Regulatory T cells clonally expand and contribute to stromal cell function in fibrotic response to synthetic implants

Fibrosis plays a key role in both chronic disease progression and failure of synthetic biomaterial implants. However, the contribution of adaptive immunity to fibrotic development remains incompletely understood, particularly for regulatory T cells (Tregs). Here, we used single-cell multiomic profiling, integrating transcriptomics with T cell receptor (TCR) sequencing, to map Treg heterogeneity and clonal dynamics in a synthetic material-induced model of fibrosis. We uncovered progressive Treg clonal expansion accompanied by TCR activation signatures and an increasingly immunosuppressive phenotype along a continuous transcriptional trajectory. These Tregs suppressed immune responses and influenced extracellular matrix and vascular gene expression. Cell-cell communication inference predicted Treg-driven activation of pro-fibrotic and vasculogenic transcriptional programs in fibroblasts and endothelial cells, including Sox-family transcription factors. Functional Treg depletion increased inflammation and significantly reduced neovascularization. Together, these findings identify Treg functions in the fibro-vascular niche through stromal cell modulation, highlighting immune-stromal interactions as an important axis in fibrosis.