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Cell Biology International (2006) 30, 714–720 (Printed in Great Britain)

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Effects of fluid shear stress on mRNA expression of carbonic anhydrase II in polarized rat osteoclasts

Qinghong Zhang^a, Xing Liang^a*, Baoming Zhu^a, Qiang Dong^a, Ling Xu^a, Lu Xia^a, Jian Hu^a, Jun Fu^a and Mengtao Liu^b

^aKey Laboratory of Oral Biomedical Engineering of Ministry of Education, West China College of Stomatology, Sichuan University, Chengdu 610041, China
^bDepartment of Prosthetics, The Red Cross Hospital of Kunming, Yunnan 650021, China

Abstract

The present study was designed to determine the effects of fluid shear stress on the mRNA expression of carbonic anhydrase II (CAII) in polarized rat osteoclasts. Cellular morphology of the polarized osteoclasts generated by a mechanical anatomical technique was examined by tartrate-resistant acid phosphatase (TRAP) staining and the osteoclastic resorption of dentine slices. The polarized osteoclasts were then stress-loaded by using a flow shear stress device newly developed by the osteoclast research group (patent number 200420034438; China), at 9dyne/cm² for various time periods [0 (control group), 15, 30, 60, and 120min], or at various stress levels [0 (control), 0.9, 2.9, 8.7, and 26.3dyne/cm²] for 30min. The mRNA expression of CAII was quantified using real-time fluorescent quantitative PCR (RT-PCR) and the data were analyzed with SPSS 12.0 software. The polarized osteoclasts were larger than regular monocytes (about 30μm diameter) with irregular configuration, and the majority of polarized osteoclasts appeared to be spherical and had approximately 2–20 nuclei. The TRAP positive polarized osteoclasts showed asymmetrical red staining in the cytoplasm, and had many filaments and vacuoles. These cells formed resorptive pits in dentine slices. The levels of CAII mRNA expression were shown to be time-dependent, with the E+5 copy numbers being 7.88±0.09, 11.14±0.12, 15.83±0.18, 1.94±0.02, and 1.37±0.01 in cells treated at 9dyne/cm² for 0, 15, 30, 60 and 120min, respectively (P<0.05). The levels of CAII mRNA expression (E+5 copy numbers) in cells treated with the stress levels of 0, 0.9, 2.9, 8.7 and 26.3dyne/cm² were 7.97±0.201, 11.26±0.688, 15.94±0.201, 31.88±1.496, and 45.08±2.639, respectively (P<0.05). These results indicate that there is a relationship between the fluid shear stress and the mRNA expression of CAII in polarized rat osteoclasts.

Key words: Osteoclast, Fluid shear stress, Carbonic anhydrase II, Morphology.

^*Corresponding author. Tel./fax: +86 28 85503570.

Received 28 October 2005/18 March 2006; accepted 3 May 2006