ASSOCIATION OF TYPE-VI COLLAGEN WITH D-PERIODIC COLLAGEN FIBRILS IN DEVELOPING TAIL TENDONS OF MICE

The process of the arrangement of D-periodic collagen fibrils and thei r growth in maturing tail tendon of mice were studied with the associa tion of type VI collagen, from fetal day 10 to 10 weeks after birth, I n tail tendons, the amount of collagen fibers gradually increased alon g with the diameters of D-periodic collagen fibrils during maturation. Type VI collagens first appeared on fetal day 10, when D-periodic col lagen fibrils were not recognizable, Type VI collagens were observed a round the fibroblastic cells in early stages of development, hut were among thick collagen fibrils in the adult tendon, While the periodic d istances of type VI collagen fibrils were over 100 nm at fetal days, t hey were packed to 80-90 nm after birth. The periodic bands were stain ed well with ruthenium red in adult but not in young tendons, indicati ng the close association of proteoglycans or glycosamino-glycans (PGs/ GAGs) with maturing type VI collagens, Since type VI collagen in nativ e form is known to associate with D-periodic collagen fibrils via PGs/ GAGs, ruthenium red-stainability on the surface of D-periodic collage n fibrils was also examined; results showed that ruthenium red-stainab le elements were D-periodically associated. When the surface morpholog y of D-periodic collagen fibrils in adult animals was examined by atom ic farce microscopy, a large depth of the groove between elevated and depressed surfaces became prominent when the fibril surface was digest ed with hyaluronidase. Thus, it is possible to observe topologically t he association of PGs/GAGs and probably that of type VI collagens with D-periodic collagen fibrils.