Objective: To assess sialyltransferase expression in peripheral blood mononuclear cells (PBMC) of patients with systemic sclerosis (SSc) and to correlate this expression with the clinical features of the disease.
Methods: Using a multiplex reverse transcription polymerase chain reaction (RT-PCR) method, we simultaneously measured the expression of 5 sialyltransferases (ST3Gal IV, ST3Gal III, ST3Gal I, ST3Gal II, and ST6Gal I) and of one reference housekeeping gene, Tata box binding protein (TBP), in PBMC of 28 patients with SSc and 18 healthy controls. Expression of each sialyltransferase was defined by the ratio sialyltransferase amplification product intensity/TBP amplification product intensity, and was evaluated according to the skin sclerosis extension and the presence of lung fibrosis and/or of pulmonary hypertension.
Results: ST3Gal I and ST6Gal I expressions were lower in patients with SSc than in healthy controls (median 0.48 vs 1.30, p < 0.0001, and 0.71 vs 1.96, p < 0.01, respectively). No difference was observed for ST3Gal III and ST3Gal IV expression. ST3Gal IV/ST6Gal I ratio was higher in SSc patients than in controls (0.37 vs 0.28, p = 0.03). ST3Gal II was either weakly or more often not expressed in both groups. Ten patients had isolated pulmonary hypertension. They had higher ST3Gal IV expression than patients without pulmonary hypertension (0.73 vs 0.29, p = 0.04) and a higher ST3Gal IV/ST6Gal I ratio than patients without pulmonary hypertension (1.03 vs 0.27, p = 0.03) and controls (1.03 vs 0.28, p = 0.02). No difference was found in the sialyltransferase expression and soluble E-selectin concentration according to the cutaneous sclerosis extension or the presence of lung fibrosis.
Conclusion: Sialyltransferase expression is modified in PBMC of patients with SSc compared to healthy subjects. Low ST6Gal I expression associated with normal ST3Gal IV expression, resulting in a higher ST3Gal IV/ST6Gal I ratio, suggests an enhanced expression of Sialyl-LewisX at the surface of PBMC in SSc, and therefore an active interaction between activated endothelial cells and PBMC through the binding between E-selectin and Sialyl-LewisX. This suggested that higher expression of Sialyl-LewisX concerned patients with isolated pulmonary hypertension more specifically. Binding between PBMC surface Sialyl-LewisX and activated endothelial cell E-selectin might therefore play a role in the pathogenesis of SSc-related isolated pulmonary hypertension.