Increases in cytosolic calcium, but not fluid flow, affect aggrecan mRNA levels in articular chondrocytes
✍ Scribed by A.I. Alford; C.E. Yellowley; C.R. Jacobs; H.J. Donahue
- Book ID
- 102302480
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 125 KB
- Volume
- 90
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
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 [Ca^2+^]~i~. However, specific down‐stream effects of [Ca^2+^]~i~ on gene expression and phenotype in BAC remain to be defined. The present work was designed to determine whether [Ca^2+^]~i~ mobilization regulates aggrecan mRNA levels. [Ca^2+^]~i~ was transiently elevated by exposing BAC to the [Ca^2+^]‐specific ionophore, ionomycin. The results show that ionomycin increases [Ca^2+^]~i~ in a dose‐dependent fashion. Semi‐quantitative real time (RT)‐PCR was used to study the effects of increased [Ca^2+^]~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 [Ca^2+^]~i~ in BAC, it did not affect aggrecan mRNA levels. Taken together, these data suggest that ionomycin‐induced [Ca^2+^]~i~ fluctuations regulate aggrecan mRNA levels, but that flow induced [Ca^2+^]~i~ fluctuations do not. © 2003 Wiley‐Liss, Inc.