Single-cell RNA sequencing reveals association of aberrant placental trophoblasts and FN1 reduction in late-onset fetal growth restriction

Introduction: Fetal growth restriction (FGR) can lead to fetal mental development abnormalities, malformations, and even intrauterine death. Defects in the trophoblasts at the maternal -fetal interface may contribute to FGR. However, the impact of trophoblasts on FGR is still not well understood. Therefore, the objective of this study is to characterize the heterogeneity of placental cells at the single -cell level and investigate the role of trophoblast subtypes in the pathogenesis of FGR at the cellular and molecular levels. Methods: Single -cell RNA sequencing was performed on the maternal side of placentas from two normal pregnant women and two pregnant women with FGR. Lentivirus transfection was used to establish a FN1 knockout model in trophoblast HTR-8-Svneo cells. The effect of FN1 knockout on cell migration and invasion of HTR-8-Svneo cells was assessed through wound healing and transwell assays. Results: Nine cell types were annotated in 39,161 cells derived from single -cell RNA sequencing. The FGR group exhibited a decrease in the percentage of trophoblasts, especially in subtype of extravillous trophoblasts (EVTs). The expression of FN1 was reduced in trophoblasts and EVTs. Furthermore, the protein expression levels of FN1 in the placentas of FGR patients were significantly lower than those of normal pregnant women. The cell migration and invasion ability of HTR-8-Svneo cells were inhibited after the knockdown of FN1. Discussion: The dysregulation of the trophoblast subtype-EVTs is involved in placental dysplasia related to FGR. The association between aberrant placental trophoblasts and reduced FN1 expression may contribute to insufficient remodeling of spiral arteries and the formation of FGR.