Effect of various cytokines on the metabolism of intervertebral disc cells cultured in vitro

本研究旨在探讨藻酸盐微球系统中培养的髓核（Nucleus pulposus，NP）和纤维环（annulus fibrosus，AF）细胞的细胞外基质（extracellular matrix，ECM）分子的代谢及其在细胞因子如白细胞介素-1 α（interleukin-1α，IL-1α）作用下的变化。NP细胞在CM中保留基质的能力差。AF细胞比NP细胞产生更多的胶原。在NP中，超过60%的放射性标记的蛋白聚糖在初始时间点已经存在于FRM中，然而在相同时间点，不到40%的放射性标记的蛋白聚糖存在于AF的FRM中。两个基质池中NP细胞的放射性标记蛋白多糖的周转率与软骨细胞相似。纤维环和髓核CM中的放射性标记蛋白多糖的周转比FRM中的快得多（15 vs>80天）。用IL-1α处理后，NP和AF的微球蛋白多糖周转率显著增加，尤其是CM。椎间盘细胞保持其表型稳定性，并在藻酸盐微球中继续产生其特异性大分子基质。IL-1α引起的PG周转率加速，尤其是在CM中，与我们先前研究中观察到的年龄相关变化相似。IL-1α及其相关物质可能在椎间盘的正常年龄相关过程中起重要作用。通过识别不同基质隔室中发生的代谢变化，藻酸盐珠培养系统似乎适合于研究细胞因子对椎间盘细胞代谢的影响。这种培养系统具有适用性，以进一步研究其他细胞因子和生长因子的影响，其结果应该提供有用的信息，以阐明椎间盘退变的可能机制，并可能最终导致预防和逆转这些过程。

Purposes of the current studies were to investigate metabolism of various extracellular matrix molecules of nucleus pulposus (NP) and annulus fibrosus (AF) cells cultured in alginate beads system and its changes after administrations of various various cytokines such as interleukin-1α (IL-1α).Both NP and AF cells formed two different extracellular matrix pools, cell-associated (CM) and further removed (FRM) components, however, NP cells, have poor ability to retain matrix in CM.AF cells produced more collagen than NP cells. In NP, over 60% of radiolabelled proteoglycans already existed in FRM at initial time point, however less than 40% of that was in FRM of AF at the same time point. Turnover rates of radiolabelled proteoglycans of NP cells in two matrix pools were similar to that of chondrocytes. Radiolabelled proteoglycan in CM of both annulus fibrosus and nucleus pulposus turnover much faster than those in FRM (15 vs>80 days). Treatment with IL-1α caused a significant increase in the rate of proteoglycan turnover in the beads, especially in the CM, of both the NP and AF.Intervertebral disc cells retain their phenotypical stability and keep producing their specific macromolecule matrix in alginate beads. Acceleration of the rate of PG turnover, particularly in the CM, caused by IL-1α was similar to the age-related changes observed in our previous studies. IL-1α or related substances may play significant role in normal age related processes of intervertebral disc. By identifying metabolic changes occurring in distinct matrix compartments, the alginate bead culture system appears suited to study the effects of cytokines on the metabolism of disc cells. This culture system has applicability to further study the effects of other cytokines and growth factors, the results of which should provide useful information to elucidate possible mechanisms of disc degeneration and may ultimately lead to prevention and reversion of such processes.