Integrins and vascular cell adhesion molecule-1 (VCAM-1) are required for normal placental development. In this study, integrin subunits ␣4, ␣v, ␤1, and ␤3, and VCAM-1 were investigated for expression in uteroplacental units (gestation day [g.d.] 6 and 8) and placentas (g.d. 10, 12, 14, 16, and 18) of Swiss-Webster mice. All subunits and VCAM-1 mRNA (identified by reverse transcriptase polymerase chain reaction [RT-PCR]) and protein (detected by immunofluorescence) were present in all tissues

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... roughout gestation. VCAM-1 was expressed strongly in the ectoplacental cone and trophoblast giant cells, ␣4 was expressed strongly by trophoblast giant cells and moderately by spongiotrophoblast and labyrinthine trophoblast, and ␣v was expressed more strongly in the spongiotrophoblast than in the labyrinthine zone. The ␤1 was more strongly expressed in the labyrinthine than the spongiotrophoblast zone, while ␤3 and VCAM-1 were essentially equal in the two zones. Trophoblastlike SM9-1 cells were positive for all of the adhesion molecules when tested by RT-PCR and immunocytochemistry. Adhesion molecule expression in SM9-1 cells was consistent with expression in the labyrinthine zone. Collectively, the results of this study demonstrate that murine placentas contain mRNA and protein for ␣4, ␣v, ␤1, ␤3, and VCAM-1, and that expression is cell-specific. These results and the identification of an adhesion molecule-expressing trophoblastic cell line should facilitate future studies on the function of adhesion molecules in placental development.