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Effects of high frequency loading on RANKL and OPG mRNA expression in ST-2 murine stromal cells.

Kim CH, Kim KH, Jacobs CR - BMC Musculoskelet Disord (2009)

Bottom Line: Real-time RT-PCR was used to quantify mRNA levels of RANKL, OPG. 3600 cycles of OFF at 1 Hz and 10 Hz loading decreased RANKL/OPG ratio.Interestingly, these results were due to different mechanisms where at 1 Hz the decrease was due to an increase in OPG mRNA, whereas at 10 Hz the decrease was due to a decrease in RANKL mRNA.Although high frequency OFF does not appear to further enhance the decrease in the RANKL/OPG ratio, these results suggest a potential to differentially control the change in either RANKL or OPG mRNA expression by applying different loading frequencies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, Yonsei University, Gangwon Do, Korea. chihyun@yonsei.ac.kr

ABSTRACT

Background: Oscillatory fluid flow (OFF)-induced shear stress leads to positive bone remodeling through pro-formative and anti-resorptive effects on bone cells. In this study, the effects of high frequency OFF on expression of receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG), two important regulators of osteoclast differentiation, were investigated.

Methods: Cells were exposed to 1 Pa peak shear stress using three loading frequencies (1, 10, and 20 Hz) widely employed in cell, animal, and clinical studies of bone remodeling. Two separate experiments were performed where either the total number of cycles (3600 cycles) or the total loading time (60 min) was kept constant. Real-time RT-PCR was used to quantify mRNA levels of RANKL, OPG.

Results: 3600 cycles of OFF at 1 Hz and 10 Hz loading decreased RANKL/OPG ratio. Interestingly, these results were due to different mechanisms where at 1 Hz the decrease was due to an increase in OPG mRNA, whereas at 10 Hz the decrease was due to a decrease in RANKL mRNA.

Conclusion: Although high frequency OFF does not appear to further enhance the decrease in the RANKL/OPG ratio, these results suggest a potential to differentially control the change in either RANKL or OPG mRNA expression by applying different loading frequencies.

Show MeSH
RANKL, OPG, and RANKL/OPG mRNA levels in ST-2 murine stromal cells after 3600 cycles of OFF. Loading frequencies of 1, 10, or 20 Hz were used. This resulted in loading durations of 60 min (1 Hz), 6 min (10 Hz), and 3 min (20 Hz). N = 4 for each group.
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Figure 1: RANKL, OPG, and RANKL/OPG mRNA levels in ST-2 murine stromal cells after 3600 cycles of OFF. Loading frequencies of 1, 10, or 20 Hz were used. This resulted in loading durations of 60 min (1 Hz), 6 min (10 Hz), and 3 min (20 Hz). N = 4 for each group.

Mentions: Immediately after application of 3600 cycles of OFF, the RANKL/OPG ratio significantly decreased in 1 Hz (60 min) and 10 Hz (6 min) loading groups compared to no flow controls (p < 0.05) (Figure 1). The RANKL/OPG ratio decreased by approximately 60% using a loading frequency of 1 Hz and approximately 30% using a loading frequency of 10 Hz. Interestingly though, the decreases in RANKL/OPG ratio at these two loading frequencies (i.e., 1 Hz and 10 Hz) compared to no flow controls resulted occurred in different ways. For 1 Hz loading, RANKL mRNA expression displayed no change compared to no flow controls whereas OPG mRNA expression significantly increased by over 2-fold leading to an overall significant decrease in RANKL/OPG ratio. On the other hand, for 10 Hz loading, RANKL mRNA expression significantly decreased by 35% whereas OPG mRNA expression showed no change compared to no flow controls. This decrease in RANKL resulted in an overall significant decrease in RANKL/OPG ratio.


Effects of high frequency loading on RANKL and OPG mRNA expression in ST-2 murine stromal cells.

Kim CH, Kim KH, Jacobs CR - BMC Musculoskelet Disord (2009)

RANKL, OPG, and RANKL/OPG mRNA levels in ST-2 murine stromal cells after 3600 cycles of OFF. Loading frequencies of 1, 10, or 20 Hz were used. This resulted in loading durations of 60 min (1 Hz), 6 min (10 Hz), and 3 min (20 Hz). N = 4 for each group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2742507&req=5

Figure 1: RANKL, OPG, and RANKL/OPG mRNA levels in ST-2 murine stromal cells after 3600 cycles of OFF. Loading frequencies of 1, 10, or 20 Hz were used. This resulted in loading durations of 60 min (1 Hz), 6 min (10 Hz), and 3 min (20 Hz). N = 4 for each group.
Mentions: Immediately after application of 3600 cycles of OFF, the RANKL/OPG ratio significantly decreased in 1 Hz (60 min) and 10 Hz (6 min) loading groups compared to no flow controls (p < 0.05) (Figure 1). The RANKL/OPG ratio decreased by approximately 60% using a loading frequency of 1 Hz and approximately 30% using a loading frequency of 10 Hz. Interestingly though, the decreases in RANKL/OPG ratio at these two loading frequencies (i.e., 1 Hz and 10 Hz) compared to no flow controls resulted occurred in different ways. For 1 Hz loading, RANKL mRNA expression displayed no change compared to no flow controls whereas OPG mRNA expression significantly increased by over 2-fold leading to an overall significant decrease in RANKL/OPG ratio. On the other hand, for 10 Hz loading, RANKL mRNA expression significantly decreased by 35% whereas OPG mRNA expression showed no change compared to no flow controls. This decrease in RANKL resulted in an overall significant decrease in RANKL/OPG ratio.

Bottom Line: Real-time RT-PCR was used to quantify mRNA levels of RANKL, OPG. 3600 cycles of OFF at 1 Hz and 10 Hz loading decreased RANKL/OPG ratio.Interestingly, these results were due to different mechanisms where at 1 Hz the decrease was due to an increase in OPG mRNA, whereas at 10 Hz the decrease was due to a decrease in RANKL mRNA.Although high frequency OFF does not appear to further enhance the decrease in the RANKL/OPG ratio, these results suggest a potential to differentially control the change in either RANKL or OPG mRNA expression by applying different loading frequencies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, Yonsei University, Gangwon Do, Korea. chihyun@yonsei.ac.kr

ABSTRACT

Background: Oscillatory fluid flow (OFF)-induced shear stress leads to positive bone remodeling through pro-formative and anti-resorptive effects on bone cells. In this study, the effects of high frequency OFF on expression of receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG), two important regulators of osteoclast differentiation, were investigated.

Methods: Cells were exposed to 1 Pa peak shear stress using three loading frequencies (1, 10, and 20 Hz) widely employed in cell, animal, and clinical studies of bone remodeling. Two separate experiments were performed where either the total number of cycles (3600 cycles) or the total loading time (60 min) was kept constant. Real-time RT-PCR was used to quantify mRNA levels of RANKL, OPG.

Results: 3600 cycles of OFF at 1 Hz and 10 Hz loading decreased RANKL/OPG ratio. Interestingly, these results were due to different mechanisms where at 1 Hz the decrease was due to an increase in OPG mRNA, whereas at 10 Hz the decrease was due to a decrease in RANKL mRNA.

Conclusion: Although high frequency OFF does not appear to further enhance the decrease in the RANKL/OPG ratio, these results suggest a potential to differentially control the change in either RANKL or OPG mRNA expression by applying different loading frequencies.

Show MeSH