Heparan sulfate proteoglycans and their binding proteins in embryo implantation and placentation

Abstract

Complex interactions occur among embryonic, placental and maternal tissues during embryo implantation. Many of these interactions are controlled by growth factors, extracellular matrix and cell surface components that share the ability to bind heparan sulfate (HS) polysaccharides. HS is carried by several classes of cell surface and secreted proteins called HS proteoglycan that are expressed in restricted patterns during implantation and placentation. This review will discuss the expression of HS proteoglycans and various HS binding growth factors as well as extracellular matrix components and HS-modifying enzymes that can release HS-bound proteins in the context of implantation and placentation.

Figure 1. Heparan sulfate proteoglycan distribution at implantation sites

Panel A shows the pattern of perlecan (black areas) and syndecan-1 (green shaded area) in a cross section of a day 8 implantation site in the mouse. Perlecan is widely distributed in decidua as well as in both embryonic and maternal basal lamina. In contrast, syndecan-1 is restricted to the deciduas as well as embryonic tissue elements. Symbols: e, embryo; mm, mesometrial aspect of uterus. Panel B is a drawing representing main features of the human fetal-maternal interface showing the blood supply (red, arteries; blue, veins) leading to and from the umbilical cord and into the chorion as well as the maternal decidua. In panel C, an anchoring villus has been expanded from panel B to highlight the presence of invading cytotrophoblast (red cells), villar fibroblasts (purple shaded area), syncytiotrophoblast (yellow area), deciduas (gray area) and decidual vascular elements (V) surrounded by vascular smooth muscle cells (green). Perlecan is heavily deposited in areas indicated by the thick black lines. Syndecan-1 and -3 are found in the yellow region.