The synergistic effect of bone marrow mesenchymal stem cells combined with estrogen on repairing rabbit endometrial injury and inhibiting EMT via Wnt/β-catenin pathway

Background: Intrauterine adhesion (IUA) caused by endometrial injury is one of the main causes of female infertility. Bone marrow mesenchymal stem cells (BMSCs) transplantation and estrogen therapy are both promising methods to improve injury. This paper aims to exploring their synergistic effect on repairing rabbit thin endometrium and the possible underlying mechanism of restoring the endometrium morphology. Methods The IUA animal model was established by a dual damage method of mechanical curettage and lipopolysaccharide infection. Seventy-five female rabbits were randomly assigned to five groups: sham operation group, IUA model group, BMSCs group, estrogen group and BMSCs plus estrogen group. The number of endometrial glands and the degree of fibrosis were observed by H&E and Masson staining respectively. The expression in markers of fibrosis and EMT were detected using western blotting and immunohistochemistry staining. Additionally, we investigated the distribution and differentiation of PKH26-labeled BMSCs using CK7 as an epithelial marker and Vimentin as a stromal marker by immunofluorescence staining. Finally, western blotting is taken to determine the protein expression of core molecules of Wnt/β-catenin pathway in uterine tissues. Results The number of endometrial glands was significantly increased, whereas the area of endometrial fibrosis was decreased in all the treatment groups, with the best effects observed in the BMSCs plus estrogen group. Moreover, downregulated expression of fibrosis markers (fibronectin, CollagenI, a-SMA) and interstitial markers (ZEB1, Vimentin, N-cadherin), as well as upregulated E-cadherin expression were found in the combined group. Further studies showed that the PKH26-labeled BMSCs cells appeared in the endometrial glands and extracellular matrix area when orthotopic transplantation into the uterine cavity. And the abundance of CK7 was increased and Vimentin expression was decreased in the combination treatment group. Additionally, the protein levels of β-catenin, Axin2, C-myc, CycinE of Wnt/β-catenin pathway were higher in the BMSCs combined with estrogen group than in the other treatment groups. Conclusion Our study demonstrates that the synergistic effect of BMSCs combined with estrogen therapy in the treatment of injured endometrium is likely to be achieved by inhibiting EMT and activating the Wnt/β-catenin pathway, and represent a promising target for the female infertility.