Ameloblastic Differentiation Of Human Keratinocytes

Like many organ development, mammalian tooth germ is result of interaction between epithelial and mesenchyme. Tooth development undergoes various stages, with the formation of tooth crown through the differentiation of dentin-secreting odontoblasts and enamel-producing ameloblasts. Ameloblasts are lost via their transformation and apoptosis upon tooth eruption, making it impossible to repair or replace lost/damaged enamel in erupted teeth.Human keratinocytes recombine with E13.5mouse moler mesenchyme, add FGF8growth factor. After culture in the renal capsule membrane, successfully induc human keratinocytes into enamel-secreting ameloblasts, won a chimeric teeth.The formation of human keratinocytes into enamel-secreting ameloblasts still unknown.We found that, recombined keratinocytes with E13.5mouse molar mesenchyme produce chimeric tooth germ, subjected to subrenal culture, during30d, chimeric tooth germ developmental like normal tooth,also experienced epithelium aggregation and subsidence, mesenchyme aggregation, the secretion of dentin and enamel.SEM analysis the mechanical properties evaluation for chimeric teeth found that, the enamel of chimeric tooth went through a process from loose to tight. With the growth of the incubation time, the Elasticitic modulus and hardness of chimeric tooth dentin and enamelin is increased, the process also shows the teeth gradually mineralization process.Chimeric tooth germ absence of growth factor FGF8and SHH developed well-formed dentin; however, keratinocyte-derived epithelial cells failed to differentiate into elongated ameloblasts. We text MSX2, SP3and SP6, the key transcription factors about enamelin formation, found that, some chimera tooth germ absence of growth factors FGF8and SHH cann’t express SP6.Chimeric tooth germ developed a rapid development tooth crown. Existing research showed that FGF8can lead to delay in tooth germ developmental. Speculate that tooth germ developmental rate may be related to FGFs. After analyzed FGFs related gene expression patterns in chimeric tooth germ. We guess that FGF3and FGF10may be act as tooth developmental delay gene; FGF4and FGF7may has nothing to do with the growth rate; A high concentration of FGF9may lead to tooth germ development delay.To sum, the formation of human keratinocytes to enamel-secreting ameloblasts need30d, after30d, tooth germ will continue to be hardened and mineralized. These some chimera tooth germ absence of growth factors FGF8and SHH, keratinocyte-derived epithelial cells failed to differentiate into elongated ameloblasts may caused by these chimera tooth germ cann’t express SP6; FGF3, FGF9and FGF10may be act as tooth developmental delay gene; FGF4and FGF7may has nothing to do with the growth rate.