COLLAGEN AS MATRIX FOR NEO-ORGAN FORMATION BY GENE-TRANSFECTED FIBROBLASTS

Background: Genetically modified cells have been used in several anima l models for the in vivo delivery of therapeutic proteins. One of the problems encountered is early cell death after the implantation of cel ls. Materials and Methods: To improve the survival of implanted cells, we have developed a system in which transfected fibroblasts are seede d onto biodegradable collagen matrices and transplanted into animals a fter several days of in vitro culture. Since G-CSF is widely used clin ically to accelerate reconstitution of hematopoiesis after cancer chem otherapy, it was choosen to investigate in vivo delivery by transfecte d fibroblasts. Results: Expression of the human G-CSF gene is maintain ed by transfected cells when grown on collagen scaffolds in vitro. Aft er the i.p. implantation of collagen matrices seeded with G-CSF gene t ransfected fibroblasts, G-CSF serum levels could be detected for more than 2 weeks. Histological analysis of matrices explanted on day 31 an d demonstration of in vitro G-CSF production reveals that genetically modified cells call survive on these implants in vivo. Large areas of the collagen are degraded and substituted with a network of endogenous argyrophilic fibers. Also ingrowth of blood vessels into the matrices is observed leading to the formation of 'neo-organ' like structures. Conclusions: Biodegradable collagen matrices can serve as scaffolds fo r survival of transfected fibroblasts in vivo.