Bone and Cartilage Metabolism Research Unit, University of Liège, Belgium.
Osteoarthritis Cartilage. 2009 Apr;17(4):473-81. doi: 10.1016/j.joca.2008.09.007. Epub 2008 Oct 29.
In osteoarthritis (OA), mechanical factors play a key role, not only in cartilage degradation, but also in subchondral bone sclerosis. The aim of this study was to develop on original compression model for studying the effect of mechanical stress on osteoblasts.
We investigate the effects of compression on primary calvaria osteoblasts isolated from newborn mice and cultured for 28 days in monolayer. At the end of this period, osteoblasts were embedded in a newly synthesized extracellular matrix which formed a three-dimensional membrane. This membrane was then submitted to compression in Biopress Flexercell plates (1-1.7 MPa compressions at 1 Hz frequency) during 1-8h. The expression of 20 genes was investigated by real time reverse transcriptase polymerase chain reaction. Interleukin (IL)-6, matrix metalloproteinase (MMP)-3 and prostaglandin (PG)E(2) were assayed in the culture medium by specific immunoassays.
The compression highly increased IL-6 and cyclooxygenase (COX)-2 mRNA levels in osteoblasts. In parallel, increased amount of IL-6 and PGE(2) was found in the supernatant of loaded osteoblasts. This stimulation reached a maximum after 4h of 10% compression. MMP-2, MMP-3, and MMP-13 mRNA levels were also increased by compressive stress, while 15-hydroxyprostaglandin-dehydrogenase and osteoprotegerin (OPG) start to decrease at hour 4. COX-1, microsomial PG E synthase-1 (mPGES1), mPGES2 and cytosolic PGES and receptor activator of nuclear factor ligand (RANKL) were unmodified. Finally, we observed that alpha 5 beta 1 integrin, intracellular Ca(++), nuclear factor-kappaB and extracellular signal-regulated kinase 1/2 pathways were involved in the compression-induced IL-6 and PGE(2) production. IL-6 neutralizing antibodies and piroxicam inhibited the decrease OPG expression, but did not modify RANKL mRNA level, indicating that IL-6 and PGE(2) induce a decrease of the OPG/RANKL ratio.
This work demonstrates that IL-6 is mechano-sensitive cytokine and probably a key factor in the biomechanical control of bone remodeling in OA.
在骨关节炎（OA）中，机械因素不仅在软骨降解中起关键作用，而且在软骨下骨硬化中起关键作用。本研究的目的是开发一种原始的压缩模型，用于研究机械应力对成骨细胞的影响。
我们研究了压缩对从小鼠分离并在单层中培养 28 天的原代颅骨成骨细胞的影响。在这段时间结束时，将成骨细胞嵌入新合成的细胞外基质中，形成三维膜。然后，将该膜在 Biopress Flexercell 板中（1-1.7 MPa 压缩，1 Hz 频率）压缩 1-8 小时。通过实时逆转录聚合酶链反应（RT-PCR）检测 20 种基因的表达。通过特定的免疫测定法测定培养基中的白细胞介素（IL）-6、基质金属蛋白酶（MMP）-3 和前列腺素（PG）E（2）。
压缩可高度增加成骨细胞中 IL-6 和环氧化酶（COX）-2 的 mRNA 水平。同时，负载成骨细胞的上清液中发现 IL-6 和 PGE（2）的含量增加。在 10%压缩 4 小时后达到最大刺激。MMP-2、MMP-3 和 MMP-13 的 mRNA 水平也被压缩应激所增加，而 15-羟基前列腺素脱氢酶和骨保护素（OPG）在 4 小时开始下降。COX-1、微粒体 PG E 合酶-1（mPGES1）、mPGES2 和胞质 PGES 以及核因子配体受体激活剂（RANKL）未改变。最后，我们观察到，α5β1 整联蛋白、细胞内 Ca（++）、核因子-κB 和细胞外信号调节激酶 1/2 途径参与了压缩诱导的 IL-6 和 PGE（2）的产生。IL-6 中和抗体和吡罗昔康抑制了 OPG 表达的下降，但并未改变 RANKL mRNA 水平，表明 IL-6 和 PGE（2）诱导 OPG/RANKL 比值下降。
这项工作表明，IL-6 是机械敏感细胞因子，可能是 OA 中骨重塑的生物力学控制的关键因素。
