The regenerating skeletal muscle environment is capable of inducing uncommitted progenitors to terminally differentiate. The aim of this work was to determine whether adipose tissue-derived stromal cells were able to participate in muscle regeneration and to characterize the effect on muscle mass and functional capacities after transplantation of these cells. Adipose tissue stromal cells labeled with Adv cyto LacZ from 3-day-old primary cultures (SVF1) were autotransplanted into damaged tibialis anterior muscles. Fifteen days later, β-galactosidase staining of regenerated fibers was detected, showing participation of these cells in muscle regeneration. Two months after SVF1 cell transfer, muscles were heavier, showed a significantly larger fiber section area, and developed a significantly higher maximal force compared with damaged control muscles. These results are similar to those previously obtained after satellite cell transplantation. However, SVF1 transfer also generated a small amount of adipose tissue localized along the needle course. To minimize these adipose contaminants, we transferred cells from 7-day-old secondary cultures of the SVF1, containing only a small proportion of already engaged preadipocytes (SVF2). Under these conditions, no adipose tissue was observed in regenerated muscle but there was also no effect on muscle performances compared with damaged control muscles. This result provides further evidence for the existence of progenitor cells in the stromal fraction of freshly isolated adipose tissue cells, which, under our conditions, keep some of their pluripotent properties in primary cultures.

Skeletal muscle demonstrates a force deficit after repair of injured peripheral nerves. We tested the hypothesis that transplantation of satellite cells into reinnervated rabbit tibialis anterior (TA) muscles improves their properties. Adult rabbits underwent transection and immediate suture of the common peroneal nerve. In order to provide an environment favorable for cell transplantation, TA were then made to degenerate by cardiotoxin injection, either immediately or after a 2-month delay, which is sufficient for muscle reinnervation. In both cases, the injured TA were transplanted with cultured satellite cells 5 days after induction of muscle degeneration. When cells were transferred immediately after nerve repair, drastic morphological and functional muscle alterations were observed. However, when the muscles were allowed to become reinnervated before cell transplantation, muscles were heavier and developed a significantly higher maximal force compared to denervated-reinnervated muscles. Thus, application of the cell therapy protocol improved properties of denervated muscles only when they were allowed to become innervated. These results, which represent the application of cell therapy to improve force recovery of reinnervated muscles, will be of significant interest in certain clinical contexts, particularly after immediate or delayed muscle reinnervation.

Skeletal muscle demonstrates a force deficit after repair of injured peripheral nerves. Data from the literature indicate that myoblast transfer enhances recovery of muscle function. Thus, we tested the hypothesis that transfer of adult myoblasts improves the properties of reinnervated rabbit tibialis anterior (TA) muscles in both the short term (4 months) and long term (14 months). Two months after transection and immediate suture of the common peroneal nerve, TA muscles were made to degenerate by cardiotoxin injection and then transplanted with adult myoblasts cultured for 13 days. Under these conditions, muscles studied at 4 months were heavier, contained larger fibers, and developed a significantly higher maximal force than muscles that had only been denervated-reinnervated. In the long term, although muscles made to degenerate were heavier and developed a significantly higher maximal force than denervated-reinnervated muscles, myoblast transfer failed to improve these parameters. However, the overall characteristics of long-term operated muscles tended clearly to approach those of the controls. Taken together, these results may have significant implications in certain orthopedic contexts, particularly after immediate or delayed muscle reinnervation.