LOCALIZATION AND EXPRESSION OF FIBRONECTIN DURING MOUSE DECIDUALIZATION IN-VITRO - MECHANISMS OF CELL-MATRIX INTERACTIONS

During implantation, the embryonic trophoblast aggressively invades th e uterine stroma. The resulting uterine reaction, decidualization, inv olves differentiation of new cell morphologies and remodeling of the e xtracellular matrix. This creates an environment that first permits in vasion, then controls this invasion to allow the establishment of the placenta. The production, organization, and cellular interactions with the matrix are thought to underlie decidual functions. We have begun a reductional analysis of the components of the decidual matrix, focus ing on extracellular fibronectin (FN). Using decidual cell cultures pr epared from day 7 implantation sites, the synthesis, extracellular org anization, and details of decidual cell:FN interaction were studied. E mploying immunofluorescence, immunoprecipitation, and dot blot analysi s, decidualizing cultures showed a constitutive level of FN synthesis and deposition. The differentiating cells organized extracellular FN i n patterns similar to that seen in vivo. The predominant, flattened de ndritic decidual cells organized FN in long, thin fibrils. Large, roun ded decidual cells, limited to the primary decidual zone in vivo, show ed FN limited to punctate membrane patches and short, thick fibrils. U sing double labeling techniques, FN expresssion was co-localized with actin microfilament (MF) bundles during the cytoskeletal changes assoc iated with the differentiation of both decidual cell types. The functi on of MFs in maintaining morphology was demonstrated by cytochalasin B perturbation. Attachment of decidual cells to FN was calcium dependen t and gly-arg-gly-asp-ses-pro (GRGDSP) sensitive, with dendritic decid ual cells expressing the alpha(5) and beta(1) integrin subunits. This suggests that an integrin system functions to attach decidual MF bundl es to extracellular FN. This work shows that during decidual matrix re modeling, constitutive levels of FN are maintained to provide an extra cellular framework to stabilize the decidual cytoskeleton and support morphological differentiation of decidual cells. (C) 1996 Wiley-Liss, Inc.