Integration of reproductive endocrinology and innate immunity from the whole animal to the cell

Lead Research Organisation: Royal Veterinary College
Department Name: Clinical Sciences and Services

Abstract

Infection of the uterus with bacteria is common in animals such as cattle, sheep, pigs and horses, and even in humans. These uterine infections occur during sexual intercourse, in pregnancy, or after parturition, and they cause infertility, abortion, pain and suffering. Uterine disease in animals is also difficult to prevent and costly to treat. The infertility is caused by damage to the lining of the uterus, by disrupting the development of the eggs within the ovary, and by altering the concentrations of the sex steroid hormones (progesterone and oestrogen) secreted by the ovary, which normally orchestrate the function of the uterus so that it is ready to nurture the fertilised egg. However, in an intriguing twist, the risk of infection depends on these sex steroids; progesterone suppresses immunity whilst oestrogen enhances it. Why this should be the case remains unclear, yet may be vital when developing treatments and developing prevention strategies. I am a vet with a scientific interest in uterine disease. I have focussed on cattle because infection is ubiquitous after parturition and is the most costly cause of infertility in the dairy industry. I, with my research group of 5 people, have successfully identified: 1. The bacteria which cause uterine diseases, 2. Systems to measure the severity of the disease, 3. The method of detection used by the immune system to recognise bacteria or bacterial toxins in the uterus and ovary. 4. That uterine and ovarian cell functions change when these detection systems are activated. While this work has already been both scientifically and clinically productive, the next stage is to test whether the concepts developed in cows apply across mammals, and we have preliminary data to support that idea. The key questions that have to be explored are: 1. Does activation of the immune detection system for bacteria in the genital tract disrupt uterine and ovarian function? In order to approach this issue, I will use specially bred mice in which the immune detection system is missing. I will also use novel techniques with cow tissues where the detection system can be suppressed. These approaches will allow me to compare the effect of bacteria on uterine and ovarian cell function when the immune detection system is intact or absent, and work out which cells are the key players for the immune response in the uterus and ovary. 2. How do ovarian steroids influence immunity? Here, I will test how steroids modify the immune response to bacteria in the uterus, and how they regulate the immune detection system. To work out which steroid hormone pathways are important within the cell, I will compare the immune response to uterine infection in mice that have been bred with parts of the steroid pathway missing . Finally, I will explore which parts of the immune pathway may interact with the steroid pathway inside the cells of the uterus. This work will be done at the Royal Veterinary College, which has all the necessary facilities. Training in the techniques required to complete the project will be provided by partnerships I have developed with researchers at the cutting-edge of science in the UK, USA and Germany. These studies should lead to the design of better treatments for uterine disease and infertility, and drugs that can enhance the immune response to disease, whilst avoiding side-effects associated with hormonal medicines. It may also enable strategies to be developed to avoid disease at times of adverse hormone status or to exploit the hormone status to resolve uterine infections. In the long term it may be possible to identify why cattle are particularly prone to uterine infection, and use this information to breed animals that are more resistant to uterine disease.

Technical Summary

Reproductive endocrinology and innate immunity are usually treated as separate entities. Yet there is a link as pathogenic organisms often infect the genital tract of domestic animals causing infertility, whilst the immune response is modulated by the stage of the ovarian cycle. I have used cattle to study this link as uterine infection is a costly cause of infertility in the dairy industry, disrupting uterine and ovarian function. Uterine cells express the immune receptor (TLR4) for the most common pathogen, E. coli. To test the paradigm that the endocrine and immune systems are integrated in mammals, I will use murine genetic models and employ novel laboratory techniques. To determine the role of the TLR4 pathway in the uterus and ovary, TLR4-/- mice will be used and siRNA to suppress TLR4 in bovine cells. The endocrine and inflammatory response to E. coli and LPS will be measured. Which cells are central to the uterine and ovarian inflammatory response will be explored using re-aggregation of cell types with different TLR4 expression. How and where uterine TLR4 expression is regulated during the ovarian cycle will be evaluated using molecular biology and histology. The effect of ovarian steroids on the immune and endocrine responses of uterine cells will be tested, using murine and bovine cells that lack functional TLR4. To test the role of steroid nuclear receptors, the response to LPS will also be examined using mice with functional disruptions of these receptors. Interaction of intracellular pathways following hormone and/or immune challenge will be examined by measuring components of the respective pathways, transcription factors and downstream endocrine and inflammation genes, using normal cells and cells that lack functional TLR4 or steroid nuclear receptors. These studies should lead to the design of better treatments for uterine disease and infertility, and drugs that can enhance immunity, whilst avoiding side-effects associated with hormonal medication.

Publications

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Davies D (2008) Toll-like receptor and antimicrobial peptide expression in the bovine endometrium. in Reproductive biology and endocrinology : RB&E

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Donofrio G (2008) Bovine endometrial stromal cells display osteogenic properties. in Reproductive biology and endocrinology : RB&E

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