POSTIMPLANTATION MODIFICATION OF THE SPIRAL ARTERIES

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The long-term objective of the project is to determine the cellular mechanisms involved in the migration of extravillous trophoblast cells into the maternal spiral arteries and their role in the modification of the arterial wall. Adequate invasion and modification of the arteries appears necessary to provide a normal blood supply to the placenta. Inadequate invasion and remodeling has been associated with pregnancies complicated by hypertension and intrauterine growth retardation and has been suggested as a cause of miscarriages. Because of limitations associated with acquisition of human material at precise developmental ages, and the fact that this type of invasion occurs only in higher primates, we have used the macaque animal model to explore the cellular biology of this phenomenon. In the present application three specific aims are proposed that will explore three related hypotheses: I) that trophoblast cells utilize a system of cell-cell adhesion molecules to migrate along the maternal endothelium. Whereas much has been learned about leukocyte and tumor cell adhesion to endothelial cells, little is known regarding trophoblast-endothelial interactions. We will examine the molecular basis of this interaction by a combination of immunocytochemical localizations to determine what adhesion molecules are present in situ and verify their functional involvement using an in vitro cell adhesion assay. 2) that trophoblast utilizes the extracellular matrix (ECM) and a family of matrix receptors (integrins) as a means to invade the walls of the arteries. Once trophoblast cells have migrated along the artery to some depth, they then extravasate and invade the wall of the artery, disrupting the muscular and ECM components. In the process of accomplishing this, we hypothesize that the cells interact with ECM components in the basement membrane and elsewhere, using these interactions as a basis for adhesion or migration. We will determine the types of ECM present in the arterial wall, how these change in response to invasion, and how integrin expression is modulated as cells invade the arterial wall. Together, the results of these two specific aims should provide significant new insights as to the molecular mechanisms utilized by trophoblast to accomplish this physiologically important process. Finally, 3) we hypothesize that trophoblast cells in the walls of the spiral arteries remain functionally active and may be the source of vasoactive substances that could act locally or regionally to regulate maternal blood flow to the placenta. Our preliminary studies have shown the presence of immunoreactive endothelin- 1, a potent vasoconstrictor, and calcitonin gene-related peptide, a potent vasodilator, in many trophoblast cells in the walls of the spiral arteries. Experiments outlined in this proposal will confirm and extend these observations. The macaque is an excellent animal in which to explore this hypothesis and our findings should add significant new information on potential factors regulating the maternal blood supply to the placenta.