Epithelial and PGP9.5-immunoreactive cells of Malassez epithelium in the periodontal ligament of cats: a transmission electron microscopic study.
OBJECTIVE
The aim of the study was to investigate the ultrastructural features of Malassez epithelium (ME) containing protein gene product 9.5 (PGP9.5)-immunoreactive (IR) cells in the cat periodontal ligament (PDL).


METHODS
Specimens from the teeth and tooth-supporting tissues of four mature cats of both sexes, 18 to 24 months of age, were used. The fixed jaws were decalcified in EDTA. Frozen sagittal sections 20 µm thick were immunostained for PGP9.5, and the ME, containing IR cells in the PDL, were evaluated under a transmission electron microscope.


RESULTS
Several epithelial cells and PGP9.5 IR cells formed clusters and were enveloped by a basal lamina and separated from the surrounding connective tissue. A large nucleus and scanty cytoplasm were observed in most of the ME cells, which contained abundant keratin filaments and mitochondria. Caveolae-like structures and vesicles were found in the periphery of the ME. The small cytoplasmic processes of some of the epithelial cells extended toward the surrounding connective tissues. The cytoplasmic matrix of one type of cell comprising the ME showed immunoreactivity for anti-PGP9.5 antibody. The IR cell in the cell clusters was connected to adjacent epithelial cells and extended cytoplasmic processes toward the adjacent epithelial cells. The IR cell contained keratin filaments and abundant densely cored vesicles approximately 100-250 nm in diameter.


CONCLUSIONS
The findings of the study suggest endocytotic capabilities of the epithelial cells and neuroendocrine functions of the IR cells. It is possible that the two different cell types react to extrinsic stimuli and interact with cells comprising the clusters and cords in the PDL. These ultrastructural evidences may imply functional heterogeneity of the ME in the PDL.
Tadokoro
Osamu
O
Department of Oral Anatomy 1, School of Dentistry, Matsumoto Dental University, Nagano, Japan. osamut@po.mdu.ac.jp
D000818:Animals; D001485:Basement Membrane / Q000201:enzymology / Q000648:ultrastructure; D002415:Cats; D002467:Cell Nucleus / Q000201:enzymology / Q000648:ultrastructure; D003239:Connective Tissue Cells / Q000201:enzymology / Q000648:ultrastructure; D003593:Cytoplasm / Q000201:enzymology / Q000648:ultrastructure; D022083:Cytoplasmic Structures / Q000648:ultrastructure; D003599:Cytoskeleton / Q000648:ultrastructure; D003739:Dental Cementum / Q000166:cytology; D003896:Desmosomes / Q000648:ultrastructure; D004847:Epithelial Cells / Q000201:enzymology / Q000648:ultrastructure; D005260:Female; D007633:Keratins / Q000032:analysis; D008297:Male; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000648:ultrastructure; D009685:Nuclear Envelope / Q000648:ultrastructure; D010513:Periodontal Ligament / Q000166:cytology / Q000201:enzymology*; D043222:Ubiquitin Thiolesterase / Q000032:analysis*; D014617:Vacuoles / Q000648:ultrastructure
D007633:Keratins; D043222:Ubiquitin Thiolesterase