RESEARCH PROJECTS
The Prostaglandin F Receptor (PTGFR) and Birth
We are defining the regulation and role of the prostaglandin (PG)F2a receptor (FP) in the control of parturition at term and preterm. It appears from our work that PGF2a is an “amplifier” of the cascade of events that promote labour in the uterus. With Dr. Sylvain Chemtob at the University of Monteal, we intend to develop new allosteric activators of FP downregulation or tocolytics, drugs that delay preterm labour and prolong pregnancy, based on the actions of this receptor. In the mouse we showed an increase in FP mRNA at term and preterm birth, and that preterm birth was more associated with an increase in FP mRNA than an increase in the tissue concentration of its ligand, PGF2a . These data suggest tissue sensitivity to contractile agonists is regulated and important for preterm birth, justifying our attention on receptors. In collaboration with Dr. Sarah Robertson (U of Adelaide) we found that interleukin (IL)-6 knockout mice deliver one day late, due in part to absent or attenuated increases in FP and oxytocin receptor mRNA. We have sequenced for the first time the human and mouse FP promoters and have identified repressor and activator sequences. This information helps us study the regulation of FP in cultured human myometrial cells. Both interleukin (IL)-6 and IL-1 beta stimulate FP expression and IL-1 beta does so via an NFkB mechanism. Forskolin activation of adenylate cyclase also increases FP mRNA expression and does so via a protein kinase A pathway and a MAP kinase kinase pathway. The ligand, PGF2a , stimulates receptor internalization and suppresses FP mRNA expression via protein kinase C. In sheep in preterm labour, we suppressed uterine contractility and delayed birth in sheep with a specific FP antagonist, THG113.31, in collaboration with Dr. Jon Hirst at Monash U. Recently we have shown that FP is present in decidua and increases in this tissue at term. It may be a key regulator of decidual activation in preparation for preterm or term birth. Our latest work is to identify which FP isoforms are responsible for myometrial contraction and downregulation in collaboration with Dr. Donna Slater (U of Calgary).
Single Nucleotide Polymorphisms and Stress in the Etiology of Spontaneous Preterm Birth
Currently, the majority of preterm deliveries are still unexplained. Pregnancy and parturition involve complex pathways in both mother and fetus, some of which may be termed environmental. These include stress, inflammation, hemorrhage and pathologic uterine distension. Most commonly. they are present in various degrees of combination. In addition to these environmental factors, there is also a strong genetic basis for preterm birth.
In new studies, We are exploring gene-environment interactions and seeking a transcriptomic predictor of preterm birth and collaborating with Drs. Steve Lye and Alan Bocking, U of Toronto and Dr. Craig Pennell of the U of Western Australia with the genomics and transcriptomic aspects of these projects, and with Dr. Kathleen Hegadoren, Dr. Radha Chari and Dr. Martin Somerville from the U of Alberta. We are seeking gene-environment correlations between maternal perceived chronic stress (environmental factor) and maternal single nucleotide polymorphisms (SNPs) (genetic factor) and preterm birth. This study should inform us whether a gene-environment interaction indicates a higher risk for preterm birth. We are also seeking with our collaborators a transcriptomic signature that predicts preterm delivery in peripheral leukocytes of asymptomatic women (those not in preterm labour).With an international group of scientists led by PreHOT member, Craig Pennell, and sponsored by PreHOT, the World Health Organization and the March of Dimes, we just recently announced a SNP signature that is highly associated with Caucasian women who delivered preterm at < 34 weeks of gestation. We have confirmed that this signature is robust, i.e. it is replicated (p<1x10^-8) in similar cohorts of women around the world, including our Edmonton cohort. We have filed a provisional patent for the signature. The prognostic test we will develop to predict risk for women of preterm delivery can be taken by non-pregnant women.
Studies on mechanisms of uterine activation for labour: interactions between corticotropin-releasing hormone and prostaglandins
During most of pregnancy, the myometrium remains in a relatively quiescent state until it is activated to initiate the contractions required for labour and delivery of the baby. Although the mechanisms that control the transition of the myometrium from a quiescent to an active state remain unknown, increasing lines of evidence suggest the local stimulators, corticotropin-releasing hormone (CRH) and prostaglandins (PGs), may have a synergistic relationship of mutual amplification that leads to uterine activation and labour. Our objective is to investigate the interactions between CRH and PGs in human pregnant myometrium and thereby explore the mechanisms of uterine activation for labour. We intend to identify targets for intervention to delay preterm birth.
Our first specific aim is to test the effects of CRH stimulation on PGs and PG receptors in human myometrial cells. Our preliminary evidence indicates that CRH stimulates expression of PG synthetic enzymes and receptors, but a coordinated study has never been performed. Primary human myometrial cell cultures prepared by Dr. Slater and Dr. Wood will be challenged in the Slater and Olson laboratories with increasing concentrations of CRH and then PGE2 secretion and expression of cPLA2, sPLA2, and COX-2, the synthetic enzymes of PG production, as well as EP1-4, FP and CRH-R1 and CRH-R2 will be determined. CRH-R1 antagonists will be used to elucidate the specific CRH receptor subtype responsible for CRH actions. The role of CRH will be established.
Preterm Birth & Inflammation in the rat model. Evaluation of uterine activation for labour: Leukocyte recruitment, invasion, adherence and activation
Preterm birth is the most serious health problem resulting from pregnancy for the newborn as it not only has immediate adverse effects, but the possibility of life-long handicap as well. Preterm birth is a syndrome having several different causes and pathways. One of these receiving a lot of attention currently is stress. Mothers experiencing chronic stress are thought to have a greater risk of delivering early. We wish to study the effect of stress on the physiological pathways leading to preterm delivery in an animal model.
Dr. Gerlinde Metz of the University of Lethbridge has just developed a rat model of stress-induced preterm delivery that is highly reliable. It is generational, too, in that pregnant rats are stressed during the second half of their pregnancies, but they do not delivery early. However, their behaviours are changed so that they do not care normally for their offspring, which affects their behaviours. When these stressed daughter rats mature and become pregnant, the same stress stimuli their mothers received are sufficient to cause them to deliver 8 hours early.
Our goal is to determine the sequence of immunological, biochemical, structural, and physiological events that lead from stress to the initiation of preterm delivery. We have a team of experts assembled who can monitor all these factors. In addition we have two unique blockers that should inhibit the orderly sequence of events that causes labour and delivery which we can use as checks to confirm our observed orderly procession of events leading to labour and delivery. We anticipate that not only will we understand our stress-induced preterm birth rat model better; we will also know the sequence of events leading steadily and orderly towards labour. We hope to apply this information to our understanding of human parturition and preterm birth. Last, the two antagonists we will use will hopefully have human application as drugs to delay human preterm labour and to prolong pregnancy, thereby improving newborn health outcomes.
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