Progenitor cells harvested from bovine follicles become endothelial cells

The Molecular Quality and Mitochondrial Activity of Porcine Cumulus-Oocyte Complexes Are Affected by Their Exposure to Three Endocrine-Active Compounds under 3D In Vitro Maturation Conditions

Thus far, the potential short- and long-term detrimental effects of a variety of environmental chemicals designated as endocrine-active compounds (EACs) have been found to interfere with histo- and anatomo-physiological functions of the reproductive system in humans and wildlife species. For those reasons, this study sought to examine whether selected EACs, which encompass the fungicide vinclozolin (Vnz), the androgenic anabolic steroid nandrolone (Ndn) and the immunosuppressant cyclosporin A (CsA), affect the developmental competence and molecular quality (MQ) of porcine cumulus–oocyte complexes (COCs) subjected to in vitro maturation (IVM) under 3D culture conditions. The COCs underwent 3D-IVM in the presence of Vnz, Ndn or CsA for 48 h. To explore whether the selected EACs induce internucleosomal DNA fragmentation in cumulus cells (CCs), TUNEL-assisted detection of late apoptotic cells was performed. Additionally, for the detailed evaluation of pro- and antiapoptotic pathways in COCs, apoptosis proteome profiler arrays were used. To determine changes in intracellular metabolism in COCs, comprehensive assessments of mitochondrial ultrastructure and activity were carried out. Moreover, the relative abundances (RAs) of mRNAs transcribed from genes that are involved in scavenging reactive oxygen species (ROS), such as SIRT3 and FOXO3, and intramitochondrial bioenergetic balance, such as ATP synthase subunit (ATP5A1), were ascertained. Finally, to investigate the extent of progression of oocyte maturation, the intraooplasmic levels of cAMP and the RAs of mRNA transcripts encoding regulatory and biocatalytic subunits of a heterodimeric meiosis-promoting factor, termed cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2), were also estimated. The obtained results provide, for the first time, strong evidence that both Vnz and Ndn decrease the developmental competence of oocytes and stimulate apoptosis processes in CCs. The present study is also the first to highlight that Vnz accelerates the maturation process in immature oocytes due to both increased ROS production and the augmented RA of the CCNB1 gene. Furthermore, Vnz was proven to trigger proapoptotic events in CCs by prompting the activity of the FOXO3 transcription factor, which regulates the mitochondrial apoptosis pathway. In turn, Ndn was shown to inhibit oocyte maturation by inducing molecular events that ultimately lead to an increase in the intraooplasmic cAMP concentration. However, due to the simultaneous enhancement of the expression of TNF-β and HSP27 proteins in CCs, Ndn might be responsible for the onset of their neoplastic transformation. Finally, our current investigation is the first to clearly demonstrate that although CsA did not interfere with the nuclear and cytoplasmic maturation of oocytes, by inducing mitophagy in CCs, it disrupted oocyte metabolism, consequently attenuating the parameters related to the MQ of COCs. Summing up, Vnz, Ndn and CsA reduced not only the processes of growth and IVM but also the MQ of porcine COCs, which might make them unsuitable for assisted reproductive technologies (ARTs) such as in vitro fertilization by either gamete co-incubation or intracytoplasmic sperm injection (ICSI) and cloning by somatic cell nuclear transfer (SCNT).

Human Granulosa Cells-Stemness Properties, Molecular Cross-Talk and Follicular Angiogenesis

The ovarian follicle is the basic functional unit of the ovary, comprising theca cells and granulosa cells (GCs). Two different types of GCs, mural GCs and cumulus cells (CCs), serve different functions during folliculogenesis. Mural GCs produce oestrogen during the follicular phase and progesterone after ovulation, while CCs surround the oocyte tightly and form the cumulus oophurus and corona radiata inner cell layer. CCs are also engaged in bi-directional metabolite exchange with the oocyte, as they form gap-junctions, which are crucial for both the oocyte’s proper maturation and GC proliferation. However, the function of both GCs and CCs is dependent on proper follicular angiogenesis. Aside from participating in complex molecular interplay with the oocyte, the ovarian follicular cells exhibit stem-like properties, characteristic of mesenchymal stem cells (MSCs). Both GCs and CCs remain under the influence of various miRNAs, and some of them may contribute to polycystic ovary syndrome (PCOS) or premature ovarian insufficiency (POI) occurrence. Considering increasing female fertility problems worldwide, it is of interest to develop new strategies enhancing assisted reproductive techniques. Therefore, it is important to carefully consider GCs as ovarian stem cells in terms of the cellular features and molecular pathways involved in their development and interactions as well as outline their possible application in translational medicine.

Stem Cells in Mammalian Gonads

Stem cells have great value in clinical application because of their ability to self-renew and their potential to differentiate into many different cell types. Mammalian gonads, including testes for males and ovaries for females, are composed of germline and somatic cells. In male mammals, spermatogonial stem cells maintain spermatogenesis which occurs continuously in adult testis. Likewise, a growing body of evidence demonstrated that female germline stem cells could be found in mammalian ovaries. Meanwhile, prior studies have shown that somatic stem cells exist in both testes and ovaries. In this chapter, we focus on mammalian gonad stem cells and discuss their characteristics as well as differentiation potentials.

Swine Granulosa Cells Show Typical Endothelial Cell Characteristics

Granulosa cells, which belong to the somatic compartment of the ovarian follicle, are actively involved as endocrine cells in follicle growth. Recently, it has been proposed that these cells are not terminally differentiated and possess multipotency. Therefore, we cultured swine granulosa cells in specific endothelial cell culture medium (EBM-2), and phenotypic and functional characteristics of endothelial cells were assessed. The collected data suggest that these endocrine cells can also behave as endothelial cells, therefore potentially contributing to follicular angiogenesis, a crucial process in follicle growth and selection.

Stem cells, progenitor cells, and lineage decisions in the ovary

Exploring stem cells in the mammalian ovary has unleashed a Pandora's box of new insights and questions. Recent evidence supports the existence of stem cells of a number of the different cell types within the ovary. The evidence for a stem cell model producing mural granulosa cells and cumulus cells is strong, despite a limited number of reports. The recent identification of a precursor granulosa cell, the gonadal ridge epithelial-like cell, is exciting and novel. The identification of female germline (oogonial) stem cells is still very new and is currently limited to just a few species. Their origins and physiological roles, if any, are unknown, and their potential to produce oocytes and contribute to follicle formation in vivo lacks robust evidence. The precursor of thecal cells remains elusive, and more compelling data are needed. Similarly, claims of very small embryonic-like cells are also preliminary. Surface epithelial cells originating from gonadal ridge epithelial-like cells and from the mesonephric epithelium at the hilum of the ovary have also been proposed. Another important issue is the role of the stroma in guiding the formation of the ovary, ovigerous cords, follicles, and surface epithelium. Immune cells may also play key roles in developmental patterning, given their critical roles in corpora lutea formation and regression. Thus, while the cellular biology of the ovary is extremely important for its major endocrine and fertility roles, there is much still to be discovered. This review draws together the current evidence and perspectives on this topic.

Apoptosis in ovarian granulosa cells of cattle: morphological features and clearance by homologous phagocytosis

Apoptosis is involved in many physiological processes of the ovary, such as recruitment of prenatal germ cells, follicular atresia, ovulation, and luteolysis. Based on the need for the involvement of phagocytic cells to achieve apoptosis clearance and that follicular atresia is triggered by weak apoptotic stimuli, we postulate that granulosa cells engullng apoptotic corpses (ACs) must carry out this macrophagic process. Since apoptosis was early defined in terms of morphological aspects, here we describe apoptosis induced by a GnRH analog (leuprolide acetate, LA) at histological level on bovine granulosa cells (primary culture, CPGB, and an established cell line, BGC-1). We observed two main types of apoptosis. In type A, the whole cell or most of it is compacted into a single large AC that is then engulfed by neighboring cells or simply detached. In type B, small portions of cells, either with or without nuclear material, become ACs that are also phagocytosed. Apoptosis and homologous phagocytosis were confirmed by TUNEL and immunocytochemistry for Bax and active caspase 3. Induction of apoptosis was significant in BGC-1 cells treated for 24 h with 100 nM LA. CPGB cells showed two types of response with different doses of LA. Fetal calf serum was necessary to find apoptosis induced by LA.

Effect of single-oocyte culture system on in vitro maturation and developmental competence in mice

Purpose

To investigate whether single-culture systems influence the quality of in vitro-matured oocytes, we examined the maturation and developmental competence of oocytes obtained by grouped in vitro maturation (IVM) or single IVM.

Methods

In vitro-matured oocytes were obtained using the culture drop (CD) method for the grouped IVM experiments, and the CD and hanging drop (HD) method for the single IVM experiments. To evaluate oocyte developmental competence, we performed in vitro fertilization and culture, and counted the number of blastocysts. To evaluate the oocyte cytoplasmic maturation, we measured the maturation promoting factor (MPF) expression levels.

Results

Oocytes cultured singly had lower maturity and developmental competence than the grouped IVM oocytes. However, enhanced oocyte fertility and blastocyst quality was achieved by the HD single IVM method. Additionally, the MPF activity level increased in all culture methods, compared to the control; however, it lagged behind nuclear maturation.

Conclusions

These results suggest that the HD method is efficient for single IVM.