Izumi T, Scully S P, Heydemann A, Bolander M E
Orthopaedic Research Unit, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland.
J Bone Miner Res. 1992 Jan;7(1):115-21. doi: 10.1002/jbmr.5650070116.
Chondrogenesis can occur during a bone repair process, which is related to several growth factors. Transforming growth factor beta 1 (TGF-beta 1) downregulates the expression of type II collagen by chondrocytes in vitro, but injection of TGF-beta 1 into the periosteum in vivo increases type II collagen mRNA levels and initiates chondrogenesis. We examined the effect of TGF-beta 1 on collagen gene expression in a bovine periosteum-derived cell culture system to evaluate its direct effect on the periosteum. Cultured cells expressed alkaline phosphatase and collagen pro alpha 1(I) and pro alpha 1(II) mRNAs. A low level of type II collagen synthesis was demonstrated by immunoprecipitation. TGF-beta 1 had no effect on periosteal cell proliferation. Expression of collagen pro alpha 1(I) mRNA did not change with TGF-beta 1 treatment, but alkaline phosphatase mRNA showed a dose-dependent decrease. Expression of collagen pro alpha 1(II) mRNA was stimulated 2.7-fold by TGF-beta 1. TGF-beta 1 also caused a 2.6-fold increase in type II collagen synthesis by immunoprecipitation. These findings indicate that TGF-beta 1 is an enhancer of the expression of the chondrocyte phenotype of the periosteal cells and suggest that TGF-beta 1 is important in initiating and promoting cartilage formation in vivo.
软骨形成可发生在骨修复过程中，这与多种生长因子有关。转化生长因子β1（TGF-β1）在体外可下调软骨细胞中II型胶原蛋白的表达，但在体内将TGF-β1注入骨膜会增加II型胶原蛋白mRNA水平并启动软骨形成。我们在牛骨膜来源的细胞培养系统中研究了TGF-β1对胶原蛋白基因表达的影响，以评估其对骨膜的直接作用。培养的细胞表达碱性磷酸酶以及胶原蛋白原α1（I）和原α1（II）mRNA。免疫沉淀显示II型胶原蛋白合成水平较低。TGF-β1对骨膜细胞增殖没有影响。TGF-β1处理后，胶原蛋白原α1（I）mRNA的表达没有变化，但碱性磷酸酶mRNA呈剂量依赖性下降。TGF-β1使胶原蛋白原α1（II）mRNA的表达增加了2.7倍。TGF-β1还通过免疫沉淀使II型胶原蛋白合成增加了2.6倍。这些发现表明，TGF-β1是骨膜细胞软骨细胞表型表达的增强剂，并提示TGF-β1在体内启动和促进软骨形成中起重要作用。
