Functional angiogenesis in the rat epigastric island flap after genetic modification of fibroblasts is ischemia-dependent

Background: Our previous studies have shown that angiogenesis can be induce d in flap tissue by means of genetic modification and transplantation of is ogenic cells. Methods: Isogenic rat fibroblasts (female Lewis inbreds) were grown, harves ted, cultured and retrovirally transfected to produce PD GF-AA, an angiogen etically active protein. Stable gene expression was monitored by PDGF-AA EL ISA. 80 animals were divided into 2 groups (I and II) with each 4 subgroups with 10 animals (I.I.-I.IV and II.I-II.IV). The angiogenic target was a 7 x 7 cm epigastric island flap, based on the right inferior epigastric pedic le. This flap represents after elevation and replacement into its wound bed a flap necrosis model for the non-pedicled left flap side. Group I receive d nap treatment 1 week prior to flap elevation by injection of a test subst ance into its panniculus carnosus: 10(7) GMFB (genetically modified fibrobl asts) plusl ml DMEM as medium (I.I), 10(7) NMFB (non modified fibroblasts) plus 1 ml medium (I.II), 1 ml DMEM (I.III) and 1 ml NaCl 0.9% as a control (I.IV). Group II had the same flap treatment at the day of flap elevation. All flaps were sutured back and the animals provided with an autocannibalis m protector. 7 days later, the flaps were harvested, the amount of necrosis measured and histologically/immunhistochemically examined. Results: In vitro the GMFB produced up th 560 - times more PDGF-AA than the NMFB for at least 6 cell generations. In vivo Group II.I developed signifi cantly less flap necrosis compared to all other groups, including group I.I . Accordingly, only group II.I gave histological and immunhistochemical evi dence for massive angiogenesis within the flap tissue. Fibroblasts persiste d in all flaps of groups I.I,I.II.,II.I. and II.II without major inflammato ry reaction. Conclusion: 1. After retroviral gene transfer isogenic rat fibroblasts prod uce high amounts of PDGF-AA. 2. Both GMFB and NMFB can be successfully tran splanted into the panniculus carnosus in this model. 3. PDGF-AA produced by GMFB can induce flap angiogenesis only under ischemic conditions in this m odel. 4. PDGF-AA induced angiogenesis results in significantly higher flap survival in this model.