Effects of BPAF exposure on endometrial remodeling: A focus on the homeostasis of the extracellular matrix and the immune status.

Bisphenol AF (BPAF), a substitute for bisphenol A (BPA), is frequently found in the environment and daily necessities and has garnered significant attention due to its endocrine-disrupting effects. Uterus is a potential target of BPA while more evidences about BPAF are needed, especially at human-relevant levels. The aim of this study was to determine the effects of BPAF exposure with realistic human exposure pathway and dosage on the uterus, as well as to explore its molecular mechanisms through transcriptome sequencing (RNA-seq) and alternative splicing (AS) analysis. Female CD-1 mice were continuously exposed to BPAF at levels of 30, 300, and 3000 μg/kg/day for six weeks through diet. Following euthanasia, blood and uterus were collected. The results showed that mice in BPAF exposure group exhibited symptoms of endometrial hyperplasia in the uterus, characterized by thickening of the endometrium. In addition, BPAF exposure altered the levels of nine hormones, including pregnenolone, androsterone, estrone, testosterone and so on, and led to prolonged estrus cycle. Transcriptomic analysis revealed a significant disruption in the balance of extracellular matrix (ECM) and humoral immune biological processes, to which matrix metallopeptidase 7 (Mmp7) and indian hedgehog (Ihh) were identified as key genes related. Additionally, AS analysis indicated intron retention occurred in collagen type I alpha 2 chain (Col1a2), which resulted in a protein structure alternation and further led to uterine abnormality. These findings suggest that BPAF exposure at relatively low levels disturbs the balance of the extracellular matrix and the immune system in the uterus. Our study provides data reference for the toxicological evaluation and threshold setting of BPA substitute, and provides a new research paradigm for the progress of related toxicology research.