Expression of extracellular matrix proteins during blastulation in bovine embryos and factors affecting bovine endodermal cell outgrowth In Vitro

During early embryonic development, endodermal cells leave the inner cell mass (ICM) and migrate over an extracellular matrix (ECM), located on the blastocoelic side of the trophectoderm, to form a continuous layer of extraembryonic endoderm. Cell migration events depend on a family of cell surface...

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Bibliographic Details
Main Author: CoreyAyne, Singleton
Other Authors: Menino, Alfred R. Jr
Language:en_US
Published: 2012
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Online Access:http://hdl.handle.net/1957/31845
Description
Summary:During early embryonic development, endodermal cells leave the inner cell mass (ICM) and migrate over an extracellular matrix (ECM), located on the blastocoelic side of the trophectoderm, to form a continuous layer of extraembryonic endoderm. Cell migration events depend on a family of cell surface proteins known as integrins that bind specific ECM proteins. In an effort to understand the mechanisms involved in bovine endodermal cell migration, two experiments were conducted. In the first experiment, expression of the ECM proteins fibronectin, laminin and vitronectin was evaluated by immunofluorescent staining in in vivo and in vitro developing embryos during Day 6-10 and Day 7-10, respectively (Day 0=onset of estrus). Fibronectin was detected in all stages of in vivo and in vitro embryos, however no difference (P>0.10) was observed due to day or developmental stage. Laminin staining was moderately expressed in all stages of in vivo embryos, with an increase (P<0.05) in Day 10 in vivo embryos. Laminin staining in Day 9 in vitro embryos was less intense (P<0.05) than Day 7 and 8 in vitro embryos. Higher (P<0.05) expression of laminin was observed in Day l0 in vivo embryos as compared to Day 10 in vitro. Vitronectin staining was expressed throughout all stages of development. Day 6 in vivo embryos exhibited more intense (P<0.05) staining compared to Day 8 in vivo embryos. Day 10 in vivo embryos expressed more (P<0.05) vitronectin than Day 10 in vitro embryos. In the second experiment, the effects of ECM-type and inhibitors of integrin binding on bovine endodermal cell outgrowth from the ICM were evaluated. Day 7 embryos were nonsurgically collected and cultured for 96 h on either fibronectin-layered microdrops containing 0 (control), 0.5 or 1.0 mg/ml RGD and/or EILDV peptides or vitronectin-layered microdrops containing 0, 0.5 or 1.0 mg/ml RGD peptides. At 24-h intervals, ICM were photographed and the numbers of cells leaving the ICM were counted. Areas of cellular outgrowth were calculated from the photomicrographs. Compared to the control, addition of 0.5 or 1.0 mg/ml RGD, EILDV or RGD and EILDV did not (P>0.10) reduce the areas of cellular outgrowth from the ICM on matrices of fibronectin. Numbers of cells in outgrowths were greater (P<0.05) in control ICM compared to 0.5 mg/ml RGD, but this effect was eliminated (P>0.10) when the inhibitor concentration was increased to 1.0 mg/ml. Addition of 0.5 or 1.0 mg/ml RGD did not reduce (P>0.10) the area of cellular outgrowth from the ICM on vitronectin and had no effect (P>0.10) on numbers of cells in the outgrowths. Detection of fibronectin, laminin and vitronectin by immunofluorescence suggests these proteins are present in the developing bovine embryo to support endodermal cell migration and stabilization in extraembryonic endoderm formation. Because cell migration over fibronectin and vitronectin was not inhibited by the RGD and EILDV peptides, endodermal cells must use either an integrin that recognizes alternative binding sites in fibronectin and vitronectin or an alternative cell adhesion system. === Graduation date: 2003