Effects of bone marrow mesenchymal stem cells on repair and receptivity of damaged endometrium in rats

New advances in the treatment of thin endometrium

Thin endometrium (TE) is defined as a mid-luteal endometrial thickness ≤7mm. TE can affect endometrial tolerance, leading to lower embryo implantation rates and clinical pregnancy rates, and is also associated with impaired outcomes from assisted reproductive treatment. Herein, we systematically review TE causes, mechanisms, and treatments. TE pathogenesis has multiple causes, with the endometrium becoming thinner with age under hormonal influence. In addition, uterine cavity factors are important, as the inflammatory environment may affect expressions of certain genes thereby inhibiting endometrial stromal cell proliferation and promoting apoptosis. Long-term oral contraceptive use or the use of ovulation-promoting drugs are also definite factors contributing to endometrial thinning. Other patients have primary factors, for which the clinical etiology remains unknown. The main therapeutic strategies available for TE are pharmacological (including hormonal and vasoactive drugs), regenerative medicine, intrauterine infusion of growth factor-granulocyte colony-stimulating factor, autologous platelet-rich plasma, and complementary alternative therapies (including traditional Chinese herbal medicine and acupuncture). However, the associated mechanisms of action are currently unclear. Clinical scholars have proposed various approaches to improve treatment outcomes in patients with TE, and are exploring the principles of efficacy, offering potentials for novel treatments. It is hoped that this will improve TE tolerance, increase embryo implantation rates, and help more couples with infertility with effective treatments.

Impaired receptivity of thin endometrium: therapeutic potential of mesenchymal stem cells

The endometrium is a resilient and highly dynamic tissue, undergoing cyclic renewal in preparation for embryo implantation. Cyclic endometrial regeneration depends on the intact function of several cell types, including parenchymal, endothelial, and immune cells, as well as adult stem cells that can arise from endometrial or extrauterine sources. The ability of the endometrium to undergo rapid, repeated regeneration without scarring is unique to this tissue. However, if this tissue renewal process is disrupted or dysfunctional, women may present clinically with infertility due to endometrial scarring or persistent atrophic/thin endometrium. Such disorders are rate-limiting in the treatment of female infertility and in the success of in vitro fertilization because of a dearth of treatment options specifically targeting the endometrium. A growing number of studies have explored the potential of adult stem cells, including mesenchymal stem cells (MSCs), to treat women with disorders of endometrial regeneration. MSCs are multipotent adult stem cells with capacity to differentiate into cells such as adipocytes, chondrocytes, and osteoblasts. In addition to their differentiation capacity, MSCs migrate toward injured sites where they secrete bioactive factors (e.g. cytokines, chemokines, growth factors, proteins and extracellular vesicles) to aid in tissue repair. These factors modulate biological processes critical for tissue regeneration, such as angiogenesis, cell migration and immunomodulation. The MSC secretome has therefore attracted significant attention for its therapeutic potential. In the uterus, studies utilizing rodent models and limited human trials have shown a potential benefit of MSCs and the MSC secretome in treatment of endometrial infertility. This review will explore the potential of MSCs to treat women with impaired endometrial receptivity due to a thin endometrium or endometrial scarring. We will provide context supporting leveraging MSCs for this purpose by including a review of mechanisms by which the MSC secretome promotes regeneration and repair of nonreproductive tissues.

Apoptotic bodies of bone marrow mesenchymal stem cells inhibit endometrial stromal cell fibrosis by mediating the Wnt/β-catenin signaling pathway

Background

Intrauterine adhesions (IUAs) are a common illness of the uterine cavity. Endometrial fibrosis is the main pathological feature. In addition to a high recurrence rate, patients with severe IUAs have a low pregnancy rate. However, there are few effective treatments for IUAs. This study aims to confirm the influence of apoptotic bodies of bone marrow mesenchymal stem cells (BMSCs) on endometrial stromal cell fibrosis by mediating the Wnt/β-catenin signaling pathway and to provide new insight for the clinical treatment of IUAs.

Methods

Human endometrial stromal cells (HESCs) were used to establish an IUA cell model by treatment with TGF-β1, and a rat IUA model was established by the double injury method. Apoptosis of BMSCs was detected by TUNEL assays, and cell morphology was observed by the CM-DiI tracer. The morphology of apoptotic vacuoles and apoptotic bodies (ABs) was detected by TEM. We used Western blotting to detect the expression of histone H3.3, histone H2B, C3b, cyclin D1, C1QC, α-SMA, COL1A1, COL5A2, FN, CTGF, Wnt2b, c-MYC, CK-18 and VIM. The expression levels of α-SMA, COL1A1, COL5A2, FN and CTGF were detected by RT‒qPCR. The expression levels of α-SMA, COL1A1, FN and CTGF were detected by immunofluorescence. Immunohistochemistry was used to detect the expression of TGF-β, CK-18 and VIM. Flow cytometry, cell scratch assays, CCK-8 assays, and H & E and Masson staining were used to detect the cell cycle, cell migration, cell proliferation, and endometrial pathology, respectively.

Results

We found that ultraviolet light (UV) irradiation induced apoptosis of BMSCs and increased the production of ABs. TGF-β1 treatment can induce HESCs to form extracellular matrix (ECM), and aggravate cell fibrosis, and adding ABs or FH535, an inhibitor of the Wnt/β-catenin signaling pathway, can inhibit TGF-β1-induced HESC fibrosis. However, the inhibitory effect of ABs on TGF-β1-induced fibrosis of HESCs was attenuated by the addition of LiCl. In the Wnt/β-catenin signaling pathway, LiCl is an activator after coculture with TGF-β1. In vivo, IUA-induced narrowing of the uterine cavity was accompanied by intrauterine adhesions, increased deposition of collagen fibers, upregulation of TGF-β1, VIM, α-SMA, COL1A1 and COL5A2, and downregulation of CK-18. These changes in expression were reversed after treatment with ABs or FH535. When ABs and LiCl were added at the same time, the inhibitory effect of ABs on IUA fibrosis was weakened.

Conclusion

BMSC-derived ABs inhibit the fibrosis of HESCs by inhibiting the Wnt/β-catenin signaling pathway. These results provide a new direction for the clinical treatment of IUAs.

Exosomes from bone mesenchymal stem cells alleviate mifepristone-induced human endometrial stromal cell injury by inhibiting TLR3 via delivering miR-941

Objective

We aim to investigate the protective effect and underlying mechanisms of BMSCs-exo on human endometrial stromal cells (HESCs) induced by mifepristone in this study.

Methods

BMSCs-exo were extracted and then identified by transmission electron microscopy and western-blot assay. RT-PCR assay was used to determine the level of miR-941. MiR-941 mimics or inhibitor were transfected into BMSCs and the exosomes were extracted. Then, Cell activity, apoptosis rate, cell migration and invasion, as well as the expression of angiogenic proteins were determined in HESCs stimulated by mifepristone and BMSCs-exo. Next, Dual-luciferase reporting assay was used to verify the targeted binding of miR-941 to TLR3, and the TLR3 expression in HESCs was detected by RT-PCR and western-blot. Finally, TLR3 was overexpressed to evaluate the effects of miR-941 from BMSCs-exo on cell apoptosis, cell invasion and angiogenesis in HESCs induced by mifepristone.

Results

miR-941 was highly expressed in BMSCs-exo. Exosome miR-941 in BMSCs-exo inhibited the cell apoptosis, and promoted cell activity, cell migration, invasion as well as angiogenesis were also improved in HESCs induced by mifepristone. TLR3 was a target of miR-941, which was up-regulated in mifepristonetreated HESCs. We further found that miR-941 derived from BMSCs-exo down-regulated the expression of TLR3 in HESCs treated by mifepristone. In addition, TLR3 overexpression blocked the inhibition of miR-941 on mifepristone-induced cell apoptosis, as well as cell migration and angiogenesis in HESCs.

Conclusions

Thus, we concluded that BMSCs-exo has protective effect on mifepristone-induced cell damage by delivering miR-941 which targeted TLR3 and regulated cell activity, migration, and angiogenesis in HESCs.

Uterus: A Unique Stem Cell Reservoir Able to Support Cardiac Repair via Crosstalk among Uterus, Heart, and Bone Marrow

Clinical evidence suggests that the prevalence of cardiac disease is lower in premenopausal women compared to postmenopausal women and men. Although multiple factors contribute to this difference, uterine stem cells may be a major factor, as a high abundance of these cells are present in the uterus. Uterine-derived stem cells have been reported in several studies as being able to contribute to cardiac neovascularization after injury. However, our studies uniquely show the presence of an “utero-cardiac axis”, in which uterine stem cells are able to home to cardiac tissue to promote tissue repair. Additionally, we raise the possibility of a triangular relationship among the bone marrow, uterus, and heart. In this review, we discuss the exchange of stem cells across different organs, focusing on the relationship that exists between the heart, uterus, and bone marrow. We present increasing evidence for the existence of an utero-cardiac axis, in which the uterus serves as a reservoir for cardiac reparative stem cells, similar to the bone marrow. These cells, in turn, are able to migrate to the heart in response to injury to promote healing.