Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA.
Ann Biomed Eng. 2011 Mar;39(3):1101-11. doi: 10.1007/s10439-010-0221-1. Epub 2010 Dec 4.
Mechanical loading of the intervertebral disc (IVD) plays an important role in governing the function of nucleus pulposus (NP) cells. In situ, the loading environment of the NP is neither fully confined nor unconfined. To investigate the potential influences of these idealized loading modes, we utilized an alginate cell culture system to compare the effects of 1 h confined and unconfined compression on glycoprotein gene expression in mixed population NP cells. For dynamic compression, we applied 10 kPa peak stress using a sinusoidal waveform at 0.5 Hz. For static compression, displacements were applied at a constant rate and held at 20% strain. Aggrecan, laminin, fibronectin, glypican, biglycan, and fibromodulin were generally stimulated, and trends were similar between confined and unconfined compression. On the other hand, lumican expression was differentially regulated between confined and unconfined groups. More interestingly, trends under static loading were opposite that under dynamic loading; lumican was upregulated in static confined compression and in dynamic unconfined compression. We theorize that this pattern is indicative of regulation by fluid flow within loaded alginate disks. Calculations using the linear biphasic model suggest that spatial pressure gradients exist in static confined specimens for the majority of the loading duration. Using a parallel plate flow chamber, we report for the first time that NP cells are sensitive to fluid shear stress and confirm that lumican expression can be regulated by short durations of exposure to fluid shear.
椎间盘（IVD）的机械加载对于控制髓核（NP）细胞的功能起着重要作用。在体内，NP 的加载环境既不是完全封闭的也不是非封闭的。为了研究这些理想化加载模式的潜在影响，我们利用藻酸盐细胞培养系统比较了 1 小时约束和非约束压缩对混合 NP 细胞糖蛋白基因表达的影响。对于动态压缩，我们使用 0.5 Hz 的正弦波施加 10 kPa 的峰值应力。对于静态压缩，以恒定速率施加位移并保持在 20%应变。聚集蛋白聚糖、层粘连蛋白、纤连蛋白、聚糖蛋白、双糖蛋白聚糖和纤维连接蛋白通常受到刺激，并且在约束和非约束压缩之间的趋势相似。另一方面，亮蛋白聚糖的表达在约束和非约束组之间存在差异调节。更有趣的是，静态加载下的趋势与动态加载下的趋势相反；亮蛋白聚糖在静态约束压缩和动态非约束压缩中上调。我们推测这种模式表明在加载的藻酸盐盘中流体流动的调节。使用线性双相模型的计算表明，在大多数加载时间内，静态约束标本中存在空间压力梯度。使用平行板流动室，我们首次报道 NP 细胞对流体切应力敏感，并证实亮蛋白聚糖的表达可以通过短暂暴露于流体切应力来调节。
