Single-nucleus RNA sequencing decodes abnormal cell-collagen communication in a sheep endometrial fibrosis model

Endometrial fibrosis in sheep reduces reproductive performance with elusive therapeutic targets. The fibrotic endometrium is a complex ecosystem with heterogeneous cells and their interactions. The molecular characterization of key cells and the mechanisms of these interactions are unclear. To uncover the key molecular features of sheep endometrial fibrosis tissue, we used single-nucleus RNA sequencing to profile the transcriptional characterization of sheep endometrial cells from both normal and fibrotic tissues, aiming to clarify the mechanisms of fibrosis development. Histomorphological analysis revealed significant collagen deposition in fibrotic endometrial tissue. The transcription atlas of sheep endometrial cells was created, identifying eight main endometrial cell types. Key findings include the abnormal expression of collagen-related genes in fibrotic cells and the identification of endothelial cells and fibroblasts as major contributors to fibrogenesis with aberrant receptor-ligand interactions involving collagen-related genes. Fibroblasts had a tendency to differentiate into myofibroblasts in fibroblast-mediated fibrosis progression. In vitro experiments demonstrated the role of fibroblasts in fibroblast activation through the PERK/eIF2α/CHOP stress pathway. Additionally, fibrosis disturbs the immune microenvironment. This study highlights that high collagen gene expression in injured endometrial cells leads to abnormal tissue repair and fibrosis, offering valuable insights for understanding endometrial fibrosis at the single-cell level.