The incidence and long-term effects of traumatic brain injury (TBI) make it a major healthcare and socioeconomic concern. Cell transplantation may be an alternative therapy option to target prolonged neurological deficits;​ however, safety and efficacy of the cells must be determined. Bone marrow-derived mesenchymal stem cells (MSCs) are an accessible and expandable cell source which circumvent the many of the accessibility and ethical concerns associated with fetal tissues. A major impediment to recent clinical trials for cell therapies in the central nervous system has been the lack of consistency in functional recovery where some patients receive great benefits while others experience little, if any, effect (Watts and Dunnett 2000;​ Lindvall and Bjorklund 2004). There are many possible explanations for this patient-to-patient variability including genetic and environmental factors, surgical techniques, and donor cell variability. Of these, the most easily addressable is to increase the reproducibility of donor cells by standardizing the isolation and pre-transplantation protocols, which is the central goal of this dissertation. First, we present an animal study in which transplants of MSCs and neural stem cells (NSCs) were given to brain-injured mice, however, the efficacy of the treatment had high variability between individual subjects. Second, we designed a method to produce MSC-spheres and characterize them in vitro. Last, we employed an in vitro 3-D culture testbed as a pre-transplant injury model to assess the effects of the MSC-spheres on neural cells. The electrophysiological function of the uninjured testbed was assessed, and then MSC-spheres were injected into the testbed and apoptosis of the host cells were measured. The results of this study contribute to our understanding of how extracellular context may influence MSC-spheres and develop MSCs as a donor cell source for transplantation.