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According to classical knowledge of reproductive biology, in the ovary of female mammals there is a limited number of oocytes and there is no possibility of renewal if the oocytes are lost due to disease or injury. However, in recent years, the results of some studies on renewal and formation of oocytes and follicles in the adult mammalian ovary have led to the questioning of this opinion. The aim of our study is to demonstrate the presence of putative germline and pluripotent stem cells in the adult mouse ovary and their differentiation potential into germ and somatic cells. In ovary tissues and cells harvested from pre-differentiation step, the expression of pluripotent and germline stem cell markers was analysed by reverse transcription-polymerase chain reaction (RT-PCR), immunofluorescence staining and western blotting. Embryoid bodies that formed in this step were analysed using immunofluorescence staining and transmission electron microscopy. Ovarian stem cells were induced to differentiate into oocyte, osteoblast, chondrocyte and neural cells. Besides morphological observation, differentiated cells were analysed by RT-PCR, histochemical and immunofluorescence staining. Expression of germline and pluripotent stem cell markers both in mRNA and at the protein level were detected in the pre-differentiated cells and ovary tissues. As a result of the differentiation process, the formation of oocyte-like cells, osteoblasts, chondrocytes and neural cells was observed and characteristics of differentiated cells were confirmed using the methods mentioned above. Our study results revealed that the adult mouse ovary contains germline and pluripotent stem cells with the capacity to differentiate into oocyte-like cells, osteoblasts, chondrocytes and neural cells.

Human chorionic gonadotropin (hCG) is a luteotropic hormone that promotes the survival and steroidogenic activity of corpus luteum (CL) by acting through luteinizing hormone receptors (LHRs) expressed on luteinized theca and granulosa cells (GCs). Therefore, it is used to support luteal phase in in vitro fertilization (IVF) cycles to improve clinical pregnancy rates and prevent miscarriage. However, the molecular mechanism underlying this action of hCG is not well characterized. To address this question, we designed an in vitro translational research study on the luteal GCs obtained from 58 IVF patients. hCG treatment at different concentrations and time points activated c-Jun N-terminal kinase (JNK) pathway and significantly increased its endogenous kinase activity along with upregulated expression of steroidogenic enzymes (steroidogenic acute regulatory protein (stAR), 3β-Hydroxysteroid dehydrogenase (3β-HSD)) in a dose-dependent manner in the luteal GCs. As a result, in vitro P production of the cells was significantly enhanced after hCG. When JNK pathway was inhibited pharmacologically or knocked-down with small interfering RNA luteal function was compromised, P4 production was declined along with the expression of stAR and 3β-HSD in the cells. Further, hCG treatment after JNK inhibition failed to correct the luteal defect and promote P4 output. Similar to hCG, luteinizing hormone (LH) treatment improved luteal function as well and this action of LH was associated with JNK activation in the luteal GCs. These findings could be important from the perspective of CL biology and luteal phase in human because we for the first time identify a critical role for JNK signaling pathway downstream LHR activation by hCG/LH in luteal GCs. Summary Sentence JNK signaling pathway plays a central role in the upregulated expression of the steroidogenic enzymes StAR and 3b-HSD and augmented progesterone production by hCG/LH in human luteal granulosa cells.

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The possible presence of oocyte and granulosa cells originated from stem cells in the adult mammalian ovaries was claimed by some studies which will lead to major changes in reproductive biology and infertility treatments. Purpose of this research is to investigate the possible existence and the location of the potential stem cells in mouse ovaries. In this study, the ovaries from 2-week (pre-puberty) and 8-week (adult) old BALB-C mice were used. For the investigation of the presence of possible stem cells, the expression profiles of three well known stem cell markers, Oct-4, Nanog and Sox2 were determined in the ovaries of two different age groups by real time quantitative RT-PCR (qRT-PCR). Protein expression levels and their localization in the ovary cells were immunohistochemically evaluated on fresh-frozen ovary tissue sections by using monoclonal antibodies specific to Sox2, Nanog and Oct-4. The gene expression levels of Oct-4 and Nanog were found to be significantly differentiated between 2-week old and 8-week old mice whereas no significant difference was observed in the expression level of Sox2 between two age groups. Immunohistochemistry results showed the presence of both Sox2 and Oct-4 protein in the cytoplasm of ovarian epithelial cells, granulosa cells, oocytes and theca cells. Nanog protein was observed only in the nucleus of the oocytes and furthermore the expression of Nanog was higher in eight weeks old samples compared to two weeks old ones according to qRT-PCR results. These results suggest for the first time that Nanog protein is expressed both in adult and pre-puberty mouse ovaries and locate at the nucleus of the oocytes and to the best of our knowledge this is the first study that shows the differential expression of Oct-4, Nanog and Sox2 in pre-puberty and adult mouse ovaries by qRT-PCR. Collectively, our results may suggest that both pre-puberty and adult mice ovaries accommodate cells carrying stem cell features