Ueki Masashi, Tanaka Nobuaki, Tanimoto Kotaro, Nishio Clarice, Honda Kobun, Lin Yu-Yu, Tanne Yuki, Ohkuma Satoru, Kamiya Takashi, Tanaka Eiji, Tanne Kazuo
Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Hiroshima, 734-8553, Japan.
Ann Biomed Eng. 2008 May;36(5):793-800. doi: 10.1007/s10439-008-9462-7. Epub 2008 Feb 16.
It is well known that mechanical loading influences the endochondral bone formation essential for the growth and development of longitudinal bones. The question was, however, asked whether the effect of mechanical loading on the chondrocyte metabolism is dependent on the loading frequency. This study was aimed at evaluating the effect of tensile loadings with various frequencies on the proliferation of growth plate chondrocytes and extracellular matrix synthesis. The chondrocytes obtained from rib growth plate cartilage of 4-week-old male Wistar strain rats were cultured by day 4 and day 11 and used as proliferating and matrix-forming chondrocytes, respectively. Intermittent tensile stresses with different frequencies were applied to each stage chondrocyte. DNA syntheses were examined by measuring the incorporation of [(3)H]thymidine into the cells. Furthermore, the rates of collagen and proteoglycan syntheses were determined by measuring the incorporation of [2,3-(3)H]proline and [(35)S]sulfate into the cells, respectively. At the proliferating stage, intermittent tensions with the frequencies of 30 cycles/min and 150 cycles/min significantly (p < 0.05) upregulated the syntheses of DNA, which indicates the promotion of chondrocyte proliferation. At the matrix-forming stage, collagen, and proteoglycan syntheses also enhanced with increase of the loading frequency. In particular, the intermittent tension with the frequencies of 30 cycles/min and 150 cycles/min increased significantly (p < 0.05 or p < 0.01) both the collagen and proteoglycan syntheses. These results suggest that the proliferation and differentiation of growth plate chondrocytes are regulated by the mechanical loading and that the chondrocyte metabolism enhanced with increase of loading frequency. These may give more insight into the possible mechanism leading to endochondral bone formation.
众所周知，机械负荷影响纵向骨骼生长发育所必需的软骨内成骨。然而，问题是机械负荷对软骨细胞代谢的影响是否取决于负荷频率。本研究旨在评估不同频率的拉伸负荷对生长板软骨细胞增殖和细胞外基质合成的影响。从4周龄雄性Wistar品系大鼠的肋生长板软骨中获取的软骨细胞，分别在第4天和第11天进行培养，分别用作增殖软骨细胞和基质形成软骨细胞。对每个阶段的软骨细胞施加不同频率的间歇性拉伸应力。通过测量[(3)H]胸苷掺入细胞来检测DNA合成。此外，分别通过测量[2,3-(3)H]脯氨酸和[(35)S]硫酸盐掺入细胞来测定胶原蛋白和蛋白聚糖的合成速率。在增殖阶段，频率为30次/分钟和150次/分钟的间歇性张力显著（p<0.05）上调了DNA的合成，这表明促进了软骨细胞增殖。在基质形成阶段，胶原蛋白和蛋白聚糖的合成也随着负荷频率的增加而增强。特别是，频率为30次/分钟和150次/分钟的间歇性张力显著（p<0.05或p<0.01）增加了胶原蛋白和蛋白聚糖的合成。这些结果表明，生长板软骨细胞的增殖和分化受机械负荷调节，并且软骨细胞代谢随着负荷频率的增加而增强。这些可能为软骨内成骨的可能机制提供更多见解。
