Allogeneic stem cell transplantations (SCT) are currently being used as a therapy for hematological malignancies, some solid tumors and non-malignant bone marrow deficiencies. Nevertheless, clinical applicability is limited due to toxicity of conditioning regimens, graft-versus-host disease (GVHD) and the scarcity of HLA-identical family donors. New concepts are based on nonmyeloablative conditioning to reduce toxicity, prevention or amelioration of GVHD and the use of haploidentical donors to increase donor availability.
To meet these requirements, we have developed a nonmyeloablative conditioning regimen in a haploidentical F1 F1 mouse model. These mini-transplantations, consisting of low dose total body irradiation and cyclophosphamide-based chemotherapy, resulted in stable full donor chimerism, but also in the development of GVHD. Administration of keratinocyte growth factor (KGF) before and after SCT resulted in reduced GVHD, evident as reduced weight loss and a lesser degree of dermatitis than in saline-treated controls. KGF preserved plasma citrulline and TNF-a levels, both indicative for reduced radiation-induced injury to the gastrointestinal tract. Citruline has recently been described as a new marker for gastrointestinal toxicity. Six months after transplantation, survival rates were significantly higher in KGF-treated animals (57% as compared to PBS-treated controls (5.3%).
These data indicate that nonmyeloablative haploidentical transplantations might be feasible and that KGF might contribute substantially to reduction of lethal GVHD, also after nonmyeloablative procedures. For clinical transplantation such an effect would be significant if intensive T cell depletion might be prevented in haploidentical transplantation protocols and therefore reduced infection rates can be obtained.