TRANSPLANTATION OF RETROVIRAL PRODUCER CELLS FOR IN-VIVO GENE-TRANSFER INTO MOUSE SKELETAL-MUSCLE

We describe a new strategy for efficient in vivo gene transfer into sk eletal muscle using retroviral vectors. Recombinant retroviral produce r cells, previously treated with the cytostatic drug mitomycin C, were injected into regenerating muscle of adult nude, nude/mdx, and C57BL/ 10 mice. Using LacZ reporter gene activity, we detected efficient tran sduction in all mouse strains (Nude, mean 11%, range 4.2-21%; C57BL/10 , mean 12 %, range 3,4-20 %; Nude mdx, mean 4.3 %, range 2.1-7 % at 4 weeks post-injection and 6.6%, range 1.3-12 % at 12 weeks post-injecti on). Foreign gene expression was sustained at high levels for at least 3 months. This strategy allows muscle satellite cells to be transfect ed in vivo, forming a reservoir of the transgene for incorporation int o new myofibers in subsequent rounds of degeneration and regeneration. Because of its efficiency and potentially broad application, this pro cedure represents a new strategy for in vivo genetic transfer in skele tal muscle and potentially in other tissues.