GENETICALLY-MODIFIED FIBROBLASTS INDUCE ANGIOGENESIS IN THE RAT EPIGASTRIC ISLAND FLAP

Methods: Gene therapy was tested for inducing functional angiogenesis in the superficial rat epigastric island flap to allow earlier pedicle division. Autologous rat fibroblasts were grown, harvested, cultured and retrovirally transfected to produce platelet-derived growth factor AA (PDGF-AA), an angiogenetically active protein. Stable gene express ion was monitored by PDGF-AA enzyme-linked immunosorbent assay (ELISA) . One hundred and eighty animals were divided into three groups (I-III ) and a bilateral flap created in each animal. In all experiments, the right-sided flap was subjected to experimental treatment and the left -sided flap served as control (1 ml saline 0.9%). During flap elevatio n, group I received 5 x 10(6) GMFB (genetically modified fibroblasts) plus 1 ml Dulbecco's modified Eagle's medium. Group TT was treated wit h 5 x 10(6) NMFB (non-modified fibroblasts) plus 1 ml medium and group III received 1 ml medium only. The flaps were sutured back and the va scular pedicle was bilaterally ligated and divided in each of ten anim als during the following 6 days. After 7 days, the flaps were harveste d, the amount of necrosis measured and histologically examined. Result s: The GMFB produced up to 560 times more PDGF-AA than the NMFB, measu red by ELISA. The GMFB-treated flaps tolerated surgical division of th e vascular pedicle significantly earlier than groups II and III. Histo logically, fibroblasts persisted in all flaps of groups I and II, with out major inflammatory reaction. In all GMFB-treated naps, massive ang iogenesis could be demonstrated. Conclusion: By means of retroviral ge ne transfer, autologous rat fibroblasts can be genetically modified fo r stable expression of the PDGF-A gene to produce high amounts of PDGF -AA, which is angiogenetically active. After injection into the pannic ulus carnosus, these cells induce functional angiogenesis to permit ea rlier division of the vascular pedicle in this flap model.