Ultrastructure of the rat periodontal ligament as observed with quick-freeze, deep-etch and replica methods: arrangement of collagen and related structures.
The ultrastructure of the periodontal ligament of rat molars was examined with the quick-freeze, deep-etch replica methods. It was mainly composed of elongated fibroblast-like cells and 40- to 50-nm-wide collagen fibrils that are arranged parallel to one another to form fibers approximately 1 micron in width. Collagen fibrils are composed of 10-nm-wide substructures that may run helically against the long axis of the fibril. Numerous rod-like structures ('rods') approximately 10 nm in width are present around the collagen fibrils. Individual or groups of rods span spaces between neighboring collagen fibrils to interconnect them. The surfaces of the fibroblast-like cells are also connected to the nearest collagen fibrils through the rods. In place, strands with a thickness similar to that of the rods were seen self-assembled into irregular meshwork structures. The treatment of the tissue with 10% sodium hydroxide for up to 5 days removed most of these rods and strands, thus exposing a three-dimensional arrangement of collagen fibrils that is often not fully visualized in untreated tissues. With histochemical staining of thinly sectioned tissues using Alcian blue, these rods and strands were positively stained, and thus they were demonstrated to be composed of proteoglycans. The ultrastructural arrangement of the periodontal ligament, observed in this study as a delicate interaction of collagen and proteoglycan components, is likely to play a significant role in the transmission of occlusal forces applied to the tissue and in the dissipation of mechanical shock.
Kuroiwa
M
M
2nd Department of Oral Anatomy, School of Dentistry, Showa University, Japan.
Tachikawa
T
T
Izumiyama
N
N
Takubo
K
K
Yoshiki
S
S
Higashi
S
S
D000818:Animals; D003094:Collagen / Q000648:ultrastructure*; D005260:Female; D005347:Fibroblasts / Q000648:ultrastructure; D005613:Freeze Etching / Q000379:methods*; D006651:Histocytochemistry; D008297:Male; D010513:Periodontal Ligament / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016628:Replica Techniques
D003094:Collagen