Single-cell transcriptomics identifies regulatory T cell heterogeneity in gestational diabetes mellitus

<h4>Background</h4>Gestational diabetes mellitus (GDM) is a common pregnancy complication associated with hyperglycaemia, chronic inflammation and adverse health outcomes. Regulatory T cells (Tregs) are thought to contribute to GDM due to their role in suppressing inflammation. However, whether specific Treg subsets are transcriptionally dysregulated in patients with GDM remains unclear.<h4>Methods</h4>To investigate Treg transcriptional variation in GDM, we applied single-cell RNA sequencing to Tregs and CD4 + T cells isolated from the blood of 13 healthy pregnant women and 10 female patients with GDM.<h4>Results</h4>We observed no significant differences in Treg cluster proportions with disease status, however, Memory CD4 + T cells were more abundant in patients diagnosed with GDM, substantiated by mass cytometry. We report Treg subsets altered in GDM, including naive Tregs with reduced expression of AP-1 transcription factor subunits and effector Tregs with increased signalling of genes associated with angiogenesis. Expression levels of genes dysregulated in GDM Tregs were informative of GDM status in pseudobulk, placental and whole blood mRNA from independent cohorts. TXNIP, which regulates glucose levels, emerged as the most significant discriminator of GDM status from bulk mRNA.<h4>Conclusions</h4>This study uncovers transcriptional differences of Treg cell subsets from GDM patients and transcriptional markers informative of GDM status.