Journal of Dental Research, Vol 71, 36-42, Copyright © 1992 by International & American Associations for Dental Research Online Journals
Expression of type I collagen pro-alpha 2 chain mRNA in adult human permanent teeth as revealed by in situ hybridization
P. L. Lukinmaa, A. Vaahtokari, S. Vainio and I. Thesleff
Department of Dental Radiology/Oral Pathology, University of Helsinki, Finland.
The expression of the gene COL1A2, coding for the pro-alpha 2 chain of type
I pro-collagen, was analyzed in fully developed human permanent teeth. The
teeth were fixed with formalin, demineralized with EDTA for about ten
weeks, and embedded in paraffin. Pro-alpha 2(I) mRNA was localized in the
sections by in situ hybridization, with use of [35S)]-labeled
single-stranded RNA probes. The amount of mRNA for pro-alpha 2(I) collagen
chain, as indicated by the relative densities of silver grains and the
grain counts per cell in autoradiography, was high in odontoblasts, whereas
in pulpal fibroblasts it was low. High levels of pro-alpha 2(I)mRNA
expression were also present in those odontoblasts which had elaborated new
dentin matrix in response to dental caries. Expression in the periodontal
ligament, including the cementoblast layer, was slightly stronger than that
in odontoblasts. The intense expression of pro-alpha 2(I) mRNA in
odontoblasts of adult teeth suggests that even after the completion of
primary dentin formation, they continue to synthesize heterotrimeric type I
collagen molecules. Cell type-specific differences in the expression of
pro-alpha 2(I) mRNA imply that type I collagen probably plays a major role
in the regulation of the structure and function of dental tissues. Finally,
in situ hybridization enabled pro-alpha 2(I) collagen mRNA to be detected
in tissue sections even after prolonged demineralization, and thus it
proved to be a valuable technique for analysis of gene expression in adult
dental tissues, as shown here for COL1A2.
