Makoto Orisaka

Oocyte-granulosa-theca cell interactions during preantral follicular development

The preantral-early antral follicle transition is the penultimate stage of follicular development in terms of gonadotropin dependence and follicle destiny (growth versus atresia). Follicular growth during this period is tightly regulated by oocyte-granulosa-theca cell interactions. Formation of the theca cell layer is a key event that occurs during this transitional stage. Granulosal factor(s) stimulates the recruitment of theca cells from cortical stromal cells, while oocyte-derived growth differentiation factor-9 (GDF-9) is involved in the differentiation of theca cells during this early stage of follicular development. The preantral to early antral transition is most susceptible to follicular atresia. GDF-9 promotes follicular survival and growth during transition from preantral stage to early antral stage by suppressing granulosa cell apoptosis and follicular atresia. GDF-9 also enhances preantral follicle growth by up-regulating theca cell androgen production. Thecal factor(s) promotes granulosa cell proliferation and suppress granulosa cell apoptosis. Understanding the intraovarian mechanisms in the regulation of follicular growth and atresia during this stage may be of clinical significance in the selection of the best quality germ cells for assisted reproduction. In addition, since certain ovarian dysfunctions, such as polycystic ovarian syndrome and gonadotropin poor-responsiveness, are consequences of dysregulated follicle growth at this transitional stage, understanding the molecular and cellular mechanisms in the control of follicular development during the preantral-early antral transition may provide important insight into the pathophysiology and rational treatment of these conditions.

Decreased pregnancy rate is linked to abnormal uterine peristalsis caused by intramural fibroids

BACKGROUND The relationship between fibroids and infertility remains an unsolved question, and management of intramural fibroids is controversial. During the implantation phase, uterine peristalsis is dramatically reduced, which is thought to facilitate embryo implantation. Our aims were to evaluate (i) the occurrence and frequency of uterine peristalsis in infertile women with intramural fibroids and (ii) whether the presence of uterine peristalsis decreases the pregnancy rate. METHODS Ninety-five infertile patients with uterine fibroids were examined using magnetic resonance imaging (MRI). Inclusion criteria were as follows: (i) presence of intramural fibroids, excluding submucosal type; (ii) no other significant infertility factors (excluding endometriosis); and (iii) regular menstrual cycles, and MRI performed at the time of implantation (luteal phase day 5-9). The frequency of junctional zone movement was evaluated using cine-mode-display MRI. After MRI, patients underwent infertility treatment for up to 4 months, and the pregnancy rate was evaluated prospectively. RESULTS Fifty-one patients fulfilled the inclusion criteria, and 29 (57%) and 22 (43%) patients were assigned to the low (0 or 1 time/3 min) or high frequency (≥ 2 times/3 min) uterine peristalsis group, respectively. Endometriosis incidence was the same in both groups. Ten out of the 29 patients (34%) in the low-frequency group achieved pregnancy, compared with none of the 22 patients (0%) in the high-frequency group (P< 0.005). Comparing pregnant and non-pregnant cases, 4 of 10 patients (40%) and 9 of 41 patients (22%), respectively, had endometriosis (not significant). CONCLUSIONS A higher frequency of uterine peristalsis during the mid-luteal phase might be one of the causes of infertility associated with intramural-type fibroids.

Growth Differentiation Factor 9 Promotes Rat Preantral Follicle Growth by Up-Regulating Follicular Androgen Biosynthesis

The transition from preantral to early antral stage is the penultimate stage of ovarian follicular development in terms of gonadotropin dependence and follicle destiny. Although oocyte-somatic cell communication is important in early follicular development, our knowledge of the precise role of the oocyte-derived growth differentiation factor (GDF)-9 during preantral follicle growth is incomplete. We examined whether and by what means oocyte-derived GDF-9 controls follicular development and steroidogenesis during the preantral to early antral transition, by a combination of in vitro gene manipulation (i.e. intraoocyte injection of GDF-9 antisense oligos) and preantral follicle culture. Intraoocyte injection of GDF-9 antisense suppressed rat preantral follicle growth in vitro, whereas GDF-9 enhanced follicular development. GDF-9 augmented testosterone production in preantral follicles. GDF-9 antisense suppressed androgen production and CYP17A1 mRNA expression in cultured follicles, a response attenuated by exogenous GDF-9. The nonaromatizable androgen 5alpha-dihydrotestosterone rescued the follicular growth arrest caused by GDF-9 down-regulation. The specific androgen receptor antagonist flutamide suppressed GDF-9-induced preantral follicle growth in vitro. The data suggest that GDF-9 plays an important role in promoting preantral follicle growth by up-regulating follicular androgen biosynthesis. GDF-9 is essential for CYP17A1 expression during follicular development from the preantral to the early antral stage.

PPAR-γ Coactivator-1α Regulates Progesterone Production in Ovarian Granulosa Cells with SF-1 and LRH-1

Previously, we demonstrated that bone marrow-derived mesenchymal stem cells (MSCs) differentiate into steroidogenic cells such as Leydig and adrenocortical cells by the introduction of steroidogenic factor-1 (SF-1) and treatment with cAMP. In this study, we employed the same approach to differentiate umbilical cord blood (UCB)-derived MSCs. Despite UCB-MSCs differentiating into steroidogenic cells, they exhibited characteristics of granulosa-luteal-like cells. We found that peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) was expressed and further induced by cAMP stimulation in UCB-MSCs. Consistent with these results, tissue-specific expression of Pgc-1alpha was observed in rat ovarian granulosa cells. PGC-1alpha binds to the NR5A family [SF-1 and liver receptor homolog-1 (LRH-1)] of proteins and markedly enhances their transcriptional activities. Reporter assays revealed that PGC-1alpha activated the promoter activities of SF-1 and LRH-1 target genes. Infection of KGN cells (a human cell line derived from granulosa cells) with adenoviruses expressing PGC-1alpha resulted in the induction of steroidogenesis-related genes and stimulation of progesterone production. PGC-1alpha also induced SF-1 and LRH-1, with the latter induced to a greater extent. Knockdown of Pgc-1alpha in cultured rat granulosa cells resulted in attenuation of gene expression as well as progesterone production. Transactivation of the NR5A family by PGC-1alpha was repressed by Dax-1. PGC-1alpha binds to the activation function 2 domain of NR5A proteins via its consensus LXXLL motif. These results indicate that PGC-1alpha is involved in progesterone production in ovarian granulosa cells by potentiating transcriptional activities of the NR5A family proteins.

Effects of Ovarian Theca Cells on Apoptosis and Proliferation of Granulosa Cells: Changes During Bovine Follicular Maturation

Abstract We have investigated the role of theca cells in the control of apoptosis and proliferation of granulosa cells during bovine ovarian follicular development using a coculture system in which granulosa and theca cells were grown on opposite sides of a collagen membrane. A DNA fluorescence flow cytometry was used to determine the extent of apoptosis and proliferation in populations of granulosa cells. When granulosa cells were isolated from small follicles (3–5 mm), the percentage of apoptotic cells gradually increased by 1.8-fold during the 3 days of culture. This change was reduced (3.1-fold) by the presence of theca cells. When the cells were isolated from large follicles (15–18 mm), the percentage of apoptotic granulosa cells was gradually reduced (3.4-fold) during the 3 days of culture in single-cultured groups. The percentage of apoptosis on Day 1 was reduced (1.6-fold) by the presence of theca cells. However, such an effect was not detected on Days 2 and 3 of the culture. Theca cells did not affect the proliferation of granulosa cells obtained from either small or large follicles. The present study suggests that theca cells regulate the fate of granulosa cells throughout the follicular maturation process by secreting factors that suppress apoptosis.

Myomectomy Decreases Abnormal Uterine Peristalsis and Increases Pregnancy Rate

BACKGROUND The relationship between fibroids and infertility remains a critical and unresolved question. During the implantation phase, it is known that uterine peristalsis is dramatically reduced, which is thought to facilitate implantation of the embryo to the endometrium. In the previous study, using a cine MRI mode, we found that less than half of the patients with intramural fibroids exhibited abnormal uterine peristalsis during the mid-luteal phase. In the present study, we further investigated whether myomectomy for patients in the high peristalsis group is a constructive method to normalize uterine peristalsis. METHODS The frequency of junctional zone movement was evaluated using a cine MRI mode during the mid-luteal phase. Fifteen infertility patients, who had intramural myomas and exhibited abnormal uterine peristalsis (≥2 times/3 min) in their first MRI, underwent myomectomy and a second MRI. After receiving the second MRI, patients underwent infertility treatment for at least 8 months, and pregnancy rate was evaluated prospectively. RESULTS Among 15 patients, the frequency of uterine peristalsis was normalized (0 or 1 time/3 min) in 14 patients. Following myomectomy and second MRI test, 6 of the 15 patients achieved pregnancy (n = 15, pregnancy rate: 40%). CONCLUSIONS The presence of uterine fibroids might induce abnormal uterine peristalsis in some patients, leading to infertility, and myomectomy may improve fertility in these patients.

Granulosa Cells Promote Differentiation of Cortical Stromal Cells into Theca Cells in the Bovine Ovary

Abstract Formation of a theca cell (TC) layer is an important physiologic event that occurs during early follicular development. Nevertheless, little is known concerning the nature and regulation of the formation of the TC layer during follicular growth. Using an established coculture system in this study, we examined the hypothesis that stromal cells differentiate into TCs during early follicular development and that this process involves interaction with granulosa cells (GCs). Ovarian stromal cells from the bovine ovarian cortex (SC) and medulla (SM) were cultured with or without GCs from small antral follicles. The presence of GCs increased the number of lipid droplets and mitochondria, and it stimulated androstenedione production in SC and SM. However, luteinizing hormone/choriogonadotropin receptor (LHCGR) mRNA abundance and hCG-induced cAMP and androstenedione production were increased in SC but not in SM by the presence of GCs. The present results indicate that GCs are involved in the functional differentiation and the acquisition of LH responsiveness in stromal cells of the ovarian cortex. We suggest that GC-SC interaction is important in the formation of the TC layer during early follicular development, although the nature of this interaction remains to be determined.

Luteinizing hormone-induced Akt phosphorylation and androgen production are modulated by MAP Kinase in bovine theca cells

BackgroundTheca cells play an important role in controlling ovarian steroidogenesis by providing aromatizable androgens for granulosa cell estrogen biosynthesis. Although it is well established that the steroidogenic activity of theca cells is mainly regulated by LH, the intracellular signal transduction mechanisms that regulate thecal proliferation and/or steroidogenesis remain obscure. In this study, we examined whether and how LH controls the PI3K/Akt signaling pathway and androgen production in bovine theca cells. We also explored whether this LH-induced PI3K/Akt activation is modulated with other signaling pathways (i.e. PKA and MAPK).MethodsOvarian theca cells were isolated from bovine small antral follicles and were incubated with LH for various durations. Phospho-Akt and total-Akt content in the cultured theca cells were examined using Western blotting. Androstenedione levels in the spent media were determined using EIA. Semi-quantitative RT-PCR analyses were conducted to analyze the mRNA levels of CYP17A1 and StAR in the theca cells. To examine whether Akt activity is involved in theca cell androgen production, the PI3K inhibitors wortmannin and LY294002 were also added to the cells.ResultsAkt is constitutively expressed, but is gradually phosphorylated in cultured bovine theca cells through exposure to LH. LH significantly increased androstenedione production in bovine theca cells, whereas addition of the wortmannin and LY294002 significantly decreased LH-induced androstenedione production. LH significantly increased CYP17A1 mRNA level in theca cells, whereas addition of LY294002 significantly decreased LH-induced CYP17A1 expression. Neither LH nor PI3K inhibitors alter the mRNA levels of StAR in theca cells. Although H89 (a selective inhibitor of PKA) does not affect LH-mediated changes in Akt, U0126 (a potent MEK inhibitor) suppressed LH-induced Akt phosphorylation, CYP17A1 expression, and androgen production in theca cells.ConclusionThese results indicate that LH stimulates CYP17 mRNA expression and androgen production in theca cells via activation of the PI3K/Akt pathway. The LH-induced Akt phosphorylation and androgen production are modulated by the MAPK signaling in bovine theca cells.

Growth Differentiation Factor-9 Mediates Follicle-Stimulating Hormone-Thyroid Hormone Interaction in the Regulation of Rat Preantral Follicular Development

FSH regulates follicular growth in a stage-development fashion. Although preantral follicle stage is gonadotropin responsive, FSH is not required for preantral follicular growth. With the antrum, the follicles continue growing under the influence of FSH and become gonadotropin dependent. Although thyroid hormone is important for normal female reproductive function, its role and interaction with FSH in the regulation of preantral ovarian follicular growth is yet to be defined. In the present study, we have examined the action and interaction of FSH and T(3) in the regulation of the growth of preantral follicles, especially in their transition from preantral to early antral stage, using an established follicle culture system and evaluated the involvement of growth differentiation factor-9 (GDF-9) in this process in vitro. We have demonstrated that although T(3) alone had no effect on follicular development, it markedly enhanced FSH-induced preantral follicular growth. Although FSH alone significantly down-regulated FSH receptor (FSHR) mRNA abundance in the preantral follicles and T(3) alone was ineffective, expression of the message was significantly increased in the presence of both hormones. In addition, intra-oocyte injection of GDF-9 antisense oligonucleotides (GDF-9 morpholino) induced follicular cell apoptosis and suppressed follicular growth induced by FSH and T(3). These responses were attenuated by exogenous GDF-9. Our findings support the concept that thyroid hormone regulates ovarian follicular development through its direct action on the ovary and that promotes FSH-induced preantral follicular growth through up-regulation of FSHR, a mechanism dependent on the expression and action of oocyte-derived GDF-9.

Ovarian theca cells in follicular function

The role of theca cells in every aspect of ovarian follicular function is reviewed. A distinguishing feature of theca cells may be their ability to initiate follicle growth on differentiation from cortical stromal cells, stimulate follicle growth by granulosa cell mitosis through FSH-induced androgen receptor, and cause androgen-stimulated receptor formation of FSH. As LH not only stimulates androgen production by theca cells at tonic levels, but also induces morphological luteinization in addition to androgenesis at surge levels, the dual action concept of LH is proposed. Maturation of the selected dominant follicle and atresia of subordinate antral follicles is interpreted by this concept. Two-way signalling between oocytes and somatic theca cells with growth factors is shown to play a pivotal role in preantral folliculogenesis and atresia. Thus, theca cells have a more significant role in follicular function than previously thought.