Résumé
Liquid biopsy, using Cellsearch® technology, is a promising approach used in oncology, enabling the detection of circulating cells, as biomarkers. This analytical method has never been proposed for systemic autoimmune diseases. Since they include epithelial and/or endothelial involvements in their pathophysiology, two connective tissue disorders appeared as particularly interesting to study with liquid biopsy: primary Sjögren’s syndrome (pSS) and systemic sclerosis (SSc). The aim of this prospective pilot study, including pSS and SSc patients, was to determine counts of circulating epithelial cells (CEpC) and circulating endothelial cells (CEC) while describing both populations. Methods: twenty pSS and 20 SSc female patients (38 kept for the statistical analysis) were included. Blood samples collected were analyzed using the CellSearch® system. Samples were considered positive for epithelial and endothelial cells when at least 1 anti-cytokeratin (CK)(+), 4,6-diamidino-2-phenylindole (DAPI)(+), CD45(-) cell or1 CD105(+), DAPI(+), CD45(-) cell was detected respectively. Results: the median count of CECs in SSc patients (128 cells / 4 mL) was significantly higher than in pSS patients (17 cells/4 mL) (p < 0.001). In the SSc sub-group presenting a count above the median, the mean modified Rodnan skin score (mRSS) (11.10 + 8.20) was significantly higher than in the SSc subgroup presenting a count below the median (2.00 + 2.69) (p < 0.01). A linear relationship was also observed between CEC counts and mRSS (r = 0,59). Finally, an interesting trend was also observed regarding lung involvement, since patients with pulmonary fibrosis and/or lower pulmonary function parameters (FVC and DLCO) had higher counts of CECs, although not significant. Conclusion: the increased CEC counts in SSc patients probably reflect the shedding of affected endothelium, while the correlation with mRSS suggests that CECs could be a biomarker of SSc activity. As liquid biopsy allows a standardized determination of the number of cells, it could be a promising tool for monitoring the evolution of SSc, which requires further and larger studies to be confirmed.