Increased serum levels of fractalkine and mobilisation of CD34+CD45− endothelial progenitor cells in systemic sclerosis

Abstract

BackgroundThe disruption of endothelial homeostasis is a major determinant in the pathogenesis of systemic sclerosis (SSc) and is reflected by soluble and cellular markers of activation, injury and repair. We aimed to provide a combined assessment of endothelial markers to delineate specific profiles associated with SSc disease and its severity.MethodsWe conducted an observational, single-centre study comprising 45 patients with SSc and 41 healthy control subjects. Flow cytometry was used to quantify circulating endothelial microparticles (EMPs) and CD34+ progenitor cell subsets. Colony-forming unit-endothelial cells (CFU-ECs) were counted by culture assay. Circulating endothelial cells were enumerated using anti-CD146-based immunomagnetic separation. Blood levels of endothelin-1, vascular endothelial growth factor (VEGF) and soluble fractalkine (s-Fractalkine) were evaluated by enzyme-linked immunosorbent assay. Disease-associated markers were identified using univariate, correlation and multivariate analyses.ResultsEnhanced numbers of EMPs, CFU-ECs and non-haematopoietic CD34+CD45− endothelial progenitor cells (EPCs) were observed in patients with SSc. Patients with SSc also displayed higher serum levels of VEGF, endothelin-1 and s-Fractalkine. s-Fractalkine levels positively correlated with CD34+CD45− EPC numbers. EMPs, s-Fractalkine and endothelin-1 were independent factors associated with SSc. Patients with high CD34+CD45− EPC numbers had lower forced vital capacity values. Elevated s-Fractalkine levels were associated with disease severity, a higher frequency of pulmonary fibrosis and altered carbon monoxide diffusion.ConclusionsThis study identifies the mobilisation of CD34+CD45− EPCs and high levels of s-Fractalkine as specific features of SSc-associated vascular activation and disease severity. This signature may provide novel insights linking endothelial inflammation and defective repair processes in the pathogenesis of SSc.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-017-1271-7) contains supplementary material, which is available to authorized users.

Altered serum level of metabolic and endothelial factors in patients with systemic sclerosis

“…Two forms of fractalkine may be distinguished: a soluble in serum and bound with a membrane of endothelial cells. Both exhibit a potent chemotactic activity for lymphocytes T, monocytes and natural killer cells [11]. Furthermore, membrane-linked form mediates immune cells adhesion and migration through the vessel wall resulting in perivascular infiltration of inflammatory cells, which is an event preceding the development of fibrosis [12].…”

Anti-endothelial cell antibodies are associated with apoptotic endothelial microparticles, endothelial sloughing and decrease in angiogenic progenitors in systemic sclerosis

“…In contrast, CD34+/CD133+/ VEGFR2+ cells are designated as circulating angiogenic cells (CACs), are mostly bone marrow-derived and have potential to sustain angiogenesis but lack de novo vessel-forming activity. These cells better correlate with vascular endothelial status, have more potent vasoregenerative capacities and are functionally more potent with respect to homing and vascular repair [15,21,42,44,48,49]. It was also demonstrated that EPCs expressing Tie2 show enhanced regeneration of denuded ECs monolayers compared to those without Tie2 expression, regardless of their VEGFR2 status [50].…”

“…Gating strategy for endothelial microparticles (EMPs) and representative dot plots of analyzed populations 500 000 events or the total volume. The gating was based on previous experience following relevant literature [10,11,15,[19][20][21][22]. Lymphocytes and monocytes were excluded by CD45 positivity.…”

“…For CECs and EPCs determination we created five different panels based on relevant literature and used ap-propriate analysis gates to analyze various phenotypes [10,14,[20][21][22] (Table 2, Figure 2). According to Mancuso et al [10] and Rafii [23] EPCs were identified within the CD34+ population based on CD133+ expression and negative for pan-leukocyte marker CD45.…”

Inhibition of the Progression of Skin Inflammation, Fibrosis, and Vascular Injury by Blockade of the CX3CL1/CX3CR1 Pathway in Experimental Mouse Models of Systemic Sclerosis

“…Soluble CX 3 CL1 exhibits efficient chemoattractant activity for monocyte/macrophages, NK cells, and T cells expressing CX 3 CR1 . It has previously been reported that soluble CX 3 CL1 levels are increased in SSc patients with severe disease, diffuse skin sclerosis, interstitial lung disorders, or digital ulcers . Additionally, patients with SSc have augmented expression of CX 3 CL1 and increased CX 3 CR1+ leukocytes in fibrotic skin and lung lesions .…”