C. Yding Andersen

Which follicles make the most anti-Mullerian hormone in humans? Evidence for an abrupt decline in AMH production at the time of follicle selection.

Anti-Müllerian hormone (AMH) is exclusively produced by granulosa cells (GC) of the developing pre-antral and antral follicles, and AMH is increasingly used to assess ovarian function. It is unclear which size follicles make the most AMH (total content) and are the main contributors to circulating AMH concentrations. To determine AMH gene expression in GC (q-RT-PCR) and follicular AMH production (Elisa and RIA) in relation to follicular development, 87 follicles (3-13 mm diameter) including both GC and the corresponding follicular fluid (FF) were collected in connection with fertility preservation of human ovaries. Further, follicle number and diameter, graded in 1 mm increments, were determined by 3D ultrasound in 113 women in their natural menstrual cycle to determine follicle number and diameter in relation to circulating AMH levels. This study demonstrates for the first time a positive association between AMH gene expression in human and both total follicular fluid AMH (P < 0.02) and follicular fluid AMH concentration (P < 0.01). AMH gene expression and total AMH protein increased until a follicular diameter of 8 mm, after which a sharp decline occurred. In vivo modelling confirmed that 5-8 mm follicles make the greatest contribution to serum AMH, estimated for the first time in human to be 60% of the circulating concentration. Significant positive associations between gene expression of AMH and FSHR, AR and AMHR2 expression (P < 0.00001 for all three) and significant negative association between follicular fluid AMH concentration and CYP19a1 expression were found (P < 0.0001). Both AMH gene expression (P < 0.02) and follicular fluid concentration of AMH (P < 0.00001) correlated negatively with estradiol concentration.

Effects of recombinant LH supplementation in women undergoing assisted reproduction with GnRH agonist down-regulation and stimulation with recombinant FSH: an opening study

Circulating endogenous concentrations of LH are reduced in women undergoing down-regulation with gonadotrophin-releasing hormone agonists (GnRHa) and ovarian stimulation with recombinant human FSH (r-hFSH). The effect of recombinant human LH (r-hLH) supplementation on ovarian response and pregnancy outcome was evaluated in a prospective randomized study (sealed envelopes) including 231 cycles. Normogonadotrophic women were stimulated with either r-hFSH or a combination of r-hFSH and r-hLH in a ratio of 2:1. LH supplementation was started from day 8 of the cycle. Blood samples for oestradiol, LH and androstendione were prospectively collected on days 1, 8 and on the day of aspiration and analysed retrospectively. Overall, the two groups did not differ with respect to pregnancy rate. In contrast, women aged > or =35 years responded to exogenous LH supplementation with significantly increased implantation rates and significantly reduced total FSH consumption as compared with the non-supplemented group. In addition, the implantation rate for a subgroup of patients with the highest endogenous LH concentrations (i.e. > or =1.99 IU/l) on day 8 was significantly increased by LH supplementation. Exogenous LH supplementation from day 8 has no detrimental effect on ovarian response and pregnancy outcome. On the contrary supplementation with r-hLH seems to benefit treatment outcome for women above 35 years of age and for the subgroup of women exhibiting LH concentrations above 1.99 IU/l on stimulation day 8.

Rescue of corpus luteum function with peri-ovulatory HCG supplementation in IVF/ICSI GnRH antagonist cycles in which ovulation was triggered with a GnRH agonist: a pilot study

Previous studies found a poor clinical outcome when a GnRH agonist (GnRHa) was used to trigger ovulation in GnRH antagonist IVF/ICSI cycles. This study aimed to determine the clinical and endocrine effects as well the optimal timing of HCG supplementation. Forty-five normogonadotrophic IVF/ICSI patients following a flexible antagonist protocol were prospectively randomized (sealed envelopes) to triggering of ovulation with a single bolus of either 10,000 IU of HCG (group 1, n = 15) or 0.5 mg buserelin s.c. In addition, the GnRHa triggered group was randomized into two groups: group 2 (n = 17) was supplemented with HCG 1500 IU, 12 h after ovulation induction and group 3 (n = 13) was supplemented with HCG 1500 IU 35 h after ovulation induction. Group 1 and group 3 had significantly higher luteal phase concentrations of progesterone (P < 0.001) as compared with group 2. Moreover, the clinical pregnancy rate of groups 1 and 3 was similar and significantly higher (P < 0.02) than that of group 2. A larger study, however, is required to substantiate these differences. No differences were seen regarding mid-luteal inhibin A concentrations between the three groups. Triggering of ovulation with GnRHa supplemented with 1500 IU HCG 35 h later (group 3) seems to secure a normal luteal phase and a normal clinical pregnancy outcome.

In human granulosa cells from small antral follicles, androgen receptor mRNA and androgen levels in follicular fluid correlate with FSH receptor mRNA

Human small antral follicles (diameter 3-9 mm) were obtained from ovaries surgically removed for fertility preservation. From the individual aspirated follicles, granulosa cells and the corresponding follicular fluid were isolated in 64 follicles, of which 55 were available for mRNA analysis (24 women). Expressions of androgen receptor (AR) mRNA levels in granulosa cells, and of androstenedione and testosterone in follicular fluid, were correlated to the expression of the FSH receptor (FSHR), LH receptor (LHR), CYP19 and anti-Müllerian Hormone-receptor II (AMHRII) mRNA in the granulosa cells and to the follicular fluid concentrations of AMH, inhibin-B, progesterone and estradiol. AR mRNA expression in granulosa cells and the follicular fluid content of androgens both showed a highly significant positive association with the expression of FSHR mRNA in granulosa cells. AR mRNA expression also correlated significantly with the expression of AMHRII, but did not correlate with any of the hormones in the follicular fluid. These data demonstrate an intimate association between AR expression in immature granulosa cells, and the expression of FSHR in normal small human antral follicles and between the follicular fluid levels of androgen and FSHR expression. This suggests that follicular sensitivity towards FSH stimulation may be augmented by stimulation of androgens via the AR.

No evidence for the presence of oogonia in the human ovary after their final clearance during the first two years of life

BACKGROUND Conflicting results of studies on mouse and human have either verified or refuted the presence of oogonia/primordial germ cells in the post-natal ovary. The aim of this study was to trace whether oogonia recognized by immunohistochemical methods in the first trimester human ovary were present also in peri- and post-natal ovaries. METHODS For this study, 82 human ovaries were collected: 25 from embryos from 5 to 10 weeks post conception (wpc), 2 at 18 wpc, 32 from 32 wpc to 2 years and 23 from 2 to 32 years. Of these, 80 ovaries were fixed and paraffin-embedded and 2 (8 year-old) ovaries were processed for plastic sections. Serial sections were prepared for immunohistochemical detection of markers for oogonia: tyrosine kinase receptor for stem cell factor (SCF)(C-KIT), stage-specific embryonic antigen-4 (SSEA4), homeobox gene transcription factor (NANOG), octamer binding transcription factor 4 (OCT4) and melanoma antigen-4 (Mage-A4), while noting that C-KIT also stains diplotene oocytes. RESULTS Almost all oogonia exclusively stained for SSEA4, NANOG, OCT4 and C-KIT, whereas MAGE-A4 only stained a small fraction. At birth only a few oogonia were stained. These disappeared before 2 years, leaving only diplotene oocytes stained for C-KIT. From 18 wpc to 2 years, the medulla contained conglomerates of healthy and degenerating oogonia and small follicles, waste baskets (WBs) and oogonia enclosed in growing follicles (FWB). Medulla of older ovaries contained groups of primordial, healthy follicles. CONCLUSIONS We found no evidence for the presence of oogonia in the human ovary after their final clearing during the first 2 years. We suggest that perinatal medullary WB and FWB give rise to the groups of small, healthy follicles in the medulla.

Day 3 versus day 5 embryo transfer: a prospective randomized study

Transfer of embryos at the blastocyst stage has been associated with exceptionally high implantation rates. There are, however, only a few prospective randomized studies comparing day 3 versus day 5 embryo transfer. Furthermore, the number of embryos replaced in the day 3 group transfer is often higher than the number of blastocysts replaced, thereby affecting implantation rates. A total of 118 patients undergoing standard IVF/intracytoplasmic sperm injection who had developed at least three 8-cell embryos showing <20% extracellular fragmentation on day 3 were randomized for day 3 or day 5 transfer. A maximum of two embryos were replaced. In this prospective, randomized study the implantation and pregnancy potential of embryos transferred on day 3 or day 5 were compared. Equal numbers of embryos were replaced in the two groups. There was no statistically significant difference between day 3 and day 5 transfer regarding positive human chorionic gonadotrophin rates (70 versus 67%), clinical pregnancy rates (61 versus 51%), implantation rates (44 versus 37%), twinning rates (42 versus 41%) and rates of early pregnancy loss (15 versus 29%). Transfer of embryos on day 3 or 5 showed similar implantation rates when equal numbers of embryos were transferred. Embryo transfer at the blastocyst stage seems to have no advantage over day 3 transfer in patients with more than two 8-cell embryos showing less than 20% fragmentation on day 3.

Human primordial germ cells migrate along nerve fibers and Schwann cells from the dorsal hind gut mesentery to the gonadal ridge

The aim of this study was to investigate the spatiotemporal development of autonomic nerve fibers and primordial germ cells (PGCs) along their migratory route from the dorsal mesentery to the gonadal ridges in human embryos using immunohistochemical markers and electron microscopy. Autonomic nerve fibers in the dorsal mesentery, the pre-aortic and para-aortic plexuses and in the gonadal ridge were stained for beta III tubulin, neuron specific enolase and the glia fibrillary acidic protein. Electron microscopy demonstrated the presence of neurofilaments and neurotubules in these nerve fibers and their intimate contact with PGCs. PGCs expressed GAGE, MAGE-A4, OCT4 and c-Kit. Serial paraffin sections showed that most PGCs were located inside bundles of autonomic nerve fibers with the majority adjacent to the most peripheral fibers (close to Schwann cells). We also show that both nerve fibers and PGCs arrive at the gonadal ridge between 29 and 33 days pc. In conclusion, our data suggest that PGCs in human embryos preferentially migrate along autonomic nerve fibers from the dorsal mesentery to the developing gonad where they are delivered via a fine nerve plexus.

Cigarette smoking during early pregnancy reduces the number of embryonic germ and somatic cells

BACKGROUND Cigarette smoking during pregnancy is associated with negative reproductive consequences for male fetuses in adult life such as reduced testicular volume and sperm concentration. The present study evaluates the number of germ and somatic cells present in human embryonic first-trimester gonads in relation to maternal smoking. METHODS The study includes 24 human first-trimester testes, aged 37-68 days post-conception, obtained from women undergoing legal termination of pregnancy. A questionnaire was used to obtain information about smoking and drinking habits during pregnancy. Validated stereological methods were used to estimate gonadal cell numbers in histological sections. Results were also evaluated in the context of previously published data on ovaries from our laboratory. RESULTS A significant reduction in the number of germ cells by 55% [95% confidence interval (CI) 74-21% reduction, P = 0.004] and somatic cells by 37% (95% CI 59-3%, P = 0.023) was observed in testes prenatally exposed to maternal cigarette smoking, compared with unexposed. The effect of maternal smoking was dose-dependent being higher in the heavy smokers and remained consistent after adjusting for possible confounders such as alcohol and coffee consumption (P = 0.002). The number of germ cells in embryonic gonads, irrespective of gender, was also significantly reduced by 41% (95% CI 58-19%, P = 0.001) in exposed versus non-exposed embryonic gonads. CONCLUSIONS Prenatal exposure to maternal cigarette smoke reduces the number of germ and somatic cells in embryonic male and female gonads. This effect may have long-term consequences on the future fertility of exposed offspring. These findings may provide one potential cause of the reduced fertility observed during recent years.

Effect of FSH and its different isoforms on maturation of oocytes from pre-ovulatory follicles

FSH exists as a family of isohormones exhibiting distinct oligosaccharide structures, and the released FSH isoform mixtures change during the follicular phase of the menstrual cycle. In addition, the pulsatile release of gonadotrophins seems to expose follicles to bursts of more less-acidic FSH isoforms and the follicle is likely to be exposed to an almost ever changing composition of FSH isoforms. The different isoforms causes a number of different and divergent biological effects. FSH promotes oocyte maturation, and 5–10 IU/l of less-acidic FSH isoforms are sufficient to induce oocyte maturation in vitro. Exposure of cumulus–oocyte complexes to less-acidic FSH isoforms in a pulse-like fashion results in a rapid pattern of cAMP accumulation exceeding that seen with acidic isoforms, which appear to sustain lower but more constant cAMP production. The presence of particularly less-acidic isoforms for a period exceeding 30 min causes an attenuated cAMP response. In conclusion, it appears that pulsatile and intermittent release of less-acidic/short-living FSH isoforms is sufficient to induce biological responses, while allowing the granulosa cells to regain responsiveness to further FSH stimulation. Together with the interpulse release of more acidic isoforms, overall FSH secretion seems to ensure proper follicular maturation resulting in the release of developmentally competent oocytes.

The number of oogonia and somatic cells in the human female embryo and fetus in relation to whether or not exposed to maternal cigarette smoking

BACKGROUND Prenatal exposure to maternal cigarette smoking or compounds of cigarette smoke is associated with serious reproductive hazards such as apoptotic death of oogonia in murine offspring and decreased fecundability in human offspring. The present study addresses potential effects of in utero exposure to cigarette smoking. METHODS Twenty-nine human first-trimester ovaries from legal abortions [aged 38-64 days post-conception (p.c.)] were collected. Mothers filled out a questionnaire about their smoking habits and delivered a urine sample for cotinine analysis. The ovarian cell numbers were estimated using stereological methods. RESULTS A non-linear correlation between the numbers of oogonia and somatic cells in relation to age of the embryo/fetus was shown in 28 ovaries, including the first estimates performed in ovaries younger than 47 days p.c. Prenatal exposure to smoke showed a significant decrease in the number of somatic cells (P < or = 0.01). The number of oogonia was not significantly associated with prenatal exposure to maternal smoking (P < or = 0.09). The ratio between the two cell types decreased considerably from 1:45 to 1:23 from 38 to 46 days p.c. and was not affected by smoking. CONCLUSIONS Oogonia proliferate and/or invade the developing ovary at a much faster relative rate than somatic cells. In utero exposure to maternal smoking significantly reduces the number of somatic cells from Days 38 to 64 p.c. Since oocytes cannot survive without being enclosed by somatic cells in a follicle, reduction in the somatic cells number may have long-range consequences on the number of oocytes available in adult life and on the future fertility of female offspring exposed to smoking in utero.