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Cortisol decreases IGF-I mRNA levels in human osteoblast-like cells
D Swolin1, C Brantsing, G Matejka
1Department of Internal Medicine, University of Göteborg, Sweden.
Abstract:
Excess levels of glucocorticoids are known to cause osteoporosis. It is speculated that the effect of glucocorticoids could be mediated via regulation of IGF-I. The aims of the present study were to detect and quantify the expression of IGF-I and/or IGF-II mRNA transcripts in human osteoblast-like cells and to investigate whether glucocorticoids regulate the expression of IGF-I mRNA transcripts in human osteoblast-like cells. Cultures of human osteoblast-like cells from trabecular bone were established. The IGF-IA and IGF-IB transcripts were detected in human osteoblast-like cells from seven out of nine patients while the IGF-II transcript was detected in human osteoblast-like cells from eight out of nine patients, as determined by RT-PCR assays. Human osteoblast-like cells, as well as human muscle tissue, expressed approximately 1/10 of the IGF-I mRNA levels found in liver, as determined by RNase protection solution hybridization assay. The IGF-I mRNA levels did not decrease with age in the human osteoblast-like cells and no difference was seen between males and females. However, cortisol (10(-6) mol/l) decreased IGF-I mRNA levels. In summary, the present study has shown that human osteoblast-like cells express IGF-I and IGF-II mRNA transcripts and that cortisol down-regulates the IGF-I mRNA levels, indicating that some of the inhibitory effect of glucocorticoids on bone formation in humans is mediated via a reduced autocrine/paracrine expression of IGF-I.
Insights
Glucocorticoids, like cortisol, can harm bone formation by reducing insulin-like growth factor-I (IGF-I) mRNA levels in human bone cells. This study confirms IGF-I and IGF-II expression in osteoblasts and cortisol
Area of Science:
- Endocrinology
- Bone Biology
- Molecular Biology
Background:
- Excess glucocorticoids are a known cause of osteoporosis.
- Glucocorticoid-induced bone loss may involve the regulation of insulin-like growth factor-I (IGF-I).
Purpose of the Study:
- To detect and quantify IGF-I and IGF-II mRNA transcripts in human osteoblast-like cells.
- To investigate whether glucocorticoids regulate IGF-I mRNA expression in these cells.
Main Methods:
- Cultures of human osteoblast-like cells from trabecular bone were established.
- RT-PCR assays were used to detect IGF-I and IGF-II mRNA transcripts.
- RNase protection solution hybridization assay quantified IGF-I mRNA levels.
Main Results:
- IGF-I and IGF-II mRNA transcripts were detected in human osteoblast-like cells.
- Osteoblast-like cells expressed approximately 1/10 of the IGF-I mRNA levels found in liver.
- Cortisol treatment significantly decreased IGF-I mRNA levels in osteoblast-like cells.
Conclusions:
- Human osteoblast-like cells express both IGF-I and IGF-II mRNA.
- Cortisol down-regulates IGF-I mRNA levels in human osteoblast-like cells.
- This suggests glucocorticoid's inhibitory effect on bone formation may be partly mediated by reduced IGF-I expression.