Germline cells in ovarian surface epithelium of mammalians: a promising notion

Chito-oligosaccharides and macrophages have synergistic effects on improving ovarian stem cells function by regulating inflammatory factors

BACKGROUND

Chronic low-grade inflammation and ovarian germline stem cells (OGSCs) aging are important reasons for the decline of ovarian reserve function, resulting in ovarian aging and infertility. Regulation of chronic inflammation is expected to promote the proliferation and differentiation of OGSCs, which will become a key means for maintaining and remodeling ovarian function. Our previous study demonstrated that Chitosan Oligosaccharides (Cos) promoted the OGSCs proliferation and remodelled the ovarian function through improving the secretion of immune related factors,but the mechanism remains unclear, and the role of macrophages, the important source of various inflammatory mediators in the ovary needs to be further studied. In this study, we used the method of macrophages and OGSCs co-culture to observe the effect and mechanism of Cos on OGSCs, and explore what contribution macrophages give during this process. Our finding provides new drug treatment options and methods for the prevention and treatment of premature ovarian failure and infertility.

METHODS

We used the method of macrophages and OGSCs co-culture to observe the effect and mechanism of Cos on OGSCs, and explore the important contribution of macrophages in it. The immunohistochemical staining was used to locate the OGSCs in the mouse ovary. Immunofluorescent staining, RT-qPCR and ALP staining were used to identify the OGSCs. CCK-8 and western blot were used to evaluate the OGSCs proliferation. β-galactosidase(SA-β-Gal) staining and western blot were used to detect the changing of cyclin-dependent kinase inhibitor 1A(P21), P53, Recombinant Sirtuin 1(SIRT1) and Recombinant Sirtuin 3(SIRT3). The levels of immune factors IL-2, IL-10, TNF-α and TGF-β were explored by using Western blot and ELISA.

RESULTS

We found that Cos promoted OGSCs proliferation in a dose-and time-dependent manner, accompanied by IL-2, TNF-α increase and IL-10, TGF-β decrease. Mouse monocyte-macrophages Leukemia cells(RAW) can also produce the same effect as Cos. When combined with Cos, it can enhance the proliferative effect of Cos in OGSCs, and further increase IL-2, TNF-α and further decrease IL-10, TGF-β. The macrophages can enhance the proliferative effect of Cos in OGSCs is also associated with the further increase in IL-2, TNF-α and the further decrease in IL-10, TGF-β. In this study, we determined that the anti-aging genes SIRT-1 and SIRT-3 protein levels were increased by Cos and RAW respectively, whereas the senescence-associated SA-β-Gal and aging genes P21 and P53 were decreased. Cos and RAW had a protective effect on OGSCs delaying aging. Furthermore, RAW can further decrease the SA-β-Gal and aging genes P21 and P53 by Cos, and further increase SIRT1 and SIRT3 protein levels in OGSCs by Cos.

CONCLUSION

In conclusion, Cos and macrophages have synergistic effects on improving OGSCs function and delaying ovarian aging by regulating inflammatory factors.

Effects of shikonin on the development of ovarian follicles and female germline stem cells

Objective

To investigate the effects and potential mechanism of action of shikonin (SHK) on the development of ovarian follicles and female germline stem cells (FGSCs).

Methods

Female Kunming adult mice were administered SHK (0, 20 and 50 mg/kg) by oral gavage. Cultures of FGSCs were treated with SHK 32 μmol/l for 24 h. The ovarian index in mouse ovaries was calculated. Numbers of primordial, primary and atretic follicles were counted. Germline stem cell markers and apoptosis were examined. Levels of glutathione (GSH), superoxide dismutase (SOD) and reactive oxygen species (ROS) were measured.

Results

Both doses of SHK significantly decreased the ovarian index, the numbers of primordial follicles, primary follicles and antral follicles in mice. SHK significantly increased the numbers of atretic follicles and atretic corpora lutea. SHK promoted apoptosis in vivo and in vitro. SHK significantly decreased the levels of the germline stem cell markers. SHK significantly lowered GSH levels and the activity of SOD in the peripheral blood from mice, whereas SHK significantly elevated cellular ROS content in FGSCs.

Conclusions

These current results suggested that follicular development and FGSCs were suppressed by SHK through the induction of apoptosis and oxidative stress might be involved in this pathological process.

Research advances in the regulation of the putative ovarian germline stem cell niche on female germline stem cells

Stem cells are ideal seeding cells, which have the potential for self-renewal and multiple differentiation, and they play a fundamental role in maintaining homeostasis and regenerating and repairing tissue. The discovery of female germline stem cells (FGSCs) brings much hope for the postnatal renewal of oocytes and solving some female infertility problems. Ovarian function declines with increasing female age. Moreover, ovarian germline stem cell niche-aging could be the main cause of ovarian senescence, which ultimately leads to decreased follicle generation, declining female fertility, and age-related diseases, such as osteoporosis and ovarian cancer. The ovarian germline stem cell niche is the surrounding microenvironment in which FGSCs live, and it helps control the biological characteristics of FGSCs in many ways, such as nutritional supply and immunological cytokine secretion. This paper reviews the knowledge about the ovarian germline stem cell niche and its probable regulatory mechanisms on FGSCs, which provides valuable scientific information and scope for the prevention and treatment of ovarian senescence. Abbreviations: BMP: bone morphogenetic protein; Dpp: decapentaplegic; FGSC: female germline stem cell; IL, interleukin; OGSC: ovarian germline stem cells; ROS: reactive oxygen species; TGF, transforming growth factor; TNF, tumor necrosis factor.

Role of the Hedgehog Signaling Pathway in Regulating the Behavior of Germline Stem Cells

Germline stem cells (GSCs) are adult stem cells that are responsible for the production of gametes and include spermatogonial stem cells (SSCs) and ovarian germline stem cells (OGSCs). GSCs are located in a specialized microenvironment in the gonads called the niche. Many recent studies have demonstrated that multiple signals in the niche jointly regulate the proliferation and differentiation of GSCs, which is of significance for reproductive function. Previous studies have demonstrated that the hedgehog (Hh) signaling pathway participates in the proliferation and differentiation of various stem cells, including GSCs in Drosophila and male mammals. Furthermore, the discovery of mammalian OGSCs challenged the traditional opinion that the number of primary follicles is fixed in postnatal mammals, which is of significance for the reproductive ability of female mammals and the treatment of diseases related to germ cells. Meanwhile, it still remains to be determined whether the Hh signaling pathway participates in the regulation of the behavior of OGSCs. Herein, we review the current research on the role of the Hh signaling pathway in mediating the behavior of GSCs. In addition, some suggestions for future research are proposed.