[Frontiers in Bioscience E3, 1025-1033, June 1, 2011]

Stage-specific mice ovarian somatic cell is involved in primordial folliculogenesis

Ge Li, Hua Zhang, Yijing Wang, Jing Wen, Zhen Teng, Guanping Mao, Jianwei Wang, Meng Guo, Xinyi Mu, Guoliang Xia

State Key Laboratory for Agro-biotechnology, College of Biological Sciences, China Agricultural University, Beijing, 100193, P.R. China


1. Abstract
2. Introduction
3. Materials and methods
3.1. Mice
3.2. Immunohistochemistry
3.3. Plasmid DNA transfection of shRNA
3.4. Separation of OGCs and OSCs and reconstitution of PFs
3.5. PF counts
3.6. RT- and real-time PCR
3.7. Western blot analysis
4. Result
4.1. Expression of transcription factors FoxL2 and Irx3 during primordial folliculogenesis in mice OSCs
4.2. Down-regulation of FoxL2 expression moderately inhibits primordial folliculogenesis
4.3. Stage-specific OSCs are crucial for PF reconstitution in vitro
4.4. Adult OSCs cannot form PFs when co-cultured with 17.5-dpc OGCs in vitro
4.5. No spontaneous primordial folliculogenesis occurs in adult mice
5. Discussion
6. Acknowledgment
7. References


Although recent studies have shown that female germ cells can be produced from stem-cell lines in mice, whether these germ cells can interact with ovarian somatic cells (OSCs) to form primordial follicles (PFs) is still unclear. Here, we found after the PF pool is established, Irx3 and FoxL2 which were extensively expressed in the OSCs of the perinatal mouse decreased. Additionally, during primordial folliculogenesis, down-regulation of FoxL2 prevents OSCs invading germ cell cysts. Therefore, we investigated whether OSCs at different stages of folliculogenesis were able to reconstitute PFs with fetal ovarian germ cells in vitro. In this system, neither OSCs at the post-PF pool-establishment stage nor OSCs from normal or doxorubicin-treated adult mice were able to reconstitute PFs. Mice eliminated most of pre-existing PFs failed to exhibit any spontaneous regeneration of PFs. Our results suggest that OSCs can only support physiological primordial folliculogenesis during the prenatal period. OSCs lose the ability to form PFs after the establishment of the PF pool may be another reason why the PF pool is non-renewable in most adult mammals.