Correlation of VEGF-expression with VEGF-serum level and microvessel density in HHT patients

Abstract

Problem: Angiogenesis defines the physiologic process of capillary blood vessel formation. It is a multistep process that is controlled by a large number of pro-angiogenic and anti-angiogenic factors. VEGF (the vascular endothelial growth factor), perhaps the best characterized pro-angiogenic factor, plays a key role in angiogenesis. HHT (hereditary hemorrhagic telangiectasia) is an autosomal dominant, multisystemic disorder of the vessel enlargement phase of angiogenesis, clinically characterized by severe and recurrent hemorrhages. We assume in HHT patients with increased VEGF serum levels a high VEGF expression, which also correlates with the degree of microvesssel density (MVD). Methods: In 41 HHT patients and 47 healthy patients, the VEGF serum concentration was determined through the standard ELISA technique. Cryostat sections of 26 HHT patients were immunostained for VEGF and endothelial cells by an anti-vWF monoclonal antibody using a standard streptavidin-biotin complex procedure. The degree of vessel density was quantified by light microscopy (×200) within a “hot spot” area of the HHT tissue. Results: A strong positive VEGF staining was detected in 18/26 (69%) of the HHT patients. The VEGF-expression correlated with the high VEGF serum concentration and the mean MVD in HHT patients. HHT patients with weak or negative VEGF staining showed significantly lower VEGF serum concentrations and a lower mean MVD (63 ± 19.7) per microscopic field than VEGF positive tissue (93 ± 22.4). The VEGF immunoreactivity did not correlate with the clinicopathological findings of the patients, especially in regard to an HHT-induced organ manifestation. Conclusion: The high VEGF expression in patients with HHT in correlation to high VEGF serum levels and a high microvessel density supports the theory that VEGF functions as an important regulator and key protein of angiogenesis in HHT. Significance: This study helps to understand the correlation between angiogenesis and the genetic disorder HHT where angiogenic factors such as VEGF seem to play an important role in the disease′s pathophysiology. Support: This study was partly supported by the Research Fund of the University Hospital Mannheim, Germany.