Spinal movement in both upright and recumbent positions generates changes in physicochemical stresses including hydrostatic pressure (HP), deviatoric stress, and confinement within the intradiscal compartment. The nucleus pulposus (NP) of the intervertebral disc is composed of highly negatively charged extracellular matrix (ECM), which increases osmotic pressure (OP) and generates tissue swelling. In pursuing regenerative therapies for intervertebral disc degeneration, the effects of HP on the cellular responses of NP cells and the ECM environment remain incompletely understood. We hypothesized that anabolic turnover of ECM in NP tissue is maintained under HP and confinement. We first clarified the effects of the relationships among HP, OP, and confinement on swelling NP explants isolated from bovine caudal intervertebral discs over 12 h. We found that the application of confinement and constant HP significantly inhibits the free swelling of NP (p < 0.01) and helps retain the sulfated glycosaminoglycan. Since confinement and HP inhibited swelling, we incubated confined NPs under HP in high-osmolality medium mimicking ECM-associated OP for 7 days and demonstrated the effects of HP on metabolic turnover of ECM molecules in NP cells. The aggrecan core protein gene was significantly upregulated under confinement and constant HP compared to confinement and no HP (p < 0.01). We also found that confinement and constant HP helped to significantly retain smaller cell area (p < 0.01) and significantly prevent the severing of actin filaments compared to no confinement and HP (p < 0.01). Thus, we suggest that NP's metabolic turnover and cellular responses are regulated by the configuration of intracellular actin and fibrillar ECMs under HP.

中文翻译：

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静水压、渗透压和限制对离体髓核细胞外基质相关反应的影响


直立位和卧位的脊柱运动都会产生物理化学应力的变化，包括静水压力 （HP）、偏应力和椎间盘内隔室的限制。椎间盘的髓核 （NP） 由带高度负电荷的细胞外基质 （ECM） 组成，这会增加渗透压 （OP） 并产生组织肿胀。在寻求椎间盘退化的再生疗法时，HP 对 NP 细胞反应和 ECM 环境的影响仍不完全清楚。我们假设 NP 组织中 ECM 的合成代谢周转在 HP 和限制下维持。我们首先阐明了 HP 、 OP 和限制之间的关系对 12 小时内从牛尾椎间盘分离的肿胀 NP 外植体的影响。我们发现，限制和恒定 HP 的应用显着抑制 NP 的自由膨胀 （p < 0.01） 并有助于保留硫酸化糖胺聚糖。由于限制和 HP 抑制肿胀，我们将限制的 NPs 在 HP 下在模拟 ECM 相关 OP 的高渗透压培养基中孵育 7 天，并展示了 HP 对 NP 细胞中 ECM 分子代谢周转的影响。与限制和无 HP 相比，聚集蛋白聚糖核心蛋白基因在限制和恒定 HP 下显著上调 （p < 0.01）。我们还发现，与无限制和 HP 相比，限制和恒定 HP 有助于显着保留较小的细胞面积 （p < 0.01） 并显着防止肌动蛋白丝的切断 （p < 0.01）。因此，我们认为 NP 的代谢周转和细胞反应受 HP 下细胞内肌动蛋白和纤维 ECM 的构型调节。