AbstractThe effects,in vivo, of the exogenous administration of bFGF on myogenesis of regenerating skeletal muscle was assessed either morphometrically or autoradiographically in three separate models of muscle injury in mice: crush-injured, denervated, and dystrophic (mdx) muscles. The bFGF was administered at various doses and different time schedules, sometimes in combination with heparin, into injured tibialis anterior muscles of mice. Delivery of the bFGF was either by direct intramuscular injection or by the sustained release from polymers (Hydron or Elvax) implanted into the muscles. The bioactivity of bFGF was confirmedin vitroby measuring its ability to stimulate the proliferation of BALB/c-3T3 fibroblasts and muscle precursor cell lines. The ability of bFGF to stimulate angiogenesisin vivowas confirmed by the implantation of controlled-release polymers containing bFGF into the normally avascular cornea of rats. No measurable effect of bFGF was seen in any of the models of skeletal muscle injury under these experimental conditions, indicating that the availability of biologically active bFGF is not a limiting factor in the regeneration of skeletal muscle following injury.