Esophageal Ulceration Triggers Expression of Hypoxia-Inducible Factor-1 and Activates Vascular Endothelial Growth Factor Gene : Implications for Angiogenesis and Ulcer Healing

Abstract

Our previous studies demonstrated that enhanced epithelial cell proliferation is important for healing of experimental esophageal ulcers. However, the roles of angiogenesis, its major mediator, vascular endothelial growth factor (VEGF), and the mechanism(s) regulating VEGF expression during esophageal ulcer healing remain unknown. Esophageal ulcers were induced in rats by focal application of acetic acid. We studied expressions of hypoxia-inducible transcription factor-1alpha (HIF-1alpha), an activator of the VEGF gene, and VEGF by reverse transcriptase-polymerase chain reaction, Western blotting, and immunostaining. To determine the efficacy of VEGF gene therapy in esophageal ulcer healing, we studied whether a single local injection of plasmid cDNA encoding recombinant human VEGF(165) affects ulcer healing and angiogenesis. Esophageal ulceration induced HIF-1alpha protein expression and VEGF gene activation reflected by increased VEGF mRNA (240%) and VEGF protein (310%) levels. HIF-1alpha protein was expressed in microvessels bordering necrosis where it co-localized with VEGF. Injection of cDNA encoding VEGF(165) significantly enhanced angiogenesis and accelerated esophageal ulcer healing. These results: 1) suggest that HIF-1alpha may mediate esophageal ulceration-triggered VEGF gene activation, 2) indicate an essential role of VEGF and angiogenesis in esophageal ulcer healing, and 3) demonstrate the feasibility of gene therapy for the treatment of esophageal ulcers.