Increases in Cytosolic Calcium, but not Fluid Flow, Affect Aggrecan mRNA Levels in Articular Chondrocytes

A. I. Alford, Clare E Yellowley-genetos, C. R. Jacobs, H. J. Donahue

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Fluctuations in intracellular free calcium concentration ([Ca 2+]i) is thought to be one mechanism by which cells transduce mechanical signals into biological responses. Primary cultures of bovine articular chondrocytes (BAC) respond to oscillating fluid flow with a transient rise in [Ca2+]i. However, specific down-stream effects of [Ca2+]i on gene expression and phenotype in BAC remain to be defined. The present work was designed to determine whether [Ca2+]i mobilization regulates aggrecan mRNA levels. [Ca 2+]i was transiently elevated by exposing BAC to the [Ca2+]-specific ionophore, ionomycin. The results show that ionomycin increases [Ca2+]i in a dose-dependent fashion. Semi-quantitative real time (RT)-PCR was used to study the effects of increased [Ca2+]i on steady state levels of aggrecan mRNA. Four hours after a brief exposure to 1.5 μM ionomycin, BAC displayed a nearly four-fold decrease in aggrecan mRNA levels compared to control cells. This effect of ionomycin on aggrecan mRNA was no longer evident 6 or 10 h later. Despite previous observations that oscillating fluid flow elicits increased [Ca2+]i in BAC, it did not affect aggrecan mRNA levels. Taken together, these data suggest that ionomycin-induced [Ca2+] i fluctuations regulate aggrecan mRNA levels, but that flow induced [Ca2+]i fluctuations do not.

Original languageEnglish (US)
Pages (from-to)938-944
Number of pages7
JournalJournal of Cellular Biochemistry
Volume90
Issue number5
DOIs
StatePublished - Dec 1 2003
Externally publishedYes

Keywords

  • Aggrecan
  • Calcium
  • Cartilage
  • Mechanotransduction

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology

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