Transforming Growth Factor β Induces Vascular Endothelial Growth Factor Elaboration from Pleural Mesothelial Cellsin Vivoandin Vitro

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Abstract
Vascular endothelial growth factor (VEGF) increases vascular permeability and is important in pleural effusion formation. In studies using transforming growth factor beta (TGF-beta) to produce pleurodesis, we observed that although TGF-beta was more effective than talc or doxycycline, it induced transient production of large pleural effusions. We hypothesized that TGF-beta stimulates VEGF production in pleural tissues in vivo, and by mesothelial cells in vitro. New Zealand White rabbits (n = 33) were given TGF-beta(2) (1.7 or 5.0 microg), talc (400 mg/kg), doxycycline (10 mg/kg), or buffer intrapleurally. Pleural fluid was collected at 24 h. Intrapleural injection of TGF-beta(2) induced a dose-dependent increase in VEGF production. The pleural fluid VEGF level was 2-fold higher in rabbits given 5.0 microg of TGF-beta(2) than in those given 1.7 microg of TGF-beta(2) and 3-fold higher than in those given buffer. VEGF levels were higher after the injection of TGF-beta(2) than after administration of talc or doxycycline. The pleural fluid VEGF correlated significantly with the volume of pleural effusions (r = 0.79, p < 0.00001). In vitro, TGF-beta(2) stimulated a dose-dependent increase in VEGF production from murine pleural mesothelial cells. At 4 and 24 h, TGF-beta(2), but not talc or doxycycline, induced a significant increase in VEGF, when compared with controls. The mesothelial cell VEGF production was significantly reduced by anti-TGF-beta antibody in the TGF-beta(2), talc, and control (buffer and medium) groups. In conclusion, mesothelial cells are an important source of VEGF. TGF-beta increases the VEGF production by mesothelial cells in vivo and in vitro.

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