Mitogenicity and release of vascular endothelial growth factor with and without heparin from fibrin glue

Purpose: Fibrin glue (FG) has been used for local cytokine delivery on both vascular grafts and angioplasty sites. We measured the diffusive release of vascular endothelial growth factor (VEGF) and heparin from FG and the mitogenic activity of VEGF with and without heparin in FG on canine endothelial cells (ECs) and smooth muscle cells (SMCs). Methods: Release of VEGF labeled with iodine 125 and tritiated heparin from FG into the overlying media was serially measured over 96 hours, and the data are reported as the mean percent released ± SD. Proliferation assays measuring tritiated thymidine incorporation were performed for ECs and SMCs plated in media with 10% serum on FG containing various concentrations of VEGF and heparin. Media was placed on the FG for 24 hours and removed before plating cells to minimize the effect of the released, soluble VEGF and heparin. Results: At 24 hours, 54% ± 1% and 58% ± 1% of the radioactive VEGF and heparin were released, respectively, with minimal release thereafter (58% ± 1% and 66% ± 1% at 96 hours). The ECs, SMCs, or media only (no cells) was plated on FG containing radioactive VEGF in an immediate or 24-hour delayed fashion for 72 hours to determine the percent release of VEGF into the media with the two different methods of plating. Cell type and the presence or absence of cells did not affect VEGF release, but there was three times more VEGF in the media for the immediate versus delayed plating (P