Open Access

Osteoblast differentiation of NIH3T3 fibroblasts is associated with changes in the IGF-I/IGFBP expression pattern

  • Basem M. Abdallah1, 2
Cellular & Molecular Biology LettersAn International Journal200611:38

DOI: 10.2478/s11658-006-0038-y

Received: 17 January 2006

Accepted: 20 June 2006

Published: 26 September 2006

Abstract

Insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) are essential regulators for osteoblast proliferation and differentiation. It has been reported that Dexamethasone (Dex), an active glucocorticoid (GC) analogue, synergizes the stimulatory effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on osteoblast differentiation in the mouse fibroblastic cell line NIH3T3. I investigated whether this stimulatory effect is associated with changes in the expression pattern of the IGF/IGFBP system. Quantitative real-time PCR technology was used to quantify the gene expression levels of the IGF-system during osteoblast differentiation and in response to 1,25(OH)2D3 or Dex alone under serum-containing and serum-free culture conditions. Interestingly, NIH3T3 was shown to express high mRNA levels of IGF-I, IGF-II and IGFBP-5, and low levels of both IGFBP-2 and-6. During osteoblast differentiation (days 6-12), IGF-I mRNA was repressed by more than 60%, while the transcript of IGFBP-5 was markedly up-regulated, by more than 50-fold. Similarly, treatment with Dex alone resulted in a dose-and time-dependent increase in the expression of IGFBP-5 and a decrease in IGF-I mRNA. Treatment with 1,25(OH)2D3 alone increased the mRNA levels of IGF-I and IGFBP-6 by around 4-and 7-fold, respectively, in a dose-and time-dependent manner. In conclusion, my data demonstrated that osteoblast differentiation of NIH3T3 is associated with changes in the expression pattern of IGFs/IGFBPs, which are regulated by glucocorticoid in the presence of 1,25(OH)2D3. Modulation of the IGF/IGFBP levels by glucocorticoid might suggest important roles for the IGF-system in mediating the osteoblast differentiation of the NIH3T3 cell line.

Key words

IGFs/IGFBPs NIH3T3 Gene expression Osteoblast differentiation

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