Jester James V, Huang Jiying, Petroll W Matthew, Cavanagh H Dwight
Department of Ophthalmology, University of Texas, Southwestern Medical Center at Dallas, Dallas, TX 75390-9057, USA.
Exp Eye Res. 2002 Dec;75(6):645-57. doi: 10.1006/exer.2002.2066.
There is a growing consensus that corneal myofibroblasts are derived from adjacent stromal keratocytes which undergo an orderly phenotypic transition from quiescent keratocyte to activated fibroblast to myofibroblast. Both in vivo and in vitro studies have shown this transition to be dependent, in part, on transforming growth factor beta (TGFbeta). In many fibroblastic cells autocrine production of platelet derived growth factor (PDGF) is known to mediate the growth up-regulation by TGFbeta. In this study, blocking antibodies to PDGF significantly reduced by 80% (P<0.025) the TGFbeta1 stimulated cell cycle entry of serum-free cultured rabbit corneal keratocytes. AntiPDGF treatment also markedly reduced the TGFbeta1-induced intracellular actin filament re-organization, fibronectin fibril assembly, and focal contact formation as well as reducing by 80% the expression of alpha-smooth muscle (alpha-SM) specific isoform of actin characteristic of myofibroblast differentiation. Although PDGF treatment of quiescent keratocytes produced an activated, fibroblastic cell type, PDGF stimulated keratocytes exhibited the same temporal, myofibroblastic differentiation response to TGFbeta1 as did quiescent keratocytes. Furthermore, blocking TGFbeta1 induction of myofibroblast differentiation with the Arg-Gly-Asp containing peptide, GRGDdSP, for 3 days followed by allowing progression of myofibroblast differentiation by removing GRGDdSP did not change the temporal response or tyrosine phosphorylation cascade (2-72 hr) leading to myofibroblast differentiation. Nor did PDGF treatment of keratocytes reverse the RGD blockade of TGFbeta1 induced myofibroblast differentiation. Overall these cumulative findings indicate that myofibroblast differentiation in the rabbit corneal keratocyte requires synergistic growth factor/integrin signaling involving TGFbeta, PDGF, and the fibronectin receptor. Additionally, the similar TGFbeta1 temporal response of PDGF-stimulated compared to nai;ve keratocytes suggests that myofibroblast differentiation does not require transition through a fibroblast phenotype.
越来越多的人达成共识，即角膜肌成纤维细胞源自相邻的基质角膜细胞，这些角膜细胞经历从静止角膜细胞到活化成纤维细胞再到肌成纤维细胞的有序表型转变。体内和体外研究均表明，这种转变部分依赖于转化生长因子β（TGFβ）。已知在许多成纤维细胞中，血小板衍生生长因子（PDGF）的自分泌产生介导了TGFβ对生长的上调作用。在本研究中，针对PDGF的阻断抗体使TGFβ1刺激的无血清培养兔角膜角膜细胞的细胞周期进入显著降低了80%（P<0.025）。抗PDGF处理还显著减少了TGFβ1诱导的细胞内肌动蛋白丝重组、纤连蛋白原纤维组装和粘着斑形成，并使肌成纤维细胞分化特征性的α-平滑肌（α-SM）特异性肌动蛋白异构体的表达降低了80%。尽管用PDGF处理静止角膜细胞产生了一种活化的成纤维细胞类型，但PDGF刺激的角膜细胞对TGFβ1表现出与静止角膜细胞相同的时间性肌成纤维细胞分化反应。此外，用含精氨酸-甘氨酸-天冬氨酸的肽GRGDdSP阻断TGFβ1诱导的肌成纤维细胞分化3天，然后通过去除GRGDdSP使肌成纤维细胞分化进展，这并没有改变导致肌成纤维细胞分化的时间反应或酪氨酸磷酸化级联反应（2 - 72小时）。用PDGF处理角膜细胞也没有逆转RGD对TGFβ1诱导的肌成纤维细胞分化的阻断作用。总体而言，这些累积发现表明，兔角膜角膜细胞中的肌成纤维细胞分化需要涉及TGFβ、PDGF和纤连蛋白受体的协同生长因子/整合素信号传导。此外，与未处理的角膜细胞相比，PDGF刺激的角膜细胞对TGFβ1具有相似的时间反应，这表明肌成纤维细胞分化不需要通过成纤维细胞表型进行转变。
