The human fetal liver: development and response to maternal drug use.

It is well known that if a woman smokes while pregnant there are bad consequences for the resulting offspring, especially slowed growth in the womb. However, other serious problems are also likely to occur in children exposed to their mothers' cigarette smoke chemicals during pregnancy. These include an impaired immune system (e.g. increased asthma), poorer educational performance and a raised chance of developing obesity, diabetes and heart disease (called metabolic syndrome). Many of these effects also happen if the mother regularly drinks alcohol while pregnant, even if not to the extent of addiction. We do not know exactly how much the chance of somebody developing metabolic syndrome is altered if their mother smoked and/or drank while pregnant. However, a recent study of 74,000 women found that if their mothers smoked while pregnant, the women had a 53% higher chance of becoming obese. This would be a major added drain on the NHS and would mean that many more people would be likely to suffer these debilitating conditions since smoking and/or alcohol use during pregnancy continues in 20-40% of women. In 2006-07 costs to the English NHS of lifestyle and related conditions were: smoking £3.3 billion, alcohol £3.3 billion, overweight/obesity £5.1 billion and diabetes £3.5 billion annually.

Adult health is partly programmed by events during fetal life when the individual is still in the womb and an individual may be badly adjusted for life if the mother uses recreational drugs. Growth restriction is important in this process and the liver is one of the organs most affected by disturbed growth before birth. The fetal liver is a key organ, protecting the fetus from harmful chemicals and controlling fetal growth. Progress in understanding the effects of maternal drug use on fetal development suffers from two problems: firstly, our ignorance of the levels of drugs to which the fetus is exposed and, secondly, the mechanisms by which these drugs affect development. Two factors contribute to our ignorance. Firstly, very little research uses normal human fetuses. Secondly, there is a lack of low-cost means with which to measure how much/which chemicals (nicotine, alcohol, cannabis etc.) are getting into the human fetus during pregnancy. This project aims to resolve these issues using our uniquely large collection of normal, second trimester human fetal livers and by collecting both the liver and the placenta from further terminations of normal pregnancies.

We will use highly sophisticated methods at the National Institute on Drug Abuse (USA) to measure chemicals from tobacco, cannabis, cocaine and alcohol in the fetal liver and in matched pairs of fetal livers and placentas. This will tell us how much the fetus has been exposed to drugs taken by the mother and whether the placenta can be used to measure the fetal burden of drugs and chemicals from the mother. This would allow us to carry out much larger studies of newborn babies to measure exposure levels in the placenta and their contribution to adult ill-health.

At the same time as measuring drug levels in the fetal liver we will work out how those drugs have affected liver function. Then, by using cell culture, it will be possible to re-create the effects of drug exposure in the culture dish with a view to understanding the long-term consequences. We will also be able to find out more about how liver function develops and how it differs between male and female babies Overall, our aim is to relate changes in the control of fetal liver development to the effects of chemicals in cigarette smoke. This will allow us to understand liver mal-development turns to metabolic syndrome. The information from this study will allow us to measure, and to understand, the effects of exposing the developing fetus to its mother's recreational drug use. This will enable treatments to be designed to reverse these effects and to lower the incidence of the modern scourge of metabolic syndrome.

The human fetus is exposed to many potentially damaging chemicals, e.g. through maternal smoking and alcohol consumption. With large studies now linking such exposures with priority diseases (metabolic syndrome: cardiovascular disease, obesity and diabetes), accurate understanding of the underpinning pathophysiology is required. The human fetal liver has extensive metabolic and endocrine roles essential for normal growth and has been shown to be dysregulated by maternal drug use. This study will determine, for the first time, the exposure of the human fetal liver to maternal drug use and the effects that this has on liver function at the transcript, protein and cellular level. Understanding how maternal recreational drug use disturbs normal developmental pathways would represent a significant advance in our comprehension of mechanisms affecting fetal programming of adult health.

Initially, 120 second trimester human fetal livers (a unique resource already collected) and 40 liver+placenta pairs (to be collected) will undergo analysis through collaboration with the National Institute on Drug Abuse to measure levels of over 20 drug metabolites (e.g. of cigarette, alcohol, cannabis, heroin). RNA transcript and protein levels will then be measured in a rigorously matched subset (60) of these samples to determine the effects of drug exposure on fetal liver function. Finally, stem cell culture models will be used to examine how exposure affects activity at the cellular level.

The principal outcomes of the study will be:

(1) to show what drug exposure levels are in the human fetus.

(2) to demonstrate how these real-life exposure levels can alter fetal liver development and function, potentially affecting post-natal health and development.

A secondary outcome of the project will be to establish whether the placenta is a reliable read-out of fetal exposures and, thereby, indicative of an increased chance of ill-health and dysregulated liver development.

Beneficiaries of the project include research and healthcare professionals, pregnant women and their offspring, women intending to fall pregnant, research and regulatory organisations, the NHS, government and the tobacco/alcohol industries. These will benefit through generic knowledge of the recreational drug burden on the human fetus and the likely risks posed to the development and health of the exposed individuals, especially with respect to disease spectra such as metabolic syndrome.

Healthcare professionals benefiting include clinical practitioners, their professional bodies (RCOG, RCPCH and RCGP), and others, such as midwives, fertility clinics, reproductive health and pre-pregnancy counselling services and NHS health promotion organisations. They will benefit from knowledge of the risk of significant fetal drug exposure during development, potential post-natal health consequences and ways to minimise the risk (e.g. lifestyle changes to avoid drug use intake). Health professionals in general will benefit from the potential to screen neonates for recreational drug exposures via measurement drug metabolites in the term placenta, a readily available tissue after birth. The project will inform on the Barker hypothesis, linking fetal antecedents of disease, with relation to drug exposures. Pregnant women and intending mothers will benefit from knowledge allowing minimisation of fetal exposures. Knowledge will become available in tranches, the 120 liver drug metabolite data and the RNA-seq and proteomics data late in the first half of the project, the validation and stem cell findings in the second half and the data on liver:placenta agreement for drug metabolite data late in the project lifespan. We do not expect that there will be significant delay before the project begins to impact on stakeholders. The involvement of Dr Huestis in the project allows direct introduction of our findings into the NIH, a massive federal research body in the USA.

Research and regulatory organisations benefiting will include the NHS, Department of Health and policy makers and regulators, e.g. the EC. Data generated by this project will provide comprehensive knowledge upon which policies concerning drug transfer to the fetus and mechanisms of exposure reduction can be formulated. These data will also fulfil the immediate requirements for developing better screening protocols in order to detect at risk neonates. They will also inform on design and implementation of regulations concerning recreational drug use. There may be some delay before the data from this project will be used to inform policy, but, if effective knowledge exchange pathways are used, this should be medium term.

The subsequent commercial potential of the project may be significant if placental burdens of single and combined exposures (e.g. smoking AND drinking during pregnancy) are can be characterised reliably in comparison with the fetal liver (and confirmed in the term placenta subsequently). If wide-scale neonatal screening, using the placenta, for potential drug exposure were available it would benefit the individual and the health service. By indicating the potential likelihood of a neonate developing health problems, such as metabolic syndrome, in the future these tests would interest a commercial healthcare partner and would allow the development of more preventative strategies.

Overall, outcomes from this project are likely to have impact on a range of beneficiaries and, within a long-term timescale, would be expected to lead to improvement in specific aspects of the nation's health.