Stem cell therapy for traumatic brain injury TBI will focus on secondary brain injury, which is the result of biochemical and physiological events, ultimately leading to neuronal cell death. Recent research has indicated that the potential therapeutic benefit of stem cell therapy could be the result of the following mechanisms: 1. Secretion of growth factors to promote functional outcome after brain injury via neurogenesis and synaptogenesis; 2. Production and inducement of many cytokines and trophic factors to enhance angiogenesis and vascular stabilization in the lesion boundary zone; 3. Decrease of the glial scar formation and promotion of glial-axonal remodeling. Thus, stem cells act in a pleiotropic way to stimulate brain remodeling after brain injury by influencing several neural restorative functions such as synaptogenesis, angiogenesis, and neurogenesis.