HGF and polymyositis: 15, 16 Upon muscle injury, HGF activates muscle stem cells that reside in muscle fiber, leading to regeneration of damaged muscle.14, 17 Exogenously added recombinant HGF protein has been shown to ameliorate pathological conditions in mouse models for hypoxia-induced muscle atrophy18, polymyositis and dermatomyositis19. It has been reported that HGF can promote the survival of motor neurons in vitro20 and that HGF overexpression might attenuate the death of motor neurons and axon degeneration in ALS mice.21