Expression of SOX2, NANOG and OCT4 in a mouse model of lipopolysaccharide-induced acute uterine injury and intrauterine adhesions.

BACKGROUND: Activation of inflammation-mediated endometrial injury is suggested to play a decisive role in pathogenesis of intrauterine adhesion (IUA). The stem cell theory of endometrial diseases has been given a hotspot, in that human endometrial stem cells have been isolated from the endometrium. Three transcription factors that play key roles in maintaining pluripotency and self-renewal in stem cells are sex-determining region Y-box2 (SOX2), Nanog homebox (NANOG), and octamer-binding protein (OCT4), which may be responsible for the damage or repair process of uterine endometrium. We aim to investigate the expression of SOX2, NANOG and OCT4 in a mouse model of acute uterine injury induced by peritoneal injection of lipopolysaccharide (LPS) and also analyze their changes in endometrium of women with IUA.

METHODS: The mouse uterine horns were collected at 0 h, 6 h, 12 h, 18 h or 24 h after a single dose of LPS or PBS injection. Meanwhile, we recruited 19 women with IUA diagnosed by hysteroscopy and 16 disease-free women as control group. Endometrial tissue samples were collected. SOX2, NANOG, and OCT4 expression were analyzed with Quantitative Real-time Polymerase Chain Reaction and Western blotting assay.

RESULTS: In a mouse model of acute uterine injury, there was significant upregulation of NANOG at 6 h, SOX2 and OCT4 at 12 h compared with the values before injection or PBS injection. NANOG expression reached a peak at 6 h, while SOX2 and OCT4 peaked later at 12 h after LPS treatment. NANOG mRNA and protein expressions were significantly higher in endometrium of IUA patients compared to those of the control group.

CONCLUSIONS: Expression of pluripotency factors SOX2, NANOG and OCT4 increased in a mouse model of LPS-induced acute uterine injury. NANOG peaked earlier followed by the other two factors before returning to baseline levels. NANOG but not SOX2 and OCT4 expression was overexpressed in the endometrium of women with IUA. They may be involved in the formation or restoration of IUA, and their roles in pathogenesis of IUA need to be further studied.