Saadeh P B, Mehrara B J, Steinbrech D S, Dudziak M E, Greenwald J A, Luchs J S, Spector J A, Ueno H, Gittes G K, Longaker M T
Department of Surgery, University of Connecticut, Farmington, Connecticut 06032, USA.
Am J Physiol. 1999 Oct;277(4):C628-37. doi: 10.1152/ajpcell.1999.277.4.C628.
Angiogenesis is essential to both normal and pathological bone physiology. Vascular endothelial growth factor (VEGF) has been implicated in angiogenesis, whereas transforming growth factor-beta1 (TGF-beta1) modulates bone differentiation, matrix formation, and cytokine expression. The purpose of this study was to investigate the relationship between TGF-beta1 and VEGF expression in osteoblasts and osteoblast-like cells. Northern blot analysis revealed an early peak of VEGF mRNA (6-fold at 3 h) in fetal rat calvarial cells and MC3T3-E1 osteoblast-like cells after stimulation with TGF-beta1 (2.5 ng/ml). The stability of VEGF mRNA in MC3T3-E1 cells was not increased after TGF-beta1 treatment. Actinomycin D inhibited the TGF-beta1-induced peak in VEGF mRNA, whereas cycloheximide did not. Blockade of TGF-beta1 signal transduction via a dominant-negative receptor II adenovirus significantly decreased TGF-beta1 induction of VEGF mRNA. Additionally, TGF-beta1 induced a dose-dependent increase in VEGF protein expression by MC3T3-E1 cells (P < 0.01). Dexamethasone similarly inhibited VEGF protein expression. Both TGF-beta1 mRNA and VEGF mRNA were concurrently present in rat membranous bone, and both followed similar patterns of expression during rat mandibular fracture healing (mRNA and protein). In summary, TGF-beta1-induced VEGF expression by osteoblasts and osteoblast-like cells is a dose-dependent event that may be intimately related to bone development and fracture healing.
血管生成对于正常和病理性骨生理过程都至关重要。血管内皮生长因子（VEGF）与血管生成有关，而转化生长因子-β1（TGF-β1）调节骨分化、基质形成和细胞因子表达。本研究的目的是探讨TGF-β1与成骨细胞及成骨样细胞中VEGF表达之间的关系。Northern印迹分析显示，在用TGF-β1（2.5 ng/ml）刺激后，胎鼠颅骨细胞和MC3T3-E1成骨样细胞中VEGF mRNA出现早期峰值（3小时时增加6倍）。TGF-β1处理后，MC3T3-E1细胞中VEGF mRNA的稳定性并未增加。放线菌素D抑制了TGF-β1诱导的VEGF mRNA峰值，而环己酰亚胺则没有。通过显性负性受体II腺病毒阻断TGF-β1信号转导可显著降低TGF-β1对VEGF mRNA的诱导作用。此外，TGF-β1诱导MC3T3-E1细胞VEGF蛋白表达呈剂量依赖性增加（P < 0.01）。地塞米松同样抑制VEGF蛋白表达。TGF-β1 mRNA和VEGF mRNA同时存在于大鼠膜性骨中，并且在大鼠下颌骨骨折愈合过程中两者的表达模式相似（mRNA和蛋白）。总之，TGF-β1诱导成骨细胞及成骨样细胞表达VEGF是一个剂量依赖性事件，可能与骨发育和骨折愈合密切相关。
