Gene therapy using bone marrow transplantation.

As a result of new techniques in molecular biology, the basic defects in a variety of genetic diseases have been characterized and the corresponding normal genes cloned. Methods have been devised for transferring specific genes with high efficiency into various cell types that exploit the use of replication-defective retroviruses as vectors. Bone marrow may be the ideal target for these attempts to transfer genes, because it contains self-renewing stem cells and because it can readily be collected by standard techniques, manipulated ex vivo as required with comparative ease and then reinfused. In a murine system, recent studies have shown that genes can indeed be incorporated into haemopoietic stem cells that can then completely reconstitute the marrows of syngeneic recipients. Thus far, such genes after transfer have not been appropriately expressed in vivo, although appreciable expression has been documented in cell culture studies in vitro. It is reasonable to expect that improvements in the design of retroviral vectors should permit appropriate expression of a transferred gene. When this is achieved, the use of bone marrow transplantation for gene transfer will offer new options for therapy.