Formation of Primordial Follicles and Immunolocalization of PTEN, PKB and FOXO3A Proteins in the Ovaries of Fetal and Neonatal Pigs

Abstract

Abstract. The assembly of primordial follicles and subsequent development and transition of the primordial follicle to the primary follicle are critical processes in ovarian biology. In order to examine follicle formation and development in fetal and neonatal pigs, ovarian samples were obtained from a famous local breed of Chinese pigs, Erhualian pigs, ranging in age from 50 days postcoitum to 1 day postpartum in our current study. Morphological changes in the ovaries of the fetal and neonatal pigs indicated that egg nests were the earliest recognizable gamete cells. The proportion of egg nests decreased from 98.4 to 25.6% and the proportion of single follicles increased from 1.6 to 74.4% between 70 and 90 days postcoitum. The proportions of primordial follicles increased between 70 and 90 days postcoitum but decreased from 90 days postcoitum to 1 day postpartum. Our results suggested that the key stage of primordial follicle formation was between 70 and 90 days postcoitum and that the major stage of transition from primordial follicles into primary follicles was between 90 days postcoitum and 1 day postpartum. Experiments were also conducted to examine the localization of PTEN, PKB and FOXO3A proteins in the porcine ovaries by immunohistochemistry and immunoblotting. The results indicated that PTEN, PKB and FOXO3A were localized in the germ cells of egg nests, cytoplasm of oocytes and granulosa cells of follicles ranging from the primordial to secondary stages and that the staining intensity was weak in granulosa cells but strong in oocytes. The different staining patterns of PTEN, FOXO3A and PKB suggested that these proteins were expressed in a stage-and cell-specific manner during ovarian follicle formation and development in the fetal and neonatal pig. Key words: FOXO3A, Ovary, Pig, Primordial follicle, PTEN (J. Reprod. Dev. 56: [162][163][164][165][166][167][168] 2010) he mammalian ovary is a heterogeneous organ consisting of follicles and corpora lutea at various developmental stages. In the fetal ovaries, germ cells remain in clusters, which here will be referred to as egg nests [1][2][3]. Cells of a nest die, causing the nest to break into smaller nests. This process is repeated until a few individual eggs remain. At the time of birth, the mouse ovary is populated predominantly by primordial follicles, each composed of a meiotically-arrested primordial oocyte enclosed within several flattened pregranulosa cells [4][5][6]. Although many reports have indicated that primordial follicles mainly form in fetal porcine ovaries [7][8][9], the precise stage of egg nest breakdown to form primordial follicles is not clear.The oocytes in primordial follicles are thought to represent the entire pool of gametes available to a female throughout her reproductive life, although it has been suggested that there are postnatal germ line stem cells in the adult ovary [10]. Primordial follicle activation is irreversible, and is the metered process by which primordial follicles are removed from the long-lived reserve pool t...

Cell proliferation and apoptosis in the fetal and neonatal ovary of guinea pigs

“…In 1945, Bookhout found that guinea pigs initiated their ovarian follicular formation and development before birth (during pregnancy). Results of the present study indicate that primordial follicle assembly and developmental kinetics in guinea pigs are similar to embryos of humans, pigs, and sheep (McGee and Hsueh, 2000;Sawyer et al, 2002;Ding et al, 2010). This suggests that the guinea pig is also a good animal model to study early ovarian development in large animals and humans.…”

Antiandrogen flutamide affects folliculogenesis during fetal development in pigs

“…It was also shown that androgens promoted activation of primordial follicle recruitment by FOXO3 phosphorylation and its translocation into the nucleus. As FOXO3 was identified in porcine fetal and neonatal ovaries (Ding et al 2010), it is possible that FOXO3 inactivation resulting from the inhibition of androgen action was partially responsible for the delayed folliculogenesis.…”

“…Proportion of examined ovarian structures was calculated as the percentage of EN or follicles on the number of total EN and follicles per section (Ding et al 2010). The counting was performed in each field using a microscope with a !20 objective.…”

Effect of the IGF-1/PTEN/Akt/FoxO signaling pathway in the duodenal mucosa of rats subjected to water immersion and restraint stress

“…Substrate cleavage was measured with a spectrofluorometer at 405 nm and was corrected as protein content in the lysate. The activity of caspase-3 was expressed as a value of enzyme activity compared with that in the control (Wang et al, 2010).…”

“…The sample sections were mounted on slides and processed for immunohistochemical analysis, which was conducted using a protocol similar to that described in our previous reports (Ding et al, 2010). Briefly, sections were incubated overnight at room temperature with a polyclonal rabbit immunoaffinitypurified antiserum directed against IGF-1 (1:200), PTEN (1:400), total Akt (1:400), FoxO3a (1:400), and FoxO4 (1:500).…”