Hascall V C, Handley C J, McQuillan D J, Hascall G K, Robinson H C, Lowther D A
Arch Biochem Biophys. 1983 Jul 1;224(1):206-23. doi: 10.1016/0003-9861(83)90205-9.
Proteoglycan synthesis by slices of adult bovine articular cartilage is stimulated two-to threefold when tissue is cultured in the presence of fetal calf serum for 5-6 days. After this, essentially steady-state conditions are achieved for up to 14 days in which the high synthetic rates are maintained and the amount of proteoglycan in the tissue remains nearly constant. In the absence of fetal calf serum, synthesis declines to a lower level and there is a gradual, net loss of proteoglycan from the tissue. Tissue maintained without serum for several days rapidly increases synthetic rates to the higher levels over 2-3 days after transferring into medium with serum, and vice versa, indicating that the response of the chondrocytes to serum factors is reversible. The structures of the proteoglycans synthesized under all medium conditions were typical for cartilage. Only small differences in glycosaminoglycan chain sizes and a consistent decrease in the relative amount of keratan sulfate to chondroitin sulfate during the first days in the culture were observed. The net capacity of the cells for chondroitin sulfate synthesis, as estimated by incubation in the presence of exogenous beta-xyloside acceptor, increased (or decreased) in parallel with the changes in endogenous proteoglycan synthesis when cultures were transferred from medium without to medium with serum (or vice versa), suggesting that changes in the net amounts of the enzymes for chondroitin sulfate synthesis are closely coordinated with changes in the amount of core protein being processed to proteoglycans. The responses of calf articular cartilage in the same system were somewhat different. Serum in the medium was required to maintain initial high levels of synthesis. The proteoglycans synthesized contained a lower proportion of keratan sulfate than those initially synthesized in the adult tissue, and there was no change in this proportion with time in culture. The maintenance of steady-state conditions for proteoglycan metabolism by either adult or calf tissue in the presence of serum in these cultures should provide a useful model for studying the regulation of synthesis and catabolism of proteoglycans by chondrocytes residing in a nearly normal extracellular matrix for long periods of time.
当成年牛关节软骨切片在胎牛血清存在的情况下培养5 - 6天时，蛋白聚糖的合成会被刺激两到三倍。在此之后，在长达14天的时间里基本达到稳态，其中高合成率得以维持，组织中的蛋白聚糖量几乎保持不变。在没有胎牛血清的情况下，合成下降到较低水平，并且组织中蛋白聚糖逐渐出现净损失。在无血清条件下维持数天的组织，在转入含血清培养基后的2 - 3天内，合成率迅速增加到较高水平，反之亦然，这表明软骨细胞对血清因子的反应是可逆的。在所有培养基条件下合成的蛋白聚糖结构都是软骨的典型结构。仅观察到糖胺聚糖链大小存在微小差异，并且在培养的最初几天硫酸角质素与硫酸软骨素的相对量持续减少。通过在存在外源性β - 木糖苷受体的情况下孵育来估计，当培养物从无血清培养基转移到含血清培养基（或反之亦然）时，细胞硫酸软骨素合成的净能力与内源性蛋白聚糖合成的变化平行增加（或减少），这表明硫酸软骨素合成酶净量的变化与被加工成蛋白聚糖的核心蛋白量的变化密切相关。小牛关节软骨在同一系统中的反应略有不同。培养基中需要血清来维持最初的高合成水平。合成的蛋白聚糖中硫酸角质素的比例低于成年组织中最初合成的比例，并且在培养过程中该比例没有变化。在这些培养物中，成年或小牛组织在血清存在下维持蛋白聚糖代谢的稳态条件，应该为研究长时间处于近乎正常细胞外基质中的软骨细胞对蛋白聚糖合成和分解代谢的调节提供一个有用的模型。
