title: A novel Saa3-promoter reporter distinguishes inflammatory subtypes in experimental arthritis and human synovial fibroblasts.
abstract: OBJECTIVE
  To evaluate the applicability of a lentiviral (LV) serum amyloid A3 (Saa3)-promoter luciferase (Luc) reporter for assessing inflammation in experimental arthritis, synovial fibroblasts (SF) from osteoarthritis (OA) and rheumatoid arthritis (RA) patients.
  
  
  METHODS
  In mice, synovium was transduced in vivo by cholesterol optimised LV, and two flares of acute joint inflammation were induced by injection of streptococcal cell wall (SCW) material into the knee-joint cavity. The time course of synovial inflammation was assessed using ex vivo luciferase assays, and histology. Uptake of (99m)technetium (Tc) was used to assess oedema. SF (n=12) of RA and OA patients were stratified by hierarchical clustering of whole genome expression profiles. Relative Saa3-promoter responses were determined in cytokine- or toll-like receptor (TLR)-stimulated SF subgroups.
  
  
  RESULTS
  In vivo, the Saa3-promoter reporter activity was strongly upregulated at 1 and 2 days after the first and second SCW challenge. The Saa3-promoter activities during acute inflammation correlated with Tc uptake measurements but were more sensitive and able to respond to the ongoing synovitis in the chronic phase of SCW arthritis. Molecular stratification defined two inflammatory SF subtypes, unrelated to disease classification. Relative Saa3-promoter responses to interleukin 1β, tumour necrosis factor α and TLR4 agonist were significantly increased in OA/RA SF with a high compared to a low inflammatory profile subtype. Serum stimulation of the Saa3-promoter reporter cell-line could distinguish between healthy and RA patients.
  
  
  CONCLUSIONS
  The Saa3-promoter reporter demonstrates a robust and feasible tool for assessing the course and severity of experimental arthritis and for distinguishing molecularly distinct inflammatory SF subtypes from a heterogeneous patient population.
authors.affiliation: Rheumatology Research and Advanced Therapeutics, Department of Rheumatology, Radboud University Nijmegen Medical Centre, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Geurts
authors.forename: Eline A
authors.initials: EA
authors.lastname: Vermeij
authors.forename: Dirk
authors.initials: D
authors.lastname: Pohlers
authors.forename: Onno J
authors.initials: OJ
authors.lastname: Arntz
authors.forename: Raimund W
authors.initials: RW
authors.lastname: Kinne
authors.forename: Wim B
authors.initials: WB
authors.lastname: van den Berg
authors.forename: Fons A J
authors.initials: FA
authors.lastname: van de Loo
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D001169:Arthritis, Experimental / Q000175:diagnosis* / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000175:diagnosis; D002784:Cholesterol / Q000494:pharmacology; D016000:Cluster Analysis; D003937:Diagnosis, Differential; D004305:Dose-Response Relationship, Drug; D005240:Feasibility Studies; D005347:Fibroblasts / Q000473:pathology; D020869:Gene Expression Profiling / Q000379:methods; D005822:Genetic Vectors; D006801:Humans; D016086:Lentivirus / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D010003:Osteoarthritis / Q000175:diagnosis; D011401:Promoter Regions, Genetic; D000685:Serum Amyloid A Protein / Q000235:genetics*; D013583:Synovial Membrane / Q000473:pathology*; D013667:Technetium; D014161:Transduction, Genetic
chemical_list: C489625:SAA3P protein, human; D000685:Serum Amyloid A Protein; D013667:Technetium; D002784:Cholesterol