Multichannel polymer scaffold seeded with activated Schwann cells and bone mesenchymal stem cells improves axonal regeneration and functional recovery after rat spinal cord injury

Abstract

The adult mammalian CNS has a limited capacity to regenerate after traumatic injury. In this study, a combinatorial strategy to promote axonal regeneration and functional recovery after spinal cord injury (SCI) was evaluated in adult rats. The rats were subjected to a complete transection in the thoracic spinal cord, and multichannel scaffolds seeded with activated Schwann cells (ASCs) and/or rat bone marrow-derived mesenchymal stem cells (MSCs) were acutely grafted into the 3-mm-wide transection gap. At 4 weeks post-transplantation and thereafter, the rats receiving scaffolds seeded with ASCs and MSCs exhibited significant recovery of nerve function as shown by the Basso, Beattie and Bresnahan (BBB) score and electrophysiological test results. Immunohistochemical analyses at 4 and 8 weeks after transplantation revealed that the implanted MSCs at the lesion/graft site survived and differentiated into neuron-like cells and co-localized with host neurons. Robust bundles of regenerated fibers were identified in the lesion/graft site in the ASC and MSC co-transplantation rats, and neurofilament 200 (NF) staining confirmed that these fibers were axons. Furthermore, myelin basic protein (MBP)-positive myelin sheaths were also identified at the lesion/graft site and confirmed via electron microscopy. In addition to expressing mature neuronal markers, sparse MSC-derived neuron-like cells expressed choline acetyltransferase (ChAT) at the injury site of the ASC and MSC co-transplantation rats. These findings suggest that co-transplantation of ASCs and MSCs in a multichannel polymer scaffold may represent a novel combinatorial strategy for the treatment of spinal cord injury.