This study investigated (1) the release of recombinant human vascular endothelial growth factor ([rh]VEGF(165)) from an in vitro fibrin matrix, (2) the effects of (rh)VEGF(165) released from an in vivo fibrin matrix on ischemic flap necrosis in the rat dorsal skin flap model, and (3) the effects of (rh)VEGF(165) released from an in vivo fibrin matrix on VEGF-R2 expression in transgenic VEGF-R2/luc mice. In vitro fibrin matrices were spiked with (rh)VEGF(165) and demonstrated (rh)VEGF(165) release over 88 hours with 66% recovery. Ischemic dorsal flaps were treated with a fibrin sealant (FS), FS spiked with (rh)VEGF(165), or left untreated. Flaps treated with FS spiked with (rh)VEGF(165) showed greater viability than controls as measured by planimetric analysis. Immunohistochemical analyses revealed stronger neovascularization than that exhibited by controls. Transgenic mice implanted with FS spiked with (rh)VEGF(165) had significant increases in VEGF-R2 expression relative to controls at days 5-13 after implantation. Conclusions drawn from this work are that (1) (rh)VEGF(165) is released from an in vitro fibrin matrix at clinically appropriate times, (2) (rh)VEGF(165) increases the viability of tissue flaps in vivo, and (3) (rh)VEGF(165) induces the expression of VEGF-R2 expression. This work demonstrates the clinical ability of sprayed FS to locally deliver growth factors to ischemic tissue of patients.

Treatment of delayed bone healing and non-unions after fractures, osteotomies or arthrodesis still is a relevant clinical challenge. Artificially applied growth factors can increase bone healing and progressively gain importance in clinical routine. The aim of this study was to determine the effects of rhPDGF-BB, rhVEGF-165, and rhBMP-2 in fibrin matrix on bone healing in a delayed-union rat model. Thirty-seven rats underwent a first operation where a standardized femoral critical size defect was created. A silicone spacer was implanted to impair vascularization within the defect. At 4 weeks the spacer was removed in a second operation and rhPDGF-BB, rhVEGF-165, or rhBMP-2 were applied in a fibrin clot. Animals in a fourth group received a fibrin clot without growth factors. At 8 weeks fibrin bound rhBMP-2 treated animals showed a significantly increased union rate and bone volume within the defect compared to the other groups. Single application of fibrin bound rhPDGF-BB and rhVEGF-165 failed to increase bone healing in our atrophic non-union model. ß

We conclude that fibrin matrix is an excellent carrier for BMP-2 and that it provides equivalent results with a sevenfold lower dose of BMP-2 compared with ACS.