During gametogenesis in mammals, meiosis ensures the production of haploid gametes. The timing and length of meiosis to produce female and male gametes differ considerably. In contrast to males,... Show moreDuring gametogenesis in mammals, meiosis ensures the production of haploid gametes. The timing and length of meiosis to produce female and male gametes differ considerably. In contrast to males, meiotic prophase I in females initiates during development. Hence, the knowledge regarding progression through meiotic prophase I is mainly focused on human male spermatogenesis and female oocyte maturation during adulthood. Therefore, it remains unclear how the different stages of meiotic prophase I between human oogenesis and spermatogenesis compare. Analysis of single-cell transcriptomics data from human fetal germ cells (FGC) allowed us to identify the molecular signatures of female meiotic prophase I stages leptotene, zygotene, pachytene and diplotene. We have compared those between male and female germ cells in similar stages of meiotic prophase I and revealed conserved and specific features between sexes. We identified not only key players involved in the process of meiosis, but also highlighted the molecular components that could be responsible for changes in cellular morphology that occur during this developmental period, when the female FGC acquire their typical (sex-specific) oocyte shape as well as sex-differences in the regulation of DNA methylation. Analysis of X-linked expression between sexes during meiotic prophase I suggested a transient X-linked enrichment during female pachytene, that contrasts with the meiotic sex chromosome inactivation in males. Our study of the events that take place during meiotic prophase I provide a better understanding not only of 16 female meiosis during development, but also highlights biomarkers that can be used to study infertility and offers insights in germline sex dimorphism in humans. Show less
Metzemaekers, J.; Lust, E.E.R.; Rhemrev, J.P.T.; Geloven, N. van; Twijnstra, A.R.H.; Westerlaken, L. van der; Jansen, F.W. 2021
Background: Subfertility occurs in 30-40% of endometriosis patients. Regarding the fertilisation rate with in vitro fertilisation (IVF) and endometriosis, conflicting data has been published. This... Show moreBackground: Subfertility occurs in 30-40% of endometriosis patients. Regarding the fertilisation rate with in vitro fertilisation (IVF) and endometriosis, conflicting data has been published. This study aimed to compare endometriosis patients to non-endometriosis cycles assessing fertilisation rates in IVF.Methods: A population-based cohort study was conducted at the Leiden University Medical Center. IVF cycles of endometriosis patients and controls (unexplained infertility and tubal pathology) were analysed. The main outcome measurement was fertilisation rate.Results: 503 IVF cycles in total, 191 in the endometriosis group and 312 in the control. The mean fertilisation rate after IVF did not differ between both groups, 64.1%+/- 25.5 versus 63.9%+/- 24.8 (p=0.95) respectively, independent of age and r-ASRM classification. The median number of retrieved oocytes was lower in the endometriosis group (7.0 versus 8.0 respectively, p=0.19) and showed a significant difference when corrected for age (p=0.02). When divided into age groups, the statistical effect was only seen in the group of <= 35 years (p=0.04). In the age group <= 35, the endometriosis group also showed significantly more surgery on the internal reproductive organs compared to the control group (p<0.001). All other outcomes did not show significant differences.Conclusion: Similar fertilisation rates were found in endometriosis IVF cycles compared to controls. The oocyte retrieval was lower in the endometriosis group, however this effect was only significant in the age group <= 35 years. All other secondary outcomes did not show significant differences. In general, endometriosis patients with an IVF indication can be counselled positively regarding the chances of becoming pregnant, and do not need a different IVF approach. Show less
The ovary is perhaps the most dynamic organ in the human body, only rivaled by the uterus. The molecular mechanisms that regulate follicular growth and regression, ensuring ovarian tissue... Show moreThe ovary is perhaps the most dynamic organ in the human body, only rivaled by the uterus. The molecular mechanisms that regulate follicular growth and regression, ensuring ovarian tissue homeostasis, remain elusive. We have performed single-cell RNA-sequencing using human adult ovaries to provide a map of the molecular signature of growing and regressing follicular populations. We have identified different types of granulosa and theca cells and detected local production of components of the complement system by (atretic) theca cells and stromal cells. We also have detected a mixture of adaptive and innate immune cells, as well as several types of endothelial and smooth muscle cells to aid the remodeling process. Our results highlight the relevance of mapping whole adult organs at the single-cell level and reflect ongoing efforts to map the human body. The association between complement system and follicular remodeling may provide key insights in reproductive biology and (in)fertility. Show less
