High efficiency of muscle regeneration after human myoblast clone transplantation in SCID mice.

Abstract

SCID mouse tibialis anterior muscles were first irradiated to prevent regeneration by host myoblasts and injected with notexin to damage the muscle fibers and trigger regeneration. The muscles were then injected with roughly 5 million human myoblasts. 1 mo later, 16-33% of the normal number of muscle fibers were present in the injected muscle, because of incomplete regeneration. However, > 90% of these muscle fibers contained human dystrophin. Some newly formed muscle fibers had an accumulation of human dystrophin and desmin on a part of their membrane. Such accumulations have been demonstrated at neuromuscular junctions before suggesting that the new muscle fibers are innervated and functional. The same pool of clones of human myoblasts produced only < 4% of muscle fibers containing human dystrophin when injected in nude mice muscles.Several of the human myoblasts did not fuse and remained in interstial space or tightly associated with muscle fibers suggesting that some of them have formed satellite cells. Moreover, cultures of 98% pure human myoblasts were obtained from transplanted SCID muscles. In some mice where the muscle regeneration was not complete, the muscle fibers containing human dystrophin also expressed uniformly HLA class 1, confirming that the fibers are of human origin. The presence of hybrid muscle fibers containing human dystrophin and mouse MHC was also demonstrated following transplantation.These results establish that in absence of an immune reaction, transplanted human myoblasts participate to the muscle regeneration with a high degree of efficacy even if the animals were killed only 1 mo after the transplantation. (J. Clin. Invest.

Normal growth and regenerating ability of myoblasts from unaffected muscles of facioscapulohumeral muscular dystrophy patients

“…In the present study, the evaluation of transplantation outcome has been performed 1 month after transplantation, a time course that is of general use in human and animal MT assays. 9,16,17,20,31,47,49 This model was not regarded helpful to evaluate the longterm persistence of muscle fibers harboring the human mutated genes. Indeed, a negative selection of muscle fibers expressing the mutated gene could occur with time in the healthy environment of mouse muscle fibers, and this selection would not be representative of the situation presented in FSHD.…”

“…At 1 month after MT, the expression of human proteins validated the implantation of human cells into mouse muscle fibers. 16,[47][48][49] Human dystrophin was observed in all cell-injected muscles, and was absent from muscles injected with a saline solution (Table 3, Figure 5). No significant differences were observed between muscles receiving FSHD or control myoblasts (P40.8).…”

“…The mice were killed 4 weeks after the last series of cell injections, which is a delay compatible with complete mouse muscle regeneration and the expression of donor markers. 16,[47][48][49] The muscles were snap frozen in nitrogen-cooled isopentan and serially sectioned (8 mm) using a cryostat. The participation of human cells in muscle formation was detected by the specific expression of human dystrophin beneath the basement membrane of muscle fibers.…”

“…The MT concept has been validated in normal and dystrophic mouse models, where injection of healthy myoblasts increased muscle mass and function. 14,15 Despite positive results in these small rodents, [16][17][18][19][20] clinical trials have presented limited success. [21][22][23][24][25][26][27][28][29] Improvements of injection and immunosuppression parameters have recently been achieved in primates 9,10,30 and translated to the human situation with encouraging, although localized success.…”

Muscle-derived cell-mediated ex vivo gene therapy for urological dysfunction

“…[7][8][9][10] However, the transplantation of donor muscle cells into host muscle has been hindered by various limitations, such as immune rejection that consequently leads to poor spreading and survival of injected cells. [11][12][13][14][15][16][17][18][19][20] The success of cell transplantation may be dramatically improved by using a specific population of cells that has the capacity to overcome these hurdles.…”