Fetale Hirnentwicklung und Programmierung von Krankheiten

Efforts towards achieving an increased healthy lifespan have a long history and have inspired mankind over the centuries. In one of the earliest known literary works, the Epic of Gilgamesh, the hero sets out on a long and dangerous journey to search for the secret of eternal life to be found in a plant somewhere at the bottom of an ocean.

Today, in view of the worldwide ageing population, understanding the biology of healthy ageing is more relevant than ever. Healthy brain ageing is a major determinant of quality life-long health, since typical age-associated diseases are brain disorders such as cognitive decline, dementia or stroke. Stroke is the third most common cause for disability and invalidism in Europe. Apart from the element of personal tragedy, this situation also has socioeconomic implications: costs for preventive measures, treatment, rehabilitation as well as care consume 4% of the national health budgets. This figure is expected to rise with increase in life expectancy.

A major goal of the European Community is to find ways to ensure that increase in longevity is also accompanied by an improvement in disease-free life expectancy. The question is how can preventive and therapeutic measures delay the onset of typical age-associated diseases? To answer this question, we need to better understand the roots of health and disease in later life.

Human epidemiological and animal studies indicate that in addition to life style and genetic factors, environmental influences in prenatal life have a major impact on brain ageing and age-associated brain disorders.

The first indication that ageing may already start in the womb came from a study performed almost 20 years ago in Hertfordshire which showed that people born small lived shorter lives than people who were born larger. Studies in numerous populations worldwide have since shown that a small size at birth, which serves as a proxy of the suboptimal early life experiences is associated with increased risks of chronic degenerative diseases such as type 2 diabetes, cardiovascular disease, several forms of cancer, chronic obstructive airways disease, osteoporosis and sarcopenia. It was hypothesized that adaptations made by the fetus in response to undernutrition result in permanent changes in physiology and metabolism that later induce chronic degenerative disease. The first direct evidence for this hypothesis in humans has come from the studies by Roseboom’s group showing that prenatal exposure to the Dutch famine may lead to an increased risk for type 2 diabetes, cardiovascular disease, breast cancer, renal and lung diseases.

It is well established now that epigenetic modifications during the fetal period induced by maternal stress, therapies with stress hormones (glucocorticoids) or nutrient restriction have a significant impact on health for the entire duration of an individual’s life. Analysis of this link is the key to identifying preventive and therapeutic procedures. Hence, in the present project, the focus is placed on analyzing the link between human development and brain ageing and age-associated diseases such as cognitive decline and stroke.

Prenatal stressors
There is only sparse knowledge available on the effects of the different prenatal stressors on brain structure and function during ageing. Stress sensitivity is programmed prenatally mainly due to maternal stress, stress hormone (glucocorticoid treatment) and nutrient restriction. Many questions on how timing, type, intensity, and duration of environmental disturbances are related to altered neurobehavioral development and early brain ageing still remain unanswered.

Maternal stress during pregnancy
Indications that maternal stress results in alteration of cognitive functioning, behavioral and emotional problems are to be had from human cohorts aged up to 30y from van den Bergh's group. Other studies focusing on offspring CNS structures or structure-functioning relationships following maternal stress during pregnancy have shown altered brain function at the neurophysiological level in the newborn and gray matter volume reductions in the 6-9y old offspring at the structural level. The fact that maternal anxiety and stress during human pregnancy is linked with behavior abnormalities during childhood and adolescence, even after controlling for effects of postnatal maternal mood and other relevant prenatal and post-natal confounders, suggests that, as in animal models, a programming effect on the fetal brain had taken place.

Glucocorticoid treatment during pregnancy
Almost 10% of all pregnant women threatening preterm delivery are treated with glucocorticoid to enhance fetal lung maturation. This treatment ensures that preterm babies can artificially be ventilated and leads to survival.

Numerous effects of prenatal glucocorticoid treatment at doses used clinically to enhance fetal lung maturation on brain development and brain function during later life were observed in rodents, sheep and non-human primates in the studies from Nathanielsz's and Schwab's groups. In contrast, the effects of prenatal glucocorticoid exposure are much less clear in humans. There is one exception which refers to the few studies that followed-up offspring until the age of 32y and who showed no behavior or neurocognitive abnormalities after one course of prenatal betamethasone. Multiple courses of betamethasone to enhance fetal lung maturation, however, induced abnormalities of functional brain development and behavior disorders between 3 and 6 years of age.

In addition to direct effects of increased stress sensitivity on neuronal activity complex, there is evidence that indirect effects may also play a role. For example, resistance of peripheral glucocorticoid receptors to immunosuppressive GC leads to a pro-inflammatory state that has negative effects on neuronal function.

Nutrient restriction
Moderate undernutrition during pregnancy is common in both developing countries and in western societies such as the EU. In industrialized countries, a lifestyle comprising of dieting (including global food reduction) for cosmetic purposes is widespread and is a common cause of moderate undernutrition. A recent study showed that most women do not improve their dietary and lifestyle patterns during pregnancy. Finally, poor fetal nutrition is also present in teenage and in elderly primigravid pregnancies.

Roseboom's group has shown in the Dutch famine cohort and Nathanielsz's and Schwab's groups have shown in non-human primates that maternal malnutrition during pregnancy have effects on cognition that were independent of size and weight at birth. The evidence obtained recently by Roseboom's group from the mid-fifties suggests that cognitive function may also deteriorate faster in those prenatally exposed to the famine in early gestation, but not among those exposed in late gestation. In the British 1946 birth cohort, birth weight was positively associated with cognition in adult age.

There is no precise understanding of how prenatal stress induces cognitive disturbances in later life. Both a changed activity of the stress system and a different trajectory of brain development are likely.

Programming of stress sensitivity
Stress sensitivity depends on the activity of the stress axis with the two limbs, the autonomous nervous system and the hypothalamo-pituitary adrenal axis. The current (somewhat simplified) concept is that stress sensitivity is programmed prenatally in the last third of gestation when the hypothalamo pituitary adrenal axis matures. If, at this time fetal glucocorticoid concentrations are higher than appropriate for the current stage of maturation, glucocorticoid receptor expression and sensitivity in the hippocampus and hypothalamus, both critical for normal negative feedback to "turn off" the stress response, are permanently reduced by epigenetic modification of the glucocorticoid receptor genes. These mechanistic changes result in hypothalamo pituitary adrenal axis hyperdrive in the presence of glucocorticoid receptor resistance in many animal studies. Importantly, prenatal stress does not only alter activity of the hypothalamo-pituitary adrenal axis permanently, but also changes activity of the second limb of the stress axis, the autonomic nervous system.

Apart from this general mechanism, we do not have a detailed understanding of how the stress axis in later life is altered after prenatal stress. For example, following prenatal stress exposure, human and animal studies show that the HPA axis and the ANS are even less active during certain stages of life. Generally, effects of prenatal stress on stress sensitivity during later life seem to depend on poorly determined conditions such as stress sensitive periods during early life, the amount of stress, and the adversity of the stressor.

Effects of increased stress sensitivity
Hypothalamo-pituitary adrenal axis hyperactivity leads to increased stress sensitivity. Increased stress sensitivity contributes to biological ageing through both excessive catecholamine and glucocorticoid secretion and through glucocorticoid receptor resistance. The latter increases the production of pro-inflammatory cytokines, accentuating potential neuronal damage. There are hints that prenatal stress may not only affect brain ageing but also predispose to brain-related diseases. Data from Roseboom's group from the Dutch famine cohort suggest that the cognitive function may deteriorate faster in those subjects who were prenatally exposed to the famine.

Van den Bergh's group is the only group who has tested whether the hypothalamo-pituitary adrenal axis mediates the link between prenatal maternal stress and offspring behavioral problems in humans. It was shown in the 15-year-old offspring that maternal anxiety during weeks 12 to 22 of pregnancy is associated with a high flattened diurnal cortisol profile that shows elevated cortisol secretion in the evening.

Moreover, the interaction of increased stress sensitivity and the serotonergic system may explain the occurrence of depressive disorders since cortisol inhibits this amine system. Indeed, van den Bergh's group has shown an effect of prenatal anxiety on depressed mood that, in part, can be due to a flattened cortisol profile. Depression can impact on the objective age-related cognitive impairment.

Changes in the trajectory of brain development
Maternal stress, glucocorticoid treatment and nutrient restriction during pregnancy may also change the trajectory of fetal brain development. Nathanielsz's and Schwab's groups have shown that prenatal glucocorticoid treatment at the clinical dose used to enhance fetal lung maturation affects neurogenesis and myelination in fetal sheep. Studies in rodents clearly show that nutrient restriction alters brain development and cognitive function in later life. Nathanielsz's and Schwab's groups have shown that even moderate maternal undernutrition affects neurogenesis and development of neuronal network formation in the fetal non-human primate. Similarly, abnormalities in brain structure were found in schizophrenic patients exposed to the Dutch famine winter.

While early intervention is desirable (prevention of stress in the womb), it is also necessary to identify treatment strategies for those individuals who have an increased risk for early brain ageing and age-associated brain disease. Currently, there are millions of people in the EU and all over the world who are already struggling with the effects of prenatal stress on their health. This population also needs targeted interventions.

Bea van den Bergh´s group is involved in developmental neuroscience and biological developmental psychology. She is a pioneer in studying the developmental origins of behavior, adding to the efforts of researchers worldwide who are working on the developmental origins of health and disease. Study of the Developmental Origins of Behavior, Health and Diseases (DOBHaD) addresses timely and much needed research issues related to the interface between medical and behavioral sciences. Her DOBHaD research program focuses on physiological and psychological processes and their interplay; thus, contributing to the understanding of  mechanisms underlying DOBHaD and enhancing care for infants, children and adolescents with a prenatally acquired vulnerability for behavioural problems, psychopathology or chronic medical conditions. More specific goals are:

1. To develop instruments or methods that identify infants and children who are at high risk for poor mental and physical health outcomes as soon as possible before or after birth.
2. To better understand the biological and behavioral mechanisms that can explain enhanced vulnerability.
3. To test and implement biomedical and behavioral interventions that are successful at preventing disease or disorder onset, improving prognosis and enhancing quality of life.

Christian Gaser leads the group on Structural Brain Mapping at the Dept. of Neurology. He has substantial experience to plan, perform, and lead independent and internationally distributed research projects. This is particularly documented by the achievements of his Independent Junior Research Group ”Neuroimaging” which has contributed to scientific progress in a wide range of topics in neuroscience, often working across field boundaries. His research group is supported by the Federal Ministry of Education and Research (BMBF) to develop and apply methods for patient classification using computational morphometry. He has carried out a great amount of work in the field of neuroimaging with a specific focus on the development of valuable analysis methods for structural brain data. Amongst these methods, he has developed and implemented the VBM (voxel-based morphometry) toolboxes as an extension to the algorithms used by SPM8 (Wellcome Department of Cognitive Neurology), the software package that is the central processing software for MR morphometry of this project. In addition, he has pioneered the analysis of use-dependent plasticity. Furthermore, he uses state-of-the-art techniques to assess the stage of age progression by estimating the individual BrainAGE scores with applications for the early detection of Alzheimer’s disease.

Biocrates is a leading biotech company in the field of metabolic biomarker research and kit development. Using a targeted, mass spectrometry-based metabolomics approach, Biocrates identifies and quantifies endogenous metabolites in body fluid or tissue samples and develops them into powerful biomarkers. Biocrates has a strong background in biological sciences and (bio-) informatics as well as long-standing experience in analytical method development, method application, data analysis, and project management. Biocrates is well equipped with a state-of-the-art mass spectrometry platform that, in combination with its comprehensive methodological knowledge, allows the accurate quantification of a vast range of metabolites across several biochemical classes in a targeted metabolomics approach. Biocrates has been involved in various international and national research consortia and by applying its analytical services, directly contributed to neonatal research projects like e.g. the EU-funded NEOBRAIN project.

Dr. Peter Nathanielsz, formerly director of the Center for Pregnancy and Newborn Research at the University of Texas Health Sciences Center, is now the Distinguished Research Professor of Life Course Studies within the UW College of Agriculture and Natural Resources´ Department of Animal Science.

Peter W. Nathanielsz has researched fetal development for over forty years and was recently named as one of the top 5% of funded NIH investigators in the United States. For his work on fetal development he has been made a Fellow ad Eundem of the Royal College of Obstetricians in England. He delivered the 2011 Messenger Lectures at Cornell University, that university’s highest scientific recognition. He wrote the first book for the general reader on Developmental Programming entitled Life in the Womb: The origin of health and disease, published in 1999.

The group is the only one in the world owning adult non-human primate cohorts that were prospectively exposed to different prenatal stressors (glucocorticoid exposure and nutrient restriction) and are dedicated to study Developmental Programming of Health and Disease in later life.

His mission is to understand the molecular mechanisms that underlie the ageing process and that lead to age-related diseases with the hope that eventually this knowledge can contribute to a more healthy ageing of the human population. Cooperating with clinical partners, the group is involved in detection and functional analyses of genetic & epigenetic variations that determine the individual susceptibility to complex disorders (inflammation, obesity, cancer) and ageing. They are also engaged in the sequence analysis of eukaryotic model organisms, prokaryotic genomes and metagenomes. The group is one of the first laboratories in Germany applying next-generation sequencing for genome and transcriptome analysis.

Dr. Juan Camilo Estrada received his Bachelor in Biochemistry from the Autonomous University of Madrid. He earned his Ph.D. in Molecular Biology at the prestigious National Center for Cardiovascular Diseases (CNIC). During his Ph.D. program he focused in the study of oxidative stress on genetic stability and biosafety of human stem cells for his therapeutic application. After his doctorate, he specialized in the study of non-canonical activity of telomerase in the cell metabolism and senescence. His works has allowed him to participate in various international conferences and publish several scientific articles in the arena of regenerative medicine and ageing, and develop a patent to identifying new genetic and transcriptional biomarkers of cellular senescence in culture. Dr. Estrada has extensive experience in the field of human molecular cytogenetic with strong handling of different probes (PNA, CEP and LSI) for the chromosome labeling by classic fluorescence in situ hybridization (FISH) and derived techniques as multicolor FISH (M-FISH) and quantitative FISH (Q-FISH).

The AMC is one of the most prominent medical centers in the Netherlands with a leading position in medical research, both nationally and internationally. Tessa Roseboom is one of the AMC´s Principal Investigators leading the Fetal Origins Research group within the Academic Medical Center. She obtained funding from the Dutch Heart Foundation, the Netherlands Organisation for Scientific Resaerch, The European Science Foundation (Eurostress Program), Medical Resaerch Courncil and the Diabetes Fund with a volume of nearly 1 million Euros. She established the healthy WOMB study center to investigate the role of various influences during early human development on later health.

She has long standing experience in studying the early origins of later disease. She has worked on the Dutch famine birth cohort study for the past 15 years, and has led that study during the past 10 years. This cohort consists of 2.414 singletons who were born around the time of the Dutch famine in 1944-45. The cohort has been followed up extensively, focussing not only on metabolic and cardiovascular disease, but also on psychiatric diseases, infections, wellbeing, and certain types of cancer. She was the first to demonstrate that undernutrition during gestation in humans is associated with a doubled rate of heart disease, and of late, she also found suggestions of earlier brain ageing. She has been involved in investigateing research into gene environmental interactions, transgenerational effects, and outcome on reproductive succcess and epigenetic mechanisms.

Matthias Schwab is a trained pathophysiologist and neurologist. He is a senior member of the Department of Neurology and Head of the Research Group 'Fetal Brain Development and Programming of Diseases in Later Life' for more than 15y and strongly committed to the link between human development and ageing. His focus is on fetal brain development and the programming of brain-related disorders with a strong emphasis on stress effects and inflammation. He represents one of the first scientist who dealt with effects of prenatal glucocorticoid exposure on the brain using large animal models. He has a long-standing and successful cooperation with many partners in Europe and worldwide which have resulted in many joint publications. Prof. Schwab is head of the interdisciplinary sleep research unit with focus on autonomous and vascular dysregulation during prenatal development of sleep and during ageing. He has developed innovative nonlinear methods of EEG analysis.

Jan Tuckermann and his group’s aim is the deeper understanding of the action of GCs via their nuclear receptor (GR) in age-related processes. They use a combinatorial approach employing functional characterization of mouse strains conditionally mutated both in the GR and selected target genes in disease models, together with the development of functional screening tools for relevant cell types in age-related disorders. Here the goal is to decipher new mechanisms and to identify new mediators of therapeutic and side effects of GCs. Thus, by understanding GC-mediated effects in organs and tissues, knowledge about about degenerative processes during ageing can be acquired.