Quantitative analysis of cell turnover in the enamel organ of the rat incisor. Evidence for ameloblast death immediately after enamel matrix secretion

Abstract

During renewal of the enamel organ in the rat incisor cohorts of epithelial cells are transported sequentially through presecretory, secretory and maturation zones to the gingival margin where the life cycles of these cells terminate. This process was examined kinetically by determining the absolute flux of cells within each of these zones of amelogenesis. It was found that the efflux of ameloblasts, stratum intermedium and papillary layer cells from the presecretory zone was about equal to the efflux plus expected growth within the secretory zone. However, between the secretory and maturation zones about 50% more ameloblasts entered the maturation zone than were required to account for the egress at the gingival margin and the expected growth. Since there was no similar imbalance between these zones for papillary layer cells, it was concluded that this discrepancy must represent a 50% reduction in the size of the ameloblast population during the maturation stage of amelogenesis. It was calculated that a little over 25% of the loss occurred immediately at the start of maturation within the region of postsecretory transition and the remaining 25% of the loss occurred throughout the subsequent regions of the maturation zone. In addition to the kinetic analysis graphic reconstructions, or surface maps, of ameloblast nuclei were prepared. These maps illustrated the characteristics of ameloblast nuclear packing within the three zones of amelogenesis and they provided quantitative confirmation that as ameloblasts progress through the maturation zone, there is a loss of cells in an amount predicted by the kinetic analysis.

In vivo experimentation on rat incisor enamel organs through a surgical window

“…ln the rat incisor, continuous attrition at the incisaI end of the tooth 1& balanced by continuous production of dentin and enalDel at the apical end of the --t:ooth. More precisely, the odontogenic organ ls reaponsible, either directly or indirectly, for the production of aIl the ( hard tissues of the tooth (Smith and Warshawsky, 1977).…”

Proliferation and apoptosis in early molar morphogenesis - voles as models in odontogenesis

“…in early stages of morphogenesis (Lesot et al, 1996;Vaahtokari et al, 1996;Viriot et al, 1997;Jernvall et al, 1998;Lesot et al, 1999;Viriot et al, 2000, Matalova et al, 2004b, dentinogenesis (Bronckers et al, 1996;Vermelin et al, 1996;Franquin et al, 1998), amelogenesis (Smith and Warshawsky, 1977;Moe, 1979;Nishikawa and Sasaki, 1995;Kaneko et al, 1997) and during eruption (Schellens et al, 1982;ten Cate and Anderson, 1986). The restricted distribution patterns of apoptotic cells at these different stages suggest multiple roles for apoptosis in dental development (Peterkova et al, 2003;Matalova et al, 2004a).…”

The relationship between the cusp pattern and plural stem cell compartments in guinea pig cheek teeth by chasing BrdU-labeling

“…Previous cell proliferation assays in rodent incisors reconfirmed the presence of the stem cells as the source of cells for continuous growth of this type of tooth (Smith and Warshawsky, 1975, 1976, 1977Smith, 1980;Nakasone et al, 2006). Harada et al (1999) demonstrated the existence of self-renewing adult stem cells in the apical region by molecular biological Total n 2 n 2 n 2 n 2 Fig.…”