A. Spahr et L. Hammarstrom, Response of dental follicular cells to the exposure of denuded enamel matrix in rat molars, EUR J OR SC, 107(5), 1999, pp. 360-367
Recent studies have indicated that cementum formation can be induced when d
ental follicular cells are exposed to enamel matrix. The purpose of the pre
sent investigation was to study this cementum formation and the appearance
of the cells involved, including their expression of collagen types alpha 1
(I), alpha 1(II) and alpha 1(III) mRNAs, during this process by means of li
ght microscopy and in situ hybridisation. The mandibular first molars of 5-
d-old rats were surgically taken out, their enamel epithelium was removed,
and then the crowns were re-inserted with the occlusal surface downwards in
their crypts to allow the follicular cells to come in contact with the den
uded enamel matrix. After observation periods of 2-14 d, the teeth were pre
pared for light microscopic examination and in situ hybridisation. A monola
yer of follicular cells in contact with the exposed enamel matrix changed t
heir morphology and increased their expression of collagen type I mRNA as e
arly as 2-4 d after exposure to the enamel matrix. A cementum-like tissue w
as formed at the surface of the enamel matrix. Collagen type II mRNA was ne
ver expressed in the tissues studied, whereas collagen type III mRNA was we
akly expressed in the follicular cells throughout the experiment.