The ultrastructure of the rat primary decidual zone

Abstract

The rat primary decidual zone (PDZ) is a transitory, avascular region of transformed fibroblasts surrounding the implanting embryo. Tracer studies have indicated that the PDZ is selectively permeable to macromolecules, permeability decreasing with increasing molecular weight of the tracer. To clarify the morphological basis of the permeability barrier, we have studied the ultrastructure of the PDZ with particular emphasis on the intercellular features and cellular junctions. The cells of the PDZ were large and tightly packed; their apposed membranes showed extensive interdigitations in some regions, but elsewhere they were relatively straight. Tight junctions, gap junctions, and desmosomelike junctions were observed between decidual cells. The tight junctions usually consisted of one or two points of membrane fusion, and they were oriented both parallel and perpendicular to the long axis of the PDZ. These junctions were frequently associated with gap junctions. Scattered pockets of dilated extracellular space between decidual cells contained collagen fibrils and an amorphous, dense material. These extracellular components were also sequestered by the decidual cells in deep invaginations of the cell surface that were continuous with the extracellular space. Decidual cells also exhibited flangelike processes that penetrated the basal laminae of the adjacent epithelium and capillary endothelium. Our present observations indicate that decidual cells are connected by tight junctions, and a previous study demonstrated that macromolecules up to 40 kDa readily cross the PDZ; hence, the tight junctions appear to be discontinuous. We suggest that the structures restricting the movement of large macromolecules (66 kDa and larger) across the PDZ from blood vessels to the embryo may include discontinuous tight junctions, membrane interdigitations, and amorphous intercellular material.

Complex patterns of expression suggest extensive roles for the α2β1 integrin in murine development

“…During this process, the underlying decidual cells extend f lange-like processes that penetrate and subsequently displace the basal lamina of the uterine epithelium, thus, facilitating trophoblast invasion (Schlafke et al, 1985). Decidual cells also interrupt the basal lamina of the maternal blood vessels and form attachments to adjacent endothelial cells before they degenerate and are replaced by trophoblasts (Parr et al, 1986;Welsh and Enders, 1987).…”

Label-Retaining Stromal Cells in Mouse Endometrium Awaken for Expansion and Repair After Parturition

“…For menstruating and nonmenstruating species, the stromal cells surrounding the implanting embryo undergo remarkable transformation in the early stages of pregnancy [5,6]. Signals generated by the decidual tissue and placenta are crucial to the maintenance of pregnancy and development of the fetuses [7,8]. Immediately after parturition, dynamic tissue repair processes, such as apoptosis, proliferation, extracellular matrix degradation, and reorganization, are involved in the remodeling of the endometrium [5,[9][10][11][12].…”

Perlecan a multifunctional extracellular proteoglycan scaffold

“…For example, a C-terminal fragment released from endothelial cell-derived perlecan protects fibroblasts from apoptosis (Laplante et al 2006) and may play a similar role in decidua. A similar fragment (endorepellin) has been shown to be antiangiogenic (Gonzalez et al 2005) and could contribute to the lack of vasculature observed in primary decidual tissue (Parr et al 1986). …”