Proteoglycans and hyaluronan in human fetal membranes

The aim of this study was to describe the distributions of major extracellular matrix components, such as proteoglycans, collagen and hyaluronan, in the fetal membranes at term.

Fetal membranes were obtained from elective cesarean deliveries at term. Guanidinium extracts were analyzed for proteoglycans with alcian blue precipitation, sodium dodecyl sulfate- polyacrylamide gel electrophoresis, and Western blotting and for hyaluronan with a radioimmunoassay. Collagen was measured by estimating hydroxyproline content. Tissue sections were immunostained for decorin and biglycan and stained for hyaluronan with a biotin-labeled hyaluronan-binding protein.

The fetal membranes contained predominantly smaller proteoglycans, such as biglycan and decorin. The amnion consisted of typical fibrous connective tissue with a high concentration of collagen. The amnion was dominated by decorin located in close connection with the collagen fibrils. The chorion was composed of a fibroblastic part containing collagen and decorin and a trophoblastic part mainly containing biglycan. In addition, large amounts of hyaluronan were found, especially in the amnion and in the decidual cell layers.

The distributions of proteoglycans, collagen, and hyaluronan in human fetal membranes may explain the biomechanical properties of this tissue. We suggest that changes in the relative proportions of these extracellular molecules are crucial for the proposed maturation process in the fetal membranes during the last weeks of pregnancy.