Nestin expression in embryonic and adult human teeth under normal and pathological conditions

Nestin is an intermediate Filament most related to neurofilaments and expre ssed predominantly In the developing nervous system and muscles. In the pre sent study we examined the in vivo distribution of nestin in human teeth du ring embryonic development and In permanent teeth under normal and patholog ical conditions, The results show that nestin is first expressed at the hel l stage and that its distribution is restricted in pulpal cells located at the cusp area of the fetal teeth. In young permanent teeth, nestin is found only in functional odontoblasts, which produce the hard tissue matrix of d entin, Expression is progressively down-regulated and nestin is absent from older permanent teeth. In carious and injured teeth, nestin expression is up-regulated in a selective manner in odontoblasts surrounding the injury s ite, showing a link between tissue repair competence and nestin up-regulati on under pathological conditions, In an la vitro assay system of human dent al pulp explants, nestin is up-regulated after local application of bone mo rphogenic protein-4 A similar effect is seen In cultures of primary pulp ce lls during their differentiation into odontoblasts. Taken together, these r esults suggest that nestin plays a potential role in odontoblast differenti ation during normal and pathological conditions and that bone morphogenic p rotein-4 is involved in nestin up-regulation.