Failure of delayed intravenous administration of bone marrow stromal cells after traumatic brain injury.

Traumatic brain injury (TBI) is a leading cause of mortality and morbidity worldwide. Currently, there is no effective strategy to treat the functional sequelae associated with TBI. Experimental evidence shows that the intravenous administration of bone marrow stromal cells (BMSC) during the first week after TBI prevents neurological deficits, but no experimental studies have shown evidence of the effect of intravenous BMSC on chronic brain injury sequelae. Here we studied the effect of intravenous administration of BMSC on functional outcomes 2 months after experimental TBI in rats. Adult Wistar rats were subjected to weight-drop impact causing severe brain injury, and 2 months later BMSC in saline, or saline alone, was intravenously injected. All experimental groups were evaluated by means of the modified Neurological Severity Score (mNSS), and internal zone Permanence Time (izPT) after video-tracking box (VTB) analysis, over the following 2 months to test the efficacy of BMSC therapy. At the end of the study period the animals were sacrificed and their brains were studied to evaluate possible differences between groups. Two months after BMSC administration no significant differences were detected in the motor and sensory evaluation between animals treated with BMSC and controls, and no differences were detected after histological study of the brains. Our present results suggest that intravenous administration of BMSC after TBI, when the neurological deficits are well established, has no beneficial effect in neurological outcomes or on brain tissue.