Cells Subjacent to Odontoblast Layer Express DSP-only Transcript

Objectives: To compare the expression patterns of two multiple transcripts derived from DSP-PP gene during tooth development. One is DSP-only transcript (i.e. does not encode PP) and the other is DSP-PP₅₂₃ transcript, a main DSP-PP transcript.
Methods: Unique antisense and sense riboprobes were generated from DSP-only and DSP-PP₅₂₃ cDNAs for in situ studies to examine DSP-only and DSP-PP₅₂₃ transcript expression in developing molars. Following the manufacturer’s in situ hybridization procedures, paraffin-embedded sections (5–7 mm) from embryonic 20 day, postnatal 2, 3 and 6 days were deparaffined and hydrated. Tissues were prehybridized, then hybridized with DSP-only and DSP-PP₅₂₃ anti-sense (AS) or sense (S) Digoxigenin labeled-riboprobes overnight, and washed. Anti-Digoxigenin antibodies conjugated to alkaline phosphatase were used to detect the presence of bound riboprobes by color reaction with NBT/BCIP. Stro-1 antibody was used for immunohistochemical analysis of Stro-1 protein expression in rat molars.


Results: We found that unlike the DSP-PP₅₂₃ transcript, the DSP-only transcript does not express in mature polarized odontoblasts but is expressed by small cells located both subjacent to the mature odontoblast layer as well as in dental pulp near the cusp. Interestingly, Stro-1 protein, a stem cell marker, was also identified in the cells subjacent to odontoblasts and in dental pulp near the cusp.


Conclusions: Differential expression of DSP-only and DSP-PP₅₂₃ transcripts suggest that these two kinds of transcripts may play different roles during dentinogenesis. DSP-PP₅₂₃. These data also suggest the presence of a group of cells subjacent to the odontoblast leyer.