Centrella M, Casinghino S, Ignotz R, McCarthy T L
Department of Research, Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105.
Endocrinology. 1992 Dec;131(6):2863-72. doi: 10.1210/endo.131.6.1446624.
Transforming growth factor-beta (TGF beta) stimulates bone formation in vivo and in vitro, related in part to an increase in type I collagen production. In osteoblast-enriched cultures from fetal rat bone, 24- to 48-h TGF beta 1 treatment enhanced collagen synthesis rates by 2.5- to 6-fold, while it increased collagen accumulation by 5- to 10-fold. These effects were not accounted for by similar changes in acid-soluble radioisotope, cell number, or steady state type I procollagen transcripts. Basal collagen synthesis and accumulation were markedly reduced when mRNA transcription was blocked with alpha-amanitin, but the relative stimulatory effects of TGF beta 1 persisted in toxin-treated cultures. Newly synthesized collagen was rapidly secreted into the culture medium. While pulse-chase studies demonstrated that total (medium plus cell-associated) collagen levels were stable throughout the 48-h period, TGF beta 1 increased the fraction of cell-associated collagen between 24-48 h, and this was partially blocked by alpha-amanitin, but not by antibody to fibronectin or beta 1-integrin subunit. TGF beta 1, therefore, has multiple effects on type I collagen in fetal bone-derived cell cultures, including small increases in mRNA, large increases in polypeptide synthesis, and enhanced association of secreted collagen to the cell layer, which may require synthesis of extracellular components unrelated to fibronectin or the beta 1-integrin subunit.
转化生长因子-β（TGF-β）在体内和体外均可刺激骨形成，部分原因与I型胶原蛋白生成增加有关。在来自胎鼠骨骼的富含成骨细胞的培养物中，24至48小时的TGF-β1处理使胶原蛋白合成速率提高了2.5至6倍，同时使胶原蛋白积累增加了5至10倍。酸溶性放射性同位素、细胞数量或I型前胶原转录本的稳态水平的类似变化并不能解释这些效应。当用α-鹅膏蕈碱阻断mRNA转录时，基础胶原蛋白合成和积累显著减少，但TGF-β1的相对刺激作用在毒素处理的培养物中仍然存在。新合成的胶原蛋白迅速分泌到培养基中。虽然脉冲追踪研究表明，在整个48小时期间，总（培养基加细胞相关）胶原蛋白水平保持稳定，但TGF-β1在24至48小时之间增加了细胞相关胶原蛋白的比例，这被α-鹅膏蕈碱部分阻断，但未被纤连蛋白抗体或β1整合素亚基抗体阻断。因此，TGF-β1对胎骨来源细胞培养物中的I型胶原蛋白有多种作用，包括mRNA的小幅增加、多肽合成的大幅增加以及分泌的胶原蛋白与细胞层的结合增强，这可能需要合成与纤连蛋白或β1整合素亚基无关的细胞外成分。
