A Combination of Bone Marrow Mesenchymal Stem Cells with Estrogen Improves Rabbit Endometrial Injury Repair by a Mechanism Involved in an Activation of Wnt/β-catenin Signaling

Abstract Background: Although the effect of bone marrow mesenchymal stem cells (BMSCs) combined with estrogen therapy in the repair of endometrial injury has been confirmed, its underlying molecular mechanism in intrauterine adhesion (IUA) remains unclear. In this study, we aim to investigate the effect and involvement of a combination of BMSCs with estrogen in restoration of injured endometrium by applying a rabbit endometrial injury model. Method: BMSCs were isolated and labeled with PKH26 fluorescent dye. The IUA animal model was generated by a dual damage method of mechanical curettage and lipopolysaccharide infection. Rabbits were randomly assigned to the following 5 groups: sham operation group, IUA model group, E2 treatment group, BMSCs treatment group, and BMSCs combined with E2 treatment group. Bilateral uterus were obtained at different time points for the further study. HE and Masson staining were used to evaluate the number of endometrial glands and the degree of fibrosis. The expression of fibrosis and EMT related markers were observed by Immunohistochemical, immunofluorescence staining and Western blot. The expression of core molecules in the Wnt/β-catenin signaling pathway was examined by Western blot.Results: In the present study, it is found that PKH26 fluorescent dye can successfully label BMSCs and track the distribution and differentiation of transplanted BMSCs. BMSCs differentiated into endometrial epithelial cells and mainly located around the endometrial glands and extracellular matrix at 3 or 5 days post-transplantation, while BMSCs primarily differentiated into endometrial stromal cells at 7 days after orthotopic transplantation. Furthermore, after combined treatment of BMSCs and estrogen, the number of glands increased significantly, and the area of fibrosis reduced evidently, accompanied by a downregulation of mesenchymal markers and upregulation of epithelial markers when compared with each single treatment group. The expression levels of core molecules in the Wnt/β-catenin signaling pathway were higher in the BMSCs+E2 group than in the other treatment groups. Conclusions: Our study demonstrates that BMSCs combined with estrogen can improve the repair after endometrial injury by promoting the proliferation of endometrial epithelial cells and inhibiting EMT and endometrial fibrosis. This combined effect is achieved in part through activation of the Wnt/β-catenin signaling pathway.