Ultrastructural studies of effects of proline analogue L-azetidine-2-carboxylic acid on in vitro development of mouse tooth germ

Abstract

The effects of L-azetidine (an analogue of proline) on the development of mouse tooth germs cultivated in vitro were studied. Tooth germs removed on the 18 th day were cultivated in the presence of 50, 100 or 150μg/0.5ml L-azetidine. Light microscopically, after 4 days of culture in the presence of L-azetidine, the growth of tooth germs was clearly inhibited, while predentine was almost non-existent. The suppressed tooth germs which were removed from the medium containing L-azetidine and placed in a control medium for 2 days resumed development. Electron microscopically, at 50μg/0.5ml L-azetidine, odontoblasts showed the reduction and vesiculation of r-ER and many lysosomal granules containing abnormal fibers which were about a quarter of SLS in length appeared in the cytoplasms of odontoblasts. At 100 or 150μg/0.5ml Lazetidine, following the prominent increase of cytosegresomes and a moderate or severe loss of cytoplasmic organelles in the cytoplasms, the odontoblasts became gradually small in size. Also, the inner enamel epithelial cells, which had been in the progressive stage of the differentiation to ameloblasts, displayed regression and disorganization. After being removed from the medium containing L-azetidine, the inhibited odontoblasts in a control medium for 2 days showed varying degrees of differentiation, and the inner enamel epithelium once again began to be polarized to come ameloblasts. These results suggest that L-azetidine has reversible inhibitory effects on the cytodifferentiation and function of odontoblasts. The relationship between cytodifferentiation and the function of odontoblasts, and the development of tooth germs are discussed in some detail.