Assessment of In Vitro-Derived Germ Cells Contribution in Oogenesis in Female Mice Ovaries

Introduction: Contrary to a common belief, most mammalian females lose the ability of Germ Cell (GC) renewal and oogenesis during fetal life. Although, it has been claimed that germ line stem cells preserve oogenesis in postnatal mouse ovaries, that postnatal oogenesis keeps producing functional and sufficient GCs in the case of infertility (caused by different reasons) is doubtful. On the other hand, there are many studies showing derivation of primordial GCs and late GCs from Embryonic Stem Cells (ESCs) in vitro. This study aimed to clarify the role of ESC-derived GCs in oogenesis. Methods: Mouse ESCs via Embryoid Body (EB) formation were differentiated into GC lineage by adding Bone Morphogenetic Protein 4 (BMP4) and Retinoic Acid (RA) to the culture medium. Expression of GC markers was characterized by using Reverse Transcription Polymerase Chain Reaction (RT-PCR) and immunohistochemistry. Several 6- to 10-week-old female mice, sterilized using chemical agents, were injected with ESCs-derived GCs thorough their tail veins. To track the transplanted cells, their ovaries were immunohistochemically stained after two months. Results: Expression of GC specific markers such as mouse vasa homologue (Mvh) and Deleted in Azoospermia-Like (DAZL) indicated that GCs were successfully developed from ESCs. Interestingly, there was no evidence of homing of GCs in the transplanted ovaries after transplantation of ESCs-derived GCs.  Conclusion: Our findings do not suggest any contribution of ESC-derived GCs within the sterilized mice ovaries.