Identification of Mechanotransduction Pathways in Bone Formation induced by Low Intensity Pulsed Ultrasound

在大鼠骨髓细胞中研究了对低强度脉冲超声的合成代谢反应以及相关的机械转导途径。在原代大鼠骨髓细胞和小鼠骨髓来源的 ST2 细胞中检查了低强度脉冲超声暴露 20 分钟的影响。在暴露于超声波之前，将在存在和不存在抗坏血酸的情况下培养的骨髓源性细胞用地塞米松处理1、7和14天，以便区分它们在不同发育阶段的反应。我们通过 RT-PCR 分析确定了 IGF-I、骨钙素和其他骨蛋白 mRNA（包括立即早期基因，如 c-fos 或 cox 2）的稳态水平。我们在 ST2 细胞中报道的 mRNA 水平上调 (BBRC 268 : 216, 2000) 仅在有限条件下才可重现，这表明低强度脉冲超声仅在成骨谱系的早期阶段诱导细胞中的合成代谢反应。我们的研究结果表明，某些细胞群对低强度脉冲超声的直接反应会以旁分泌方式影响其他细胞，从而加速骨折修复的各个阶段。

Anabolic response to low-intensity, pulsed ultrasound and the associated mechanotransduction pathways were studied in rat bone marrow cells. Effects of 20-min exposure to low intensity, pulsed ultrasound were examined in both primary rat bone marrow cells and mouse bone marrow derived ST2 cells. The marrow-derived cells cultured in the presence and absence of ascorbate were treated with Dexamethazone for 1, 7, and 14 days prior to the exposure to the ultrasound so that their responses at different developmental stages can be distinguished. We determined the steady state levels of IGF-I, osteocalcin and other bone protein mRNAs including immediate early genes such as c-fos or cox 2 by using RT-PCR analysis. Upregulation of the mRNA levels that we have reported in ST2 cells (BBRC 268 : 216, 2000) was reproducible only under limited conditions, suggesting that the low intensity, pulsed ultrasound induce anabolic responses in cells only at early stages of osteogenic lineage. Our findings indicate that the direct reaction of certain population of cells to low intensity, pulsed ultrasound influences other cells in a paracrine manner resulting in acceleration of various phases of fracture repair.