1 Fertility

Specific questions addressed in this part of the program are mainly dealing with the development of follicles, ovulation and non-invasive screening of patients for predictive factors of reproductive problems. Among these, infections play an important role. Infertility is increasingly diagnosed and has become a major health problem, among others by delaying pregnancy to later female ages. In 2006 the work concentrated on Chlamydia. It has focused on unraveling the mechanisms of disease, in particular the role of persistent infections and genetic susceptibility determinants in the host. The ultimate goal is to identify high risk patients for tubal factor subfertility by non-invasive means.

2 Early Embryonic Development

Early embryonic development is focusing on pre-implantation as well as early post-implantation development. Pre-implantation research is only possible since the clinical IVF programme can be brought in contact with basic research. Pre- implantation development is studied with respect to the start of the embryonic genome expression, the role of chromosome abnormalities and the influence of environmental factors. Post-implantation development focuses on neurulation and neural tube closure defects.
With respect to the latter morphological, molecular and genetic aspects of neural tube closure in the Axial defects mouse in order to elucidate the aetiology of spina bifida aperta (SBA). The Axd research is divided into three major components: 1) identification of the Axd gene by positional cloning, 2) reduction of the penetrance of the Axd phenotype by dietary intervention and 3) analysis of the pathogenesis resulting in SBA in Axd.

3 Epigenetics and Gene Expression

Differentiation is most pronounced during embryogenesis, when many different cell types arise. In the nucleus, altered regulation of gene transcription ultimately determines the fate of cells. This is closely linked to chromatin structure modification: the structure and composition of chromatin determine DNA accessibility of many regulatory proteins. This phenomenon, which surpasses genetic programming encoded in the DNA sequence, is referred to as epigenetic control of gene expression. Studies are focussed on polycomb group protein complexes, which maintain transcriptional repression of silenced genes through chromatin structure modification. Recent findings suggest crucial roles for MAPKAPKs and PcG, as loss of either of these two proteins classes in established cell lines results in cell cycle exit (established cell lines) or defective differentiation, in addition to abnormal expansion (progenitor/stem cells). A second project was started to study the hypothesis that in female carriers of X-linked mental retardation, mutation of X-chromosome encoded chromatin remodeling factors disturb X-inactivation in female offspring, which in turn affects cognitive outcome.

Finally a novel method to generate chondrogenic tissue in vivo was developed: the in situ incubator (ISI). ISI involves creating a space between bone and periosteum, this space is filled by a biogel to generate extra-articular cartilage and thereby differs radically from current Tissue Engineering techniques.

4 Clinical Genetics

Genetic studies are devoted to all aspects of reproduction including, the causes of infertility. This starts with the notion, that human gametes do not always contain a correct haploid set. At fertilization this may result in aneuploid zygotes. Through abnormalities arising at fertilization normal gametes may give rise to chromosomal abnormal embryos as well. Finally it is possible that a perfectly normal zygote will become a mosaic embryo. With the introduction of IVF and other ART techniques it has become possible to monitor genetic abnormalities in gametes and zygotes.
The aim of the project is to optimise efficient and accurate diagnosis throughout the Special attention is paid to genetic studies of mitochondrial disease, characterized by the extreme heterogeneity with a possible defect in the mtDNA or in one of the several hundreds of nuclear genes. Using high-throughput CHIP-based resequencing technology it was possible to explain the heterogenic clinical expression of patients with Leber Hereditary Optic Neuropathy (LHON).
Linkage analysis in these families revealed a nuclear locus on the X-chromosome, which could be involved in the reduced penetrance of the disease.

5 Genital Tract and Implantation

The research in this research line focuses on the genital tract, more specifically on the interaction between the embryo and the genital tract (fallopian tube, endometrium, myometrium) and the implantation of the embryo in the endometrium. The endometrium is subject to research into physiology and pathology (endometriosis) of fertility, fertility regulation and the delicate balance between endometrial proliferation, differentiation and menstrual shedding in the context of early embryonic development and implantation, menstrual cycle disorders and endocrine modulation, regulation, and artificial manipulation of the endometrium. Endometriosis research focuses on retrograde menstruation, peritoneal defence mechanisms, apposition and adhesion of endometrial tissue to the peritoneal lining, remodeling of the mesothelial cells by retrograde menstrual effluent, and subsequent invasion of the extra cellular matrix, with the resulting angioneogenesis. Pharmacological ways to address the processes involved in the early development of this still enigmatic disease are tested in experimental in vitro and in vivo (animal) models.

6 Maternal Physiology

The studies in this research line are divided over 3 areas of interest: 1) pre­eclampsia, 2) hemodynamic adaptation to pregnancy and 3) trophoblast Invasion and differentia­tion.
Since 2005 the importance of the first research topic has increased in conjunction with our growing role as a referral center for patients at high risk to develop hypertensive complications in pregnancy. In the area of "hemodynamic adaptation to pregnancy" basic (ex-vivo) studies using rat arteries, aimed to explore the physiologic mechanisms of vasodilatation in early pregnancy are completing.
With respect to "Trophoblast Invasion and Differentiation" a novel double-tissue culture system, with emphasis on the role of oxygen as a regulator was developed.

7 Perinatal Stress

This program aims to study the adaptive response and damage/repair mechanisms of the foetus and newborn to a poor pre- and perinatal environment as during severe preeclampsia (asphyxia, hypoxia, growth restriction), chronic intrauterine infections and perinatal insults related to hypoxia and inflammation. The particular emphasis lies on alternations in the developing cardiovascular (systemic or pulmonary circulation), pulmonary and central nervous system that eventually may give rise to long-term morbidity. The latter includes the study of the neurophysiological development and behavioral states (e.g. habitation) in the normal and growth-restricted foetus. As these systems are responsible for most of the morbidity, a better understanding of these mechanisms will help to develop strategies to prevent, or at least minimize, short and long-term sequels.