Abstract
BackgroundTreatment of spinal cord injury is dependent on neuronal survival, appropriate synaptic circuit preservation, and inflammatory environment management. In this sense, mesenchymal stem cell (MSC) therapy is a promising tool that can reduce glial reaction and provide trophic factors to lesioned neurons.MethodsLewis adult female rats were submitted to a unilateral ventral funiculus cut at the spinal levels L4, L5, and L6. The animals were divided into the following groups: IA (intramedullary axotomy), IA + DMEM (Dulbecco’s modified Eagle’s medium), IA + FS (fibrin sealant), IA + MSC (106 cells), and IA + FS + MSC (106 cells). Seven days after injury, qPCR (n = 5) was performed to assess gene expression of VEGF, BDNF, iNOS2, arginase-1, TNF-α, IL-1β, IL-6, IL-10, IL-4, IL-13, and TGF-β. The cellular infiltrate at the lesion site was analyzed by hematoxylin-eosin (HE) staining and immunohistochemistry (IH) for Iba1 (microglia and macrophage marker) and arginase-1. Fourteen days after injury, spinal alpha motor neurons (MNs), evidenced by Nissl staining (n = 5), were counted. For the analysis of astrogliosis in spinal lamina IX and synaptic detachment around lesioned motor neurons (GAP-43-positive cells), anti-GFAP and anti-synaptophysin immunohistochemistry (n = 5) was performed, respectively. Twenty-eight days after IA, the gait of the animals was evaluated by the walking track test (CatWalk; n = 7).ResultsThe site of injury displayed strong monocyte infiltration, containing arginase-1-expressing macrophages. The FS-treated group showed upregulation of iNOS2, arginase-1, proinflammatory cytokine (TNF-α and IL-1β), and antiinflammatory cytokine (IL-10, IL-4, and IL-13) expression. Thus, FS enhanced early macrophage recruitment and proinflammatory cytokine expression, which accelerated inflammation. Rats treated with MSCs displayed high BDNF-positive immunolabeling, suggesting local delivery of this neurotrophin to lesioned motoneurons. This BDNF expression may have contributed to the increased neuronal survival and synapse preservation and decreased astrogliosis observed 14 days after injury. At 28 days after lesion, gait recovery was significantly improved in MSC-treated animals compared to that in the other groups.ConclusionsOverall, the present data demonstrate that MSC therapy is neuroprotective and, when associated with a FS, shifts the immune response to a proinflammatory profile.
Highlights
Treatment of spinal cord injury is dependent on neuronal survival, appropriate synaptic circuit preservation, and inflammatory environment management
We have previously shown that ventral root crush results in degeneration of spinal motoneurons, accompanied by astrocyte reactivity and microglial reaction
Spinal cord morphology after IA The cresyl violet staining revealed a large lesion in the ventral funiculus and fewer neurons in the ipsilateral side of the injury compared to in the contralateral side (Fig. 1c)
Summary
Treatment of spinal cord injury is dependent on neuronal survival, appropriate synaptic circuit preservation, and inflammatory environment management In this sense, mesenchymal stem cell (MSC) therapy is a promising tool that can reduce glial reaction and provide trophic factors to lesioned neurons. Spinal cord lesion treatment in the clinic is insufficient, and complex strategies are clearly necessary to promote functional recovery In this way, specific animal models of spinal cord injury may provide fundamental information regarding the inflammatory reaction and particular cellular responses that cannot be investigated in extensive lesions. We have previously shown that ventral root crush results in degeneration of spinal motoneurons, accompanied by astrocyte reactivity and microglial reaction Such cell loss and inflammation profoundly affects the spinal cord circuitry, decreasing immunoreactivity for presynaptic markers, such as synaptophysin and synapsin [3]. Mesenchymal stem cell therapy has been shown to improve walking parameters, including strength during the support and propulsion phases of ambulation
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