Lohmander L S, Hascall V C, Caplan A I
J Biol Chem. 1979 Oct 25;254(20):10551-61.
When chick limb bud mesenchyme cells from stage 23 to 24 embryos are plated at high density, they rapidly divide and a large proportion initiate chondrogenic expression during the first 2 to 3 days in culture. Between Days 4 and 8, the emergent chondrocytes mature and elaborate a cartilaginous matrix. The proteoglycans synthesized by the newly emergent Day 3 to 4 chondrocytes differ from those synthesized by either the prechondrogenic mesenchyme cells or the mature Day 8 chondrocytes. Cultures were grown from initial plating (Day 0) or from Day 2 in the continuous presence of 1 mM 4-methyl umbelliferyl-beta-D-xyloside, which acts intracellularly as a competitive acceptor with the endogenous core protein of proteoglycans for chondroitin sulfate synthesis. The proteoglycans synthesized by Day 8 cultures which had been maintained on xyloside or to which xyloside was added only 1 h prior to labeling were essentially identical. They were able to form aggregates, and they contained the same number of keratan sulfate chains, but only about 40% as many chondroitin sulfate chains, as normal. Additionally, both the chondroitin sulfate and keratan sulfate chains were 25% shorter than in the normal proteoglycans. The proteoglycans synthesized by cells in a culture maintained on xyloside until Day 8, and then switched to medium with no xyloside 1 h prior to labeling, were characteristic of those synthesized by normal mature Day 8 chondrocytes. These data suggest that stage 23 to 24 mesenchyme cells undergo normal chondrogenic maturation in culture in the presence of xylosides even though (a) most of the polysaccharides are synthesized onto the exogenously supplied xyloside substrate and released into the medium, (b) the proteoglycans that are synthesized are greatly reduced in polysaccharide content, and (c) the extracellular matrix as a consequence is greatly depleted in chondroitin sulfate content and, therefore, is abnormal in general morphology.
将来自23至24期胚胎的鸡胚肢芽间充质细胞高密度接种时，它们会迅速分裂，并且很大一部分细胞在培养的最初2至3天内开始软骨生成表达。在第4天至第8天之间，新出现的软骨细胞成熟并形成软骨基质。第3至4天新出现的软骨细胞合成的蛋白聚糖与软骨生成前的间充质细胞或成熟的第8天软骨细胞合成的蛋白聚糖不同。培养物从初始接种（第0天）开始生长，或者在持续存在1 mM 4-甲基伞形酮基-β-D-木糖苷的情况下从第2天开始生长，该物质在细胞内作为蛋白聚糖内源性核心蛋白的竞争性受体参与硫酸软骨素的合成。在木糖苷上维持到第8天的培养物或仅在标记前1小时添加木糖苷的培养物所合成的蛋白聚糖基本相同。它们能够形成聚集体，并且含有相同数量的硫酸角质素链，但硫酸软骨素链的数量仅为正常情况的约40%。此外，硫酸软骨素链和硫酸角质素链都比正常蛋白聚糖短25%。在木糖苷上维持到第8天，然后在标记前1小时换成不含木糖苷的培养基的培养物中的细胞所合成的蛋白聚糖，具有正常成熟的第8天软骨细胞合成的蛋白聚糖的特征。这些数据表明，23至24期的间充质细胞在木糖苷存在的情况下在培养中经历正常的软骨生成成熟，即使（a）大多数多糖是在外源供应的木糖苷底物上合成并释放到培养基中，（b）合成的蛋白聚糖的多糖含量大大降低，并且（c）细胞外基质因此硫酸软骨素含量大大减少，因此总体形态异常。
