Novel role of zonula occludens-1: A tight junction protein closely associated with the odontoblast differentiation of human dental pulp cells

Cell Biol Int. 2016 Jul;40(7):787-95. doi: 10.1002/cbin.10617. Epub 2016 May 11.

Abstract

Zonula occludens-1 (ZO-1), a tight junction protein, contributes to the maintenance of the polarity of odontoblasts and junctional complex formation in odontoblast layer during tooth development. However, expression and possible role of ZO-1 in human dental pulp cells (hDPCs) during repair process remains unknown. Here, we investigated the expression of ZO-1 in hDPCs and the relationship with odontoblast differentiation. We found the processes of two adjacent cells were fused and formed junction-like structure using scanning electron microscopy. Fluorescence immunoassay and Western blot confirmed ZO-1 expression in hDPCs. Especially, ZO-1 was high expressed at the cell-cell junction sites. More interestingly, ZO-1 accumulated at the leading edge of lamellipodia in migrating cells when a scratch assay was performed. Furthermore, ZO-1 gradual increased during odontoblast differentiation and ZO-1 silencing greatly inhibited the differentiation. ZO-1 binds directly to actin filaments and RhoA/ROCK signaling mainly regulates cell cytoskeleton, thus RhoA/ROCK might play a role in regulating ZO-1. Lysophosphatidic acid (LPA) and Y-27632 were used to activate and inhibit RhoA/ROCK signaling, respectively, with or without mineralizing medium. In normal cultured hDPCs, RhoA activation increased ZO-1 expression and especially in intercellular contacts, whereas ROCK inhibition attenuated the effects induced by LPA. However, expression of ZO-1 was upregulated by Y-27632 but not significantly affected by LPA after odontoblast differentiation. Hence, ZO-1 highly expresses in cell-cell junctions and is related to odontoblast differentiation, which may contribute to dental pulp repair or even the formation of an odontoblast layer. RhoA/ROCK signaling is involved in the regulation of ZO-1.

Keywords: ZO-1; cell-cell junctions; human dental pulp cells; odontoblast differentiation.

MeSH terms

  • Adolescent
  • Adult
  • Cell Differentiation / physiology
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Dental Pulp / cytology
  • Dental Pulp / metabolism*
  • Humans
  • Odontoblasts / cytology
  • Odontoblasts / metabolism
  • Phosphoproteins / metabolism
  • Tooth Calcification
  • Young Adult
  • Zonula Occludens-1 Protein / metabolism*
  • rho-Associated Kinases / metabolism
  • rhoA GTP-Binding Protein / metabolism

Substances

  • Phosphoproteins
  • TJP1 protein, human
  • Zonula Occludens-1 Protein
  • RHOA protein, human
  • ROCK1 protein, human
  • rho-Associated Kinases
  • rhoA GTP-Binding Protein