Toko Harata

PTEN and Akt expression during growth of human ovarian follicles

PurposeTo assess the expression of PTEN and total and phosphorylated Akt in human ovarian follicles during follicular growth.MethodsImmunohistochemistry of ovarian tissues and Western blotting and immunofluorescence of primary cultured luteinized granulosa cells for PTEN and Akt.ResultsImmunoreactivity of Akt was found in the oocytes, granulosa cells and theca cells in primordial follicles, follicles at each growing stage and luteal cells. As the follicles grew, staining for PTEN became intense in the granulosa cells, whereas the intensity of phospho-Akt became weak. Western blotting and immunofluorescence analysis using primary cultured granulosa-lutein cells showed Akt and PTEN expression, and phosphorylation of Akt in vitro.ConclusionsPTEN and Akt are present in the granulosa cells during folliculogenesis. An increase in PTEN may lead to changes in proliferation and/or differentiation of granulosa cells during follicular growth via regulation of Akt phosphorylation.

IGF1-induced AKT phosphorylation and cell proliferation are suppressed with the increase in PTEN during luteinization in human granulosa cells

Granulosa cells proliferate and then undergo differentiation; an inverse relationship between these processes is observed during terminal follicular growth. During terminal follicular growth and initial luteinization, there is a necessary transition of granulosa cells to a less proliferative and highly steroidogenic form in response to LH. Although the expression of several molecules has been reported to be up-regulated by LH, proliferation/differentiation transition is not fully understood. Here, we show that the expression of a tumor suppressor, phosphatase and tensin homologue deleted on chromosome 10 (PTEN) was induced with human chorionic gonadotropin (hCG) treatment in human luteinized granulosa cells. Pretreatment with hCG attenuated insulin-like growth factor (IGF)-1-induced phosphorylation of AKT and cell proliferation, not phosphorylation of ERK1/2. Moreover, suppression of hCG-induced PTEN expression with siRNA increased AKT phosphorylation and cell proliferation in response to IGF1. We also demonstrate that a PI3K inhibitor, LY294002, not a MEK inhibitor, PD98059, inhibited IGF1-induced cell proliferation. In conclusion, PTEN induced to express by hCG in luteinized granulosa cells that inactivates AKT, not ERK, and attenuates IGF1-induced cell proliferation. PTEN expression may be a trigger for proliferation/differentiation transition in human granulosa cells.

Assessment of the predictive value of follicular fluid insulin, leptin and adiponectin in assisted reproductive cycles.

Purpose. To assess the correlation of intrafollicular insulin, leptin and adiponectin levels with assisted reproductive technologies (ART) outcome. Methods. This was a retrospective study of 46 patients undergoing in vitro fertilisation/intracytoplasmic sperm injection. Follicular fluid (FF) samples collected at oocyte retrieval were assayed for insulin, leptin and adiponectin levels using enzyme-linked immunosorbent assay, and correlations with ART outcome were analysed. Results. There was no significant correlation between intrafollicular insulin, leptin and adiponectin levels. There was a significant difference in the concentration of insulin (P = 0.007), but not leptin or adiponectin, between pregnant (n = 20) and non-pregnant (n = 26) cycles. Only two pregnancies was observed in the 12 cycles in which the concentration of insulin was greater than 7 mU/l in FF, while 18 pregnancies was observed in the 34 cycles in which the concentration of insulin was less than 7 mU/l (P = 0.043). The significantly high concentration of insulin in FF was observed in non-pregnant cycles of patients with polycystic ovary syndrome (PCOS). Conclusions. Our results suggest the possible involvement of intrafollicular insulin in folliculogenesis. Insulin resistance-related substances may affect the reproductive process in patients with PCOS.

Distribution of Endothelin-converting Enzyme-1 and Neutral Endopeptidase in Human Endometrium

The expression of endothelin-1 (ET-1), which has been proposed to have a potential autocrine/paracrine role, varies during the menstrual cycle, and therefore, ET-1 may be involved in the cyclic change of the human endometrium. However, neither the synthesis nor the degradation of ET-1 in the endometrium has been determined in detail. We investigated endothelin-converting enzyme-1 (ECE-1), which converts big-ET-1 to active ET-1, and neutral endopeptidase (NEP), which cleaves and inactivates ET-1 in human endometrium in vivo and in vitro. Western blot analysis demonstrated that the change in the expression of ECE-1 during the menstrual cycle differed from that of NEP in the endometrium. ECE-1 was expressed by endometrial epithelial cells, whereas NEP was predominantly expressed by stromal cells in vivo and in vitro. In conclusion, our results suggest that spacio-temporal expression of two endopeptidases, ECE-1 and NEP, involved in the synthesis and degradation of ET-1, might regulate ET-1 action in human endometrium.