In Vivo Gene Transfer into HSC and Other Organs

One goal of any clinical treatment is the correction of the target disease by a single injection of a therapeutic vector. Our previous studies have demonstrated successful pathological and neurological correction in MPS I mice following a single injection of a third-generation therapeutic lentiviral vector at birth. More recently, the Pan laboratory has demonstrated for the first time that both hematopoietic and mesenchymal stem cells could be genetically modified by lentiviral vector-mediated gene transfer in their natural “nitch” (bone cavity) of mouse without any preconditioning (Molecular Therapy, 2006; Pan, 2009). The in vivo gene transfer approach could potentially avoid difficulties encountered by ex vivo HSC-mediated gene transfer, such as stem cell differentiation during in vitro culture, loss of engraftment potential, toxicities related to HSC enrichment procedures and cytokine stimulation, and neutropenia-related side effects. The “in situ” stem cell gene delivery approach may provide an interesting new tool to study adult stem cell plasticity and the nature of unperturbed hematopoiesis. More efforts are under way to evaluate therapeutic potentials of in vivo gene therapy in adult MPS I mice, comparing a systemic delivery to a local injection. The “window of treatment” and in vivo pre-stimulation of cell proliferation are to be explored with attempts to optimize gene transfer and transgene expression in liver, hematopoietic stem cells and the central nerve system. The potential application of an in vivo gene therapy approach may open a door to a novel approach for disease treatment.