Identifying a therapeutic target for ablating new blood vessel formation in patients with asthma

Introduction: Angiogenesis is a feature of chronic asthma with the levels of multiple proangiogenic factors, including connective tissue growth factor (CTGF) and vascular growth factor (VEGF), increased in the lungs of patients with asthma. Preliminary data from our lab suggests that the proangiogenic effect of asthmatic airway smooth muscle cells is lost if CTGF is immunoprecipitated from the media but not restored by supplementation with recombinant CTGF. These data indicate that CTGF may be exerting these proangiogenic effects by binding to another protein. Aim: To identify other factor/s that bind to CTGF Methods: Plates were coated with CTGF C-terminal fragment (amino acids 253 to 350) (90 nM) then blocked with 1% BSA. The potential binding proteins were biotinylated and added to the CTGFcoated wells. The amount of protein bound to CTGF was detected using streptavidin conjugated HRP and TMB. Results: On dose response curves, angiopoietin (Ang)-1 (34±10 units (U)/nmol protein) and Slit3 (20±5 U/nmol protein) had the strongest association constants, with Von Willebrand factor, basic fibroblast growth factor and TNFα all having moderate affinity (range of 8-15 U/nmol protein) and VEGF-A165(5±4 U/nmol protein) and VEGF-D (3±0.7 U/nmol protein) showing low association/high disassociation kinetics. VEGF-A121, VEGF-C, Ang-2, PDGF-BB, TGF-β1, placenta growth factor, EGF, IL-1β, IL-17 and human chorionic gonadotropin had little or no binding to CTGF. Conclusion: Agents aimed at preventing blood vessel formation improve airway hyperresponsiveness and asthma symptoms. Identifying the binding partner for CTGF could help develop a new therapeutic approach for targeting asthma