A 3D culture model study monitoring differentiation of dental epithelial cells into ameloblast-like cells
The present study was designed to investigate whether a three dimensional (3D) culture of the rat incisor-derived dental epithelial cell line SF2 enhances its differentiation into ameloblast-like cells. SF2 cells were incubated in a laboratory-fabricated culture device to form spheroids in the presence or absence of differentiation supplements. The size of the spheroids was monitored microscopically. Differentiation was analyzed by measuring mRNA expression or the localization of amelogenin, ameloblastin, and enamel protease KLK-4 by immunofluorescence staining. The mineralization of the spheroids was monitored by Von Kossa staining and by the hardness test using a micro force sensor. The cell morphology was observed by transmission electron microscopy. Apoptosis was also assessed. The results indicated that the 3D culture allowed the SF2 cells to form homogenous spheroids within one day that exhibited a significant increase in matrix protein mRNA compared to the two dimensional culture at 2 days of culture. Ameloblastin and KLK-4 expression was detected throughout the incubation period (up to 8 days), but amelogenin expression decreased markedly, suggesting increased KLK-4 enzymatic activity. Both medium preparations increased mineralization, hardness, and apoptosis, although the differentiation medium tended to have a stronger effect. Ultrastructural analysis indicated the presence of intracellular and extracellular secretory granules, which could represent the secretion of matrix proteins. Overall our results suggest that the spheroid culture could be a useful model for analyzing ameloblast differentiation.