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Alterations of bone matrix protein mRNA expression in rat aorta in vitro
1Department of Pathology, National Cardiovascular Center, Suita, Japan.
Abstract:
We examined the expression of matrix Gla protein (MGP), osteopontin (OPN), and osteonectin (ON) mRNAs in aortic rings excised from 3-month-, 10-month-, and 2-week-old rats during 72-hour incubations in serum-free media. In the aortic rings from 3-month-old rats, the expression of MGP mRNA was strong before incubation and increased during the 72-hour incubation. The expression of OPN mRNA was first detected after a 5-hour incubation and increased thereafter, and that of ON mRNA was strong before the incubation and decreased during the incubation. The expression of MGP and OPN mRNAs in 10-month- and 2-week-old rats was similar to that in 3-month-old rats. In contrast, expression of ON mRNA in 10-month-old rats and the expression of ON mRNA in 2-week-old rats was stronger than that in 3-month-old rats at every incubation period. In situ hybridization and immunohistochemistry identified the MGP, OPN, and ON mRNA-expressing cells as vascular smooth muscle cells. These results suggest that the expression of these mRNAs was regulated in incubation time-dependent and age-specific ways. We believe that this organ culture model is useful for further studies of the function of these bone matrix proteins and regulation of their expression in the vessel wall.
Insights
Vascular smooth muscle cells express matrix Gla protein (MGP), osteopontin (OPN), and osteonectin (ON) mRNAs. Their expression is regulated by incubation time and rat age, suggesting a useful organ culture model for further study.
Area of Science:
- Vascular Biology
- Molecular Biology
- Biochemistry
Background:
- Matrix Gla protein (MGP), osteopontin (OPN), and osteonectin (ON) are bone matrix proteins.
- Their role and regulation in the vessel wall are not fully understood.
Purpose of the Study:
- To investigate the expression patterns of MGP, OPN, and ON mRNAs in rat aortic rings.
- To determine if expression is dependent on incubation time and age.
- To identify the cell types expressing these mRNAs in the aorta.
Main Methods:
- Organ culture of aortic rings from rats of different ages (2 weeks, 3 months, 10 months).
- Incubation for 72 hours in serum-free media.
- Analysis of mRNA expression using in situ hybridization and immunohistochemistry.
Main Results:
- MGP and OPN mRNA expression increased during incubation in 3-month-old rats.
- ON mRNA expression decreased during incubation in 3-month-old rats.
- ON mRNA expression was higher in 2-week-old and 10-month-old rats compared to 3-month-old rats at all time points.
- MGP, OPN, and ON mRNAs were localized to vascular smooth muscle cells.
Conclusions:
- Aortic expression of MGP, OPN, and ON mRNAs is regulated in an incubation time-dependent and age-specific manner.
- Vascular smooth muscle cells are the source of these mRNAs in the aorta.
- The established organ culture model is suitable for studying the function and regulation of these proteins in the vessel wall.