HYPOXIA REGULATION OF VEGF/VEGF RECEPTORS IN KELOIDS

我们假设，根据临床和组织学观察，血管稳态失衡可能导致瘢痕疙瘩病变的炎症边界（红斑）的高血管状态或稳定部分（典型瘢痕疙瘩）的低血管状态。稳定部存在的低血管或缺氧状态是诱导和延长高血管和高渗透性特征的关键因素。这些特征是肉芽组织表型的特征，负责维持细胞因子和生长因子的丰富环境，以继续支持皮肤生长。我们的研究将集中在血管内皮生长因子（VEGF）作为瘢痕疙瘩血管稳态的主要调节因子。提出的瘢痕疙瘩研究模型将建立在三个临床不同的病变部位-炎症（红斑），稳定（经典瘢痕疙瘩）和中心部分（退行性瘢痕疙瘩）-代表瘢痕疙瘩形成的病理过程。转录因子、缺氧诱导因子HIF-1和缺氧反应因子HRE在瘢痕疙瘩稳定部分缺氧诱导的VEGF表达调控中的作用将与炎症边界观察到的肉芽组织表型相关。血管生成刺激因子VEGF、HIF-1和细胞外蛋白酶、尿激酶纤溶酶原激活剂uPA及其抑制剂PAI-1之间的相互作用将通过我们独特的三不同位点方法进行研究，以阐明瘢痕疙瘩中血管形成差异的分子基础。我们假设伤口血管生成的失调导致了血管网络的不同分布，病变稳定部分的低血管或缺氧与炎症边界的高血管和高通透性，建立了瘢痕疙瘩表型的良性生长。我们的假设将通过以下具体目的进行验证：1)证实与邻近临床正常皮肤相比，VEGF/VEGF受体和uPA/PAI-1在瘢痕疙瘩的三个不同部位的人体微血管内皮中表达差异；2)研究缺氧应激对uPA/PAI-1、VEGF/VEGF受体表达、受体亲和力、磷酸化等生物学功能及体外血管生成活性的影响；3)研究VEGF对uPA /PAI-1表达的影响及其在瘢痕疙瘩血管稳态中的作用；4)探讨转录因子、HIF-1和HRE在缺氧诱导的VEGF表达中的作用。

We postulate that an imbalance in vascular homeostasis could contribute to a hypervascular state at the inflammatory border (erythematous) or a hypovascular state at the stable portion (classical keloid) of the keloid lesion, as observed clinically and histologically. The hypovascular or hypoxic state present at the stable portion is the key factor for induction and prolongation of the hypervascular and hyperpermeable features. These features, characteristic of the granulation tissue phenotype, are responsible for the maintenance of an enriched milieu of cytokines and growth factors for continuing support of dermal growth. Our study will focus on vascular endothelial growth factor (VEGF) as a major regulator of keloid vascular homeostasis. The proposed keloid study model will be established on three clinically distinct lesional sites--inflammatory (erythematous), stable (classical keloid) and central portion (regressing scar)--which represent the pathologic course of keloid formation. The role of transcription factor, hypoxia- inducible factor, HIF-1, and hypoxia-responsive element, HRE, in the regulation of hypoxic-induced VEGF expression at the stable portion of the keloid will be determined in correlation with the granulation tissue phenotype observed at the inflammatory border. The interaction between angiogenic stimuli, VEGF, HIF-1, and the extracellular proteases, urokinase plasminogen activator, uPA, and its inhibitor, PAI-1, will be investigated in our unique three-distinct-sites approach to elucidate the molecular basis of differential vascular formation in keloids. We hypothesize that a dysregulation in wound angiogenesis contributes to a differential distribution of vascular network, hypovascular or hypoxic at the stable portion of the lesion versus hypervascular and hyperpermeable at the inflammatory border, establishing the benign growth of the keloid phenotype. Our hypothesis will be tested using the following specific aims: 1) To confirm that VEGF/VEGF receptor(s) and uPA/PAI-1 are differentially expressed in human microvascular endothelium of keloids at the three distinct sites compared to adjacent clinically normal skin; 2) To study the effect of hypoxic stress on the expression of uPA/PAI-1 and VEGF/VEGF receptor(s), receptor affinity, biological functions including phosphorylation and in vitro angiogenic activity; 3) To study the effect of VEGF on the expression of uPA /PAI-1 and their role in keloid vascular homeostasis; and 4) To delineate the role of transcription factor, HIF-1, and HRE on hypoxia-induced VEGF expression.