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Peroxisome proliferator-activated receptors (PPARs) play an important role in different compartments of the female reproductive system in rodents and humans. However, expressional profiles and physiological functions of PPARs in the endometrium prior to the placentation are not well understood. In this study, we determined expressional profiles of the PPARs during early pregnancy. Immunocytochemistry revealed that both PPARα and PPARβ/δ were strongly detected in the endometrial stroma on days 4.5-6.5 of pregnancy, which is just a starting time of implantation. Delayed implantation animal model showed that the expressions of PPARα and PPARβ/δ occurred after the initiation of implantation in the endometrial stroma. Moreover, an in vitro decidualization model further revealed that the expression of PPARα increased in the cultured rat endometrial stromal cells at 24 h after the decidualization treatment, but the expression of PPARβ/δ was delayed and increased at 48 h after the treatment. PPARγ was expressed in the endometrial stroma and its expression decreased significantly at 2.5 days post-coitum and maintained a low level of expression during the period of implantation. These results indicate that PPARα is expressed and induced by the initiation of implantation, prior to the expression of PPARβ/δ in decidualized endometrium. Increasing expression of PPARγ during fertilization and its decline during the period of implantation further suggest that PPARs may play important roles during early pregnancy. [ABSTRACT FROM AUTHOR]

Ovarian steroid hormones, progesterone (P4), and estradiol (E2) strictly regulate the endometrial tissue remodeling required for successful embryo implantation. Indian hedgehog ( Ihh) is up-regulated by P4 and critically mediates uterine receptivity in the mouse. However, the regulation of Ihh expression during the implantation period still remains unclear. The present study was conducted to elucidate the mechanism of the steroidal regulation in the expression of Ihh and Gli1, the mediator of the Ihh pathway. Ihh mRNA was expressed in the rat uterus on 3.5–5.5 days post-coitus (dpc), while Gli1 expression transiently increased at 3.5 dpc but decreased significantly on 5.5 dpc ( P < 0.001). In delayed implantation, the expression of Ihh was induced by the implantation-induced E2 treatment in the primed rat uterus. In contrast, expression of Gli1 was significantly decreased by E2 treatment ( P = 0.016). In the case of ICI182.780 (ICI) treatment, Ihh expression was eliminated by ICI, whilst Gli1 expression increased. These results suggest that Ihh expression is maintained at a high level until the initiation of implantation, while the expression of Gli1 is decreased just prior to the initiation of implantation depending on the E2 action. This observation aids in the understanding of the Ihh signaling pathway mediating uterine remodeling for implantation. [ABSTRACT FROM AUTHOR]

The induction of the decidualization of endometrial stromal cells is possible in an in vitro cell culture system. However, thus far, methods differ according to species or cell type, and a more stable or universal system has not yet been developed. The purpose of the present study has been to establish an in vitro decidualization system in primary cultured rat endometrial stromal cells (RES). The RES were treated with medroxyprogesterone acetate and dibutyryl-cyclic adenosine monophosphate (MPA treatment), estradiol and progesterone, or arachidonic acid. After 24 h of treatment, cells responded to all of the stimulations by expressing desmin mRNA. However, decidual/trophoblast prolactin-related protein (dPRP) mRNA was only expressed in the MPA-treated cells. Desmin and dPRP mRNA were not expressed after MPA treatment of the RES derived from immature rat uteri. However, mRNA from both desmin and dPRP were expressed in RES derived from gonadotrophin-injected immature rats. The expression of matrix metalloproteinase-2 (MMP-2) and MMP-9 mRNA did not change after the decidual treatment of RES examined by real-time polymerase chain reaction. However, the results of gelatin zymography showed that the active forms of MMP-2 and MMP-9 significantly increased after in vitro decidualization ( P < 0.05). We conclude that MPA treatment is the most effective method for stimulating decidualization in RES. Use of this system has revealed that sexual maturation and gonadotrophins are important for RES with regard to decidualization. Furthermore, the activity of MMP-2 and MMP-9 might increase during decidualization without a corresponding increase of the expression of these genes. [ABSTRACT FROM AUTHOR]

Chicken primordial germ cells (PGCs) dynamically migrate towards the prospective gonadal area through the germinal crescent region and bloodstream at early embryonic stages. To date, chicken PGCs have been mainly identified by histochemical and immunohistochemical methods or by their morphological characteristics. However, their origin, migration and differentiation are not fully understood because of the lack of specific PGC molecular markers. Here, we have isolated the chicken dead end homologue (CDH) in order to clone its full-length cDNA with an open reading frame of 329 amino acids. The RNA-binding motif present in CDH at amino acids 54–133 was highly homologous to those in the dead end proteins of human, mouse and Xenopus. The temporal and spatial distribution of PGCs was also investigated by in situ hybridization (ISH) on whole-mount embryos with CDH cRNA as a probe. Chicken embryos from stage X to stage 20 were subjected to ISH. The hybridized samples were then sectioned to analyse the translocation of PGCs. CDH-positive cells could be counted from stage X to stage 4, with minimally 30 cells at the blastderm and approximately 260 cells at the germinal crescent. Thus, specific expression of CDH mRNA has been established in chicken PGCs located at the blastderm, germinal crescent and prospective gonadal area by ISH and reverse transcription/polymerase chain reaction. We conclude that isolated CDH is specifically expressed in chicken PGCs during embryogenesis. [ABSTRACT FROM AUTHOR]