In vitro differentiation of tooth buds from embryos and adult lizards ( L. gravenhorsti ): An ultrastructural comparison

It is well established that the capacity for teeth to differentiate “in vitro” depends upon: (a) the age of the embryonic rudiments at the time of excision and (b) the number of cells within each tissue type which are capable of differentiating into organ culture. This paper studies ultrastructural aspects of tooth buds grown in vitro from lizard embryos and compares these characteristics with those observed in dental germs grown in situ in older lizard embryos. Moreover, we report the self‐differentiation in vitro dental tissues from adult lizard and compare this phenomenon with the main features of a morphogenetic field. Our results suggest that approximately in the first third of gestation in L. gravenhorsti the dental buds has already acquired the capacity for self‐differentiation in vitro. The ultrastuctural observations show that there are no significant differences between odontoblasts and ameloblasts in situ and in vitro. The tooth from “adult lizards,” isolated by combined microsurgical and enzymatic procedure and cultured in semisolid‐liquid medium were also able to differentiate teeth. This phenomenon implies that self‐differentiation is not rigidly determined, and that in these animals the tooth tissues represents a continuous morphogenetic field throughout the animal's life. This property is intrinsic, resides in the isolated tooth tissues, and is relatively independent of external factors. In addition, these studies indicate that the chick chorio–allantoic membrane and the semisolid‐liquid culture medium supply the majority of the factors required for development of these tissues.