Leukocyte Migration and Parturition

• Author / Creator

  Lee, Han

• Parturition is a complex phenomenon that is regulated by leukocyte invasion, progesterone withdrawal, and local inflammation. Of these regulatory mechanisms, leukocyte invasion is of interest for diagnostic development. Leukocyte invasion is thought to be mediated by an increase in output of chemotactic factors (chemokines) from intrauterine tissues and an enhancement of peripheral leukocytes to respond to chemotactic signals. Once these leukocytes are recruited from the plasma to the uterine tissues where they become anchored, they release an array of inflammatory mediators that amplify this response thereby facilitating uterine transition from pregnancy to parturition, cervical softening, and fetal membrane breakdown, which culminates in expulsion of the fetus and initiation of uterine involution.Leukocyte invasion is therefore a signal for parturition, and it has been studied previously using a tool called the Leukocyte Migration Assay (LMA). Our lab has previously demonstrated that the LMA can predict labour onset within 7 days. I streamlined the LMA and reduced the time and cost required to perform the assay by over 60% and 80% respectively, making it more feasible for clinical implementation. The streamlined LMA was also used to study the mechanisms that regulate leukocyte invasion during normal and preterm labour. In our study, intrauterine administration of IL-1β was used to induce preterm birth (PTB) in mice. We determined that mouse gestational chemotactic factors (GCF) in the lower uterus peak just prior to labour, coinciding with the timing of leukocyte invasion. This increase in GCF was not detected during PTB despite observing a greater density of neutrophils in the lower uterus. Induction of PTB resulted in the increased abundance of proinflammatory cytokine mRNA in peripheral leukocytes, as well as the enhanced responsiveness of leukocytes to respond to chemokines. This suggests that IL-1β mediates leukocyte invasion by enhancing leukocyte chemotaxis and not by increasing GCF secretion. Moreover, we demonstrated that in humans, IL-1β does not enhance leukocyte chemotaxis directly, but likely stimulates the secretion of an intermediary priming factor from the fetal membranes. Our finding that leukocytes can be enhanced for chemotaxis artificially through incubation with maternal serum from term labouring women suggests that the intermediary priming factor may be released into circulation where they may exert a priming effect on peripheral leukocytes.In addition, we studied whether 101.10 (aka Rytvela), a novel allosteric modulator of the IL-1β receptor and potential therapeutic for PTB, could reverse IL-1β-mediated PTB, neutrophil infiltration of maternal and fetal tissues, leukocyte priming, and detection of proinflammatory cytokine mRNA in peripheral leukocytes. These effects of IL-1β in the mouse were successfully reversed with 101.10 co-treatment. The LMA forms the basis of a clinical diagnostic test that estimates the time until the spontaneous labour onset, whether term or preterm. Furthermore, our results suggest that the LMA can be used to assess the level of maternal, and by proxy, fetal, inflammation during pregnancy. Additionally, the LMA can be used to assess the degree of inflammatory suppression that is provided by anti-inflammatory inhibitors, including 101.10. Combined, our findings offer new opportunities for diagnosing, treating and assessing the efficacy of treatment of maternal and fetal inflammation. They may also lead to new and important questions about the origins and effects of maternal and fetal inflammation.

• Subjects / Keywords

  • Parturition, Preterm Birth, Leukocyte Invasion

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-6b3x-3932

• License

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