Experimental in vivo and in vitro Formation of Type VI Collagen Periodic Fibrils in Chorionic Villi of Human Placenta

Abstract

The distribution of type VI collagen in the chorionic villi of normal human term placenta was studied. Since 100 nm periodic fibrils (type VI collagen periodic fibrils) are known to form in the tendon, cornea and cultured fibroblasts by incubation with acidic ATP solution, we incubated the placental tissue with 20 mM ATP, fixed it with Karnovsky's fixative and examined under an electron microscope. Type VI collagen periodic fibrils widely occurred in the interstitial connective tissue, especially close to the basal lamina. By cryo-immunoelectron microscopy, labeling for collagen type VI was found in the area between the trophoblastic basal lamina and the endothelial basal lamina. Furthermore, we extracted type VI collagen from the human placenta and brought both extract and residues into ATP treatment. Periodic structure formation was rare in extracted preparation compared with residues. The results served to clarify the mechanism of fibril formation in the tissue.