Synthesis, Storage, and Release of Vascular Endothelial Growth Factor/Vascular Permeability Factor (VEGF/VPF) by Human Mast Cells: Implications for the Biological Significance of VEGF₂₀₆

Abstract

Mast cells have been implicated in various diseases that are accompanied by neovascularization. The exact mechanisms by which mast cells might mediate an angiogenic response, however, are unclear and therefore, we have investigated the possible expression of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) in the human mast cell line HMC-1 and in human skin mast cells. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that mast cells constitutively express VEGF121, VEGF165, and VEGF189. After a prolonged stimulation of cells for 24 h with phorbol 12-myristate 13-acetate (PMA) and the ionophore A23187, an additional transcript representing VEGF206 was detectable, as could be verified by sequence analysis. These results were confirmed at the protein level by Western blot analysis. When the amounts of VEGF released under unstimulated and stimulated conditions were compared, a significant increase was detectable after stimulation of cells. Human microvascular endothelial cells (HMVEC) responded to the supernatant of unstimulated HMC-1 cells with a dose-dependent mitogenic effect, neutralizable up to 90% in the presence of a VEGF-specific monoclonal antibody. Flow cytometry and postembedding immunoelectron microscopy were used to detect VEGF in its cell-associated form. VEGF was exclusively detectable in the secretory granules of isolated human skin mast cells. These results show that both normal and leukemic human mast cells constitutively express bioactive VEGF. Furthermore, this study contributes to the understanding of the physiological role of the strongly heparin-binding VEGF isoforms, since these were found for the first time to be expressed in an activation-dependent manner in HMC-1 cells.

Mast cells correlate with angiogenesis and poor outcome in stage I lung adenocarcinoma

“…Such matrix degradation is crucial in the early stages of angiogenesis. Mast cells have been shown to produce VEGF [17,18]. This article documents VEGF expression in intratumoural stromal mast cells in stage I NSCLC.…”

“…Recent investigations [4,6,7] have demonstrated that VEGF is one of the significant cytokines in the angiogenesis of lung carcinoma, and its expression in lung carcinoma cells correlates with clinical outcome. However mast cells have recently been shown to be a rich source of VEGF [17,18]. In addition, VEGF is reported to induce chemotactic migration of mast cells [21].…”

Correlation of bone marrow angiogenesis and mast cells with tryptase activity in myelodysplastic syndromes

“…MC release a variety of factors known to enhance angiogenesis, namely heparin and histamine, 15,16 a variety of cytokines, such as transforming growth factor-beta, tumor necrosis factor-␣, 17 interleukin-8, 18 basic fibroblast growth factor or fibroblast growth factor-2 (FGF-2) 19 and vascular endothelial growth factor (VEGF) 20 implicated in normal, as well as tumorassociated angiogenesis. Blair et al 21 have shown that tryptase released by MC plays an important role in neovascularization.…”

Mast Cell Granule Heparin Proteoglycan Induces Lacunae in Confluent Endothelial Cell Monolayers

“…7,19 Rat mast cell secretory granules contain, in addition to histamine and serotonin, high molecular weight heparin proteoglycan, chymase, carboxypeptidase A, tryptase, ␤-hexosaminidase, ␤-glucuronidase, TNF-␣, 20 FGF-2, 21,22 and VEGF. 23 The mast cell granule matrix is formed by ionic bonding between basic proteins of modest molecular weight and heparin proteoglycan. 2,16 The compact intracellular granule structure is transformed to a more diffuse organization during the process of secretion.…”