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Phagocytosis and inflammation in crystal-induced arthritis: a synovial fluid and in vitro study


1, 2, 3, 4, 5, 6, 7, 8, 9

 

  1. Department of Medicine - DIMED, Campus Biomedico Pietro D’Abano, and Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Italy.
  2. Department of Medicine - DIMED, University of Padova, Italy.
  3. Department of Medicine - DIMED, University of Padova, Italy.
  4. Department of Medicine - DIMED, Campus Biomedico Pietro D’Abano, University of Padova, Italy.
  5. Department of Medicine - DIMED, Campus Biomedico Pietro D’Abano, University of Padova, Italy.
  6. Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Italy.
  7. Department of Medicine - DIMED, University of Padova, Italy.
  8. Department of Medicine - DIMED, University of Padova, Italy.
  9. Department of Medicine - DIMED, Campus Biomedico Pietro D’Abano, University of Padova, Italy. francesca.oliviero@unipd.it

CER13159
2021 Vol.39, N°3
PI 0494, PF 0500
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PMID: 32828141 [PubMed]

Received: 30/01/2020
Accepted : 05/05/2020
In Press: 21/07/2020
Published: 21/05/2021

Abstract

OBJECTIVES:
The aim of this study was to investigate the relationship between the degree of crystal phagocytosis and the magnitude of the local inflammatory process using fresh synovial fluid (SF) collected from patients with crystal-induced arthritis. In parallel, an in vitro model of crystal-induced inflammation was used to assess the effect of cell priming on crystal phagocytosis and IL-1ß production.
METHODS:
SF was collected from 20 patients with gout and 20 with pyrophosphate crystal-induced arthritis and examined under ordinary and polarised light microscopy for total and differential white blood cell (WBC) count and crystal search. The total phagocytosis index was determined in SF along with IL-1β, IL-8, IL-10, and TGFβ levels. The in vitro studies were performed using primed or unprimed THP-1 cells stimulated with calcium pyrophosphate (CPP) crystals, monosodium urate (MSU) crystals and/or cytochalasin D.
RESULTS:
We demonstrated that the phagocytosis index calculated on the total number of cells was independent from the inflammatory local indices such as WBC and the percentage of polymorphonuclear cells but showed a positive correlation with pro-inflammatory cytokines. By contrast, the local inflammatory indices (WBC and IL-1ß) showed a strong positive correlation with the percentage of polymorphonuclear cells with crystals internalised and a negative correlation with the percentage of mononuclear cells with crystals internalised. The in vitro study showed that phagocytosis represents a fundamental step in the induction of the inflammatory response to MSU and CPP crystals, but it also occurs in absence of cell priming.
CONCLUSIONS:
The results of this study indicate a possible role of non-inflammatory phagocytosis in limiting the acute attack of crystal-induced arthritis.

Rheumatology Article