title: Circulating endothelial progenitor cells in systemic sclerosis: association with disease severity.
abstract: BACKGROUND
  Heterogeneous data have been reported regarding the detection and number of circulating endothelial progenitor cells (EPCs) in systemic sclerosis (SSc).
  
  
  OBJECTIVE
  We investigated the number of circulating EPCs using recent recommendations and we quantified their late outgrowth in patients with SSc and healthy controls.
  
  
  METHODS
  EPCs, defined as Lin-/7AAD-/CD34+/CD133+/VEGFR-2+ cells, were quantified in 50 patients with SSc (mean age: 55 (16) years, disease duration: 9 (9) years) and 26 controls (mean age: 53 (19) years) by cell sorting/flow cytometry and by counting late outgrowth colony-forming units (CFU).
  
  
  RESULTS
  Patients with SSc displayed higher circulating EPC counts than controls (median 86 (5-282) vs 49 (5-275)) EPCs for 1 million Lin- mononuclear cells; p = 0.01). Lower EPC counts were associated with the higher Medsger's severity score (p = 0.01) and with the presence of past and/or current digital ulcers (p = 0.026). There was no difference for the number of late outgrowth EPC-CFUs between patients with SSc and controls in cell culture evaluation. The formation of colonies was associated with higher levels of circulating EPCs (p = 0.02) and the number of colonies correlated with levels of EPCs (R = 0.73, p = 0.0004), validating our combination of fluorescence-activated cell sorter surface markers.
  
  
  CONCLUSIONS
  We quantified circulating EPCs with an accurate combination of markers herein validated. Our data demonstrate increased circulating EPC levels in SSc, supporting their mobilisation from bone marrow. Furthermore, the subset of patients with digital vascular lesions and high severity score displayed low EPC counts, suggesting increased homing at this stage. The predictive value of this biomarker now warrants further evaluation.
authors.affiliation: Paris Descartes University, Rheumatology A Department, Cochin Hospital, APHP, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Avouac
authors.forename: F
authors.initials: F
authors.lastname: Juin
authors.forename: J
authors.initials: J
authors.lastname: Wipff
authors.forename: P O
authors.initials: PO
authors.lastname: Couraud
authors.forename: G
authors.initials: G
authors.lastname: Chiocchia
authors.forename: A
authors.initials: A
authors.lastname: Kahan
authors.forename: C
authors.initials: C
authors.lastname: Boileau
authors.forename: G
authors.initials: G
authors.lastname: Uzan
authors.forename: Y
authors.initials: Y
authors.lastname: Allanore
mesh_terms: D000328:Adult; D000368:Aged; D002469:Cell Separation / Q000379:methods; D003114:Colony-Forming Units Assay; D004730:Endothelium, Vascular / Q000473:pathology*; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012595:Scleroderma, Systemic / Q000097:blood*; D012720:Severity of Illness Index; D013234:Stem Cells / Q000473:pathology*