Muscle regeneration induced by cells autografted in adult rats

Right triceps surae of 3-week-old Wistar rats were minced and devitalized with liquid nitrogen, a treatment which completely inhibits their ability to regenerate when they are orthotopically autografted. In a first series of experiments, cells were isolated from the left triceps surae, mixed with the devitalized right mince and autografted; in a second series, cells were moreover allowed to proliferate in vitro for a few weeks before being grafted. The regenerates were examined 60 days after surgery. In the first series, all the regenerates were contractile and developed a maximal isometric tetanic force of 18 +/- 6 mN (n = 5); they contained 152 +/- 80 muscle fibres located proximally, the number of which decreased along the proximo-distal axis, being 24 +/- 24 in the median part of the regenerate. The muscle fibres appeared histologically normal except for their shortness (less than 10 mm) and narrowness (mean luminal diameter: 30 microns). In the second series, 2 out of 5 regenerates were comparable with those of the first series except that their fibres were shorter; the 3 other regenerates were unexcitable. These experiments demonstrate that cells isolated from an adult striated muscle are able to regenerate striated muscle fibres in an adult animal and that these cells can retain this property if they are grown in culture.