Changes in vascular permeability and deciduoma formation during the peri-implantation period of the rat in response to exogenous gonadotropins

Superovulation at a specific stage of the estrous cycle determines the reproductive performance in mice

Inconsistent reproductive performance has been reported in superovulated mice. Hence, the aim of this study was to analyze the effect and possible mechanism of superovulation timing on mouse reproductive performance. The results showed that mice superovulated at the metestrous (23.08±6.08%) and diestrous stages (33.33±11.45%) presented significantly lower pregnancy rates compared with those superovulated at the estrous stage (66.67±9.20%). After superovulation at the proestrous and estrous stages, mucin 1 (MUC1) and let-7a/let-7b microRNA (miRNA) expression levels were significantly attenuated and enhanced on embryonic day 3.5 (E3.5), respectively, whereas no significant differences in the expression level were found in mice superovulated at the other two stages. A higher number of developing and Graafian follicles was observed in the ovarian sections 48h after the administration of pregnant mare serum gonadotropin (PMSG) at the proestrous and estrous stages. The sections from mice treated at the metestrous and diestrous stages, however, presented more corpora lutea. Therefore, mice superovulated at the proestrous and estrous stages exhibited the best pregnancy rates. Furthermore, the disordered expression of MUC1 and let-7a/let-7b miRNA in mice superovulated at the metestrous and diestrous stages may impair reproduction performance.

The effect of hyperstimulation on transforming growth factor beta(1) and beta(2) in the rat uterus: possible consequences for embryo implantation

OBJECTIVE

To investigate the effect of exogenous gonadotropins on the expression of transforming growth factor (TGF) beta(1) and beta(2) in the rat uterus and its consequences for successful embryo implantation.

DESIGN

Controlled experimental research study.

SETTING

School of Anatomical Sciences, University of the Witwatersrand.

PATIENT(S)

Thirty-six adult, virgin, female Sprague-Dawley rats and two fertile males.

INTERVENTION(S)

Follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG) were superimposed upon the normal hormonal milieu of normal, cycling female rats before mating. Uterine tissue was collected at peri-implantation stages (i.e., at 4.5, 5.5, and 6.5 days) after mating. Enzyme-linked immunosorbent assay (ELISA) was performed to estimate the blood estrogen and progesterone levels, and immunohistochemistry was performed to localize the TGF-beta(1) and TGF-beta(2) in the uterus.

MAIN OUTCOME MEASURE(S)

Hyperstimulation affecting the expression of both TGF-beta(1) and TGF-beta(2) during the peri-implantation period.

RESULT(S)

The release of ovarian steroids was altered, causing a change in the endogenous hormonal environment. A marked increase in the expression of TGF-beta(2) was distinct in the glandular epithelium. Expression of both TGF-beta(1) and TGF-beta(2) was weaker in the subluminal stroma when compared with the deeper stromal region.

CONCLUSION(S)

Hyperstimulation with exogenous hormones affects the expression of both TGF-beta(1) and TGF-beta(2), which may contribute to the disruption of the endometrial environment required for successful embryo implantation.

Spectrotemporal changes in electrical activity of myometrium due to recombinant follicle-stimulating hormone preparations follitropin alfa and beta

OBJECTIVE

To investigate the effects of follitropin alfa and beta on the myoelectrical activity of rat myometrium using signal-processing techniques.

DESIGN

Prospective, placebo-controlled study.

SETTING

Animal and pharmacology laboratory at Inonu University.

ANIMAL(S)

Forty-five female Wistar albino rats.

INTERVENTION(S)

Thirty of 45 animals involved in the experiment were registered as the superovulation group. After two successive normal estrous cycles, these animals were put into three equal subgroups. Group 1 was the control; animals were given 0.9% saline. Groups 2 and 3 were treated with follitropin alfa (Gonal-f) and follitropin beta (Puregon), respectively. The other 15 animals were ovariectomized (OVX) and subjected to the same protocol. The uterine myoelectrical signals were recorded and analyzed using a Matlab environment.

MAIN OUTCOME MEASURE(S)

Power/second, variance, and the effects of recombinant human follicle-stimulating hormone (FSH) on myoelectrical signals were assessed through temporal, spectral, and joint time-frequency analysis. The uterine endometrium and ovarian morphology were also assessed concerning primary follicles, antral follicles, and corpora lutea.

RESULT(S)

The power and some characteristic spectral components of myoelectrical signal were reduced with the administration of follitropin alfa and beta. No statistically significant difference was detected between endometrial and ovarian histology of the rats treated with these follitropins.

CONCLUSION(S)

Uterine myoelectrical signals change with administration of recombinant human FSH preparations. Follitropin beta and, more precisely, follitropin alfa suppress the spectral components and power of the myoelectrical signals, which provides uterine quiescence.

The only effects of recombinant follicle-stimulating hormone for ovulation induction in the pre-implantation period of rats

OBJECTIVE

The aim of this study was to evaluate the changes in follicular development, serum hormonal levels, and endometrium in the pre-implantation period of rats by using recombinant FSH (rFSH) without human chorionic gonadotropin (hCG).

METHODS

Thirty female rats were studied in six groups of five specimens. Two groups determined as controls (groups 1 and 2). Two groups received constant doses of rFSH (groups 3 and 4) and other two decreasing doses (groups 5 and 6). One of the paired groups was mated. Uterus, ovaries, and blood samples were taken from non-mated groups (groups 1, 3, and 5) at the proestrus period and from mated groups (groups 2, 4, and 6) in the pre-implantation period.

RESULTS

In non-mated groups antral follicles and corpus luteum periodicum and in mated groups antral follicles, corpus luteum periodicum, and corpus luteum graviditatis were increased in rFSH groups, especially in decreasing dose groups. Estradiol (E2) levels were increased and progesterone (P)/E2 ratio was significantly decreased in decreasing dose groups. Endometrium surface epithelium was columnar, irregular, and folded in rFSH groups. Endometrium glandular epithelium was cuboidal in all groups. In decreasing dose groups endometrial stroma was smooth and fibroblastic. Mitotic indices of endometrium surface, glandular epithelium, and stroma were significantly decreased in rFSH groups. Primary follicles and P levels showed no change.

CONCLUSION

It seems likely that decreasing doses of rFSH might be used in order to improve follicular development, although it has negative effects with E2 on endometrium in the pre-implantation period of rats.

Expression of nidogens in rat uterus and embryo during decidualization and implantation

The purpose of this study was to demonstrate the expression of nidogen-1 and nidogen-2 and their possible role in decidualization and implantation events during early pregnancy in rats. The tissue samples were examined from pregnant animals between gestational days 1-8 using immunocytochemistry. The uterine luminal epithelium, the glandular epithelium, and the myometrial smooth muscle cells stained strongly from gestational days 1-8 with both nidogen antibodies. At day 4 the decidual reaction areas began to appear in the stromal matrix and immunostaining of both nidogens revealed that the basement membrane of the surface epithelium was discontinuous. The differentiation of stromal cells into decidual cells was seen at gestational day 5 and both nidogens were weakly expressed in the decidualizing cells. At day 6, nidogen-2 immunoreactivity was higher in the primary decidual cells close to the embryo than nidogen-1, and during development of the decidual tissue both nidogens appeared in the endometrial stromal cells. At day 7, while expression of both nidogens declined in the primary decidual cells, their expression was markedly observed in the secondary decidual cells close to the myometrium. At day 8, expression of both nidogens was also observed to increase in the primary decidual cells. While nidogen-2 expression was seen in the parietal endoderm and primary ectoderm of the rat embryos at this developmental stage, nidogen-1 expression was only detected in the parietal endoderm. These results indicate that nidogen-1 and nidogen-2 could play important roles during embryogenesis, decidualization, and implantation in the endometrium of rat uterus.

Morphometric changes in the endometrium and serum leptin levels during the implantation period of the embryo in the rat in response to exogenous ovarian stimulation

OBJECTIVE

To determine the changes in endometrium and serum leptin levels during the periimplantation period of the ovum in the rat in response to exogenous ovarian stimulation by hMG and recombinant FSH (rFSH).

DESIGN

Experimental animal study.

SETTING

University hospital.

INTERVENTION(S)

A total of 100 female rats were stimulated with low and high doses of hMG (groups 1 and 2, respectively) and low and high doses of rFSH (groups 3 and 4, respectively) before mating after the regular cycle was observed. The control group of animals was not injected (group 5). The endometrium of the pregnant rats (n = 53) was analyzed by the morphometric method, and serum samples were obtained for leptin and E2 levels at baseline and on the day of implantation. The mitotic index was determined separately for endometrial surface, glandular epithelium, and endometrial stroma by light microscope.

MAIN OUTCOME MEASURE(S)

Morphometric analysis of endometrium, mitotic index, and serum leptin and E2 levels

RESULT(S)

The mean number of corpora lutea was significantly higher in groups 2 and 4. The measurement of mucosal depth was found to be significantly higher in group 4 compared with the control group (0.361 +/- 0.03 vs. 0.289 +/- 0.04). The depth of the endometrial surface epithelium was found to be significantly higher in all study groups (groups 1-4) compared with the control group. The depth of the surface epithelium was found to be significantly lower in group 1 compared with the other study groups (groups 2, 3, and 4). The depth of the surface epithelium was also significantly lower in group 2 compared with group 3 (21.58 +/- 3.56 vs. 28.21 +/- 3.56). Mitotic indices that were determined at the endometrial surface epithelium and stroma were all significantly lower in all study groups (groups 1-4) compared with the control group. There was no significant increase for the baseline leptin levels compared with the levels measured on the day of implantation.

CONCLUSION(S)

In an animal model, exogenous administration of gonadotropins significantly affects the morphology of the endometrium and the mitotic index in the implantation period of the embryo. These morphological effects become more pronounced as we increase the administered dose of exogenous gonadotropins. However, no differences in leptin levels were observed relative to different gonadotropin type and dose regimens.

Effects of 4-hydroxyandrostenedione and hyperstimulation with pregnant mare serum gonadotrophin on early embryonic development in rats

A possible role of high oestradiol levels in mediating the adverse effects of hyperstimulation with pregnant mare serum gonadotrophin (PMSG) on early embryonic development in the rat was investigated using an aromatase inhibitor, 4-hydroxyandrostenedione (4-OHA), to inhibit endogenous oestradiol production. Three experiments were conducted in this study. In the first, varying doses of 4-OHA were administered either concurrently with human chorionic gonadotropin (hCG) to pro-oestrus female rats hyperstimulated at early di-oestrus stage with 20 IU PMSG or alone into nonhyperstimulated pro-oestrus females. At high doses of 1000, 2000, or 5000 µg/rat, 4-OHA substantially improved the survival of embryos in hyperstimulated females, while low doses of 100 and 500 µg/rat were ineffective. The protective effect of 4-OHA on embryo count was optimum at 2000 µg. When administered alone, only the highest dose of 5000 µg/rat 4-OHA increased embryo count. In the second experiment, higher doses of PMSG were studied (30 or 40 IU), with or without 5000 µg/rat 4-OHA given at the time of hCG injection. PMSG proved to be more detrimental with increasing dose, and 5000 µg/rat 4-OHA was able to rescue embryos from death in the 30, but not 40, PMSG group. In the third experiment, the influence of the timing of 4-OHA treatment on its ability to improve the embryo count in hyperstimulated females was examined by introducing 4-OHA 24 h earlier, rather than at the time of hCG treatment. The results showed the importance of timing of 4-OHA administration, as 5000 µg/rat 4-OHA was able to restore embryo survival in the 40 PMSG hyperstimulated group only when it was administered 24 h before hCG injection. Together, these results highlighted that 4-OHA, when administered at the appropriate time and dose, could reverse the negative effects of hyperstimulation from PMSG on early embryonic development. This may be due to its potent aromatase inhibiting properties that lead to the suppression of oestrogen production, thereby alleviating the supraphysiological level of oestradiol, which is typically present in PMSG-treated females. Interestingly, 4-OHA treatment on its own was able to positively influence embryo count when given at a high dose of 5000 µg/rat, and this may be associated with its weak androgenic properties. In conclusion, this study supports the hypothesis that excessive oestradiol is responsible for the negative effects of hyperstimulation with PMSG on early embryonic development.Key words: 4-hydroxyandrostenedione, embryonic development, PMSG, rat.

Leptin induces vascular permeability and synergistically stimulates angiogenesis with FGF-2 and VEGF

Most endocrine hormones are produced in tissues and organs with permeable microvessels that may provide an excess of hormones to be transported by the blood circulation to the distal target organ. Here, we investigate whether leptin, an endocrine hormone, induces the formation of vascular fenestrations and permeability, and we characterize its angiogenic property in the presence of other angiogenic factors. We provide evidence that leptin-induced new blood vessels are fenestrated. Under physiological conditions, capillary fenestrations are found in the leptin-producing adipose tissue in lean mice. In contrast, no vascular fenestrations were detected in the adipose tissue of leptin-deficient ob/ob mice. Thus, leptin plays a critical role in the maintenance and regulation of vascular fenestrations in the adipose tissue. Leptin induces a rapid vascular permeability response when administrated intradermally. Further, leptin synergistically stimulates angiogenesis with fibroblast growth factor (FGF)-2 and vascular endothelial growth factor (VEGF), the two most potent and commonly expressed angiogenic factors. These findings demonstrate that leptin has another new function-the increase of vascular permeability.