Journal of Dental Research, Vol 69, 883-889, Copyright © 1990 by International & American Associations for Dental Research Online Journals
Endocytosis in odontoclasts and osteoclasts using microperoxidase as a tracer
T. Tanaka, T. Morioka, N. Ayasaka, T. Iijima and T. Kondo
First Department of Oral Anatomy, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
Microperoxidase (MP, a peptide tracer) was intravenously injected into rats
after six days of tooth movement by the Waldo method. Bone resorption was
seen along the distal bone surface of the inter-radicular septum of the
upper first molar, and tooth root resorption occurred along the mesial and
distal surfaces of the distal root of the same molar. Odontoclasts were
smaller in size and numbers than osteoclasts, but had the same organelles
[multiple nuclei, ruffled borders (RB), clear zones, vacuoles,
mitochondria, and specific granules] as osteoclasts. MP was deposited on
the resorbed area through the clear zone and was transported into the
vacuoles along the channels of the RB. The uptake of MP by odontoclasts was
small, compared with that by osteoclasts. Collagen fibrils were found in
the channels of the RB but were not detected in the vacuoles. Instead,
filament-like structures were seen in the vacuoles and were located very
near the collagen fibrils in the channels. Fibroblasts outside the resorbed
lacunae had endocytosed collagen. In contrast, some cells close to
odontoclasts (osteoclasts) in the dentin (bone)-resorbed lacunae had not
endocytosed any collagen fibrils. These findings suggest (1) that
odontoclasts resorb the dentin or cementum just as osteoclasts do in bone
resorption, (2) that the resorbed area connects with the extracellular
spaces of the odontoclasts or osteoclasts, and (3) that the organic
components (e.g., collagen fibrils) of dentin or cementum are endocytosed
through the channels of the RB in the same manner as that for MP. However,
the endocytotic ability of odontoclasts appears inferior to that of
osteoclasts.
