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Integrin and extracellular matrix interactions at the maternal conceptus interface in pigs
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Osteopontin (OPN), an extracellular matrix protein (ECM), has been hypothesized to bind integrins expressed on the apical surfaces of the conceptus Tr and uterine LE to: 1) stimulate changes in morphology of conceptus Tr and extraembryonic membranes resulting in conceptus elongation, and 2) to induce adhesion between the LE and Tr necessary for implantation. Therefore, the following studies were conducted with pigs to determine 1) OPN expression and function in the porcine uterus and conceptus (embryo and associated extraembryonic placental membranes) and 2) the activation of signal transduction pathways which may mediate the functions of ECM proteins during implantation. The first study determined the spatial and temporal expression of OPN in endometria, uterine flushings, and conceptus in the pig. OPN protein is expressed on the apical surfaces of the uterus and conceptus where it may bind integrins to induce adhesion between these tissues. Functional analysis of potential OPN-integrin interactions at the apical surfaces of porcine conceptus trophectoderm (Tr) and endometrial epithelial cells was performed. OPN binding to integrin receptors induced cytoplasmic reorganization and formation of focal adhesions in these cells. The second study verified integrin expression in conceptus Tr and endometrial epithelial cells and the ability of these cells to bind the ECM proteins, OPN and fibronectin (FN) in vitro. Treatment of these cells with OPN or FN differentially activated the signaling pathways, focal adhesion kinase (FAK), mitogen activated protein kinase (MAPK), and phosphotidylinositol-3 kinase (PI3K), known to mediate the functions of ECM proteins. Collectively, these results suggest that OPN, expressed at the maternal-conceptus interface, may play an important role in mediating changes in the conceptus Tr necessary for conceptus elongation and inducing adhesion between the conceptus and uterus during implantation and placentation. OPN and FN treatment activates various signal transduction pathways in conceptus Tr and endometrial epithelial cells, suggesting that the various and overlapping functions of these proteins are mediated through the actions of different signal transduction pathways in the different cell types.
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Includes bibliographical references (leaves 108-133).
Issued also on microfiche from Lange Micrographics.
Garlow, Jane Elizabeth (2002). Integrin and extracellular matrix interactions at the maternal conceptus interface in pigs. Master's thesis, Texas A&M University. Available electronically from
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