Temporal and spatial expression of TGF-β 2 in tooth crown development in mouse first lower molar

Transforming Growth Factor β2 (TGF-β2) is involved in the regulation of many important cellular processes during tooth development. In this study we systematically characterized the expression pattern of TGF-β2 in vivo and further analyzed its possible roles during different developmental stages of mouse first lower molar using immunofluorescence histochemical method with confocal microscopy. TGF-β2 signaling was detected in different developing stages in both dental epithelium and surrounding dental mesenchyme. For the first time, we found that the basement membrane and epithelial cells in the basal layer showed no immunostaining from embryonic day 11 to 13; the primary enamel knot and secondary enamel knot exhibited pronounced immunostaining with different expression patterns at embryonic day 14 and 16. In addition, the mature ameloblast lost immunoreactivity, but the secretory ameloblast still exhibited positive immunoreaction at day 2 of postnatal development. Collectively, the temporospatial distribution patterns of TGF-β2, especially in the basement membrane, epithelial cells in the basal layer, enamel knot, mature odontoblast and ameloblast, suggested a close association between TGF-β2 signaling and tooth crown development, and indicated that TGF-β2 might participate in tooth initiation, epithelial morphogenesis, formation of dentine matrix, and ameloblast differentiation.