Novel therapeutic strategies for injured endometrium: intrauterine transplantation of menstrual blood­derived cells from infertile patients.

BACKGROUND: Menstrual blood-derived cells show regenerative potential as a mesenchymal stem cell and may therefore be a novel stem cell source of treatment for refractory infertility with injured endometrium. However, there have been few pre-clinical studies using cells from infertile patients, which need to be addressed before establishing an autologous transplantation. Herein, we aimed to investigate the therapeutic capacity of menstrual blood-derived cells from infertile patients on endometrial infertility. METHODS: We collected menstrual blood-derived cells from volunteers and infertile patients and confirmed their mesenchymal stem cell phenotype by flow cytometry and induction of tri-lineage differentiation. We compared the proliferative and paracrine capacities of these cells. Furthermore, we also investigated the regenerative potential and safety concerns of the intrauterine transplantation of infertile patient-derived cells using a mouse model with mechanically injured endometrium. RESULTS: Menstrual blood-derived cells from both infertile patients and volunteers showed phenotypic characteristics of mesenchymal stem cells. In vitro proliferative and paracrine capacities for wound healing and angiogenesis were equal for both samples. Furthermore, the transplantation of infertile patient-derived cells into uterine horns of the mouse model ameliorated endometrial thickness, prevented fibrosis, and improved fertility outcomes without any apparent complications. CONCLUSIONS: In our pre-clinical study, intrauterine transplantation of menstrual blood-derived cells may be a novel and attractive stem cell source for the curative and prophylactic therapy for injured endometrium. Further studies will be warranted for future clinical application.

Embryonic ß-Catenin Is Required for Priming of the Uterus to Implantation.

Repeated implantation failure is a major cause of infertility among healthy women. Uterine ß-catenin (CTNNB1) plays a critical role in implantation. However, the role of embryonic CTNNB1 during implantation remains unclear. We addressed this topic by analyzing mice carrying Ctnnb1-deficient (Ctnnb1Δ/Δ) embryos. Ctnnb1Δ/Δ embryos were produced by intercrossing mice bearing Ctnnb1-deficient eggs and sperms. We found that Ctnnb1Δ/Δ embryos developed to the blastocyst stage; thereafter, they were resorbed, leaving empty decidual capsules. Moreover, leukemia inhibitory factor, a uterine factor essential for implantation, was undetectable in Ctnnb1Δ/Δ blastocysts. Furthermore, CDX2, a transcription factor that determines the fate of trophectoderm cells, was not observed in Ctnnb1Δ/Δ blastocysts. Intrauterine injection with uterine fluids (from control mice) and recombinant mouse leukemia inhibitory factor proteins rescued the uterine response to Ctnnb1Δ/Δ blastocysts. These results suggest that embryonic CTNNB1 is required for the secretion of blastocyst-derived factor(s) that open the implantation window, indicating that the uterine response to implantation can be induced using supplemental materials. Therefore, our results may contribute to the discovery of a similar mechanism in humans, leading to a better understanding of the pathogenesis of repeated implantation failure.

Endometrial regeneration with endometrial epithelium: homologous orchestration with endometrial stroma as a feeder.

BACKGROUND: Thin endometrium adversely affects reproductive success rates with fertility treatment. Autologous transplantation of exogenously prepared endometrium can be a promising therapeutic option for thin endometrium; however, endometrial epithelial cells have limited expansion potential, which needs to be overcome in order to make regenerative medicine a therapeutic strategy for refractory thin endometrium. Here, we aimed to perform long-term culture of endometrial epithelial cells in vitro. METHODS: We prepared primary human endometrial epithelial cells and endometrial stromal cells and investigated whether endometrial stromal cells and human embryonic stem cell-derived feeder cells could support proliferation of endometrial epithelial cells. We also investigated whether three-dimensional culture can be achieved using thawed endometrial epithelial cells and endometrial stromal cells. RESULTS: Co-cultivation with the feeder cells dramatically increased the proliferation rate of the endometrial epithelial cells. We serially passaged the endometrial epithelial cells on mouse embryonic fibroblasts up to passage 6 for 4 months. Among the human-derived feeder cells, endometrial stromal cells exhibited the best feeder activity for proliferation of the endometrial epithelial cells. We continued to propagate the endometrial epithelial cells on endometrial stromal cells up to passage 5 for 81 days. Furthermore, endometrial epithelium and stroma, after the freeze-thaw procedure and sequential culture, were able to establish an endometrial three-dimensional model. CONCLUSIONS: We herein established a model of in vitro cultured endometrium as a potential therapeutic option for refractory thin endometrium. The three-dimensional culture model with endometrial epithelial and stromal cell orchestration via cytokines, membrane-bound molecules, extracellular matrices, and gap junction will provide a new framework for exploring the mechanisms underlying the phenomenon of implantation. Additionally, modified embryo culture, so-called "in vitro implantation", will be possible therapeutic approaches in fertility treatment.