Ultrastructural localization of glycosaminoglycans in human term placenta

Sulfated glycoconjugates were stained in normal human term placentas using Spicer's high-iron diamine (HID) method with thiocarbohydrazide and silver proteinate (TCH-SP) enhancement. Specific identification of glycosaminoglycans (GAG) was accomplished by digestion of the stained material with chondroitinase ABC or AC for removal of chondroitin sulfates and nitrous acid for removal of N-sulfated GAGs. The syncytiotrophoblast apical surface demonstrated moderate to intense staining with HID-TCH-SP, which was removed by prior digestion with the chondroitinases, but not by nitrous acid. The syncytiotrophoblast basal surface and endothelial cell surfaces lacked sulfate staining. A few cytoplasmic granules in syncytiotrophoblast cells demonstrated staining similar to the apical surface. Three layers of the basal lamina were identified in these preparations. The lamina lucida immediately beneath the syncytiotrophoblast and the majority of the lamina densa stained weakly or not at all, whereas the underlying lamina diffusa and stroma demonstrated moderate to intense staining. The majority of lamina diffusa staining was removed by chondroitinase ABC or AC; the remaining material was removed by nitrous acid digestion. Thus the syncytiotrophoblast surface contains a chondroitin sulfate and the basal lamina contains a mixture of intensely stained chondroitin sulfate and a weakly stained N-sulfated GAG.