Telomerase allows the immortalization of T antigen-positive DMD myoblasts:a new source of cells for gene transfer application

The limited proliferative capacity of DMD myoblasts severely limits their a bility to be genetically modified and used for myoblast transplantation. Tr ansformation by SV40 large T antigen (Tag) delays senescence of mouse and h uman myoblasts but fails to immortalize these cells. The cells ceased to pr oliferate and entered into crisis. Reconstitution of telomerase activity ha s been shown sufficient to enable different types of transformed cells to e scape crisis. DMD myoblasts, previously transformed by Tag, were therefore infected with a telomerase retrovirus. The expression of telomerase was suf ficient to allow DMD-Tag myoblasts to escape crisis. The telomerase-positiv e transformed myoblasts continued to divide for more than 55 doublings whil e Tag myoblasts stopped proliferating after 35 doublings. These cells are a ble to fuse and to differentiate normally. The average telomere length of t hese telomerase-positive DMD-Tag myoblasts seems to continue to elongate. T hus, transiently genetically modified myoblasts could constitute an importa nt pool of DMD myoblasts for autologous transplantation in DMD patients.