Bonewald L F, Mundy G R
University of Texas Health Science Center, Department of Medicine, San Antonio 78284-7877.
Clin Orthop Relat Res. 1990 Jan(250):261-76.
Transforming growth factor-beta (TGF-beta) plays a critical role in bone remodeling. TGF-beta stimulates matrix protein synthesis, has dramatic effects on the bone cells responsible for bone formation and resorption, and is abundant in bone and bone-conditioned media. Multiple sources of TGF-beta have been described. It was initially purified from platelets. Two distinct forms of TGF-beta have been purified from bone. The second form, TGF-beta II, was initially purified from bone but was then identified in platelets and also as the major TGF-beta in the monkey kidney BSC-1 cell line. The two bone-derived factors were called cartilage-inducing Factor A (CIF-A) and cartilage-inducing Factor B (CIF-B), based on their capacity to induce the formation of extracellular matrix proteins, which are characteristic of cartilage. CIF-A is identical to the TGF-beta purified from platelets, which is called TGF-beta I. CIG-B is the same as TGF-beta II, which was sequenced soon after CIF-B was discovered and characterized. There is 70% sequence homology between the two forms. The largest source of TGF-beta in the body is present in bone (200 micrograms/kg tissue), although the most concentrated source is in platelets. TGF-beta has multiple effects on bone cells depending on their phenotype and/or stage of differentiation. Osteoblasts, the cells responsible for formation of new bone and perhaps cellular control of bone remodeling, are directly affected by TGF-beta, which can induce differentiation or proliferation, depending on the osteoblastic cell type examined. TGF-beta inhibits the formation of osteoclast precursors and bone resorption and, in greater concentrations, has inhibitory effects on isolated osteoclasts, the cells responsible for bone resorption. TGF-beta may act as a bone-coupling factor linking bone resorption to bone formation.
转化生长因子-β（TGF-β）在骨重塑过程中发挥着关键作用。TGF-β刺激基质蛋白合成，对负责骨形成和吸收的骨细胞具有显著影响，并且在骨组织和骨条件培养基中含量丰富。TGF-β有多种来源。它最初是从血小板中纯化出来的。已经从骨中纯化出两种不同形式的TGF-β。第二种形式，即TGF-β II，最初是从骨中纯化出来的，但随后在血小板中被鉴定出来，并且也是猴肾BSC-1细胞系中的主要TGF-β。这两种源自骨的因子根据其诱导细胞外基质蛋白形成的能力被称为软骨诱导因子A（CIF-A）和软骨诱导因子B（CIF-B），细胞外基质蛋白是软骨的特征。CIF-A与从血小板中纯化出的TGF-β相同，后者被称为TGF-β I。CIG-B与TGF-β II相同，在CIF-B被发现和表征后不久对其进行了测序。这两种形式之间存在70%的序列同源性。体内TGF-β的最大来源存在于骨中（200微克/千克组织），尽管最浓缩的来源是血小板。TGF-β对骨细胞有多种影响，这取决于它们的表型和/或分化阶段。成骨细胞负责新骨的形成以及可能对骨重塑的细胞控制，直接受到TGF-β的影响，根据所检测的成骨细胞类型，TGF-β可以诱导分化或增殖。TGF-β抑制破骨细胞前体的形成和骨吸收，并且在更高浓度下，对分离的破骨细胞（负责骨吸收的细胞）有抑制作用。TGF-β可能作为一种骨耦联因子，将骨吸收与骨形成联系起来。
