Phosphate and calcium uptake by rat odontoblast-like MRPC-1 cells concomitant with mineralization

J Bone Miner Res. 2002 Oct;17(10):1801-13. doi: 10.1359/jbmr.2002.17.10.1801.

Abstract

It has been suggested that odontoblasts are instrumental in translocating Ca2+ and inorganic phosphate (Pi) ions during the mineralization of dentin. The aim of this study was to characterize cellular Pi and Ca2+ uptake in the novel rat odontoblast-like cell line mineralizing rat pulpal cell line (MRPC) 1 during mineralization to see if changes in the ion transport activity would occur as the cultures develop and begin forming a mineralized matrix. MRPC-1 cells were cultured in chemically defined medium containing ascorbate and Pi, and cultures were specifically analyzed for cellular P, and Ca2+ uptake activities and expression of type II high-capacity Na+-Pi cotransporters. The odontoblast-like phenotype of the cell line was ascertained by monitoring the expression of collagen type I and dentin phosphopoprotein (DPP). Mineralized nodule formation started at day 9 after confluency and then rapidly increased. Ca2+ uptake by the cells showed a maximum during the end of the proliferative phase (days 5-7). Pi uptake declined to a basal level during proliferation and then was up-regulated simultaneously with the onset of mineralization to a level fourfold of the basal uptake, suggesting an initiating and regulatory role for cellular Pi uptake in mineral formation. This up-regulation coincided with a conspicuously increased glycosylation of NaPi-2a, indicating an activation of this Na+-Pi cotransporter. The study showed that MRPC-1 cells express an odontoblast-like phenotype already at the onset of culture, but that to mineralize the collagenous extracellular matrix (ECM) that formed, a further differentiation involving their ion transporters is necessary.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Cell Line / metabolism
  • Collagen Type I / biosynthesis
  • Culture Media
  • Dentin / metabolism
  • Dentinogenesis / physiology*
  • Glycosylation
  • Ion Transport
  • Odontoblasts / metabolism*
  • Odontogenesis / physiology*
  • Phosphates / metabolism*
  • Protein Processing, Post-Translational
  • Rats
  • Sodium / metabolism
  • Sodium-Calcium Exchanger / metabolism
  • Sodium-Phosphate Cotransporter Proteins
  • Sodium-Phosphate Cotransporter Proteins, Type I
  • Sodium-Phosphate Cotransporter Proteins, Type II
  • Sodium-Phosphate Cotransporter Proteins, Type IIa
  • Symporters / metabolism

Substances

  • Collagen Type I
  • Culture Media
  • Phosphates
  • Slc34a1 protein, rat
  • Sodium-Calcium Exchanger
  • Sodium-Phosphate Cotransporter Proteins
  • Sodium-Phosphate Cotransporter Proteins, Type I
  • Sodium-Phosphate Cotransporter Proteins, Type II
  • Sodium-Phosphate Cotransporter Proteins, Type IIa
  • Symporters
  • Sodium
  • Calcium