In vitro differentiation of tooth rudiments of embryonic mice. I. Transfilter interaction of embryonic incisor tissues

Abstract

The mandibular incisor rudiment of the 16 day mouse embryo may be separated by enzymatic treatment into an epithelial covering and an inner mesenchyma1 papilla. Each separated tissue fails to differentiate when grown singly in vitro, but odontocytes, amelocytes, and their extracellular matrices are noted in cultures of recombined tissues. Separated tissues also fail to differentiate on collagen gels. Both the mesenchymal papilla and the internal dental epithelium differentiate when placed on opposite sides of a Millipore membrane. Cultures of 11 days growth show odontocytes with deposited alcian blue positive matrix; this matrix is found both within and on the surface of the membrane. Amelocytes deposit eosin-positive extracellular matrix onto the filter surface. Calcification of odontocyte-deposited matrix, similar to that of dentinal matrix of neonatal incisors, is shown by staining with von Kossa's stain. Transfilter interaction of these embryonic tissues leads, therefore, to their differentiation and deposition of characteristic extracellular matrices.Embryonic tissue interaction, as a prerequisite for both tissue and cellular differentiation, has been documented in vivo and in vitro. Differentiation of young tissues in vitro depends upon factors inherent both in the environment and in associations with other tissues; examples of such factors are: ( 1 ) the effects of differing media on the growth of tissues in culture (Biggers and Heyner, '60, '61; Franks, '61; Wessells, %1), (2) the effects of environmental temperature and gas levels (Moscona, '62), (3) the associations between cells of differing ages (Grover, '62), (4) the capabilities of effective epithelial-mesenchymal interactions leading to differentiation in complex organ rudiments (Grobstein, '53, '55; Grover, '61; Golosow and Grobstein, '62; Wessells, '62; and others), (5) the correlated passage of materials from one interacting tissue to the other (Koch and Grobstein, '63; Kallman and Grobstein, '65), and (6) the correlated development of cytological characteristics of one tissue with a developmental response of another tissue (Cooper, '65).As in the tissue systems noted above, numerous in vivo observations and experiments exist which suggest developmentally J. EXP. ZOOL., 165: 155-170.important interactions between the tissues of embryonic teeth. These studies, mostly tissue transplantation experiments, have suggested an essential interaction between the covering ameloblastic epitheliumthe internal dental epithelium -and the internal core of mesenchyme (Legros and Magitot, 1874; Huggins, McCarrolI and Dahlburg, '34; Fleming, '52, '56; Glasstone, '54; Bejdl and Weizenberg, '57; Myers and Flanagan, '58; Lefkowitz, '62; Zussman, '66a,'66b; and many others). This interaction is said to lead to the differentiation of the ameloblasts and odontoblasts and deposition of the dissimilar organic matrices of dentin and enamel.With the development of in vitro procedures permitting consistent diff erentiation of tooth tissues and deposition of char...

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