Increased expression of tissue vascular endothelial growth factor and foetal liver kinase-1 receptor in seasonal allergic rhinitis and relevance to asthma component

BACKGROUND: There is a difference in the extent of remodelling in allergic rhinitis (AR) and asthma. This may be attributed to the difference in local tissue response to these mediators. OBJECTIVES: The aim of this study was to compare vascular endothelial growth factor (VEGF) and its receptor foetal liver kinase (Flk)-1 expression between seasonal AR patients with or without asthma and non-allergic controls as well as that between AR patients with and without asthma. METHODS: Thirteen subjects with seasonal AR and six non-allergic controls were included in the study. Allergic sensitization was demonstrated by a skin prick test. Inferior turbinate thiny biopsies were obtained from both groups. Monoclonal mouse antibodies were used to demonstrate VEGF and Flk-1. Nasal mucosal endothelial cells' staining intensity was graded semi-quantitatively and the histochemical score (HSCORE) was calculated. In all samples, VEGF- and Flk-1-labelled vessels were counted for the assessment of vascular surface density (VSD). RESULTS: The mean HSCORE for VEGF and anti-VEGF-based VSD were significantly higher in the patient group (P=0.001 and 0.002, respectively). The mean HSCORE for Flk-1 and anti-Flk-1-based VSD in the patient group were significantly higher than those in the control group (P=0.016 and 0.028, respectively). Differences between the mean HSCORE for VEGF and anti-VEGF-based VSD in patients with pure AR and AR and asthma were insignificant (P=0.16 and 0.39, respectively). The mean HSCORE for Flk-1 and anti-Flk-1-based VSD in patients with pure AR were significantly lower than those in patients with AR and asthma (P=0.004 and 0.018, respectively). CONCLUSION: Angiogenic factor VEGF and its receptor Flk-1 is increased in AR. A similar increase in VEGF in AR with and without asthma despite a higher Flk-1 in AR patients with asthma may be a possible explanation for the presence of angiogenesis in the airway wall in patients with asthma but not in those with pure AR.