Augmentation of hematopoiesis by fibroblast-mediated interleukin-6 gene therapy in mice with chemotherapy

Murine fibroblast NIH3T3 cells engineered to secrete interleukin-6 (NIH3T3-IL-6) were implanted intraperitoneally into mice and observed for their hematopoietic effects with or without 5-fluorouracil (5-FU) administration. In normal mice, the platelet and neutrophil counts in peripheral blood increased significantly after implantation of NIH3T3-IL-6 cells, but the total white blood cell numbers showed no obvious elevation. The granulocyte-macrophage colony-forming unit (CFU-GM) and megakaryocyte colony-forming unit (CFU-MK) numbers formed by stem cells in bone marrow and spleen were also found to be significantly increased after implantation of NIH3T3-IL-6 cells when compared with those in mice after implantation of NIH3T3 cells transduced with neomycin gene (NIH3T3-Neo). To observe the protective effects of NIH3T3-IL-6 cells on hematopoietic depression in chemotherapy-treated mice, the mice were preinjected with 5-FU at a dosage of 150 mg/kg before implantation of NIH3T3-IL-6 cells. The platelet and neutrophil counts showed accelerated recovery after implantation of NIH3T3-IL-6 cells. The numbers of CFU-GM and CFU-MK in bone marrow and spleen were also found to be markedly increased in hematopoietic-depressed mice when compared with those in mice implanted with NIH3T3-Neo cells. These data suggest that fibroblast-mediated IL-6 gene therapy, which can augment hematopoiesis in mice with or without chemotherapy, will be of great help in the recovery from hematopoietic depression after chemotherapy.