Severe critical illness is often complicated by Intensive Care Unit - Acquired Weakness (ICU-AW), which is associated with increased in and post-ICU mortality, with delayed weaning from mechanical ventilation and with long-term functional. Several mechanisms have been incriminated in the pathophysiology of ICU-AW, but muscle regeneration has not been well investigated in this context, even though its involvement is suggested by the protracted functional consequences of ICU-AW. Recent data suggest that muscle regeneration could be impaired after sepsis, and that Mesenchymal Stem Cells (MSCs) treatment could improve the post-injury muscle recovery.