Gerstenfeld L C, Finer M H, Boedtker H
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
J Biol Chem. 1989 Mar 25;264(9):5112-20.
A quantitative determination of collagen expression was carried out in cultured chondrocytes obtained from a tissue that undergoes endochondral bone replacement (ventral vertebra) and one that does not (caudal sterna). The "short chain" collagen, type X is only expressed in the former while the other "short chain" collagen type IX, was primarily expressed in the latter. These two tissues also differ in that vertebral chondrocytes express moderate levels of both type I procollagen mRNAs which were translated into full length procollagen chains both in vivo and in vitro, while caudal sternal chondrocytes did not. The percent of collagen synthesis was about 50% in both cell types, but sternal cells expressed twice as much collagen as vertebral cells even though type II procollagen was more efficiently processed to alpha-chains in vertebral chondrocytes than in sternal chondrocytes. The number of type II procollagen mRNA molecules/cell was found to be about 2300 in vertebral chondrocytes and about 8000 in sternal cells, in good agreement with the results reported by Kravis and Upholt (Kravis, D., and Upholt, W. B. (1985) Dev. Biol. 108, 164-172). There were about 630 copies of type I procollagen mRNAs with an alpha 1/alpha 2 ratio of 1.6 in vertebral chondrocytes compared with 5100 copies and an alpha 1/alpha 2 ratio of 2.2 in osteoblasts, and less than 40 copies in sternal cells. Since the rate of type I collagen chain synthesis was 50 times greater in osteoblasts than in vertebral cells, type I procollagen mRNAs were about six times less efficiently translated in vertebral cells than in osteoblasts. The type I mRNAs in vertebral chondrocytes were polyadenylated and had 5' ends that were identical in osteoblasts, fibroblasts, and myoblasts. Moreover, type I mRNAs isolated from vertebral chondrocytes were translated into full length preprocollagen chains in vitro in rabbit reticulocyte lysates. Thus, chondrocytes isolated from cartilage tissues with different developmental fates differed quantitatively and qualitatively in total collagen synthesis, procollagen processing, and distribution of collagen types.
对取自经历软骨内骨替代的组织（椎体）和未经历该过程的组织（尾胸骨）的培养软骨细胞进行了胶原蛋白表达的定量测定。“短链”胶原蛋白X型仅在前一种组织中表达，而另一种“短链”胶原蛋白IX型主要在后一种组织中表达。这两种组织的另一个不同之处在于，椎体软骨细胞表达中等水平的I型前胶原mRNA，这些mRNA在体内和体外都能被翻译成全长前胶原链，而尾胸骨软骨细胞则不能。两种细胞类型中胶原蛋白合成的百分比约为50%，但胸骨细胞表达的胶原蛋白是椎体细胞的两倍，尽管II型前胶原在椎体软骨细胞中比在胸骨软骨细胞中更有效地加工成α链。发现椎体软骨细胞中II型前胶原mRNA分子/细胞的数量约为2300个，胸骨细胞中约为8000个，这与Kravis和Upholt报道的结果一致（Kravis, D., and Upholt, W. B. (1985) Dev. Biol. 108, 164 - 172）。椎体软骨细胞中有约630个I型前胶原mRNA拷贝，α1/α2比值为1.6，而成骨细胞中有5100个拷贝，α1/α2比值为2.2，胸骨细胞中则少于40个拷贝。由于成骨细胞中I型胶原链的合成速率比椎体细胞大50倍，I型前胶原mRNA在椎体细胞中的翻译效率比成骨细胞低约6倍。椎体软骨细胞中的I型mRNA是多聚腺苷酸化的，其5'端与成骨细胞、成纤维细胞和成肌细胞中的相同。此外，从椎体软骨细胞中分离出的I型mRNA在兔网织红细胞裂解物中能在体外被翻译成全长前胶原链。因此，从具有不同发育命运的软骨组织中分离出的软骨细胞在总胶原蛋白合成、前胶原加工和胶原类型分布上存在数量和质量上的差异。
