Trehalose 6,6 '-dimycolate (cord factor) enhances neovascularization through vascular endothelial growth factor production by neutrophils and macrophages

Trehalose 6,6'-dimycolate (TDM) plays important roles in the development of granulomatous inflammation during infection with Mycobacterium spp., Rhodo coccus spp., etc. To reveal the augmenting effect of TDM on vascular endoth elial growth factor (VEGF) production and neovascularization, we investigat ed murine granulomatous tissue air pouches induced by Rhodococcus sp. strai n 4306 TDM dissolved in Freund's incomplete adjuvant (FIA), comparing them to pouches treated with FIA alone. Histologically, granulomatous tissue and new vessel formation, which reached a maximum at day 7, was greatly enhanc ed by treatment with TDM. At day I, 7;EGF-positive neutrophils accumulated in the pouch wall with frequency of 95% of total infiltrating cells, adheri ng to TDM-containing micelles. By day 3, granulomatous tissue and new vesse ls started to develop, and VEGF-positive macrophages appeared in a small nu mber and gradually increased in number thereafter. The pouch contents of VE GF, interleukin-1 beta, tumor necrosis factor alpha, and transforming growt h factor beta were significantly elevated in TDM-treated pouches, with peak s at days 1, 0.5, 1, and 3, respectively, compared to those of control pouc hes, while that of basic fibroblast growth factor showed no significant inc rease. Treatment with anti-VEGF antibody inhibited TDM-induced granulomatou s tissue formation and neovascularization, and administration of recombinan t VEGF into pouches treated with FIA alone induced neovascularization compa rable to that in the TDM-treated pouches. Incubation of neutrophils and mac rophages on TDM-coated plastic dishes increased the VEGF release. The prese nt results indicate that TDM augments VEGF production by neutrophils and ma crophages and induces neovascularization in the granulomatous tissue.