PURPOSE: Our studies on animal and in vitro models have sought to clarify mechanisms of pleurodesis and produce more specific treatments for recurrent pleural effusions. At CHEST 2007, we presented tissue histology in a rabbit model using talc, doxycycline and blood as sclerosants which demonstrated a significant increase in vascular endothelial growth factor (VEGF) that correlated with pleurodesis in vivo. In this study we evaluated for toxicity and VEGF upregulation in a model of non-transformed human pleural mesothelial cells (MeT-5A) exposed to four clinically-effective sclerosants: talc, doxycycline, erythromycin and human blood.
METHODS: A concentration of each sclerosant was added to MeT-5A cells based on cell number and culture well area comparable to the sclerosant concentration and pleural area treated in humans. MTT (formazan formation) assays determined sclerosant cellular toxicity at 1x, 10x and 0.1x the in vivo concentration. Cell supernatants cultured for 24 and 48 hours were tested by ELISA for human VEGF and the data was analyzed.
RESULTS: MTT assays (6 replicates) showed doxycycline and erythromycin were minimally toxic at 100μg/mL, talc at 320 μg/mL, and blood at 8.4αL/well. Talc appeared more toxic at 1x the in vivo concentration compared to doxycycline (p=0.07), erythromycin (p=0.002) and untreated MeT-5A cells. VEGF concentration, minimal at 24 hours, showed drug-related differences at 48 hours. Blood and erythromycin yielded lower VEGF (113.1±2.7 and 137.5±7.1 pg respectively) than doxycycline and talc (158.7±0 and 160.2±2 pg respectively; p<0.001 ANOVA and post-tests). Doxycycline and talc had nearly identical VEGF production.
CONCLUSION: VEGF, a tissue marker of mesothelial cell activation and angiogenesis, was elevated in this tissue culture and in vivo pleurodesis models with common sclerosants. VEGF levels correlated with in vivo sclerosant effectiveness.
CLINICAL IMPLICATIONS: This mesothelial cell culture pleurodesis model appears to demonstrate that VEGF is a mechanistic marker of effective pleurodesis and could be used to identify other more effective, less toxic sclerosants.
DISCLOSURE: Anthony Hericks, No Financial Disclosure Information; No Product/Research Disclosure Information