Functional Role of Arg-Gly-Asp (RGD)-Binding Sites on β1 Integrin in Embryo Implantation Using Mouse Blastocysts and Human Decidua1

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Abstract
Amino acid residues 140-164 of integrin beta1 comprise an Arg-Gly-Asp (RGD) cross-linking region. The present study was undertaken to study the role of the RGD cross-linking region of integrin beta1 subunit in embryo implantation. Decidual cells attached to fibronectin (FN)-coated dishes. A peptide corresponding to integrin beta1[140-164] (DDL; DYPIDLYYLMDLSYSMKDDLENVKS) inhibited decidual cell attachment to FN-coated dishes in a dose-dependent manner. A variant integrin peptide in which Asp 157 and Asp 158 were replaced by Ala (AAL; DYPIDLYYLMDLSYSMKAALENVKS) did not affect decidual cell attachment to FN. Inhibition by DDL peptide was reversed by prior treatment with an RGD-containing peptide but not by prior treatment with an RGE-containing peptide. Mouse blastocysts became attached to cultured human decidual cells after embryos hatched from the zona pellucida. The majority of hatched blastocysts attached to human decidual cells within 24 h of culture. Blastocysts that attached to decidual cells exhibited extensive outgrowth after 48 h. Treatment of decidual cells with synthetic peptides did not affect the rates of hatching and attachment of blastocysts. The outgrowth of embryos on decidual cells was inhibited by DDL peptide in a dose-dependent manner, but not by AAL peptide. These findings suggest that integrin beta1[140-164] on decidual cells may be important in embryonic development and differentiation following attachment.