Objectives To investigate the role of X chromosomal inactivation (XCI) in systemic sclerosis (SSc) and its effects on forkhead box P3 (Foxp3) expression in T regulatory cells (Tregs).
Methods 217 women with SSc and 107 healthy women (controls) were included in the study. From these subjects, DNA was isolated from total peripheral blood mononuclear cells, plasmacytoid dendritic cells, T cells, B cells, myeloid dendritic cells and monocytes after magnetic bead separation. All samples were assessed for skewed XCI patterns with the Human Androgen Receptor Assay. The outcome was assessed by linear regression. CD4+CD25+ cells were then isolated and intracellular Foxp3 expression was assessed by flow cytometry.
Results Skewing was not associated with increased age in patients with SSc, in contrast to the control population (r=0.45, p<0.0001). Taking this into account, a significantly higher frequency of skewed XCI was found in patients with SSc compared with controls (p=0.001). No difference in skewing was observed between the immune cell subsets. In addition, a higher concentration of Foxp3+ cells exhibiting a lower Foxp3 mean fluorescence intensity was found in the patients with SSc, with profound XCI skewing (both p<0.001) associated with less efficient suppressive activity (p=0.012).
Conclusions Skewed XCI plays a role in susceptibility to SSc, is not restricted and influences Foxp3 expression and the suppressive capacity of Tregs.
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TRDJR and AWL contributed equally to this study
Funding TRDJR was sponsored by an unrestricted grant from the Dutch Arthritis Foundation and is a VENI and VIDI laureate from the Dutch Association of Research (NWO).
Competing interests None.
Ethics approval This study was conducted with the approval of the Radboud University Nijmegen Medical Center and the Boston University Medical Center and both patients and controls gave written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.