Background Endothelial dysfunction is a key feature of Systemic sclerosis (SSc). MicroRNAs (miRs) are novel post-transcriptional regulators implicated in SSc pathogenesis. MiR-34a and miR-155 are related to endothelial senescence and inflammation.
Objectives To investigate the expression of miR-34a and miR-155 in peripheral blood mononuclear cells (PBMCs) in SSc.
Methods Twenty-seven consecutive patients with Raynaud phenomenon (RP) were enrolled in this exploratory study. Patients were divided into 3 different groups: SSc patients fulfilling the 1987 ACR criteria (n=10), SSc patients fulfilling the Very Early Diagnosis Of Systemic Sclerosis (VEDOSS) criteria (n=9) and patients with primary RP (n=8). Matched healthy controls (HC) (n=7) were enrolled.
Expression of miR-34a and miR-155 was evaluated by qPCR on PBMCs isolated by gradient hystopaque technique from peripheral blood (PB) of all patients. Using HumanTargetScan cross-referenced methodology, IL-6 receptor (IL6-R) was selected as target of miR-34a and miR-155 while VEGF-RII as target of miR-155. Targets were experimentally confirmed by qPCR. VEGF, VEGF-RII, IL-6 and IL-6R plasma levels were determined by ELISA.
Results MiR-155 is overexpressed either in VEDOSS (p=0.0002) and SSc (p=0.04) patients compared to HC. MiR-34a expression is increased only in SSc compared to HC (p=0.01). Patients with primary RP did not differ according to miR-155 and miR-34a expression from HC (p>0.05).
IL-6R and VEGF-RII expression is significantly lower in SSc and VEDOSS patients compared to primary RP (p=0.03 and p=0.03). Moreover, IL-6R/miR-155 and VEGF-RII/miR-155 ratios were significantly lower in SSc and VEDOSS compared to primary RP (p<0,0001 for all comparisons). IL-6r/miR-34a ratio was significantly lower only in SSc patients compared to primary RP as well as VEDOSS (p<0,0001 for both). VEGF plasma levels were significantly higher in SSc patients compared to HC (p=0.01) as well as IL-6 plasma levels (p=0.02), whereas no significant differences were found in VEGF-RII and IL-6R plasma levels comparing the different patients' cohorts. The expression of miR-34a directly correlated with the skin score value (R=0.52, p=0.03) in both SSc and VEDOSS patients and with IL-6 plasma levels (R=0.42, p=0.01).
Dividing SSc and VEDOSS patients according to the autoimmune profile, anti-Scl70+ patients have higher expression of miR-34a compared to anti-centromere+ patients (p=0.04). Furthermore, considering SSc related clinical vascular manifestations, patients with digital ulcers have significantly higher miR-34a expression compared to patients without ulcers (p=0,01). Moreover, SSc patients with skin ulcers have lower IL-6R/miR-34a ratio compared to patients without ulcers (p=0,02).
Conclusions MiR-34a and miR-155 expression is unbalanced in SSc and VEDOSS acting on IL-6/IL-6R and VEGF/VEGF-RII pathways. This contributes to a decreased expression of IL-6R and VEGF-RII associated to the increase of IL-6 and VEGF plasma levels characterizing different disease clinical features.
Disclosure of Interest : None declared