Chronic spinal cord lesions respond positively to tranplants of mesenchymal stem cells

Purpose: Despite substantial advances in surgical care and rehabilitation, the consequences of spinal cord injury (SCI) continue to present major challenges. Here we investigate whether transplantation of mesenchymal stem cells (MSCs) in mice during the chronic stage of SCI has benefits in terms of morphological and functional outcomes. Methods: Mice were subjected to laminectomy at the T9 level, followed by a 1 minute spinal cord compression with a vascular clip. Four weeks later, 8 × 10 5 MSCs obtained from GFP mice were injected into the injury site. After eight weeks the analyses were performed. Results: The spinal cords of MSC-treated animals exhibited better white-matter preservation, greater numbers of fibers, higher levels of trophic factor expression, and better ultrastructural tissue organization. Furthermore, transplanted MSCs were not immunoreactive for neural markers, indicating that these cells mediate functional recovery through a paracrine effect, rather than by transforming into and replacing damaged glia in the spinal cord. MSC-treated mice also showed better functional improvement than control animals. Conclusion: We conclude that MSC-based cell therapy, even when applied during the chronic phase of SCI, leads to changes in a number of structural and functional parameters, all of which indicate improved recovery.