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体系中培养的髓核（NP）和纤维环（AF）细胞各种细胞外基质分子的代谢及其在白细胞介素-1α (IL-1α)等多种细胞因子作用后的变化。NP细胞和AF细胞形成两种不同的细胞外基质池，细胞相关成分（CM）和进一步去除成分（FRM），但NP细胞在CM中保留基质的能力较差。AF细胞比NP细胞产生更多的胶原蛋白。在NP中，初始时间点FRM中已经存在超过60%的放射性标记蛋白多糖，而在同一时间点AF的FRM中，放射性标记蛋白多糖的比例不到40%。两种基质池中NP细胞放射性标记蛋白聚糖的周转率与软骨细胞相似。放射标记蛋白多糖在纤维环和髓核CM中的转化比在FRM中的快得多（15天比80天）。用IL-1α处理可显著增加NP和af细胞中蛋白多糖的周转率，特别是在CM中。椎间盘细胞保持其表型稳定性，并继续在海藻酸盐珠中产生其特定的大分子基质。由IL-1α引起的PG转换速率的加速，特别是在CM中，与我们之前研究中观察到的年龄相关变化相似。IL-1α或相关物质可能在椎间盘正常年龄相关过程中发挥重要作用。通过鉴定不同基质室中发生的代谢变化，藻酸珠培养体系似乎适合于研究细胞因子对盘细胞代谢的影响。该培养系统适用于进一步研究其他细胞因子和生长因子的作用，其结果应该为阐明椎间盘退变的可能机制提供有用的信息，并可能最终导致预防和逆转这一过程。

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.