Dose-dependency of low-energy HeNe laser effect in regeneration of skeletal muscle in mice

We evaluated the effect on mice skeletal muscle regeneration of different d oses (2.6, 8.4, and 25 J/cm(2)) of HeNe laser (lambda 632.8 nm; power, 2.6 mW; spot size, 0.007 cm(2)) applied directly to intact skin of injured musc le. Muscle injury was induced in both right and left Tibialis anterior (TA) muscles by ACL myotoxin (5 mg/kg). Right TA muscles were irradiated daily for 5 days while contralateral muscles received a sham treatment. Only the 2.6 J/cm(2) dose resulted in changes such as increased mitochondrial densit y and muscle fibre in the TA muscles as compared to sham groups (3280 +/- 7 04 mum(2) versus 2110 +/- 657 mum(2), p = 0.02). We concluded that the HeNe effect on mouse muscle regeneration is dose-specific: only 2.6 J/cm(2) inc reased muscle fibre area and mitochondrial density.