Ripamonti U, Crooks J, Matsaba T, Tasker J
Bone Research Laboratory, Medical Research Council/University of the Witwatersrand, Medical School, Johannesburg, South Africa.
Growth Factors. 2000;17(4):269-85. doi: 10.3109/08977190009028971.
Members of the transforming growth factor-beta (TGF-beta) superfamily, the bone morphogenetic and osteogenic proteins (BMPs/OPs) but not the TGF-beta proteins themselves, induce endochondral bone formation in vivo, when implanted in extraskeletal heterotopic sites of rodents. Here we show that recombinant human TGF-beta2 (hTGF-beta2) induces endochondral bone formation 30 days after implantation in heterotopic intramuscular sites of the baboon (Papio ursinus) at doses of 1, 5 and 25 microg per 100 mg of guanidinium-inactivated collagenous bone matrix as carrier. On day 90 there was generation of large radiopaque and corticalized intramuscular ossicles. Five and 25 microg hTGF-beta2 induced large ossicles in the rectus abdominis of the primate as evaluated by key parameters of bone formation, including generated tissue area, mineralized bone and osteoid volumes, and tissue alkaline phosphatase activity. On day 30 and 90 after healing, hTGF-beta2 also induced bone formation when implanted in the rectus abdominis in conjunction with a sintered porous hydroxyapatite as carrier. mRNA expression in tissues from heterotopic specimens showed OP-1 (BMP-7) and BMP-3 transcripts in low abundance and with a linear dose-dependent increase both in collagenous matrix and hydroxyapatite samples. Type IV collagen mRNA expression, a marker of angiogenesis, was stronger in collagenous than hydroxyapatite samples. Growth and differentiation factor-10 (GDF-10) mRNA transcripts were expressed in ossicles with a distinctly chondrogenic phase, but its expression was greater in ossicles generated in porous hydroxyapatites, in which bone formation is not via a chondrogenic phase, but is rather intramembranous, without expression of type II collagen mRNA. In the same animals, however, 10 and 100 microg of the recombinant morphogen delivered by identical carriers (collagenous matrix and sintered hydroxyapatite) failed to heal calvarial defects. Thus in the primate, TGF-betas themselves are inducers of endochondral bone formation, although the present data strongly indicate that the bone inductive activity of hTGF-beta2 is site and tissue specific, since a single application of hTGF-beta2, or hTGF-beta1 in previously published experiments, did not induce bone in calvarial defects, but did induce endochondral bone differentiation in heterotopic sites.
转化生长因子-β（TGF-β）超家族成员，即骨形态发生蛋白和成骨蛋白（BMPs/OPs），而非TGF-β蛋白本身，当植入啮齿动物的骨骼外异位部位时，可在体内诱导软骨内成骨。在此我们表明，重组人TGF-β2（hTGF-β2）以每100 mg胍灭活胶原骨基质为载体，分别以1、5和25 μg的剂量植入狒狒（山魈）的异位肌内部位后30天，可诱导软骨内成骨。在第90天时，产生了大的不透射线且已皮质化的肌内小骨。通过骨形成的关键参数评估，包括生成组织面积、矿化骨和类骨质体积以及组织碱性磷酸酶活性，5 μg和25 μg的hTGF-β2在灵长类动物的腹直肌中诱导形成了大的小骨。在愈合后的第30天和第90天，当hTGF-β2与烧结多孔羟基磷灰石作为载体一起植入腹直肌时，也诱导了骨形成。异位标本组织中的mRNA表达显示，OP-1（BMP-7）和BMP-3转录本含量较低，且在胶原基质和羟基磷灰石样品中均呈线性剂量依赖性增加。IV型胶原mRNA表达作为血管生成的标志物，在胶原样品中比在羟基磷灰石样品中更强。生长分化因子-10（GDF-10）mRNA转录本在具有明显软骨生成阶段的小骨中表达，但其在多孔羟基磷灰石中生成的小骨中表达更高，在多孔羟基磷灰石中骨形成不是通过软骨生成阶段，而是膜内成骨，且不表达II型胶原mRNA。然而，在同一动物中，由相同载体（胶原基质和烧结羟基磷灰石）递送的10 μg和100 μg重组形态发生蛋白未能修复颅骨缺损。因此在灵长类动物中，TGF-β本身是软骨内成骨的诱导剂，尽管目前的数据强烈表明hTGF-β2的骨诱导活性具有部位和组织特异性，因为在先前发表的实验中，单次应用hTGF-β2或hTGF-β1并未在颅骨缺损处诱导骨形成，但在异位部位却诱导了软骨内骨分化。
