HYPOXIA REGULATION OF VEGF/VEGF RECEPTORS IN KELOIDS

我们推测，正如临床和组织学观察到的那样，血管稳态的失衡可能导致炎症边界(红斑性)处的血管丰富状态或瘢痕疙瘩病变稳定部分(经典瘢痕疙瘩)处的低血管状态。稳定部位的低血管或低氧状态是诱导和延长高血管和高渗透特征的关键因素。肉芽组织表型的这些特征负责维持丰富的细胞因子和生长因子环境，以继续支持真皮生长。我们的研究将集中于血管内皮生长因子(VEGF)作为瘢痕疙瘩血管稳态的主要调节因子。建议的瘢痕疙瘩研究模型将建立在三个临床上不同的病变部位--炎性(红斑性)、稳定性(经典瘢痕疙瘩)和中央部分(退行性瘢痕)--这三个部位代表了瘢痕疙瘩形成的病理过程。转录因子、低氧诱导因子HIF-1和低氧反应元件HRE在调节低氧诱导的瘢痕疙瘩稳定部分血管内皮生长因子表达中的作用将与炎症边界观察到的肉芽组织表型相关联。血管生成刺激、血管内皮生长因子、缺氧诱导因子-1与细胞外蛋白、尿激酶型纤溶酶原激活物、尿激酶型纤溶酶原激活剂及其抑制物纤溶酶原激活物抑制物-1之间的相互作用将通过我们独特的三个不同位点的方法来研究，以阐明瘢痕疙瘩不同血管形成的分子基础。我们假设，伤口血管生成的失调导致病变稳定部分的血管网络的不同分布，低血管或低氧与炎性边界的高血管和高渗透，从而确立了瘢痕疙瘩表型的良性生长。1)证实血管内皮生长因子/血管内皮生长因子受体(S)和uPA/PAI-1在3个不同部位的人瘢痕疙瘩微血管内皮细胞中的表达与临床正常皮肤相比存在差异；2)研究低氧应激对瘢痕疙瘩微血管内皮细胞uPA/PAI-1和血管内皮生长因子受体(S)表达的影响、受体亲和力、包括磷酸化在内的生物学功能和体外血管生成活性；3)研究血管内皮生长因子对瘢痕疙瘩微血管内皮细胞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在低氧诱导的血管内皮生长因子表达中的作用。

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.