DYNAMIC VARIATIONS IN THE EXPRESSION OF TYPE-I COLLAGEN AND ITS MOLECULAR CHAPERONE HSP47 IN CELLS OF THE MOUSE DENTAL FOLLICLE DURING TOOTH ERUPTION

Tooth eruption is a precisely timed and sequenced event that brings th e tooth from within bone into a functional position in the mouth. Ever y part of the developing tooth has been theoretically implicated as a primary factor in this process, but it now appears that eruption is mu ltifactorial, with the dental follicle and type I collagen playing an important part. Immunological probes were used here to investigate in vivo and in vitro the temporal and spatial expression of type I collag en and its molecular chaperone Hsp47 in the dental follicle during eru ption. Mandibles were dissected from 2-, 5-, 9- and ii-day-old neonata l mice and fixed in 95% ethanol overnight. Sections of 7 mu m were obt ained and reacted with antibodies directed against type I collagen. De ntal follicles were isolated from 2-, 5-, 9- and 11-day-old neonates a nd cells were grown in culture for 8 days. Slides were then reacted wi th antibodies directed against type I collagen and Hsp47. The producti on of type I collagen and Hsp47 in the follicle varied with the stage of dental development and eruption. There was a progressive decrease o f type I collagen in the coronal part of the follicle, leading to an a rrest of its production in these areas. These findings support the not ion that cells of the coronal portion of the dental follicle stop prod ucing type I collagen as a prerequisite to the initiation of tooth eru ption and that this phenotype persists in vitro.