Localization of Runx2, Osterix, and Osteopontin in Tooth Root Formation in Rat Molars

Abstract

(HN) S U M M A R Y Cementogenesis starts with the differentiation of cementoblasts. Mature cementoblasts secrete cementum matrix. Cementum components are similar to bone; moreover, cementoblasts possess many characteristics similar to those of osteoblasts. Runx2 and osterix, the transcriptional factors for osteoblast differentiation, participate in tooth formation. However, the characteristics of Runx2 and osterix during the differentiation process of cementoblasts remain unclear. In this study, we examined the immunolocalization patterns of Runx2, osterix, and osteopontin during rat molar tooth formation. Periodontal ligament cells and osteoblasts located on the alveolar bone surface showed immunoreactivity for Runx2. Colocalization of Runx2 and osterix was detected in cementoblasts, which penetrated the ruptured Hertwig's epithelial root sheath and attached to root dentin. Moreover, osteopontin was observed in Runx2-positive cementoblasts facing the root surface. However, the cells adjacent to cementoblasts showed only Runx2 reactivity. Neither Runx2 nor osterix was seen in cementocytes. These results suggest that both Runx2 and osterix are important for differentiation into cementoblasts. Additionally, osterix may be indispensable for transcription of osteopontin expression. (J Histochem Cytochem 57:397-403, 2009)

Extracellular heat shock protein 70 promotes osteogenesis of human mesenchymal stem cells through activation of the ERK signaling pathway

“…The runt family transcription factor Runx2 is an essential transcription factor for osteoblastic differentiation [28]. A downstream gene of Runx2 [29], Osx, is a zinc finger-containing transcription factor required for osteoblastic differentiation [30,31].…”

Localization of osteopontin and osterix in periodontal tissue during orthodontic tooth movement in rats

“…OPN reactivity in the cement line and surface of cementum and alveolar bone might be induced by osterix expression. Their strong localization in periodontal tissues when 100 g of heavy force was applied indicates that they might be molecules linking mechanostressing and osteogenic and odontogenic differentiation 20,23,24 and might be involved in bone, PDL, and cementum remodeling during orthodontic tooth movement. The precise relationship between OPN and osterix during periodontal tissue remodeling in response to heavy force could not be ascertained with the current methodology.…”

“…16 Osterix triggers the formation and secretion of matrix such as cementum, dentin, and bone, indicating that osterix might be a useful marker of differentiation of cementoblasts, osteoblasts, and odontoblasts. 20 Previous studies showed that the heavy forces produced less tooth movement and more root resorption compared with light forces. Orthodontic tooth movement with heavy forces led to the increased expression of proteins related to cementum and alveolar bone remodeling.…”

Recombinant Human Plasminogen Activator Inhibitor-1 Promotes Cementogenic Differentiation of Human Periodontal Ligament Stem Cells

“…Recent studies indicated that Runx2 and its downstream target OSX play critical roles in cementogenic differentiation, which is important for osteogenesis. 30,31 Furthermore, OSX particularly controls the formation of cellular cementum. 32 During in vitro cementogenic differentiation, rhPAI-1 increased Runx2 expression at 7 days and subsequently increased OSX expression at 14 days.…”