell viability, invasion and cartilage degradation by >30%. Inflammatory mediators interleukin (IL)-1β, cadherin-11 and/or NF-κB were significantly reduced in both control and TNF-α stimulated conditions. Expression and/or activation of MAP kinase ERK, p38, JNK, were also markedly decreased in cells transfected with EPCR siRNA. Further analysis revealed that sPLA2V was expressed by RASF and co-localised with EPCR. Blocking endogenous sPLA2V increased APC binding to RASF and recombinant sPLA2V pre-incubation blocked APC binding to RASF. Suppression of sPLA2V by siRNA reduced cell viability and cartilage degradation and addition of recombinant sPLA2V increased cartilage degradation by ~30%. 

Conclusion: EPCR is overexpressed by RASF and suppressing EPCR inhibits the invasion, inflammation and cartilage degradation by RASF. Contrary to its cytoprotective role in other settings, this function of EPCR is likely driven by sPLA2V.